0000950170-25-038427 | 10-K | XBRL Viewer

Net loss from continuing operations

Operating Expenses

$ 121,315

$ 195,097

$ 179,914

(125,771)

(190,130)

(183,581)

Net income (loss) from discontinued operations, net of tax

125,907

76,406

(66,576)

Net income (loss)

136

(113,724)

(250,157)

Operating Segments [Member]

R&D personnel-related (including stock-based compensation)

28,689

65,251

68,059

G&A personnel-related (including stock-based compensation)

22,679

36,069

30,653

Professional fees

9,805

18,784

23,529

Facility-related and other

20,699

22,647

16,081

Other segment expense (income)

^[1]

8,089

(3,722)

5,426

Net loss from continuing operations

(125,771)

(190,130)

(183,581)

Net income (loss) from discontinued operations, net of tax

^[2]

125,907

76,406

(66,576)

Net income (loss)

136

(113,724)

(250,157)

Live Biotherapeutics Platform [Member] | Operating Segments [Member]

SER-155 [Member] | Operating Segments [Member]

Operating Expenses

29,006

43,342

34,764

Summary of Accrued Expenses and Other Current Liabilities

Operating Expenses

$ 6,804

$ 7,759

$ 5,069

[1]	Other segment (expense) income includes research and development expenses on early stage programs, manufacturing services expenses, gain on sale of VOWST Business, interest income and other (expense) income, net.
[2]	See Note 3, Discontinued Operations and TSA, for further details.

Commitments and Contingencies - Additional Information (Detail) - USD ($)	Dec. 31, 2024	Dec. 31, 2023
Indemnification Agreement [Member]
Other Commitments [Line Items]
Obligations accrued	$ 0	$ 0
Legal Contingencies [Member]
Other Commitments [Line Items]
Obligations accrued	$ 0	$ 0

Nature of the Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands					1 Months Ended	9 Months Ended	12 Months Ended
	Jul. 01, 2025	Jan. 15, 2025	Aug. 05, 2024	Jun. 29, 2022	Sep. 30, 2024	Sep. 30, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2025
Nature Of Business And Basis Of Presentation [Line Items]
Entity incorporated month and year							2010-10
Entity incorporation, state or country code							DE
Payments to acquire business						$ 15,000	$ 15,000
Stock issued during period, shares, new Issues				8,738,243		14,285,715	14,285,715
Share Price					$ 1.05	$ 1.05	$ 1.05
Milestone Prepayment			$ 60,000		$ 60,000
Payment in cash for first sales milestone			150,000
Future milestone payment			125,000
Closing period milestone payment one			400,000
Closing period milestone payment two			150,000
Closing period milestone payment three			750,000
Accumulated deficit							$ 978,099	$ 978,235
Cash and cash equivalents							30,793	127,965
Net loss from continuing operations							(125,771)	(190,130)	$ (183,581)
Net operating cash outflows							148,609	$ 117,354	$ 228,816
Forecast [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Payment reduced amount of employment obligation	$ 1,500	$ 1,500
Business combination percentage of all rent and other cost due										80.10%
Forecast [Member] \| Transition Services Agreement [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Payments to acquire other productive assets	$ 25,000
Subsequent Event [Member] \| Transition Services Agreement [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Payments to acquire other productive assets		$ 50,000
Nestle Health Science [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Payments to acquire business			100,000
Satisfaction fee paid							$ 9,016
Adjusted account settlement amount			$ 17,857
Fixed interest rate			10.00%
Derivative fixed interest rate thereafter			5.00%

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2024

Payables and Accruals [Abstract]

Accrued expenses and other current liabilities consisted of the following:


	December 31,
	2024		2023
Clinical and development costs	$	422	$	1,404
Manufacturing and quality costs		478		1,868
Payroll and employee-related costs		7,656		16,465
Facility and other		2,163		2,772
	$	10,719	$	22,509

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2024

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

7. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following:


	December 31,
	2024		2023
Clinical and development costs	$	422	$	1,404
Manufacturing and quality costs		478		1,868
Payroll and employee-related costs		7,656		16,465
Facility and other		2,163		2,772
	$	10,719	$	22,509

Leases - Summary of Operating Lease Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Assets:
Operating lease assets	$ 80,903	$ 90,417
Liabilities:
Operating lease liabilities	8,674	5,587
Operating lease liabilities, net of current portion	82,966	91,652
Total operating lease liabilities	$ 91,640	$ 97,239

Leases (Tables)

12 Months Ended

Dec. 31, 2024

Leases [Abstract]

Summary of Operating Lease Assets and Liabilities

The following table summarizes the presentation in the Company’s consolidated balance sheets of its operating leases (in thousands):


	December 31,
	2024		2023
Assets:
Operating lease assets	$	80,903	$	90,417

Liabilities:
Operating lease liabilities	$	8,674	$	5,587
Operating lease liabilities, net of current portion		82,966		91,652
Total operating lease liabilities	$	91,640	$	97,239

Summary of Lease Costs

The following table summarizes the effect of lease costs in the Company’s consolidated statements of operations and comprehensive income (loss) (in thousands):


	Year Ended December 31,
	2024			2023		2022
Operating lease costs	$	19,514		$	22,324	$	8,830
Short-term lease costs		—			1,477		1,375
Variable lease costs		6,589			7,229		4,547
Sublease income		(2,708	)		—		—
Total lease costs	$	23,395		$	31,030	$	14,752

Schedule of Future Payments of Operating Lease Liabilities

As of December 31, 2024, future payments of operating lease liabilities are as follows (in thousands):


	As of December 31, 2024
2025	$	19,442
2026		19,983
2027		20,582
2028		20,862
2029		20,132
2030 and thereafter		36,850
Total future payments of operating lease liabilities	$	137,851
Less: imputed interest		(46,211	)
Present value of operating lease liabilities	$	91,640

Net Loss per Share

12 Months Ended

Dec. 31, 2024

Earnings Per Share [Abstract]

Net Loss per Share

12. Net Loss per Share

Basic and diluted net loss per share attributable to common stockholders was calculated as follows (in thousands, except share and per share data):


	Year Ended December 31,
	2024			2023			2022
Numerator:
Net loss from continuing operations attributable to common stockholders	$	(125,771	)	$	(190,130	)	$	(183,581	)
Net income (loss) from discontinuing operations attributable to common stockholders	$	125,907		$	76,406		$	(66,576	)
Net income (loss) attributable to common stockholders	$	136		$	(113,724	)	$	(250,157	)

Denominator:
Weighted average common shares outstanding, basic and diluted		155,400,760			128,003,294			108,077,043
Net loss from continuing operations per share attributable to common stockholders, basic and diluted	$	(0.81	)	$	(1.49	)	$	(1.70	)
Net income (loss) from discontinued operations per share attributable to common stockholders, basic and diluted	$	0.81		$	0.60		$	(0.62	)
Net loss per share attributable to common stockholders, basic and diluted	$	0.00		$	(0.89	)	$	(2.31	)

Anti-dilutive potential common stock equivalents excluded from the calculation of net (loss) income per share:
Stock options to purchase common stock		17,720,315			14,844,112			14,940,034
Unvested restricted stock units		1,631,772			3,377,804			1,549,540
Shares issuable under employee stock purchase plan		143,214			297,784			89,593
Warrants to purchase common stock		647,589			1,177,433			—

The Company utilizes the control number concept in the computation of diluted earnings per share to determine whether potential common stock equivalents are dilutive. The control number used is loss from continuing operations. The control number concept requires that the same number of potentially dilutive securities applied in computing diluted earnings per share from continuing operations be applied to all other categories of income or loss, regardless of their anti-dilutive effect on such categories. Since the Company had a net loss from continuing operations for all periods presented, no dilutive effect has been recognized in the calculation of income from discontinued operations per share. Therefore, the weighted average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same.

The Company’s potential dilutive securities, which include stock options, unvested restricted common stock and shares issuable under the 2015 Employee Stock Purchase Plan, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share and therefore been anti-dilutive. Additionally, for the years ended December 31, 2024 and 2023, the warrants to purchase common stock were excluded because the exercise price of the Tranche A Warrants was greater than the average fair value of the Company's common shares, and the necessary conditions for exercise of the Tranche B and Tranche C Warrants had not been met.

Nature of the Business and Basis of Presentation

12 Months Ended

Dec. 31, 2024

Nature of the Business and Basis of Presentation

Seres Therapeutics, Inc. (the “Company”) was incorporated under the laws of the State of Delaware in October 2010 under the name Newco LS21, Inc. In October 2011, the Company changed its name to Seres Health, Inc., and in May 2015, the Company changed its name to Seres Therapeutics, Inc. The Company is a clinical-stage company focused on improving patient outcomes in medically vulnerable populations through novel live biotherapeutics. The Company led the successful development and approval of VOWST (previously referred to as SER-109), the first FDA-approved orally administered microbiome therapeutic, which was sold to Nestlé Health Science (as defined below) in September 2024. The Company is progressing the development of SER-155, an investigational, oral, live biotherapeutic designed to decolonize gastrointestinal (“GI”) pathogens, improve epithelial barrier integrity, and regulate immune response to prevent bacterial bloodstream infections, as well as other pathogen-associated negative clinical outcomes in patients undergoing allogeneic hematopoietic stem cell transplantation (“allo-HSCT”). SER-155 and the Company's other pipeline programs are designed to target multiple disease-relevant pathways and are manufactured from standard clonal cell banks via cultivation, rather than from the donor-sourced production process used for VOWST.

In the Company's placebo-controlled Phase 1b study of SER-155 in allo-HSCT, Cohort 2 results demonstrated that SER-155 was associated with a significant reduction in both bloodstream infections and systemic antibiotic exposure as well as a lower incidence of febrile neutropenia, as compared to placebo through day 100 post hematopoietic stem cell transplantation (“HSCT”). SER-155 was generally well tolerated, with no observed treatment-related serious adverse events. In addition to allo-HSCT, the Company intends to evaluate SER-155 and other cultivated live biotherapeutic candidates in other medically vulnerable patient populations, including autologous-HSCT patients, cancer patients with neutropenia, chimeric antigen receptors therapy recipients, individuals with chronic liver disease, solid organ transplant recipients, as well as patients in the intensive care unit and long-term acute care facilities.

The Company has built and deploys a reverse translational platform and knowledge base for the discovery and development of live biotherapeutics, and maintains extensive proprietary know-how that may be used to support future research and development efforts. This platform incorporates high-resolution analysis of human clinical data to identify microbiome biomarkers associated with disease and non-disease states; preclinical screening using human cell-based assays and in vitro/ex vivo and in vivo disease models customized for live biotherapeutics; and microbiological capabilities and a strain library that spans broad biological and functional breadth to both identify specific microbes and microbial metabolites that are associated with disease and to design consortia of bacteria with specific pharmacological properties. In addition, the Company owns a valuable intellectual property estate related to the development and manufacture of live biotherapeutics.

At a special meeting of stockholders held on September 26, 2024, the Company’s stockholders approved, and on September 30, 2024 (the "Closing Date"), the Company completed, the sale (the “Transaction”) of its VOWST microbiome therapeutic business (the “VOWST Business”), including inventory and equipment, certain patents and patent applications, know-how, trade secrets, trademarks, domain names, marketing authorizations and related rights, documents, materials, business records and data and contracts that are used or held for use primarily in the development, commercialization and manufacturing of the microbiome product sold under the brand name VOWST as provided for in accordance with the terms of the Purchase Agreement (the “Product”), to Société des Produits Nestlé S.A. (“SPN”), a wholly-owned subsidiary of Nestlé S.A., and its designated affiliates (collectively, “Nestlé Health Science”) pursuant to the Asset Purchase Agreement, dated as of August 5, 2024 (the “Purchase Agreement”), by and among the Company and SPN, and a wholly-owned subsidiary of Nestlé S.A. As consideration for the Transaction, SPN paid or agreed to pay, as applicable, the following Transaction Consideration:

(i)

a cash payment, which was paid upon completion of the Transaction (“Closing”), of $100,000, less approximately $17,857 owed by the Company to an affiliate of SPN as of March 31, 2024 under the prior license agreement between the Company and the SPN affiliate, less approximately CHF 2,000 in satisfaction of fees due under the Bacthera Manufacturing Agreement (defined below);

(ii)

cash installment payments of $50,000, which was received on January 15, 2025 and $25,000 due on July 1, 2025 (the “Installment Payments”) (to be reduced by approximately $1,500 related to certain employment obligations assumed by SPN, as described below), conditioned on the Company’s material compliance with obligations under the Transition Services Agreement (the “TSA”) (as described below) entered into at Closing between the Company and Nestlé Enterprises S.A., an affiliate of SPN, or NESA;

(iii)

prepayment of the $60,000 milestone payment tied to the achievement of worldwide annual net sales of the Product of $150,000 (the “First Sales Milestone”), which was paid in cash at Closing (the “Prepaid Milestone”), which Prepaid Milestone will accrue interest at a fixed rate of 10% per annum until the First Sales Milestone is achieved and 5% per annum thereafter until the earlier of (x) the date on which the Prepaid Milestone, plus accrued interest thereon, has been repaid in full by set-off and (y) the last day of the Milestone Period (as defined below); and

(iv)

future milestone payments of (x) $125,000 tied to the achievement of worldwide annual net sales of the Product of $400,000 and (y) $150,000 tied to the achievement of worldwide annual net sales of the Product of $750,000, during the period from

Closing until December 31 of the calendar year in which the tenth anniversary of Closing occurs (the “Milestone Period”) (together, the “Future Milestone Payments” and, together with the Prepaid Milestone, the “Milestone Payments”).

As they are earned, the Milestone Payments will be satisfied as follows: (i) first, by set-off against all accrued interest on the Prepaid Milestone until the amount of such accrued interest has been paid in full, (ii) second, by set-off against the outstanding balance of the Prepaid Milestone until the Prepaid Milestone has been repaid in full and (iii) thereafter, in cash. If any amount of the Prepaid Milestone (and any accrued interest thereon) remains outstanding as of following the last day of the Milestone Period (defined below), the balance thereof (together with any interest accrued thereon) will be forgiven and the right of set-off of SPN with respect thereto will be deemed forfeited. The Installment Payment due on July 1, 2025 will be reduced by approximately $1,500 related to certain employment obligations assumed by SPN with respect to the period ended as of the Closing Date.

The Company and SPN share 50/50 in the net profit or net loss (the “Profit Sharing Payments”) achieved during the period from the date of Closing until December 31, 2025 (the “Profit Sharing Period”), with the net profit or net loss calculated as (i) the net sales of VOWST in the United States and Canada, plus (ii) other income received in connection with the grant of a license or sublicense with respect to VOWST in the United States and Canada as described in the Purchase Agreement, minus (iii) allowable expenses directly attributable or reasonably allocable to certain development activities, commercialization activities, medical affairs activities, manufacturing activities or other relevant activities, as described in the Purchase Agreement. During the Profit Sharing Period, the Company will reimburse SPN for (i) certain payments under the exclusive license agreement between the Company and Memorial Sloan Kettering Cancer Center, (ii) certain costs incurred in connection with an ongoing post-marketing safety study of VOWST and (iii) 80.1% of all rent and other costs due to the landlord under the lease for the Company’s Waltham facility.

At Closing, in exchange for a payment to be made by SPN to Bacthera AG, the Long Term Manufacturing Agreement, dated November 8, 2021 between the Company and Bacthera AG (the “Bacthera Manufacturing Agreement”) was terminated and each of Bacthera and Seres released one another from any and all losses, liabilities or other obligations arising thereunder with respect to the period ending at the Closing Date, including without limitation any milestone payments required to be paid to Bacthera thereunder.

On the Closing Date, the Company and SPN entered into a securities purchase agreement (the “Securities Purchase Agreement”) pursuant to which SPN purchased 14,285,715 shares (the “Shares”) of common stock at Closing, at a purchase price per share of $1.05, for an aggregate purchase price of $15,000. Under the terms of the Securities Purchase Agreement, SPN agreed not to sell or transfer the Shares for a period of six months after Closing, subject to certain customary exceptions. The Company agreed to register the resale of the Shares by SPN within 90 days of Closing. On October 1, 2024, the Company filed a registration statement to register the Shares, which became effective on October 11, 2024. In addition, under the terms of the Securities Purchase Agreement, for as long as SPN, together with its affiliates, beneficially owns at least 10% of the Company’s outstanding shares of common stock, the Company has agreed to take such action within its control to include one individual designated by SPN in the slate of nominees recommended by the Company’s board of directors (or the applicable committee of the board of directors) to the Company’s stockholders for election to the board of directors at the applicable stockholder meeting. SPN designated Hans-Juergen Woerle, M.D., Ph.D. and on February 4, 2025, the Company’s board of directors appointed Dr. Woerle to the board as a Class III director, with a term expiring at the Company’s 2027 annual meeting of stockholders. The Securities Purchase Agreement contains customary representations and warranties and closing conditions.

On the Closing Date, the Company entered into a TSA with NESA, which provides for services to be performed by the Company in order to facilitate a transition of the business associated with the VOWST Business to NESA and its affiliates. The scope of the transition services includes the provision of certain manufacturing services and certain administrative functions related to the VOWST Business and operations, including the maintenance of certain manufacturing services and the related facility in which such services are currently conducted. The Company will provide the manufacturing services until December 31, 2025, which period may be extended by up to six months (solely to ensure the manufacturing facility is in a state of compliance with the biologics license application for VOWST and readiness for potential regulatory inspection), and other services for the duration specified in the schedule to the TSA for each service. NESA has agreed to pay the Company for certain fixed costs, including a monthly fixed fee and a variable per batch fee for preserved raw material suspension ("PRMS") manufacturing, and will reimburse the Company for certain costs of the transition services performed by the Company under the TSA, including labor. The know-how and other intellectual property generated in connection with the performance of the TSA will be owned by NESA with the Company having a non-exclusive license to such know-how and other intellectual property under the Cross-License Agreement. During the term of the TSA, upon NESA's request, the Company will transfer the specifications for materials and documentation necessary to enable PRMS manufacturing services to a third party service provider designated by NESA. In the event of a material failure by the Company to deliver PRMS under the TSA, NESA will have step-in rights to negotiate to enter into a direct lease with the landlord of the manufacturing facility with respect to the portion of such facility used in connection with the VOWST Business or to cause such services to be performed, with any reasonable out-of-pocket costs and expenses incurred in connection therewith reimbursed by the Company.

At the Closing Date, the Company entered into a cross-license agreement with SPN under which the Company granted to SPN a perpetual, worldwide, non-exclusive, fully paid-up license under certain Company patents that have been issued or will issue in the future and current know-how controlled by the Company that is not transferred to SPN pursuant to the Purchase Agreement. In the field of the treatment of Clostridioides difficile infections ("CDI") and recurrent CDI and associated complications (collectively, the “CDI Field”) the license to SPN under such Company patents and know-how will be exclusive to SPN for five years after Closing and co-exclusive between SPN and the Company following that five year period. The license from the Company to SPN is to issued Company patents that currently or in the future cover the Product or improvements thereof, and know-how that is used or reasonably useful in connection with the exploitation of the VOWST Business. The Company also granted SPN an exclusive, perpetual, worldwide, fully paid-up license under issued Company patents that currently or in the future cover the Product and improvements thereof and know-how that is used or reasonably useful in connection with the exploitation of the Product to exploit SER-262 in the CDI Field. SPN granted to the Company a perpetual, worldwide, non-exclusive license under the patents and know-how that are transferred to SPN pursuant to the Purchase Agreement or developed under the TSA, for the Company’s products for use outside of the CDI Field, and after five years from Closing for Company products containing designed, cultivated, bacterial consortia not manufactured using human stool (excluding SER-262) in the CDI Field. From and after Closing, certain license agreements between the Company, SPN, and/or their respective affiliates terminated and are of no further force or effect, except as contemplated by the Purchase Agreement. For example, on September 30, 2024, in connection with the Transaction, the 2016 License Agreement (the “2016 License Agreement”) with Nestec, Ltd., as succeeded by SPN (together with NHSc Rx License GmbH, their affiliates, and their subsidiaries “Nestlé”), and the 2021 License Agreement (the “2021 License Agreement”) with NHSc Pharma Partners, succeeded by NHSc Rx License GmbH (together with Société des Produits Nestlé S.A, their affiliates, and their subsidiaries “Nestlé”) were terminated upon mutual agreement of the parties, with provisions related to record retention, confidentiality obligations, indemnification obligations, intellectual property ownership, and any outstanding payment obligations surviving the termination of each of the 2016 License Agreement and 2021 License Agreement, respectively.

On the Closing Date, the parties entered into assignment and assumption of lease agreements (the “Assignment and Assumption Agreements”). Under the Assignment and Assumption Agreements, the Company assigned to SPN the Company’s rights in, to and under certain real property leases, and SPN assumed the liabilities related thereto.

On the Closing Date, the parties entered into an employee support agreement (the “Employee Support Agreement”). Under the Employee Support Agreement, among other things and subject to the terms and conditions therein, certain employees of the Company related to the VOWST Business who accepted employment with SPN or one of its designated affiliates provided the services they provided to the Company prior to the Transaction to SPN, as well as other services as SPN may reasonably request, from Closing until the day prior to the beginning of SPN’s or its designated affiliate’s next pay period following the Closing. SPN reimbursed the Company’s out of pocket costs in connection with such employees’ services, including certain compensation and benefits paid or provided to such employees pursuant to the terms of the Employee Support Agreement. All such employees have transferred to SPN as of December 31, 2024.

In connection with the Transaction, the Company fully retired its senior secured debt facility with Oaktree Capital Management. The Company intends to use the remaining proceeds to support the further advancement of SER-155 and the Company’s other wholly-owned cultivated live biotherapeutic candidates for medically vulnerable patient populations with potential to address large commercial opportunities.

The Company incurred certain significant costs relating to the Transaction, such as legal, accounting, financial advisory, printing and other professional services fees, as well as other customary payments. Through December 31, 2024, these costs amounted to approximately $9,016, which is included within the net income (loss) from discontinued operations, net of tax line item on the Company's consolidated statements of operations.

Going Concern

The Company is subject to risks common to companies in the biotechnology industry including, but not limited to, new technological innovations, protection of proprietary technology, dependence on key personnel, compliance with government regulations and the need to obtain additional financing. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its employees and consultants.

The accompanying consolidated financial statements have been prepared on a basis which assumes that the Company will continue as a going concern and which contemplates the realization of assets and satisfaction of liabilities and commitments in the normal course of business. As of December 31, 2024, the Company had an accumulated deficit of $978,099 and cash and cash equivalents of $30,793.

The Company’s product candidates are in development, and will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval, prior to potential commercialization. There can be

no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained, or maintained, that any product candidate developed will obtain necessary government regulatory approval, or that any approved product will be commercially viable. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales.

Primarily as a result of the costs associated with continuing the research and development efforts for other product candidates and preclinical programs, the Company incurred a net loss from continuing operations of $125,771, and had net operating cash outflows of $148,609 for the year ended December 31, 2024. The Company expects that its operating losses and negative cash flows will continue for the foreseeable future. Based on the Company's currently available cash resources, current and forecasted level of operations, and forecasted cash flows for the 12-month period subsequent to the date of issuance of these consolidated financial statements, the Company will require additional funding to support its ongoing operations and meet its obligations as they come due. These conditions raise substantial doubt about the Company's ability to continue as a going concern.

The Company’s ability to continue as a going concern is dependent upon its ability to obtain the necessary financing to meet its obligations and repay its liabilities arising from normal business operations when they come due, and to generate profitable operations in the future. Management plans to provide for the Company’s capital requirements through financing or other strategic transactions, including potential business development transactions, and selling shares under the Company's at the market equity offering. There can be no assurance that the Company will be able to raise additional capital to fund operations with terms acceptable to the Company, or at all. Because certain elements of management’s plans to mitigate the conditions that raised substantial doubt about the Company’s ability to continue as a going concern are outside of the Company’s control, including the ability to raise capital through an equity or other financing, those elements cannot be considered probable according to Accounting Standards Codification (“ASC”) 205-40, Going Concern ("ASC 205-40"), and therefore cannot be considered in the evaluation of mitigating factors. As a result, management has concluded that substantial doubt exists about the Company’s ability to continue as a going concern for 12 months from the date these consolidated financial statements are issued. The accompanying consolidated financial statements do not include any adjustments that may result from the outcome of this uncertainty.

Reclassifications

In late September 2024, the Company’s VOWST Business met all the conditions to be classified as held for sale and, because the Company considers the disposal of the VOWST Business to be a strategic shift that will have a major effect on its operations and financial results, represented a discontinued operation. All assets and liabilities associated with the Company’s VOWST Business were therefore classified as assets and liabilities of discontinued operations in our consolidated balance sheets for the periods presented. Further, all historical operating results for the Company’s VOWST Business are reflected within discontinued operations in the consolidated statements of operations for all periods presented. For additional information, see Note 3, Discontinued Operations and TSA.

Certain amounts in prior periods have been reclassified to reflect the impact of the discontinued operations treatment of the VOWST Business in order to conform to the current period presentation.

The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and include the accounts of the Company and its wholly owned subsidiaries after elimination of all intercompany accounts and transactions.

Net Loss per Share (Tables)

12 Months Ended

Dec. 31, 2024

Earnings Per Share [Abstract]

Basic and Diluted Net Loss Per Share Attributable to Common Stockholders

Basic and diluted net loss per share attributable to common stockholders was calculated as follows (in thousands, except share and per share data):


	Year Ended December 31,
	2024			2023			2022
Numerator:
Net loss from continuing operations attributable to common stockholders	$	(125,771	)	$	(190,130	)	$	(183,581	)
Net income (loss) from discontinuing operations attributable to common stockholders	$	125,907		$	76,406		$	(66,576	)
Net income (loss) attributable to common stockholders	$	136		$	(113,724	)	$	(250,157	)

Denominator:
Weighted average common shares outstanding, basic and diluted		155,400,760			128,003,294			108,077,043
Net loss from continuing operations per share attributable to common stockholders, basic and diluted	$	(0.81	)	$	(1.49	)	$	(1.70	)
Net income (loss) from discontinued operations per share attributable to common stockholders, basic and diluted	$	0.81		$	0.60		$	(0.62	)
Net loss per share attributable to common stockholders, basic and diluted	$	0.00		$	(0.89	)	$	(2.31	)

Anti-dilutive potential common stock equivalents excluded from the calculation of net (loss) income per share:
Stock options to purchase common stock		17,720,315			14,844,112			14,940,034
Unvested restricted stock units		1,631,772			3,377,804			1,549,540
Shares issuable under employee stock purchase plan		143,214			297,784			89,593
Warrants to purchase common stock		647,589			1,177,433			—

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Dec. 31, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Summary of Significant Accounting Policies - Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Cash and cash equivalents	$ 30,793	$ 127,965
Restricted cash, non-current	8,668	8,185
Total cash, cash equivalents and restricted cash	$ 39,461	$ 136,150	$ 171,215	$ 188,002

Common Stock and Stock-Based Awards - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Equity [Abstract]
Number of Shares, Beginning Balance	14,844,112
Number of Shares, Granted	7,817,641
Number of Shares, Exercised	0
Number of Shares, Forfeited	(4,941,438)
Number of Shares, Ending Balance	17,720,315	14,844,112
Number of Shares, Vested or expected to vest	17,720,315
Number of Shares, Options exercisable	9,850,537
Weighted Average Exercise Price, Beginning Balance	$ 9.64
Weighted Average Exercise Price, Granted	1.05
Weighted Average Exercise Price, Exercised	0
Weighted Average Exercise Price, Forfeited	7.44
Weighted Average Exercise Price, Ending Balance	6.46	$ 9.64
Weighted Average Exercise Price, Vested or expected to vest	6.46
Weighted Average Exercise Price, Options exercisable	$ 9.94
Weighted Average Remaining Contractual Term, Outstanding	6 years 7 months 2 days	5 years 8 months 15 days
Weighted Average Remaining Contractual Term	6 years 7 months 2 days
Weighted Average Remaining Contractual Term, Options exercisable	4 years 8 months 26 days
Aggregate Intrinsic Value, Outstanding	$ 87	$ 0
Aggregate Intrinsic Value, Vested or expected to vest	87
Aggregate Intrinsic Value, Options exercisable	$ 7

Investments - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Investments [Abstract]
Maximum maturity days for cash equivalents	90 days	90 days
Restricted investments	$ 0	$ 1,401

Discontinued Operations and TSA

12 Months Ended

Dec. 31, 2024

Discontinued Operations and Disposal Groups [Abstract]

Discontinued Operations and TSA

3. Discontinued Operations and TSA

On September 30, 2024, the Company completed the sale of its VOWST Business to SPN. The Company has determined the sale of the VOWST Business represents a strategic shift that will have a major effect on its business and therefore met the criteria for classification as discontinued operations on September 30, 2024. Accordingly, the VOWST Business is reported as discontinued operations in accordance with ASC 205-20, Discontinued Operations. The related assets and liabilities of the VOWST Business are classified as assets and liabilities of discontinued operations in the consolidated balance sheets and the results of operations from the VOWST Business as discontinued operations in the consolidated statements of operations. Applicable amounts in prior years have been recast to conform to this discontinued operations presentation. The Company recognized a gain on the sale of the VOWST Business upon closing.

The following table presents the assets and liabilities of the discontinued operations as of December 31, 2023:


	December 31,
	2023
Assets
Current assets:
Collaboration receivable - related party	$	8,674
Inventories		29,647
Prepaid expenses and other current assets		1,075
Total current assets of discontinued operations		39,396
Property and equipment, net		4,843
Operating lease assets		19,376
Other non-current assets		39,167
Total non-current assets of discontinued operations		63,386
Total assets of discontinued operations	$	102,782
Liabilities
Current liabilities:
Accrued expenses and other current liabilities	$	58,102
Operating lease liabilities		1,090
Deferred income - related party		7,730
Total current liabilities of discontinued operations		66,922
Operating lease liabilities, net of current portion		14,063
Deferred revenue, net of current portion - related party		95,364
Total non-current liabilities of discontinued operations		109,427
Total liabilities of discontinued operations	$	176,349

As of December 31, 2024, there were no assets or liabilities of discontinued operations.

The following table presents the gain on the sale of the VOWST Business as of December 31, 2024, pursuant to the Purchase Agreement:


	December 31,
	2024
Consideration received
Upfront payment (1)	$	79,788
Prepaid milestone		60,000
Deferred revenue from termination of 2016 License Agreement		95,364
Settlement of net collaboration payable at close		27,465
Premium on equity financing		1,484
Deferred income from termination of 2021 License Agreement		3,606
Accrued liabilities due to SPN - related party		(33,458	)
Total fair value transferred for business	$	234,249

Net assets transferred
Inventory	$	63,442
Prepaid expenses and other current assets		2,219
Property and equipment, net		3,966
Operating lease assets		17,929
Other non-current assets		39,328
Accrued expenses and other current liabilities		(31,547	)
Operating lease liabilities		(14,413	)
Net assets transferred	$	80,924

Transaction costs	$	6,618

Gain on sale, pre-tax	$	146,707
Income tax		—
Gain on sale, net of tax	$	146,707

[1] The upfront payment consists of $100,000, less $17,857 owed by the Company to an affiliate of SPN under the prior license agreement between the Company and the SPN affiliate, less approximately $2,355 in satisfaction of costs due under the Bacthera Manufacturing Agreement.

For the twelve months ended December 31, 2024, the gain from sale of the VOWST Business, net of tax of $146,707 was included in the net income (loss) from discontinued operations, net of tax line item of the Company’s consolidated statements of operations and comprehensive income (loss). While the Company has net income from discontinued operations for the twelve months ended December 31, 2024, the Company realized a tax loss for the full year ended December 31, 2024, for which it is more likely than

not that the Company will not realize a benefit. The Company has recorded a full valuation allowance against its net deferred tax assets as of December 31, 2024 and 2023.

The following table presents the financial results of the discontinued operations:


	Year Ended December 31,
	2024			2023			2022
Revenue:
Collaboration revenue - related party	$	—		$	126,325		$	7,128
Total revenue		—			126,325			7,128
Operating expenses:
Research and development expenses		5,809			28,263			63,269
General and administrative expenses		4,066			10,244			9,431
Collaboration (profit) loss sharing - related party		(1,496	)		704			1,004
Total operating expenses		8,379			39,211			73,704
(Loss) income from discontinued operations		(8,379	)		87,114			(66,576	)
Other income (expense):
Gain on sale of VOWST business		146,707			—			—
Interest expense		(12,192	)		(10,708	)		—
Other expense		(229	)		—			—
Income (loss) from discontinued operations, pre-tax	$	125,907		$	76,406		$	(66,576	)
Income tax		—			—			—
Net income (loss) from discontinued operations, net of tax	$	125,907		$	76,406		$	(66,576	)

In accordance with ASC 205-20, only expenses specifically identifiable and related to a business to be disposed may be presented in discontinued operations. As such, the research and development and general and administrative expenses in discontinued operations include corporate costs incurred directly to solely support the VOWST Business.

The Company has also entered into a Transition Services Agreement ("TSA") with NESA, an affiliate of SPN, in connection with the Transaction, through which the Company will provide certain manufacturing services until December 31, 2025, and other transition services, for the duration specified in the schedule to the TSA for each service. For the year ended December 31, 2024, the Company recognized $6,292 of TSA reimbursement income in other (expense) income, net in the Company’s consolidated statements of operations and comprehensive income (loss). For the year ended December 31, 2024, the Company has incurred $3,532 of expenses related to manufacturing services and $3,136 of TSA labor and passthrough expenses to support the transition services, including finance and accounting, information technology, human resources, operations, and other services. The difference between the TSA reimbursement income and the TSA expenses incurred is primarily due to certain non-cash expenses not reimbursed under the TSA.

As of December 31, 2024, $3,724 has been billed to NESA related to transition services performed by the Company, of which $1,656 has been paid, consistent with TSA payment terms. As of December 31, 2024, the Company has $2,068 in accounts receivable due from SPN - related party and $2,443 unbilled receivable included in prepaid expenses and other current asset in the Company’s consolidated balance sheets.

The Company has estimated costs associated with certain accrued liabilities due to SPN - related party as a loss contingency in accordance with ASC 450, Contingencies. These contingent liabilities are presented as Accrued Liabilities due to SPN - related party from continuing operations on the consolidated balance sheets as of December 31, 2024 and consist of the following (in thousands):


	December 31,
	2024
Profit Sharing Payments	$	11,230
Royalties associated with the MSK Agreement		2,786
VOWST post-marketing safety surveillance study		771
80.1% of lease cost of Waltham facility		1,501
Employment-related costs for conveying employees		1,462
Total accrued liabilities due to SPN - related party	$	17,750

The contingent liabilities accrued on the Company's consolidated balance sheets are remeasured at December 31, 2024 based on i) cash payments made by the Company to reduce the accrued liabilities due to SPN - related party and ii) revised estimates of the total remaining liabilities due to SPN - related party. For the year ended December 31, 2024, the Company recognized a gain on sale of VOWST Business of $5,684 as a result of the change in the accrued liabilities due to SPN - related party.

The Company has excluded from its consolidated balance sheets the effects of i) future fixed installment payments to be received by the Company after it performs services and is determined by SPN to be in material compliance with the terms and conditions of the TSA and ii) certain milestone payments received by the Company after the Product has achieved net sales-based milestones. These contingent receivables will be recognized as a gain contingency, in accordance with ASC 450, Contingencies, in continuing operations in the period when the contingencies are resolved.

The cash flows related to discontinued operations have not been segregated and are included in the consolidated statements of cash flows. For the years ended December 31, 2024, 2023 and 2022, capital expenditures related to the VOWST Business were $112, $2,272 and $2,971, respectively. Depreciation expense related to the VOWST Business for the same periods was $989, $2,019 and $1,459, respectively. Non-cash operating lease costs related to the VOWST Business for the years ended December 31, 2024, 2023 and 2022 were $1,447, $2,123 and $1,554, respectively, while the share based compensation expense for the same periods were $1,884, $2,773 and $1,247, respectively. The collaboration loss sharing (related party) related to the VOWST Business was $0, $5,158 and $1,004 for the years ended December 31, 2024, 2023 and 2022, respectively. Excluding the gain of $146,707 recognized on the sale of the VOWST Business presented in the consolidated statements of cash flows for the twelve months ended December 31, 2024, there were no other material operating or investing non-cash items related to the VOWST Business for either period presented.

Discontinued Operations and TSA - Summary of Assets and Liabilities of the Discontinued Operations (Details) - USD ($)
$ in Thousands

Dec. 31, 2024

Dec. 31, 2023

Current assets :

Collaboration receivable - related party

$ 8,674

Inventories

29,647

Total current assets of discontinued operations

1,075

$ 0

39,396

Property and equipment, net

4,843

19,376

Total non-current assets of discontinued operations

39,167

^[1]

63,386

Total assets of discontinued operations

102,782

Current liabilities:

Accrued expenses and other current liabilities

58,102

Deferred income - related party

1,090

7,730

Total current liabilities of discontinued operations

^[2]

66,922

Operating lease liabilities, net of current portion

14,063

Deferred revenue, net of current portion - related party

95,364

Total non-current liabilities of discontinued operations

$ 0

109,427

Total liabilities of discontinued operations

$ 176,349

[1]	Includes $38,877 as of December 31, 2023 of milestones related to the construction of the Company's dedicated manufacturing suite at BacThera AG, or Bacthera.
[2]	Includes related party amounts of $35,783 at December 31, 2023.

Segment Reporting - Schedule of reportable segment net income (loss) (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2024
Segment Reporting [Abstract]
Other segment, Description	Other segment (expense) income includes research and development expenses on early stage programs, manufacturing services expenses, gain on sale of VOWST Business, interest income and other (expense) income, net.

Restructuring - Schedule of Changes in Restructuring Liability (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Restructuring Cost and Reserve [Line Items]
Restructuring expenses		$ 5,606
Restructuring Incurred Cost Statement of Income or Comprehensive Income Extensible Enumeration Not Disclosed Flag	true
Accrued Expenses and Other Current Liabilities [Member]
Restructuring Cost and Reserve [Line Items]
Remaining liability included in accrued expenses and other current liabilities	$ 20
Accrued Expense and Other Current Liabilities [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	5,606
Less: stock-based compensation	(261)
Cash payments made	$ (5,325)

Summary of Fair Value Hierarchy for Assets and Liabilities Measured at Fair Value on Recurring Basis

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2024

Fair Value Disclosures [Abstract]

The following tables present the Company’s fair value hierarchy for its assets and liabilities that are measured at fair value on a recurring basis (in thousands):


	Fair Value Measurements as of December 31, 2023 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	81	$	—	$	—	$	81
Total assets	$	81	$	—	$	—	$	81

Warrant liabilities	$	—	$	—	$	546	$	546
Total liabilities	$	—	$	—	$	546	$	546

Schedule Of Level 3 Inputs to Warrant Liabilities

As of December 31, 2023, the Level 3 inputs to the warrant liabilities are as follows:


	December 31, 2023
Volatility		101.0	%
Term (in years)		1.3

Schedule of Reconciliation Company's Liabilities Measured at Fair Value on Recurring Basis

A reconciliation of the beginning and ending balances for the year ended December 31, 2024 for liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) is as follows (in thousands):


	Warrant Liabilities

Balance as of December 31, 2023	$	546
Issuance of warrants		—
Adjustment to fair value		(546	)
Balance as of December 31, 2024		—

Common Stock and Stock-Based Awards - Additional Information (Details) $ / shares in Units, $ in Thousands			1 Months Ended		9 Months Ended	12 Months Ended
	Jun. 29, 2022 USD ($) $ / shares shares	May 21, 2021 USD ($)	Jan. 31, 2025 USD ($) $ / shares shares	Sep. 30, 2024 USD ($) $ / shares	Sep. 30, 2024 USD ($) $ / shares shares	Dec. 31, 2024 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($)	Dec. 31, 2021 shares	Feb. 22, 2024 shares	Feb. 21, 2024 shares
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued \| shares						173,008,198	135,041,467
Common stock, shares issued \| shares	8,738,243				14,285,715	14,285,715
Share Price \| $ / shares				$ 1.05	$ 1.05	$ 1.05
Payments to acquire business					$ 15,000	$ 15,000
Common stock, shares authorized \| shares						360,000,000	240,000,000			360,000,000	240,000,000
Aggregate fair value of common stock issued					13,516	$ 13,516
Proceeds from issuance of common stock						$ 0	$ 0	$ 96,721
Common stock, par value \| $ / shares						$ 0.001	$ 0.001
VOWST Business [Member]
Subsidiary, Sale of Stock [Line Items]
Payments to acquire business				$ 100,000		$ 100,000
Proceeds from issuance of common stock					$ 1,484
Flagship Pioneering [Member]
Subsidiary, Sale of Stock [Line Items]
Proceeds from issuance of common stock	$ 27,525
Initial Public Offering ("IPO") [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued \| shares	31,746,030
Common stock, par value \| $ / shares	$ 3.15
Additional net proceeds from the registered direct offering	$ 96,721
At The Market Equity Offering Program [Member] \| 2020 and 2021 Sales Agreement [Member] \| Cowen And Company, LLC [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued \| shares									0
At The Market Equity Offering Program [Member] \| 2021 Sales Agreement [Member] \| Cowen And Company, LLC [Member]
Subsidiary, Sale of Stock [Line Items]
Gross proceeds from sale of common stock		$ 150,000,000
Common stock, shares issued \| shares						20,617,028	7,711,199
Common stock, average share price \| $ / shares						$ 1.18	$ 2.46
Proceeds from issuance of common stock						$ 23,530	$ 18,159
Percentage of commission on sale of common stock						3	3
At The Market Equity Offering Program [Member] \| 2021 Sales Agreement [Member] \| Cowen And Company, LLC [Member] \| Subsequent Event [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued \| shares			1,096,134
Common stock, average share price \| $ / shares			$ 0.93
Proceeds from issuance of common stock			$ 996
Percentage of commission on sale of common stock			3

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	360,000,000	240,000,000
Common stock, shares issued	173,008,198	135,041,467
Common stock, shares outstanding	173,008,198	135,041,467
Bacthera Agreement [Member]
Prepayments on long term contract		$ 38,877
Related Party [Member]
Related parties, current		$ 35,783
SPN [Member]
Unbilled receivable	$ 2,683

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2024

Cash, Cash Equivalents and Restricted Cash

Cash, cash equivalents and restricted cash were comprised of the following (in thousands):


	December 31,
	2024		2023
Cash and cash equivalents	$	30,793	$	127,965
Restricted cash, non-current		8,668		8,185
Total cash, cash equivalents and restricted cash	$	39,461	$	136,150

Schedule of Property and Equipment Estimated Useful Life

Depreciation expense is recognized using the straight-line method over the useful life of the asset, which are as follows:


		Estimated Useful Life (In Years)
Laboratory equipment		5
Computer equipment, furniture and office equipment		3
Leasehold improvements		Lesser of useful life or lease term

Notes Payable

12 Months Ended

Dec. 31, 2024

Debt Disclosure [Abstract]

Notes Payable

9. Notes Payable

On April 27, 2023 (the “Oaktree Closing Date”), the Company entered into the Credit Agreement and Guaranty (the “Oaktree Credit Agreement”) among the Company, the subsidiary guarantors from time to time party thereto, the lenders from time to time party thereto (the “Lenders”), and Oaktree Fund Administration, LLC, in its capacity as administrative agent for the Lenders (in such capacity, the “Agent”). The Oaktree Credit Agreement established a term loan facility of $250,000 (the “Oaktree Term Loan”) consisting of (i) $80,000 (“Tranche A-1”) and (ii) $30,000 (“Tranche A-2” and collectively, “Tranche A Loan”), funded on the Oaktree Closing Date. The Oaktree Term Loan also consisted of (i) $45,000 (the “Tranche B Loan”), (iii) $45,000 (the “Tranche C Loan”), and (iv) $50,000 (the “Tranche D Loan”), which were available upon satisfaction of certain conditions or in Oaktree’s sole discretion, but were not drawn before the extinguishment of the Oaktree Term Loan. The Oaktree Term Loan had a maturity date of April 27, 2029 (the “Maturity Date”).

Of the $110,000 Tranche A Loan advanced by the Lenders at closing, approximately $53,380 repaid the Company’s then existing credit facility with Hercules Capital, Inc. ("Hercules"). After deducting other transaction expenses and fees, the Company received net proceeds of approximately $50,446. The Company accounted for the repayment of the credit facility with Hercules as an extinguishment in accordance with the guidance in ASC 470-50, and recognized a loss on extinguishment of $1,625 in other income (expense) in the accompanying consolidated statements of operations and comprehensive loss for the year ended December 31, 2023.

Borrowings under the Oaktree Term Loan bore interest at a rate per annum equal to the three-month term Secured Overnight Financing Rate (“SOFR”) (subject to a 2.50% floor and a 5.00% cap), plus an applicable margin of 7.875%, payable quarterly in arrears. The Company was required to make quarterly interest-only payments on the Oaktree Term Loan for the first three years after the Oaktree Closing Date. The Company was obligated to pay the Lenders an exit fee equal to 1.50% of the aggregate amount of the Oaktree Term Loan funded, such exit fee was due and paid upon the prepayment of the outstanding Oaktree Term Loan. Such payment was subject to a customary make-whole for the first two years following the Closing Date plus 4.0% of the principal amount of the Oaktree Term Loan prepaid.

On the Oaktree Closing Date, the Company issued to the Lenders warrants to purchase 647,589 shares (subject to certain adjustments) of the Company’s common stock (the “Tranche A Warrant”), at an exercise price per share of $6.69. The Tranche A Warrant is immediately exercisable and the exercise period expires on April 26, 2030. Upon the funding of each of the Tranche B Loan and the Tranche C Loan, the Company was required to issue to the Lenders warrants to purchase 264,922 shares (subject to certain adjustments) of the Company’s common stock on each such funding date at an exercise price equal to the trailing volume weighted average price of the Company’s common stock for the 30 trading days prior to the funding date for each tranche (the “Tranche B Warrant” and the “Tranche C Warrant,” respectively, and together the “Additional Warrants”).

The Company determined that the Tranche A Loan, the Tranche A Warrant, the commitment by the Lenders to fund the Tranche B Loan and the Tranche C Loan, and the Tranche B Warrant and Tranche C Warrant, are all freestanding financial instruments. On the Oaktree Closing Date, the Company evaluated the Tranche A Warrant and determined that it meets the requirements for equity classification under ASC 815, Derivatives and Hedging (“ASC 815”). The net proceeds from the Tranche A Loan were allocated to the Tranche A Warrant and the Tranche A Loan using the relative fair value method, and the relative fair value of the Tranche A Warrant, $2,785, is recorded as an increase to additional paid-in-capital on the consolidated statements of stockholder’s equity (deficit), and as a discount to the Tranche A Loan that will be amortized over the life of the Tranche A Loan using the effective interest method. The Company used the Black-Scholes option pricing model to determine the fair value of the Tranche A Warrant. Assumptions used in the Black-Scholes model included the fair market value per share of common stock on the valuation date of $5.32, the exercise price per warrant equal to $6.69, the expected volatility of 111.6%, the risk-free interest rate of 3.57%, the expected term of 7 years and the absence of a dividend.

The Additional Warrants were considered outstanding instruments at the Oaktree Closing Date of the Oaktree Credit Agreement and in accordance with ASC 815, were initially recognized at their respective fair values as derivative liabilities given the variable settlement amount of their respective aggregate exercise prices. The Company adjusted the carrying values of the Additional Warrants to their respective fair values at each reporting period, until such time that the Additional Warrants were issued and their respective exercise prices became fixed, and the value of the Additional Warrants was reclassified to additional paid-in capital. The Company used a simulation model to determine the fair value of the Additional Warrants, as described in Note 4, Fair Value Measurements. As of December 31, 2024, given the Transaction and the repayment of the Oaktree Term Loan, the probability of drawing the Tranche B and C Loans that would trigger the issuance of these warrants was deemed to be remote. As a result, the fair value of Tranche B and C Warrants was deemed to be $0. The fair value of the Tranche B Warrant and Tranche C Warrant derivative liabilities was $276 and $270 as of December 31, 2023, respectively.

Changes in the fair values of the Additional Warrants were recorded as other income (expense) in the consolidated statements of operations and comprehensive income (loss). In addition to the relative fair value of the Tranche A Warrant, the original issue discount and certain debt issuance costs were recorded as a discount to the Tranche A Loan, the total of which will be accreted to the Tranche A Loan as interest expense over the life of the Tranche A Loan using the effective interest method. The fair values of the derivative liabilities associated with the Tranche B Warrant and Tranche C Warrant are recorded as loan commitment prepaid assets on the Oaktree

Closing Date, which are included in the consolidated balance sheets in other non-current assets, and will be reclassified as discounts to the associated Oaktree Term Loan balances at such time that they are drawn.

As of December 31, 2023, the carrying value of the Term Loan was $101,544, which was classified as a long-term liability on the consolidated balance sheets.

During the year ended December 31, 2023, the Company recognized $2,468 of interest expense related to the Loan and Security Agreement with Hercules, which is reflected in interest expense on the consolidated statements of operations and comprehensive income (loss).

On September 30, 2024, in connection with the sale of the VOWST Business to SPN, the Company terminated and prepaid in full all outstanding amounts due under the Oaktree Credit Agreement. The Company paid $127,905 to Oaktree, representing $110,000 of principal, $3,698 of accrued interest, $12,457 of yield protection premium, $1,650 in exit fee, and $100 in third-party fees and expenses. In connection with the termination and repayment in full of all outstanding amounts under the Oaktree Credit Agreement, Oaktree terminated and released its liens and security interests in the collateral securing the Company's obligations under the Credit Agreement. The Company accounted for the repayment of the Oaktree Term Loan as an extinguishment in accordance with the guidance in ASC 470-50, and recognized a loss associated with the extinguishment of $23,351 in other (expense) income, net in the accompanying consolidated statements of operations and comprehensive income for the year ended December 31, 2024.

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477092/405-40-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477092/405-40-50-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477092/405-40-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477092/405-40-50-1

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Leases

12 Months Ended

Dec. 31, 2024

Leases [Abstract]

Leases

8. Leases

The Company leases real estate, primarily laboratory, office and manufacturing space. The Company’s leases have remaining terms ranging from approximately one to eight years. Certain leases include one or more options to renew, exercisable at the Company’s sole discretion, with renewal terms that can extend the lease from approximately one year to ten years. The Company evaluated the renewal options in its leases to determine if it was reasonably certain that the renewal option would be exercised, given the Company’s current business structure, uncertainty of future growth, and the associated impact to real estate, the Company concluded that it is not reasonably certain that any renewal options would be exercised. Therefore, the operating lease assets and operating lease liabilities only contemplate the initial lease terms. All the Company’s leases qualify as operating leases.

In January 2024, the Company entered into a sublease agreement with an unrelated third party to sublease a portion of its office and laboratory space in Cambridge, Massachusetts. The term of the sublease agreement commenced in March 2024 and ends on January 13, 2030. The Company will receive lease payments over the sublease term totaling $10,400. The sublessee is obligated to pay all real estate taxes and costs related to the subleased premises, including cost of operations, maintenance, repair, replacement and property management. Sublease income is recorded as Other (expense) income, net in the Company’s consolidated statements of operations and comprehensive income (loss).

During the year ended December 31, 2024, the Company identified an indicator of impairment of its donor collection facility in Cambridge, Massachusetts, as the facility is no longer being used by the Company as a result of operational efficiencies implemented related to the production process and is being marketed for sublease. The Company determined that this represents a significant adverse change in the extent in which the long-lived asset was being used. The Company determined that the location contains multiple asset groups for the purpose of the long-lived asset impairment assessment. The Company concluded that the carrying value of each asset

group was not recoverable as it exceeded the future net undiscounted cash flows that are expected to be generated from the assets within the asset group. In the first quarter of 2024, the Company recognized an impairment loss of $3,267, consisting of $1,731 on the operating lease right-of-use asset and $1,536 on the leasehold improvements. $2,727 of the total impairment loss is included in research and development expenses and the remaining $540 is included in general and administrative expenses in the accompanying consolidated statements of operations and comprehensive income (loss).

The following table summarizes the presentation in the Company’s consolidated balance sheets of its operating leases (in thousands):


	December 31,
	2024		2023
Assets:
Operating lease assets	$	80,903	$	90,417

Liabilities:
Operating lease liabilities	$	8,674	$	5,587
Operating lease liabilities, net of current portion		82,966		91,652
Total operating lease liabilities	$	91,640	$	97,239

The following table summarizes the effect of lease costs in the Company’s consolidated statements of operations and comprehensive income (loss) (in thousands):


	Year Ended December 31,
	2024			2023		2022
Operating lease costs	$	19,514		$	22,324	$	8,830
Short-term lease costs		—			1,477		1,375
Variable lease costs		6,589			7,229		4,547
Sublease income		(2,708	)		—		—
Total lease costs	$	23,395		$	31,030	$	14,752

During the years ended December 31, 2024, 2023, and 2022, the Company made cash payments for operating leases of $17,330, $15,656 and $7,809, respectively.

As of December 31, 2024, future payments of operating lease liabilities are as follows (in thousands):


	As of December 31, 2024
2025	$	19,442
2026		19,983
2027		20,582
2028		20,862
2029		20,132
2030 and thereafter		36,850
Total future payments of operating lease liabilities	$	137,851
Less: imputed interest		(46,211	)
Present value of operating lease liabilities	$	91,640

As of December 31, 2024, the weighted average remaining lease term was 6.98 years and the weighted average incremental borrowing rate used to determine the operating lease liability was 13%. As of December 31, 2023, the weighted average remaining lease term was 7.95 years and the weighted average incremental borrowing rate used to determine the operating lease liability was 13%.

Discontinued Operations and TSA - Gain on the Sale of the VOWST Business (Details) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2024

Dec. 31, 2023

Dec. 31, 2022

Net assets transferred

Inventory

$ 29,647

1,075

19,376

39,167

Deferred revenue from termination of 2016 License Agreement

(1,090)

Gain on sale, pre-tax

$ 146,707

$ 0

VOWST Business [Member]

Consideration received

Upfront payment

^[1]

79,788

Prepaid milestone

60,000

95,364

Settlement of net collaboration payable at close

27,465

Premium on equity financing

1,484

Deferred income from termination of 2021 License Agreement

3,606

Accrued Liabilities due to SPN - related party

(33,458)

Total fair value transferred for business

234,249

Net assets transferred

Inventory

63,442

Property and equipment, net

2,219

3,966

17,929

Accrued expenses and other current liabilities

39,328

(31,547)

(14,413)

Net assets transferred

80,924

Transaction costs

6,618

Gain on sale, pre-tax

146,707

Income tax

$ 0

Gain on sale, net of tax

$ 146,707

[1]	The upfront payment consists of $100,000, less $17,857 owed by the Company to an affiliate of SPN under the prior license agreement between the Company and the SPN affiliate, less approximately $2,355 in satisfaction of costs due under the Bacthera Manufacturing Agreement.

Segment Reporting

12 Months Ended

Dec. 31, 2024

Segment Reporting [Abstract]

Segment Reporting

18. Segment Reporting

Our Chief Executive Officer ("CEO"), who is the Chief Operating Decision Maker ("CODM"), manages and allocates resources to the operations of our company on a total company basis by assessing the overall level of resources available and how to best deploy these resources across functions and research and development projects that are in line with our long-term company-wide strategic goals. The CODM uses the Company’s consolidated net income (loss) to monitor actual results versus the budget in assessing segment performance and the allocation of resources. The measure of segment assets is reported on the consolidated balance sheets as total assets.

The Company's reportable segment net income (loss) for the years ended December 31, 2024, 2023 and 2022, consisted of the following:


	Year Ended December 31,
	2024			2023			2022
Significant segment expenses:
Live biotherapeutics platform	$	29,006		$	43,342		$	34,764
SER-155		6,804			7,759			5,069
R&D personnel-related (including stock-based compensation)		28,689			65,251			68,059
G&A personnel-related (including stock-based compensation)		22,679			36,069			30,653
Professional fees		9,805			18,784			23,529
Facility-related and other		20,699			22,647			16,081
Other segment expense (income) (1)		8,089			(3,722	)		5,426
Net loss from continuing operations		(125,771	)		(190,130	)		(183,581	)
Net income (loss) from discontinued operations, net of tax (2)		125,907			76,406			(66,576	)
Net income (loss)	$	136		$	(113,724	)	$	(250,157	)

[1] Other segment (expense) income includes research and development expenses on early stage programs, manufacturing services expenses, gain on sale of VOWST Business, interest income and other (expense) income, net.

[2] See Note 3, Discontinued Operations and TSA, for further details.

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

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Schedule of Reconciliation of U.S Federal Statutory Income Tax Rate to Company's Effective Income Tax Rate

Common Stock and Stock-Based Awards - 2012 Stock Incentive plan - Additional Information (Details) - 2012 Stock Incentive Plan [Member]	12 Months Ended
	Dec. 31, 2024 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock incentive plan description	The exercise prices, vesting and other restrictions are determined at the discretion of the board of directors, or their committee if so delegated, except that the exercise price per share of stock options may not be less than 100% of the fair market value of the share of common stock on the date of grant and the term of stock option may not be greater than ten years. The Company generally granted stock-based awards with service conditions only (“service-based” awards).
Shares available for future grant	0
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price per share of common stock expressed as a percentage	100.00%
Stock option granted vesting period	4 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option term	10 years
Stock option granted vesting period	4 years
Stock option expiration period	10 years

Preferred Stock

12 Months Ended

Dec. 31, 2024

Equity [Abstract]

Preferred Stock

10. Preferred Stock

On July 1, 2015, in connection with the closing of the initial public offering of the Company’s common stock (“IPO”), the Company effected its Restated Certificate of Incorporation, which authorizes the Company to issue 10,000,000 shares of preferred stock, $0.001 par value per share.

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2024

Income Tax Disclosure [Abstract]

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended December 31,
	2024			2023(1)			2022(1)
Federal statutory income tax rate		(21.0	)%		(21.0	)%		(21.0	)%
Research and development tax credits		(1.8	)		(2.5	)		(4.2	)
State taxes, net of federal benefit		(3.6	)		(7.2	)		(3.9	)
Stock-based compensation		1.0			0.8			0.7
Uncertain tax position reserves		0.4			0.5			6.3
Other		(0.4	)		(0.1	)		0.2
Change in deferred tax asset valuation allowance		25.4			29.5			21.9
Effective income tax rate		—	%		—	%		—	%

[1] Prior period amounts have been retrospectively adjusted to reflect the effects of the Transaction.

Schedule of Net Deferred Tax Assets

Net deferred tax assets as of December 31, 2024 and 2023 consisted of the following:


	December 31,
	2024			2023
Deferred tax assets:
Net operating loss carryforwards	$	156,157		$	142,506
Research and development tax credit carryforwards		54,648			52,843
Section 174 capitalized research and development expenses		53,600			55,572
Stock-based compensation expense		28,819			25,898
Lease liability		23,917			29,855
Deferred revenue		—			27,452
Accrued expenses		7,032			3,540
Section 163(j) limitation		5,599			3,741
Depreciation and amortization		953			398
Other		132			169
Total deferred tax assets	$	330,857		$	341,974
Deferred tax liabilities:
Depreciation and amortization		—			—
Right of use assets		(21,115	)		(29,165	)
Total deferred tax liabilities		(21,115	)		(29,165	)
Valuation allowance	$	(309,742	)	$	(312,809	)
Net deferred tax assets	$	—		$	—

Summary of Changes In Valuation Allowance for Deferred Tax Assets

Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2024, 2023 and 2022 related primarily to the increases in NOLs, research and development tax credit carryforwards and capitalized research and development expenses pursuant to IRC Section 174, and stock-based compensation were as follows:


	Year Ended December 31,
	2024			2023			2022
Valuation allowance at beginning of year	$	(312,809	)	$	(277,370	)	$	(220,114	)
Decreases recorded as benefit to income tax provision		3,067			—			—
Increases recorded to income tax provision		—			(35,439	)		(57,256	)
Valuation allowance as of end of year	$	(309,742	)	$	(312,809	)	$	(277,370	)

Schedule of Change In Unrecognized Tax Benefits Roll Forward

The changes in the Company's unrecognized tax benefits for the years ended December 31, 2024, 2023, and 2022 were as follows:


	Year Ended December 31,
	2024		2023		2022
Balance at beginning of year	$	13,529	$	12,528	$	—
Increase in unrecognized tax benefits as a result of tax positions taken during the year		486		1,001		12,528
Reduction to unrecognized tax benefits		—		—		—
Balance at end of year	$	14,015	$	13,529	$	12,528

Fair Value Measurements

12 Months Ended

Dec. 31, 2024

Fair Value Disclosures [Abstract]

Fair Value Measurements

4. Fair Value Measurements

The following tables present the Company’s fair value hierarchy for its assets and liabilities that are measured at fair value on a recurring basis (in thousands):


	Fair Value Measurements as of December 31, 2023 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	81	$	—	$	—	$	81
Total assets	$	81	$	—	$	—	$	81

Warrant liabilities	$	—	$	—	$	546	$	546
Total liabilities	$	—	$	—	$	546	$	546

As of December 31, 2024, there were no assets or liabilities that are measured at fair value on a recurring basis.

Money market funds are valued by the Company based on quoted market prices, which represent a Level 1 measurement within the fair value hierarchy.

As of December 31, 2024 and 2023, the Company held a restricted investment of $0 and $1,401, respectively, which represents a certificate of deposit that is classified as Level 2 in the fair value hierarchy.

Level 3 financial liabilities as of December 31, 2023 consisted of the warrant liabilities for which there is no current market such that the determination of fair value requires significant judgment or estimation. Changes in fair value measurements categorized within Level 3 of the fair value hierarchy were analyzed each period based on changes in estimates or assumptions and recorded through other income (expense). The Company used a Monte-Carlo simulation model which includes the Black-Scholes option pricing model to value the Level 3 warrant liabilities at inception and on each subsequent reporting date. This model incorporates transaction details such as the Company’s stock price, contractual terms of the underlying warrants, maturity, risk free rates, volatility, as well as the term to achievement of estimated sales targets. The unobservable inputs for all of the Level 3 warrant liabilities are volatility and the term to achievement of estimated sales targets. The Company utilized its historical and implied volatility, using its closing common stock prices and market data, to reflect future volatility over the expected term of the warrants. The Company estimated the time to achievement of sales targets of VOWST using information and forecasts generated by the Company in consideration of the terms of the 2021 License Agreement. As of December 31, 2024, given the repayment of the Oaktree Term Loan, the fair value of the warrant liabilities was deemed to be $0.

As of December 31, 2023, the Level 3 inputs to the warrant liabilities are as follows:


	December 31, 2023
Volatility		101.0	%
Term (in years)		1.3


	Warrant Liabilities

Balance as of December 31, 2023	$	546
Issuance of warrants		—
Adjustment to fair value		(546	)
Balance as of December 31, 2024		—

There were no assets or liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) during the year ended December 31, 2024. There were no transfers between Level 1, Level 2, or Level 3 during the years ended December 31, 2024 and 2023.

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

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Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Pay vs Performance Disclosure
Net Income (Loss)	$ 136	$ (113,724)	$ (250,157)

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Cash flows from operating activities:

Discontinued Operations and TSA - Summary of Accrued Liabilities from Continuing Operations (Details) $ in Thousands	Dec. 31, 2024 USD ($)
Discontinued Operations and Disposal Groups [Abstract]
Profit Sharing Payments	$ 11,230
Royalties associated with the MSK Agreement	2,786
VOWST post-marketing safety surveillance study	771
80.1% of lease cost of Waltham facility	1,501
Employment-related costs for conveying employees	1,462
Total accrued liabilities due to SPN	$ 17,750

Consolidated Statements of Cash Flows - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2024

Dec. 31, 2023

Dec. 31, 2022

Net Income (Loss)

$ 136

$ (113,724)

$ (250,157)

Adjustments to reconcile net loss to net cash used in operating activities:

Stock-based compensation expense

20,971

34,101

25,482

Depreciation and amortization expense

5,468

6,243

6,629

Non-cash operating lease cost

9,230

8,871

5,224

Net (accretion) amortization of (discounts) premiums on investments

(236)

688

Gain on sale of VOWST Business, net of transaction costs

(146,707)

Amortization of debt issuance costs

1,413

1,139

705

Loss associated with extinguishment of debt

23,351

1,625

Loss on disposal of fixed assets

317

Impairment of long-lived assets

3,267

Change in fair value of warrant liabilities

(546)

(1,554)

Collaboration (profit) loss sharing - related party

5,158

1,004

Changes in operating assets and liabilities:

Accounts receivable due from SPN - related party

(2,068)

Prepaid expenses and other current and non-current assets

987

(29,124)

(12,599)

Collaboration receivable - related party

8,674

(8,674)

Inventories

(33,795)

(29,647)

Deferred income - related party

(4,124)

7,730

Deferred revenue - related party

(1,325)

(7,128)

Accounts payable

(2,940)

(11,578)

2,203

Accrued liabilities due to SPN - related party

(15,708)

Accrued expenses and other current and long-term liabilities (3)

(6,339)

(2,197)

(4,203)

^[1]

(10,196)

15,838

3,336

Net cash used in operating activities

(148,609)

(117,354)

(228,816)

Cash flows from investing activities:

Purchases of property and equipment

(380)

(7,975)

(9,821)

Purchases of investments

(4,426)

(48,221)

Sales and maturities of investments

22,983

140,470

Sales of restricted investments

1,401

Proceeds from sale of VOWST Business

141,272

Net cash provided by investing activities

142,293

10,582

82,428

Cash flows from financing activities:

Proceeds from issuance of common stock, net of issuance costs

96,721

Proceeds from at the market equity offering, net of issuance costs

23,530

18,159

4,447

Proceeds from exercise of stock options

877

966

Proceeds from Securities Purchase Agreement - related party

13,516

Issuance of common stock under ESPP

487

2,151

1,769

Proceeds from issuance of debt, net of issuance costs

103,378

27,606

Repayment of notes payable

(127,905)

(52,860)

(1,907)

Net cash (used in) provided by financing activities

(90,372)

71,705

129,602

Net decrease in cash, cash equivalents and restricted cash

(96,688)

(35,067)

(16,786)

Effect of exchange rate changes on cash, cash equivalents and restricted cash

(1)

Cash, cash equivalents and restricted cash at beginning of year

136,150

171,215

188,002

Cash, cash equivalents and restricted cash at end of year

39,461

136,150

171,215

Supplemental disclosure of cash flow information:

Cash paid for interest

10,858

12,547

4,926

Supplemental disclosure of non-cash investing and financing activities:

Property and equipment purchases included in accounts payable and accrued expenses

2,276

Lease liability arising from obtaining right-of-use assets

3,046

91,412

Prepaid rent reclassified to right-of-use assets

4,634

6,822

Recognition of warrant liabilities

2,100

Warrants issued related to Oaktree Term Loan and recorded as debt discount (Note 9)

$ 0

$ 2,785

$ 0

[1]	Includes non-cash collaboration profits and losses related to pre-launch activities; subsequent to the approval of VOWST in April 2023, collaboration (profit) loss sharing - related party is included within changes in operating assets and liabilities.

Discontinued Operations and TSA (Tables)

12 Months Ended

Dec. 31, 2024

Discontinued Operations and Disposal Groups [Abstract]

Summary of Assets and Liabilities of the Discontinued Operations

The following table presents the assets and liabilities of the discontinued operations as of December 31, 2023:


	December 31,
	2023
Assets
Current assets:
Collaboration receivable - related party	$	8,674
Inventories		29,647
Prepaid expenses and other current assets		1,075
Total current assets of discontinued operations		39,396
Property and equipment, net		4,843
Operating lease assets		19,376
Other non-current assets		39,167
Total non-current assets of discontinued operations		63,386
Total assets of discontinued operations	$	102,782
Liabilities
Current liabilities:
Accrued expenses and other current liabilities	$	58,102
Operating lease liabilities		1,090
Deferred income - related party		7,730
Total current liabilities of discontinued operations		66,922
Operating lease liabilities, net of current portion		14,063
Deferred revenue, net of current portion - related party		95,364
Total non-current liabilities of discontinued operations		109,427
Total liabilities of discontinued operations	$	176,349

The following table presents the gain on the sale of the VOWST Business as of December 31, 2024, pursuant to the Purchase Agreement:


	December 31,
	2024
Consideration received
Upfront payment (1)	$	79,788
Prepaid milestone		60,000
Deferred revenue from termination of 2016 License Agreement		95,364
Settlement of net collaboration payable at close		27,465
Premium on equity financing		1,484
Deferred income from termination of 2021 License Agreement		3,606
Accrued liabilities due to SPN - related party		(33,458	)
Total fair value transferred for business	$	234,249

Net assets transferred
Inventory	$	63,442
Prepaid expenses and other current assets		2,219
Property and equipment, net		3,966
Operating lease assets		17,929
Other non-current assets		39,328
Accrued expenses and other current liabilities		(31,547	)
Operating lease liabilities		(14,413	)
Net assets transferred	$	80,924

Transaction costs	$	6,618

Gain on sale, pre-tax	$	146,707
Income tax		—
Gain on sale, net of tax	$	146,707

The following table presents the financial results of the discontinued operations:


	Year Ended December 31,
	2024			2023			2022
Revenue:
Collaboration revenue - related party	$	—		$	126,325		$	7,128
Total revenue		—			126,325			7,128
Operating expenses:
Research and development expenses		5,809			28,263			63,269
General and administrative expenses		4,066			10,244			9,431
Collaboration (profit) loss sharing - related party		(1,496	)		704			1,004
Total operating expenses		8,379			39,211			73,704
(Loss) income from discontinued operations		(8,379	)		87,114			(66,576	)
Other income (expense):
Gain on sale of VOWST business		146,707			—			—
Interest expense		(12,192	)		(10,708	)		—
Other expense		(229	)		—			—
Income (loss) from discontinued operations, pre-tax	$	125,907		$	76,406		$	(66,576	)
Income tax		—			—			—
Net income (loss) from discontinued operations, net of tax	$	125,907		$	76,406		$	(66,576	)

Summary of Accrued Liabilities of Continuing Operations

These contingent liabilities are presented as Accrued Liabilities due to SPN - related party from continuing operations on the consolidated balance sheets as of December 31, 2024 and consist of the following (in thousands):


	December 31,
	2024
Profit Sharing Payments	$	11,230
Royalties associated with the MSK Agreement		2,786
VOWST post-marketing safety surveillance study		771
80.1% of lease cost of Waltham facility		1,501
Employment-related costs for conveying employees		1,462
Total accrued liabilities due to SPN - related party	$	17,750

Tabular disclosure of information related to a disposal group. Includes, but is not limited to, a discontinued operation, disposal classified as held-for-sale or disposed of by means other than sale or disposal of an individually significant component.

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Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

12 Months Ended

Dec. 31, 2024

Commitments and Contingencies

14. Commitments and Contingencies

Leases

Refer to Note 8, Leases, for discussion of the commitments associated with the Company’s lease portfolio.

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third-parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and its officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company does not believe that the outcome of any claims under indemnification arrangements will have a material effect on its financial position, results of operations or cash flows, and it has not accrued any liabilities related to such obligations in its consolidated financial statements as of December 31, 2024 or 2023.

Legal Contingencies

The Company accrues a liability for legal contingencies when it believes that it is both probable that a liability has been incurred and that the Company can reasonably estimate the amount of the loss. The Company reviews these accruals and adjusts them to reflect ongoing negotiations, settlements, rulings, advice of legal counsel and other relevant information. To the extent new information is obtained and the views on the probable outcomes of claims, suits, assessments, investigations or legal proceedings change, changes in the Company’s accrued liabilities would be recorded in the period in which such determination is made.

In addition, in accordance with the relevant authoritative guidance, for any matters in which the likelihood of material loss is at least reasonably possible, the Company will provide disclosure of the possible loss or range of loss. If a reasonable estimate cannot be made, however, the Company will provide disclosure to that effect. The Company expenses legal costs as they are incurred.

The Company did not accrue any liabilities related to legal contingencies in its consolidated financial statements as of December 31, 2024 or 2023.

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Accounting Policies [Line Items]
Maximum maturity days for cash equivalents	90 days	90 days
Restricted investments	$ 0	$ 1,401
Restricted cash	8,668	8,185
Impairment of long-lived assets	$ 3,267	$ 0	$ 0
Minimum percentage of likelihood of tax benefit being realized upon settlement	50.00%

Common Stock and Stock-Based Awards - Summary of Restricted Stock Unit Activity (Details) - RSU and PSU [Member]	12 Months Ended
	Dec. 31, 2024 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Unvested restricted stock units, Beginning balance \| shares	3,377,804
Number of Shares, Granted \| shares	1,503,127
Number of Shares, Forfeited \| shares	(1,053,587)
Number of Shares, Vested \| shares	(2,195,572)
Number of Shares, Unvested restricted stock units, Ending balance \| shares	1,631,772
Weighted Average Grant Date Fair Value, Unvested restricted stock units, Beginning balance \| $ / shares	$ 4.26
Weighted Average Grant Date Fair Value, Granted \| $ / shares	1.05
Weighted Average Grant Date Fair Value, Forfeited \| $ / shares	3.01
Weighted Average Grant Date Fair Value, Vested \| $ / shares	3.77
Weighted Average Grant Date Fair Value, Unvested restricted stock units, Ending balance \| $ / shares	$ 2.76

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2024	Mar. 07, 2025	Jun. 28, 2024
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	FY
Trading Symbol	MCRB
Entity Registrant Name	Seres Therapeutics, Inc.
Entity Central Index Key	0001609809
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity File Number	001-37465
Entity Tax Identification Number	27-4326290
Entity Address, Address Line One	101 Cambridgepark Drive
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02140
City Area Code	617
Local Phone Number	945-9626
Entity Public Float			$ 87,098,863
Entity Common Stock Shares Outstanding		174,358,753
Entity Incorporation, State or Country Code	DE
Document Annual Report	true
Document Transition Report	false
Entity Well Known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Documents Incorporated by Reference	Portions of the registrant’s definitive Proxy Statement relating to its 2025 Annual Meeting of Stockholders to be filed with the SEC within 120 days after the end of the fiscal year ended December 31, 2024 are incorporated herein by reference in Part III.
Auditor Firm ID	238
Auditor Name	PricewaterhouseCoopers LLP
Auditor Location	Boston, Massachusetts
Auditor Opinion [Text Block]	Opinions on the Financial Statements and Internal Control over Financial Reporting We have audited the accompanying consolidated balance sheets of Seres Therapeutics, Inc. and its subsidiaries (the “Company”) as of December 31, 2024 and 2023, and the related consolidated statements of operations and comprehensive income (loss), of stockholders' equity (deficit) and of cash flows for each of the three years in the period ended December 31, 2024, including the related notes (collectively referred to as the “consolidated financial statements”). We also have audited the Company's internal control over financial reporting as of December 31, 2024, based on criteria established in Internal Control - Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO). In our opinion, the consolidated financial statements referred to above present fairly, in all material respects, the financial position of the Company as of December 31, 2024 and 2023, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2024 in conformity with accounting principles generally accepted in the United States of America. Also in our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2024, based on criteria established in Internal Control - Integrated Framework (2013) issued by the COSO.

Common Stock and Stock-Based Awards - 2022 Employment Inducement Award Plan - Additional Information (Details) - 2022 Employment Inducement Award Plan [Member] - shares	12 Months Ended
	Dec. 31, 2024	Dec. 14, 2022
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock incentive plan description	2,500,000 shares of common stock were reserved for issuance under the 2022 Plan. Any shares subject to awards previously granted under the 2022 Plan that expire, terminate or are otherwise surrendered, canceled, or forfeited in any case, in a manner that results in the Company acquiring the shares covered by the award at a price not greater than the price (as adjusted to reflect any equity restructuring) paid by the Participant for such shares or not issuing any shares covered by the award, the unused shares covered by the award will again be available for award grants under the 2022 Plan.
Number of shares initially reserved for issuance		2,500,000
Shares available for future grant	1,696,205

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2024

Summary of Significant Accounting Policies

Discontinued Operations

The Company accounted for the sale of its VOWST Business in accordance with ASC 205 Discontinued Operations and ASU No. 2014-08, Reporting of Discontinued Operations and Disclosures of Disposals of Components of an Entity. The Company followed the held-for-sale criteria as defined in ASC 205. ASC 205 requires that a component of an entity that has been disposed of or is classified as held for sale and has operations and cash flows that can be clearly distinguished from the rest of the entity be reported as assets held for sale and discontinued operations. In the period a component of an entity has been disposed of, the results of operations for the periods presented are reclassified into separate line items in the consolidated statements of operations. In the period a discontinued operation is classified for sale, the assets and liabilities of the discontinued operation are also reclassified into separate line items on the related consolidated balance sheets for the periods presented.

Due to the sale of the VOWST Business during the third quarter of 2024 (see Note 3, Discontinued Operations and TSA), in accordance with ASC 205, Discontinued Operations, the Company has classified the results of the VOWST Business as discontinued operations in its consolidated statements of operations and cash flows for all periods presented. All assets and liabilities associated with the Company's VOWST Business were therefore classified as assets and liabilities of discontinued operations in its consolidated balance sheets for the periods presented. All amounts included in the notes to the consolidated financial statements relate to continuing operations unless otherwise noted.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting periods. In these consolidated financial statements, the Company uses estimates and assumptions related to the accrual of research and development expenses. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from the Company’s estimates.

Cash Equivalents

The Company considers all short-term, highly liquid investments with original maturities of 90 days or less at acquisition date to be cash equivalents. Cash equivalents, which consist of money market accounts, commercial paper and corporate bonds purchased with original maturities of less than 90 days from the date of purchase, are stated at fair value.

Restricted Investments

The Company held investments of $0 and $1,401 as of December 31, 2024 and 2023, respectively, in a separate restricted bank account as a security deposit for the lease of the Company’s headquarters in Cambridge, Massachusetts. The Company has classified these deposits as long-term restricted investments on its consolidated balance sheet.

Restricted Cash

The Company held restricted cash of $8,668 and $8,185 as of December 31, 2024 and 2023, respectively, which represents cash held for the benefit of the landlord for the Company's other leases. The Company has classified the restricted cash as long-term on its consolidated balance sheets as the underlying leases are greater than 1 year.

Cash, cash equivalents and restricted cash were comprised of the following (in thousands):


	December 31,
	2024		2023
Cash and cash equivalents	$	30,793	$	127,965
Restricted cash, non-current		8,668		8,185
Total cash, cash equivalents and restricted cash	$	39,461	$	136,150

Concentration of Credit Risk

Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and investments. The Company has all cash, cash equivalents and investments balances at financial institutions, in amounts that exceed federally insured limits. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships.

Fair Value Measurements

Certain assets and liabilities are carried at fair value in accordance with GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

•

Level 1—Quoted prices in active markets for identical assets or liabilities.

•

Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data.

•

Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques.

The Company’s cash equivalents and investments are carried at fair value, determined according to the fair value hierarchy described above. The Company’s investments in certificates of deposit are carried at amortized cost, which approximates fair value. The carrying values of the Company’s prepaid expenses and other current and non-current assets, accounts payable and accrued expenses approximate their respective fair values due to the short-term nature of these assets and liabilities. The carrying value of the Company’s long-term debt approximates its fair value (a level 2 measurement) at each balance sheet date due to its variable interest rate, which approximates a market interest rate. The warrant liabilities associated with the Company's credit facility with Oaktree for which there is no current market and the determination of fair value requires significant estimation are classified as Level 3 financial liabilities.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the useful life of the asset, which are as follows:


		Estimated Useful Life (In Years)
Laboratory equipment		5
Computer equipment, furniture and office equipment		3
Leasehold improvements		Lesser of useful life or lease term

Expenditures for repairs and maintenance of assets are charged to expense as incurred. Upon retirement or sale, the cost and related accumulated depreciation of assets disposed of are removed from the accounts and any resulting gain or loss is included in loss from operations.

Impairment of Long-Lived Assets

Long-lived assets consist of property and equipment and right-of-use assets associated with our lease agreements. All of the Company's long-lived assets are to be held and used and have definitive lives and accordingly are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset or asset group to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset or asset group are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset over its fair value, determined based on discounted cash flows. For the years ended December 31, 2024, 2023 and 2022, the Company recorded an impairment loss on long-lived assets of $3,267, $0 and $0, respectively.

Research and Development Costs

Research and development costs are expensed as incurred. Research and development expenses include salaries, stock-based compensation and benefits of employees, third-party license fees and other operational costs related to the Company’s research and

development activities, including allocated facility-related expenses and external costs of outside vendors engaged to conduct both preclinical studies and clinical trials, and beginning in the fourth quarter of 2024 certain costs of fulfilling the Company's obligations under the TSA which are reimbursable by Nestlé.

Research Contract Costs and Accruals

The Company has entered into various research and development contracts with research institutions and other companies. These agreements are generally cancelable, and related payments are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research costs based on reporting provided by third parties, typically contract research organizations. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued and prepaid balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.

Patent Costs

All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses.

Accounting for Stock-Based Compensation

The Company measures all stock options and other stock-based awards granted to employees, non-employees, and directors based on the fair value on the date of the grant and recognizes compensation expense of those awards over the requisite service period, which is generally the vesting period of the respective award. Generally, the Company issues stock options, restricted stock units and restricted stock awards with only service-based vesting conditions and records the expense for these awards using the straight-line method. For stock options or restricted stock units issued with performance-based vesting conditions, the stock compensation expense related to these awards is recognized based on the grant date fair value when achievement of the performance condition is deemed probable.

The Company classifies stock-based compensation expense in its consolidated statements of operations and comprehensive income (loss) in the same manner in which the award recipient’s payroll costs are classified or in which the award recipients’ service payments are classified.

The Company accounts for forfeitures of stock-based awards as they occur rather than applying an estimated forfeiture rate to stock-based compensation expense.

The fair value of each stock option grant is estimated on the date of grant using the Black- Scholes option-pricing model. The Company estimates its expected common stock volatility based on its historical common stock volatility for the same time period. The Company uses the simplified method prescribed by Securities and Exchange Commission Staff Accounting Bulletin No. 107, Share-Based Payment, to calculate the expected term of options granted to employees, non-employees and directors. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future.

Income Taxes

The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company’s tax returns. Deferred taxes are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect in the years in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense.

The Company applies ASC 740-10, Accounting for Uncertain Tax Positions. The Company accounts for uncertainty in income taxes recognized in the financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.

Segment Reporting

The Company manages its operations as a single operating segment for the purposes of assessing performance and making operating decisions, and thus reports as a single reportable segment. The Company’s singular focus is on developing live biotherapeutics for medically vulnerable patient populations to prevent bacterial bloodstream and antimicrobial resistant (AMR) infections as well as to treat GI-related immune diseases. Revenue to date has been generated solely through the Company's agreements with its collaborators, all of which has been earned in the United States. All tangible assets are held in the United States.

Comprehensive Income (Loss)

Comprehensive income (loss) includes net income (loss) as well as other changes in stockholders’ equity (deficit) that result from transactions and economic events other than those with stockholders. For the years ended December 31, 2024, 2023 and 2022, other comprehensive income consisted of changes in unrealized gains from available-for-sale investments and a currency translation adjustment.

Net Loss per Share

Basic net loss per share is computed using the weighted average number of common shares outstanding during the period. Diluted net loss per share is computed using the sum of the weighted average number of common shares outstanding during the period and, if dilutive, the weighted average number of potential shares of common stock, including the assumed exercise of stock options and unvested restricted stock. The Company applies the two-class method to calculate its basic and diluted net loss per share attributable to common stockholders. The two-class method is an earnings allocation formula that treats a participating security as having rights to earnings that otherwise would have been available to common stockholders. However, the two-class method does not impact the net loss per share of common stock as the Company was in a net loss position for each of the periods presented.

The Company’s restricted stock awards entitle the holder of such awards to dividends declared or paid by the board of directors, regardless of whether such awards are unvested, as if such shares were outstanding common shares at the time of the dividend. However, the unvested restricted stock awards are not entitled to share in the residual net assets (deficit) of the Company. Accordingly, in periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive.

Leases

In accordance with ASC 842, Leases, the Company determines if an arrangement is or contains a lease at inception. A contract is or contains a lease if the contract conveys the right to control the use of an identified asset for a period of time in exchange for consideration. The Company classifies leases at the lease commencement date as operating or finance leases and records a right-of-use

asset and a lease liability on the consolidated balance sheets for all leases with an initial lease term of greater than 12 months. Leases with an initial term of 12 months or less are not recorded on the balance sheets, but payments are recognized as expense on a straight-line basis over the lease term. The Company has elected not to record a right-of-use asset or lease liability for leases with terms of 12 months or less.

A lease qualifies as a finance lease if any of the following criteria are met at the inception of the lease: (i) there is a transfer of ownership of the leased asset to the Company by the end of the lease term, (ii) the Company holds an option to purchase the leased asset that it is reasonably certain to exercise, (iii) the lease term is for a major part of the remaining economic life of the leased asset, (iv) the present value of the sum of lease payments equals or exceeds substantially all of the fair value of the leased asset, or (v) the nature of the leased asset is specialized to the point that it is expected to provide the lessor no alternative use at the end of the lease term.

The Company enters into contracts that contain both lease and non-lease components. Non-lease components may include maintenance, utilities, and other operating costs. The Company combines the lease and non-lease components of fixed costs in its lease arrangements as a single lease component. Variable costs, such as utilities or maintenance costs, are not included in the measurement of right-of-use assets and lease liabilities, but rather are expensed when the event determining the amount of variable consideration to be paid occurs.

Finance and operating lease assets and liabilities are recognized at the lease commencement date based on the present value of the lease payments over the lease term using the discount rate implicit in the lease. If the rate implicit is not readily determinable, the Company utilizes an estimate of its incremental borrowing rate based upon the available information at the lease commencement date. Operating lease assets are further adjusted for prepaid or accrued lease payments. Operating lease payments are expensed using the straight-line method as an operating expense over the lease term. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Finance lease assets are amortized to depreciation expense using the straight-line method over the shorter of the useful life of the related asset or the lease term. Finance lease payments are bifurcated into (i) a portion that is recorded as imputed interest expense and (ii) a portion that reduces the finance liability associated with the lease.

Right-of-use assets and lease liabilities are reassessed and remeasured when amendments to the terms of the lease agreement require reassessment and remeasurement of the lease payments and other inputs to the calculation of right-of-use assets and lease liabilities. The Company accounts for remeasurements and modifications to lease liabilities using the present value of remaining lease payments and estimated incremental borrowing rate at the date of remeasurement. The adjustment to the lease liability is recognized as a gain or loss in operating expenses, or as an adjustment to the right-of-use asset, as appropriate, based on the terms and conditions within the lease that are amended.

Recently Adopted Accounting Pronouncements

In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which requires public entities to disclose significant segment expenses and other segment items on an interim and annual basis, and provide in interim periods all disclosures about a reportable segment's profit or loss and assets that are currently required annually. The ASU does not change how a public entity identifies its operating segments, aggregates them, or applies the quantitative threshold to determine its reportable segments. The new disclosure requirements are also applicable to entities that account and report as a single operating segment entity. ASU 2023-07 is effective for fiscal years beginning after December 15, 2023, and for interim periods within fiscal years beginning after December 15, 2024. The Company adopted the guidance for the annual reporting period ended December 31, 2024. There was no impact on the Company’s reportable segments identified and additional required disclosures have been included in Note 18, Segment Reporting.

Recently Issued Accounting Pronouncements

In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures which requires public entities to disclose specific categories in the effective tax rate reconciliation, as well as expanded disclosures on income taxes paid by jurisdictions. ASU 2023-09 is effective for fiscal years beginning after December 15, 2024, with early adoption permitted. The Company is currently evaluating the impact related to the adoption of ASU 2023-09 on its financial statement disclosures.

In November 2024, the FASB issued ASU 2024-03, Disaggregation of Income Statement Expenses (Topic 220), which requires disclosure in the notes to financial statements about specific types of expenses included in the expense captions presented on the face of the statement of operations. The requirements of the ASU are effective for annual periods beginning after December 15, 2026, and for interim periods beginning after December 15, 2027, with early adoption permitted. The requirements will be applied prospectively with

the option for retrospective application. The Company is currently evaluating the impact related to the adoption of ASU 2024-03 on its financial statement disclosures.

Net Loss per Share - Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Numerator:
Net loss from continuing operations attributable to common stockholders	$ (125,771)	$ (190,130)	$ (183,581)
Net income (loss) from discontinuing operations attributable to common stockholders	125,907	76,406	(66,576)
Net income (loss)	$ 136	$ (113,724)	$ (250,157)
Denominator:
Weighted average common shares outstanding, basic	155,400,760	128,003,294	108,077,043
Weighted average common shares outstanding, diluted	155,400,760	128,003,294	108,077,043
Net loss from continuing operations per share attributable to common stockholders, basic	$ (0.81)	$ (1.49)	$ (1.7)
Net loss from continuing operations per share attributable to common stockholders, diluted	(0.81)	(1.49)	(1.7)
Net income (loss) from discontinued operations per share attributable to common stockholders, basic	0.81	0.6	(0.62)
Net income (loss) from discontinued operations per share attributable to common stockholders, diluted	0.81	0.6	(0.62)
Net loss per share attributable to common stockholders, basic	0	(0.89)	(2.31)
Net loss per share attributable to common stockholders, diluted	$ 0	$ (0.89)	$ (2.31)
Employee Stock Option
Anti-dilutive potential common stock equivalents excluded from the calculation of net (loss) income per share
Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share:	17,720,315	14,844,112	14,940,034
Unvested Restricted Stock Units [Member]
Anti-dilutive potential common stock equivalents excluded from the calculation of net (loss) income per share
Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share:	1,631,772	3,377,804	1,549,540
Shares Issuable under employee stock purchase plan [Member]
Anti-dilutive potential common stock equivalents excluded from the calculation of net (loss) income per share
Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share:	143,214	297,784	89,593
Shares Issuable under employee stock purchase plan [Member] \| Warrants [Member]
Anti-dilutive potential common stock equivalents excluded from the calculation of net (loss) income per share
Anti-dilutive potential common stock equivalents excluded from the calculation of net loss per share:	647,589	1,177,433

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Assets measured at fair value	$ 0
Liabilities measured at fair value	0
Fair value, assets transfers from Level 1 to Level 2 measurement	0	$ 0
Fair value, assets transfers from Level 2 to Level 1 measurement	0	0
Fair value, assets transfers from Level 1 to Level 3 measurement	0	0
Fair value, assets transfers from Level 3 to Level 1 measurement	0	0
Restricted investments	0	$ 1,401
Fair value of warrant liabilities deemed	$ 0

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 5,468	$ 6,243	$ 6,629
Disposal of fully depreciated assets cost basis	679	$ 145
Impairment loss of leasehold improvements	$ 1,536

Consolidated Balance Sheets - USD ($)
$ in Thousands

Dec. 31, 2024

Dec. 31, 2023

Current assets:

Cash and cash equivalents

$ 30,793

$ 127,965

Accounts receivable due from SPN - related party

2,068

Current assets of discontinued operations

^[1]

5,813

8,049

39,396

Total current assets

38,674

175,410

Property and equipment, net

11,534

17,614

80,903

90,417

Restricted cash

8,668

8,185

Restricted investments

1,401

Non-current assets of discontinued operations

2,187

^[2]

63,386

Total assets

139,810

358,600

Current liabilities:

Accounts payable

4,079

3,641

Accrued expenses and other current liabilities

10,719

22,509

Accrued liabilities due to SPN - related party

17,750

Current liabilities of discontinued operations

8,674

5,587

^[3]

66,922

Total current liabilities

41,222

98,659

Long term portion of note payable, net of discount

101,544

Operating lease liabilities, net of current portion

82,966

91,652

Warrant liabilities

546

Other long-term liabilities

1,838

1,628

Non-current liabilities of discontinued operations

109,427

Total liabilities

126,026

403,456

Commitments and contingencies (Note 14)

Stockholders (deficit) equity:

Preferred stock, $0.001 par value; 10,000,000 shares authorized at December 31, 2024 and 2023; no shares issued and outstanding at December 31, 2024 and 2023

Common stock, $0.001 par value; 360,000,000 and 240,000,000 shares authorized at December 31, 2024 and 2023, respectively; 173,008,198 and 135,041,467 shares issued and outstanding at December 31, 2023 and 2022, respectively

173

135

Additional paid-in capital

991,710

933,244

Accumulated deficit

(978,099)

(978,235)

Total stockholders' equity (deficit)

13,784

(44,856)

Total liabilities and stockholders' equity

$ 139,810

$ 358,600

[1]	Includes $2,683 as of December 31, 2024 of unbilled receivable from SPN (related party) related to certain costs of the transition services performed by the Company. See Note 3, Discontinued Operations and TSA, for further details.
[2]	Includes $38,877 as of December 31, 2023 of milestones related to the construction of the Company's dedicated manufacturing suite at BacThera AG, or Bacthera.
[3]	Includes related party amounts of $35,783 at December 31, 2023.

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Line Items]
Income tax expense (benefit)	$ 0	$ 0	$ 0
Capitalized research and development costs	50,562,000	102,558,000
Unrecognized tax benefits	$ 14,015,000	$ 13,529,000	$ 12,528,000	$ 0
Massachusetts [Member]
Income Tax Disclosure [Line Items]
Net operating loss carry forwards, expiration year, start	2035
Future Tax Years [Member] \| Maximum [Member]
Income Tax Disclosure [Line Items]
Taxable income on NOL	80.00%
Federal [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 580,084,000
Research and development performance period	5 years
Federal [Member] \| Before 2018 [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 117,788,000
Net operating loss carry forwards, expiration year, start	2035
Federal [Member] \| After 2017 [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 462,296,000
Federal [Member] \| Research and Development Tax Credit [Member]
Income Tax Disclosure [Line Items]
Tax credit carryforwards	$ 55,674,000
Tax credit carryforwards, expiration year, start	2031
Federal [Member] \| Orphan Drug Credit Carryforwards [Member]
Income Tax Disclosure [Line Items]
Tax credit carryforwards	$ 25,876,000
Foreign [Member]
Income Tax Disclosure [Line Items]
Research and development performance period	15 years
State [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 543,618,000
State [Member] \| Research and Development Tax Credit [Member]
Income Tax Disclosure [Line Items]
Tax credit carryforwards	$ 11,957,000
Tax credit carryforwards, expiration year, start	2028

Income Taxes

12 Months Ended

Dec. 31, 2024

Income Tax Disclosure [Abstract]

Income Taxes

15. Income Taxes

During the years ended December 31, 2024, 2023 and 2022, the Company recorded no income tax benefits for the net operating losses incurred in each year or interim period, due to its uncertainty of realizing a benefit from those items.

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended December 31,
	2024			2023(1)			2022(1)
Federal statutory income tax rate		(21.0	)%		(21.0	)%		(21.0	)%
Research and development tax credits		(1.8	)		(2.5	)		(4.2	)
State taxes, net of federal benefit		(3.6	)		(7.2	)		(3.9	)
Stock-based compensation		1.0			0.8			0.7
Uncertain tax position reserves		0.4			0.5			6.3
Other		(0.4	)		(0.1	)		0.2
Change in deferred tax asset valuation allowance		25.4			29.5			21.9
Effective income tax rate		—	%		—	%		—	%

[1] Prior period amounts have been retrospectively adjusted to reflect the effects of the Transaction.

Net deferred tax assets as of December 31, 2024 and 2023 consisted of the following:


	December 31,
	2024			2023
Deferred tax assets:
Net operating loss carryforwards	$	156,157		$	142,506
Research and development tax credit carryforwards		54,648			52,843
Section 174 capitalized research and development expenses		53,600			55,572
Stock-based compensation expense		28,819			25,898
Lease liability		23,917			29,855
Deferred revenue		—			27,452
Accrued expenses		7,032			3,540
Section 163(j) limitation		5,599			3,741
Depreciation and amortization		953			398
Other		132			169
Total deferred tax assets	$	330,857		$	341,974
Deferred tax liabilities:
Depreciation and amortization		—			—
Right of use assets		(21,115	)		(29,165	)
Total deferred tax liabilities		(21,115	)		(29,165	)
Valuation allowance	$	(309,742	)	$	(312,809	)
Net deferred tax assets	$	—		$	—

The Tax Cuts and Jobs Act ("TCJA") requires taxpayers to capitalize and amortize research and experimental expenditures under IRC Section 174 for tax years beginning after December 31, 2021. This rule became effective for the Company during the year ended December 31, 2022 and resulted in the capitalization of research and development costs of $50,562 and $102,558 for the years

ended December 31, 2024 and 2023, respectively. The Company will amortize these costs for tax purposes over five years if the research and development was performed in the U.S. and over 15 years if the research and development was performed outside the U.S.

As of December 31, 2024, the Company had net operating loss carryforwards (“NOLs”) for federal and state income tax purposes of $580,084 and $543,618, respectively. Federal NOLs of $117,788, generated before 2018, will begin expiring in varying amounts in 2035 unless utilized. The remaining federal NOLs of $462,296, generated after 2017, will be carried forward indefinitely and could be used to offset up to 80% of taxable income in future tax years. The Company's state NOLs will expire at various times starting in 2035. As of December 31, 2024, the Company also had available gross research and development tax credit carryforwards for federal and state income tax purposes of $55,674 and $11,957, respectively, which begin to expire in 2031 and 2028, respectively. The federal research and development tax credits include an orphan drug credit carryforward of $25,876.

Utilization of the NOLs and research and development tax credit carryforwards may be subject to a substantial annual limitation under Sections 382 and 383 of the IRC due to ownership changes that have occurred previously or that could occur in the future. These ownership changes may limit the amount of carryforwards that can be utilized annually to offset future taxable income. In general, an ownership change, as defined by Section 382, results from transactions increasing the ownership of certain shareholders or public groups in the stock of a corporation by more than 50% over a three-year period. Since its formation, the Company has raised capital through the issuance of capital stock on several occasions. These financings, combined with the purchasing shareholders' subsequent disposition of those shares, may have resulted in a change of control or could result in a change of control in the future upon subsequent disposition. The Company conducted an analysis to determine if historical changes in ownership through December 31, 2020 would limit or otherwise restrict its ability to utilize these NOLs and research and development credit carryforwards. As a result of this analysis, the Company does not believe there are any significant limitations on its ability to utilize these carryforwards. However, future changes in ownership after December 31, 2020 could affect the limitation in future years. Any limitation may result in expiration of a portion of the NOLs or research and development credit carryforwards before utilization.

The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets. Management has considered the Company’s history of cumulative net losses incurred since inception and its lack of commercialization of any products or generation of any revenue from product sales since inception and has concluded that it is more likely than not that the Company will not realize the benefits of the deferred tax assets. Accordingly, a full valuation allowance has been established against the deferred tax assets as of December 31, 2024 and 2023. Management reevaluates the positive and negative evidence at each reporting period.


	Year Ended December 31,
	2024			2023			2022
Valuation allowance at beginning of year	$	(312,809	)	$	(277,370	)	$	(220,114	)
Decreases recorded as benefit to income tax provision		3,067			—			—
Increases recorded to income tax provision		—			(35,439	)		(57,256	)
Valuation allowance as of end of year	$	(309,742	)	$	(312,809	)	$	(277,370	)

During the year ended December 31, 2023, the Internal Revenue Service ("IRS") concluded their examination of the Company for the period ended December 31, 2018 related to the Company's 2018 research and development tax credits ("R&D Credit(s)"). The Company has adjusted its 2018 R&D Credits and its overall federal and state R&D Credit carryforward balance from the Company's inception to December 31, 2024 to account for the conclusions drawn by the IRS. Also, the Company has reviewed each of its overall filing positions since inception and has not identified any additional positions that do not meet the more likely than not threshold. The Company does not anticipate a material change to its uncertain tax position reserves in the next 12 months. The changes in the Company's unrecognized tax benefits for the years ended December 31, 2024, 2023, and 2022 were as follows:


	Year Ended December 31,
	2024		2023		2022
Balance at beginning of year	$	13,529	$	12,528	$	—
Increase in unrecognized tax benefits as a result of tax positions taken during the year		486		1,001		12,528
Reduction to unrecognized tax benefits		—		—		—
Balance at end of year	$	14,015	$	13,529	$	12,528

The Company has not yet conducted a study of its research and development credit carry forwards. This study may result in further adjustment to the Company’s R&D Credits; however, a full valuation allowance has been provided against the Company’s R&D Credits, and if an adjustment is required, this adjustment would be offset by an adjustment to the valuation allowance. Thus, there would be no impact to the consolidated balance sheets or statements of operations if an adjustment were required. The Company had no other unrecognized tax benefits accrued for the years ended December 31, 2024 and 2023, or related interest and penalties as of such dates. The Company will recognize any interest and penalties related to uncertain tax positions in income tax expense.

The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. The Company's tax years are still open under statute from 2011 to present. All years may be examined to the extent the tax credit or net operating loss carryforwards are used in future periods.

The entire disclosure for income tax.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 231
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482663/740-10-55-231

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12C

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12B

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477891/740-270-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-13

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/740/tableOfContent

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-14

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-21

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-17

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482603/740-30-50-2

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

12 Months Ended

Dec. 31, 2024

Property and Equipment, Net

6. Property and Equipment, Net

Property and equipment, net consisted of the following (in thousands):


	December 31,
	2024			2023
Laboratory equipment	$	24,468		$	24,665
Computer equipment		3,924			3,672
Furniture and office equipment		4,523			4,752
Leasehold improvements		30,954			32,489
Construction in progress		861			1,114
		64,730			66,692
Less: Accumulated depreciation and amortization		(53,196	)		(49,078	)
	$	11,534		$	17,614

Depreciation and amortization expense was $5,468, $6,243 and $6,629 for the years ended December 31, 2024, 2023 and 2022, respectively, which includes amounts related to both continuing and discontinued operations. During the years ended December 31, 2024 and 2023, the Company disposed of certain fully-depreciated assets with a cost basis of $679 and $145, respectively. In addition, during the year ended December 31, 2024, the Company recorded an impairment loss of $1,536 related to leasehold improvements at one of the Company's locations for which impairment indicators were determined to exist as of December 31, 2024. See Note 8, Leases, for further details.

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Operating expenses:
Research and development expenses	$ 64,600	$ 117,597	$ 109,651
General and administrative expenses	53,183	77,500	70,263
Manufacturing services	3,532	0	0
Total operating expenses	121,315	195,097	179,914
Loss from operations	(121,315)	(195,097)	(179,914)
Other (expense) income:
Gain on sale of VOWST business	5,684	0	0
Interest income	3,967	7,301	3,058
Interest expense	0	(2,468)	(6,020)
Other (expense) income, net	(14,107)	134	(705)
Total other (expense) income, net	(4,456)	4,967	(3,667)
Net loss from continuing operations	(125,771)	(190,130)	(183,581)
Net income (loss) from discontinued operations, net of tax	125,907	76,406	(66,576)
Net income (loss)	$ 136	$ (113,724)	$ (250,157)
Net loss from continuing operations per share attributable to common stockholders, basic	$ (0.81)	$ (1.49)	$ (1.7)
Net loss from continuing operations per share attributable to common stockholders, diluted	(0.81)	(1.49)	(1.7)
Net income (loss) from discontinued operations per share attributable to common stockholders, diluted	0.81	0.6	(0.62)
Net income (loss) from discontinued operations per share attributable to common stockholders, basic	0.81	0.6	(0.62)
Net loss per share attributable to common stockholders, basic	0	(0.89)	(2.31)
Net loss per share attributable to common stockholders, diluted	$ 0	$ (0.89)	$ (2.31)
Weighted average common shares outstanding, basic	155,400,760	128,003,294	108,077,043
Weighted average common shares outstanding, diluted	155,400,760	128,003,294	108,077,043
Other comprehensive income:
Unrealized gain on investments, net of tax of $0	$ 0	$ 10	$ 49
Currency translation adjustment	0	2	(1)
Total other comprehensive income	0	12	48
Comprehensive income (loss)	$ 136	$ (113,712)	$ (250,109)

Summary of Significant Accounting Policies - Schedule of Property and Equipment Estimated Useful Life (Details)	Dec. 31, 2024
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment Useful Lives (in years)	5 years
Computer Equipment, Furniture and Office Equipment
Property, Plant and Equipment [Line Items]
Property and Equipment Useful Lives (in years)	3 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment, Useful Life, Term, Description [Extensible Enumeration]	us-gaap:UsefulLifeTermOfLeaseMember

Income Taxes - Schedule of Change In Unrecognized Tax Benefits Roll Forward (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 13,529	$ 12,528	$ 0
Increase in unrecognized tax benefits as a result of tax positions taken during the year	486	1,001	12,528
Reduction to unrecognized tax benefits		0	0
Balance at end of year	$ 14,015	$ 13,529	$ 12,528

Restructuring (Tables)

12 Months Ended

Dec. 31, 2024

Restructuring and Related Activities [Abstract]

Schedule of Changes in Restructuring Liability

The following table presents changes in the restructuring liability for the year ended December 31, 2024 (in thousands):


	As of December 31, 2024
Restructuring expenses	$	5,606
Less: stock-based compensation	$	(261	)
Cash payments made		(5,325	)
Remaining liability included in accrued expenses and other current liabilities	$	20

Preferred Stock - Additional Information (Detail) - $ / shares	Dec. 31, 2024	Dec. 31, 2023	Jul. 01, 2015
Equity [Abstract]
Preferred stock, shares authorized	10,000,000	10,000,000	10,000,000
Preferred stock, par value	$ 0.001	$ 0.001	$ 0.001

Income Taxes - Summary of Changes In Valuation Allowance for Deferred Tax Assets (Detail) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2024

Dec. 31, 2023

Dec. 31, 2022

^[1]

Valuation Allowance [Abstract]

Valuation allowance at beginning of year

$ (312,809)

$ (277,370)

^[1]

$ (220,114)

Decreases recorded as benefit to income tax provision

3,067

Increases recorded to income tax provision

(35,439)

(57,256)

Valuation allowance as of end of year

$ (309,742)

^[1]

$ (312,809)

$ (277,370)

[1]	Prior period amounts have been retrospectively adjusted to reflect the effects of the Transaction.

Related Party Transactions

12 Months Ended

Dec. 31, 2024

Related Party Transactions

16. Related Party Transactions

As described in Note 1, Nature of the Business and Basis of Presentation and Note 3, Discontinued Operations, in September 2024, the Company sold the VOWST Business, including inventory and equipment, certain patents and patent applications, know-how, trade secrets, trademarks, domain names, marketing authorizations and related rights, documents, materials, business records and data and contracts that are used or held for use primarily in the development, commercialization and manufacturing of VOWST, to SPN, and SPN assumed certain liabilities from the Company. As consideration for the Transaction, the Company received an upfront cash payment of $139,788, which consists of $100,000, less $17,857 owed by the Company to an affiliate of SPN under the prior license agreement between the Company and the SPN affiliate, less approximately $2,355 in satisfaction of fees due under the Bacthera Manufacturing Agreement; plus a prepayment of the $60,000 milestone payment tied to the achievement of worldwide annual net sales of VOWST of $150,000; plus an equity investment of $15,000 based on the Securities Purchase Agreement pursuant to which SPN purchased 14,285,715 shares of common stock at a purchase price of $1.05 per share.

As of December 31, 2024, the Accrued Liabilities due to SPN - related party on the Company's consolidated balance sheets were $17,750, which represents amounts due to SPN pursuant to the Purchase Agreement, which are further described in Note 3, Discontinued Operations and TSA. During the twelve months ended December 31, 2024, the Company paid $9,608 of the outstanding amounts relating to the second and third quarters of 2024 loss sharing.

As described in Note 3, Discontinued Operations and TSA, the Company entered into the TSA with NESA, an affiliate of SPN, in connection with the Transaction, through which the Company will provide certain manufacturing services until December 31, 2025, and other transition services, for the duration specified in the schedule to the TSA for each service. For the year ended December 31, 2024, the Company recognized $6,292 of TSA reimbursement income in other (expense) income, net in the Company’s consolidated statements of operations and comprehensive income (loss). For the year ended December 31, 2024, the Company has incurred $3,532 of expenses related to manufacturing services and $3,136 of TSA labor and passthrough expenses to support the transition services, including finance and accounting, information technology, human resources, operations, and other services. The difference between the TSA reimbursement income and the TSA expenses incurred is primarily due to certain non-cash expenses not reimbursed under the TSA.

due from SPN - related party and $2,443 unbilled receivable included in prepaid expenses and other current asset in the Company’s consolidated balance sheets.

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-5

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-6

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(g)(3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(e))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/850/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-6

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Investments, Debt and Equity Securities [Abstract]

Restructuring - Additional Information (Detail) $ in Thousands		1 Months Ended	12 Months Ended
	Nov. 02, 2023 Employee	Nov. 30, 2023 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Restructuring Cost And Reserve [Line Items]
Workforce Reduction Rate	41.00%
Number of positions eliminated \| Employee	160
Restructuring Charges				$ 5,606
Research and development expenses			$ 64,600	117,597	$ 109,651
General and administrative expenses			53,183	77,500	70,263
Stock-based compensation expense			$ 20,971	34,101	$ 25,482
Restructuring Charges [Member]
Restructuring Cost And Reserve [Line Items]
Research and development expenses				3,481
General and administrative expenses				2,125
Restricted Stock Units [Member]
Restructuring Cost And Reserve [Line Items]
Stock-based compensation expense		$ 1,255
Severance and other employee costs
Restructuring Cost And Reserve [Line Items]
Restructuring Charges				5,345
Acceleration of unvested equity awards
Restructuring Cost And Reserve [Line Items]
Restructuring Charges				$ 261

Investments

12 Months Ended

Dec. 31, 2024

Investments

5. Investments

As of December 31, 2024 and 2023, the Company held restricted investments of $0 and $1,401, respectively, the cost of which approximates current fair value. The Company did not hold any other investments as of December 31, 2024 and 2023.

Investments with original maturities of less than 90 days are included in cash and cash equivalents on the consolidated balance sheets. Investments with maturities of less than 12 months are considered current assets and those investments with maturities greater than 12 months are considered non-current assets.

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2021	$ 131,507	$ 92	$ 745,829	$ (60)	$ (614,354)
Beginning balance, shares at Dec. 31, 2021		91,889,418
Issuance of common stock upon exercise of stock options, value	966		966
Issuance of common stock upon exercise of stock options, shares		326,864
Issuance of common stock upon vesting of RSUs and PSUs, net of tax withholdings, shares		282,401
Issuance of common stock under ESPP, value	1,769		1,769
Issuance of common stock under ESPP, shares		322,560
Issuance of common stock, net of issuance costs, value	96,721	$ 32	96,689
Stock issued during period, shares, new Issues		31,746,030
Issuance of common stock from at the market equity offering, value	4,447	$ 1	4,446
Issuance of common stock from at the market equity offering, shares		655,000
Stock-based compensation expense	25,482		25,482
Other comprehensive income (loss)	48			48
Net income	(250,157)				(250,157)
Ending balance at Dec. 31, 2022	10,783	$ 125	875,181	(12)	(864,511)
Ending balance, shares at Dec. 31, 2022		125,222,273
Issuance of common stock upon exercise of stock options, value	877	$ 0	877
Issuance of common stock upon exercise of stock options, shares		260,640
Issuance of common stock upon vesting of RSUs and PSUs, net of tax withholdings, value	0	$ 1	(1)
Issuance of common stock upon vesting of RSUs and PSUs, net of tax withholdings, shares		1,244,663
Issuance of common stock under ESPP, value	2,151	$ 2	2,149
Issuance of common stock under ESPP, shares		602,692
Issuance of common stock from at the market equity offering, value	18,159	$ 7	18,152
Issuance of common stock from at the market equity offering, shares		7,711,199
Issuance of warrants			2,785
Stock-based compensation expense	34,101		34,101
Other comprehensive income (loss)	12			12
Net income	(113,724)				(113,724)
Ending balance at Dec. 31, 2023	$ (44,856)	$ 135	933,244	0	(978,235)
Ending balance, shares at Dec. 31, 2023	135,041,467	135,041,467
Issuance of common stock upon exercise of stock options, shares	0
Issuance of common stock upon vesting of RSUs and PSUs, net of tax withholdings, value	$ 0	$ 2	(2)
Issuance of common stock upon vesting of RSUs and PSUs, net of tax withholdings, shares		2,475,553
Issuance of common stock under ESPP, value	$ 487	$ 1	486
Issuance of common stock under ESPP, shares		588,435
Stock issued during period, shares, new Issues	14,285,715
Issuance of common stock from at the market equity offering, value	$ 23,530	$ 21	23,509
Issuance of common stock from at the market equity offering, shares		20,617,028
Issuance of common stock from Securities Purchase Agreement, net of offering costs - related party, shares		14,285,715
Issuance of common stock from Securities Purchase Agreement, net of offering costs - related party, value	13,516	$ 14	13,502
Stock-based compensation expense	20,971		20,971
Net income	136				136
Ending balance at Dec. 31, 2024	$ 13,784	$ 173	$ 991,710	$ 0	$ (978,099)
Ending balance, shares at Dec. 31, 2024	173,008,198	173,008,198

Common Stock and Stock-Based Awards - 2015 Employee Stock Purchase Plan - Additional Information (Details) - 2015 Employee Stock Purchase Plan [Member] - shares		12 Months Ended
	Jun. 16, 2015	Dec. 31, 2024
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate shares of common stock reserved for issuance	365,000	2,078,077
Shares issued under ESPP	400,000	588,435
Percentage of common stock shares outstanding	1.00%
Percentage of eligible earning contributed toward semi-annual purchase of common stock		15.00%
Offering period under the plan		6 months
Percentage of purchase price with respect to each offering period		85.00%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Common Stock and Stock-Based Awards

Common Stock and Stock-Based Awards

12 Months Ended

Dec. 31, 2024

Equity [Abstract]

11. Common Stock and Stock-Based Awards

On September 30, 2024, the Company entered into the Securities Purchase Agreement with SPN, pursuant to which SPN purchased 14,285,715 shares at the Closing at a purchase price per share of $1.05, for an aggregate purchase price of $15,000. Under the terms of the Securities Purchase Agreement, SPN has agreed not to sell or transfer the shares for a period of six months after Closing, subject to certain customary exceptions. The Company agreed to register the resale of the Shares by SPN within 90 days of Closing. On October 1, 2024, the Company filed a registration statement to register the Shares, which became effective on October 11, 2024. In addition, under the terms of the Securities Purchase Agreement, for as long as SPN, together with its affiliates, beneficially owns at least 10% of the Company's outstanding shares of common stock, the Company has agreed to take such action within its control to include one individual designated by SPN in the slate of nominees recommended by the Company's board of directors (or the applicable committee of the board) to the Company's stockholders for election to the board at the applicable stockholder meeting. The Securities Purchase Agreement contains customary representations and warranties and closing conditions. The aggregate fair value of $13,516 for the common stock issued to SPN was recorded in equity, with the remaining $1,484 cash received from SPN under the Securities Purchase Agreement allocated to the consideration transferred for the VOWST Business.

On February 22, 2024, the Company’s board of directors adopted a resolution to amend the Restated Certificate of Incorporation, subject to stockholder approval, by increasing the number of authorized shares of the Company’s Common Stock from 240,000,000 shares to 360,000,000 shares (the “Share Increase Amendment”). At the Company’s annual meeting of stockholders held on April 4, 2024, the Company’s stockholders approved the Share Increase Amendment. On April 5, 2024, the Company amended its Restated Certificate of Incorporation to reflect the Share Increase Amendment.

In May 2021, the Company entered into a Sales Agreement (the "Sales Agreement") with Cowen and Company, LLC ("Cowen") to sell shares of the Company's common stock, with aggregate gross sales proceeds of up to $150,000, from time to time, through an "at-the-market" equity offering program ("ATM") under which Cowen acts as sales agent. During the year ended December 31, 2024, the Company sold 20,617,028 shares of common stock under the 2021 Sales Agreement, at an average price of approximately $1.18 per share, raising aggregate net proceeds of approximately $23,530 after deducting an aggregate commission of approximately 3% and other issuance costs. During the year ended December 31, 2023, the Company sold 7,711,199 shares of common stock under the 2021 Sales Agreement, at an average price of approximately $2.46 per share, raising aggregate net proceeds of approximately $18,159 after deducting an aggregate commission of approximately 3% and other issuance costs. During the year ended December 31, 2021, the Company did not sell any shares of common stock under the 2020 Sales Agreement or the 2021 Sales Agreement.

Between December 31, 2024 and January 31, 2025, the Company sold 1,096,134 shares of common stock under the 2021 Sales Agreement, at an average price of approximately $0.93 per share, raising aggregate net proceeds of approximately $996 after deducting an aggregate commission of approximately 3% and other issuance costs.

On June 29, 2022, the Company entered into securities purchase agreements with new and existing investors and certain directors and officers in a registered direct offering, or the Registered Direct Offering, of an aggregate of 31,746,030 shares of its common stock at a purchase price of $3.15 per share for total net proceeds of approximately $96,721, after deducting placement agent’s fees and other estimated offering expenses. Net proceeds included an aggregate of $27,525 received from Flagship Pioneering Fund VII, L.P. and Nutritional Health LTP Fund, L.P., affiliates of Flagship Pioneering, or Flagship, one of its significant stockholders, in exchange for 8,738,243 shares. The closing date of the Registered Direct Offering was July 5, 2022.

2012 Stock Incentive Plan

The Company’s 2012 Stock Incentive Plan, as amended, (the “2012 Plan”) provided for the Company to sell or issue common stock or restricted common stock, or to grant incentive stock options or nonqualified stock options for the purchase of common stock, to employees, members of the board of directors and consultants of the Company. The 2012 Plan is administered by the board of directors, or at the discretion of the board of directors, by a committee of the board of directors. The exercise prices, vesting and other restrictions are determined at the discretion of the board of directors, or their committee if so delegated, except that the exercise price per share of stock options may not be less than 100% of the fair market value of the share of common stock on the date of grant and the term of stock option may not be greater than ten years. The Company generally granted stock-based awards with service conditions only (“service-based” awards).

Stock options granted under the 2012 Plan generally vest over four years and expire after ten years, although options have been granted with vesting terms less than four years. As of December 31, 2024, there were no shares available for future grant under the 2012 Plan.

2015 Incentive Award Plan

On June 16, 2015, the Company’s stockholders approved the 2015 Incentive Award Plan (the “2015 Plan”), which became effective on June 25, 2015. The 2015 Plan was subsequently amended on December 14, 2022, and provides for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. The number of shares initially reserved for issuance under the 2015 Plan was the sum of (i) 2,200,000 shares of common stock and (ii) the number of shares subject to awards outstanding under the 2012 Plan that expire, terminate or are otherwise surrendered, canceled, forfeited or repurchased by the Company on or after the effective date of the 2015 Plan. In addition, the number of shares of common stock that may be issued under the 2015 Plan is subject to increase on the first day of each calendar year, beginning in 2016 and ending in 2025, equal to the lesser of (i) 4% of the number of shares of the Company’s common stock outstanding on the last day of the preceding applicable calendar year and (ii) an amount determined by the Company’s board of directors.

Stock awards granted under the 2015 Plan generally vest over four years and expire after ten years, although options have been granted with vesting terms less than four years. As of December 31, 2024, there were 4,925,721 shares available for future grant under the 2015 Plan.

2015 Employee Stock Purchase Plan

On June 16, 2015, the Company’s stockholders approved the 2015 Employee Stock Purchase Plan (the “ESPP”), which became effective on June 25, 2015. A total of 365,000 shares of common stock were reserved for issuance under the ESPP. In addition, the number of shares of common stock that may be issued under the ESPP automatically increase on the first day of each calendar year, beginning in 2016 and ending in 2025, by an amount equal to the lesser of (i) 400,000 shares, (ii) 1% of the number of shares of the Company’s common stock outstanding on the last day of the applicable preceding calendar year and (iii) an amount determined by the Company’s board of directors. Offering periods under the ESPP will commence when determined by the plan administrator. During the year ended and as of December 31, 2024, there were 588,435 shares issued and 2,078,077 shares were reserved and available for issuance under the ESPP, respectively.

The ESPP provides that eligible employees may contribute up to 15% of their eligible earnings toward the semi-annual purchase of the Company's common stock. Purchase rights issued under the ESPP are intended to be qualified under Section 423 of the Internal Revenue Code ("IRC"). The employee's purchase price is derived from a formula based on the closing price of the common stock on the first day of the offering period versus the closing price on the date of purchase (or, if not a trading day, on the immediately preceding trading day). The offering period under the ESPP has a duration of six months, and the purchase price with respect to each offering period beginning on or after such date is, until otherwise amended, equal to 85% of the lesser of (i) the fair market value of the Company's

common stock at the commencement of the applicable six-month offering period or (ii) the fair market value of the Company's common stock on the purchase date.

2022 Employment Inducement Award Plan

On December 14, 2022, the Company’s board of directors approved the 2022 Employment Inducement Award Plan (the "2022 Plan"), which became effective on such date without stockholder approval pursuant to Rule 5635(c)(4) of The Nasdaq Stock Market LLC listing rules (“Rule 5635(c)(4)”). The 2022 Plan provides for the grant of nonqualified stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock- or cash-based awards. In accordance with Rule 5635(c)(4), awards under the 2022 Plan may only be made to a newly hired employee who has not previously been a member of our board of directors, or an employee who is being rehired following a bona fide period of non-employment by us as a material inducement to the employee’s entering into employment with us. A total of 2,500,000 shares of common stock were reserved for issuance under the 2022 Plan. Any shares subject to awards previously granted under the 2022 Plan that expire, terminate or are otherwise surrendered, canceled, or forfeited in any case, in a manner that results in the Company acquiring the shares covered by the award at a price not greater than the price (as adjusted to reflect any equity restructuring) paid by the Participant for such shares or not issuing any shares covered by the award, the unused shares covered by the award will again be available for award grants under the 2022 Plan.

As of December 31, 2024, there were 1,696,205 shares available for future grant under the 2022 Plan.

Stock Options

The following table summarizes the Company’s stock option activity for the year ended December 31, 2024:


	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)
Outstanding as of December 31, 2023		14,844,112		$	9.64		5.71	$	—
Granted		7,817,641		$	1.05
Exercised		—		$	—
Forfeited		(4,941,438	)	$	7.44
Outstanding as of December 31, 2024		17,720,315		$	6.46		6.59	$	87
Vested or expected to vest as of December 31, 2024		17,720,315		$	6.46		6.59	$	87
Options exercisable as of December 31, 2024		9,850,537		$	9.94		4.74	$	7

The weighted average grant-date fair value of stock options granted during the years ended December 31, 2024, 2023, and 2022 was $0.93, $4.51, and $5.53 per share, respectively. The total intrinsic value of stock options exercised during the years ended December 31, 2024, 2023, and 2022 was $0, $438, and $981, respectively.

The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock.

During the year ended December 31, 2021, the Company granted performance-based stock options to employees for the purchase of an aggregate of 562,000 shares of common stock with a grant date fair value of $5.53 per share. These stock options are exercisable only upon achievement of specified performance targets. In April 2023, the performance target associated with 50% of the performance-based stock options was achieved. Accordingly, the Company recorded $8 and $2,051 of compensation expense during the year ended December 31, 2024 and 2023, respectively, with respect to these performance-based stock options, which represents a cumulative catch-up from the grant date through the achievement of the performance targets, and vesting of the remaining 50% of the options beginning in April 2023. The remaining compensation expense associated with these performance-based stock options was recognized as of April 2024, for all such options for which ongoing performance targets were achieved and service requirements were met.

During the three months ended March 31, 2024, the Company granted stock options to certain executives for the purchase of an aggregate of 2,550,010 shares of common stock. These awards will vest only to the extent that the 30-day trailing simple average public market closing price of the Company's common stock reaches certain price thresholds. These awards have an exercise price of $1.10 and vest and become exercisable when the market conditions are satisfied or, if later, on the first anniversary of the grant date.

These awards expire 10 years from the date of grant. The fair value of these market-based stock options was estimated using a Monte Carlo valuation method. During the twelve months ended December 31, 2024, the Company recognized $775 of compensation expense related to these awards.

During the year ended December 31, 2024, the forfeitures primarily consisted of the unvested options of certain employees of the Company related to the VOWST Business who accepted employment with SPN or one of its designated affiliates that were forfeited upon transfer.

Restricted Stock Units

The Company has granted restricted stock units with service-based vesting conditions ("RSUs") and restricted stock units with performance-based vesting conditions ("PSUs"). RSUs and PSUs represent the right to receive shares of common stock upon meeting specified vesting requirements. Restricted stock units may not be sold or transferred by the holder and vest according to the vesting conditions of each award. The table below summarizes the Company’s RSU and PSU activity for the year ended December 31, 2024:


	Number of Shares			Weighted Average Grant Date Fair Value
Unvested restricted stock units as of December 31, 2023		3,377,804		$	4.26
Granted		1,503,127		$	1.05
Forfeited		(1,053,587	)	$	3.01
Vested		(2,195,572	)	$	3.77
Unvested restricted stock units as of December 31, 2024		1,631,772		$	2.76

During the years ended December 31, 2024, 2023, and 2022, the Company granted 1,503,127, 3,101,764 and 1,302,844 RSUs, respectively. During the year ended December 31, 2024, 2023, and 2022, the Company granted 0, 1,322,715, and 0 PSUs, respectively. RSUs generally vest over four years, with 25% vesting after one year, and the remaining 75% vesting quarterly over the next 3 years, subject to continued service to the Company through the applicable vesting date. PSUs vest according to the performance requirements of the awards, generally when the Company has determined that the specified performance targets have been achieved.

The aggregate intrinsic value of RSUs, including PSUs for which the performance conditions have been met, that vested during the years ended December 31, 2024, 2023 and 2022 was $1,899, $4,729, and $1,809, respectively.

In November 2023, as part of the corporate restructuring described in Note 13, Restructuring, the Company issued retention awards to employees of the Company in the form of RSUs which vested as to the first tranche on August 15, 2024, and which will vest as to the second tranche on May 15, 2025, subject to remaining actively employed with the Company through such date. The compensation expense associated with these awards will be recognized ratably over the vesting period. For the years ended December 31, 2024 and 2023, the Company recognized $655 and $92, respectively, in compensation expense with respect to the retention awards.

During the year ended December 31, 2023, the Company granted PSUs to employees for the purchase of an aggregate of 1,322,715 shares of common stock with a grant date fair value of $5.50. These PSUs begin to vest ratably only upon achievement of specified performance targets, which were achieved in April 2023. Accordingly, the Company recorded $792 and $4,293 in compensation expense during the year ended December 31, 2024 and 2023, respectively, with respect to these PSUs. The remaining compensation expense associated with these PSUs was fully recognized as of December 31, 2024.

Stock-based Compensation Valuation

The assumptions that the Company used to determine the fair value of the stock options granted to employees and directors were as follows, presented on a weighted average basis:


	Year Ended December 31,
	2024			2023			2022
Risk-free interest rate		2.70	%		3.64	%		1.67	%
Expected term (in years)		6.0			6.0			6.0
Expected volatility		76.2	%		107.2	%		104.0	%
Expected dividend yield		0	%		0	%		0	%

The Company estimates the fair value of rights to acquire common stock under the ESPP using a Black-Scholes valuation model on the date of grant and the straight-line attribution approach to recognize the expense. The assumptions that the Company used to determine the fair value of rights to acquire common stock under the ESPP were as follows, presented on a weighted average basis:


	Year Ended December 31,
	2024			2023			2022
Risk-free interest rate		5.16	%		5.01	%		2.11	%
Expected term (in years)		0.5			0.5			0.5
Expected volatility		118.3	%		79.1	%		99.0	%
Expected dividend yield		0	%		0	%		0	%

Stock-based Compensation


	Year Ended December 31,
	2024		2023		2022
Research and development expenses	$	10,996	$	19,341	$	13,429
General and administrative expenses		9,975		14,760		12,053
	$	20,971	$	34,101	$	25,482

As of December 31, 2024, the Company had an aggregate of $15,335 of unrecognized stock-based compensation cost, which is expected to be recognized over a weighted average period of 3.7 years.

401(k) Savings Plan

12 Months Ended

Dec. 31, 2024

Retirement Benefits [Abstract]

401(k) Savings Plan

17. 401(k) Savings Plan

The Company has a defined contribution savings plan under Section 401(k) of the IRC. This plan covers substantially all employees who meet minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre-tax basis. Effective January 1, 2016, the Company elected to match 50% of the first 6% of an employee’s deferral. Company contributions are expensed in the year for which they are declared. During the years ended December 31, 2024, 2023, and 2022 the Company recorded expense of $1,068, $2,003, and $1,921, respectively, for 401(k) match contributions.

The entire disclosure for retirement benefits.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Schedule of reportable segment net income (loss)

Notes Payable - Additional Information (Detail) $ / shares in Units, $ in Thousands		9 Months Ended	12 Months Ended
	Apr. 27, 2023 USD ($) TradingDays $ / shares shares	Sep. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Debt Instrument [Line Items]
Net proceeds received from credit facility	$ 50,446
Loss on extinguishment			$ (23,351)	$ (1,625)	$ 0
Trading days prior to the funding date \| TradingDays	30
Fair value of warrant liabilities deemed			0
Repayments of Notes Payable		$ 127,905	127,905	52,860	1,907
Interest expense			0	2,468	$ 6,020
Term Loan Facility [Member]
Debt Instrument [Line Items]
Credit facility, interest rate	7.875%
Line of credit facility exit fee percentage	1.50%
Percentage of prepayment amount after the first year	4.00%
Loan and Security Agreement [Member] \| Hercules Credit Facility [Member]
Debt Instrument [Line Items]
Interest expense				2,468
Oaktree Credit Agreement [Member] \| Loan and Security Agreement [Member] \| Term Loan Facility [Member]
Debt Instrument [Line Items]
Carrying value of debt				101,544
Oaktree Fund Administration, LLC [Member] \| Term Loan Facility [Member]
Debt Instrument [Line Items]
Credit facility, aggregate principal amount	$ 250,000
Tranche A Loan [Member] \| Term Loan Facility [Member]
Debt Instrument [Line Items]
Loss on extinguishment	(1,625)
Tranche A Loan [Member] \| Oaktree Fund Administration, LLC [Member] \| Term Loan Facility [Member]
Debt Instrument [Line Items]
Credit facility, aggregate principal amount	110,000
Tranche A Loan [Member] \| Hercules Capital, Inc. [Member] \| Term Loan Facility [Member]
Debt Instrument [Line Items]
Repayments of existing credit facility	53,380
Tranche B Loan [Member] \| Oaktree Fund Administration, LLC [Member] \| Term Loan Facility [Member]
Debt Instrument [Line Items]
Credit facility, aggregate principal amount	45,000
Tranche C Loan [Member] \| Oaktree Fund Administration, LLC [Member] \| Term Loan Facility [Member]
Debt Instrument [Line Items]
Credit facility, aggregate principal amount	45,000
Tranche D Loan [Member] \| Oaktree Fund Administration, LLC [Member] \| Term Loan Facility [Member]
Debt Instrument [Line Items]
Credit facility, aggregate principal amount	50,000
First Tranche [Member] \| Oaktree Fund Administration, LLC [Member] \| Term Loan Facility [Member]
Debt Instrument [Line Items]
Credit facility, aggregate principal amount	80,000
Second Tranche [Member] \| Oaktree Fund Administration, LLC [Member] \| Term Loan Facility [Member]
Debt Instrument [Line Items]
Credit facility, aggregate principal amount	$ 30,000
Interest Rate Floor [Member] \| Term Loan Facility [Member] \| Secured Overnight Financing Rate (SOFR) [Member]
Debt Instrument [Line Items]
Debt instrument, variable rate	2.50%
Interest rate cap [Member] \| Term Loan Facility [Member] \| Secured Overnight Financing Rate (SOFR) [Member]
Debt Instrument [Line Items]
Debt instrument, variable rate	5.00%
Principal [Member]
Debt Instrument [Line Items]
Repayments of Notes Payable		110,000
Accrued Interest [Member]
Debt Instrument [Line Items]
Repayments of Notes Payable		3,698
Yield Protection Premium [Member]
Debt Instrument [Line Items]
Repayments of Notes Payable		12,457
Exit Fee [Member]
Debt Instrument [Line Items]
Repayments of Notes Payable		1,650
Third-party Fees and Expenses [Member]
Debt Instrument [Line Items]
Repayments of Notes Payable		$ 100
Tranche A Warrant [Member]
Debt Instrument [Line Items]
Adjustments To Additional Paid In Capital, Warrant Issued	$ 2,785
Volatility	111.60%
Term (in years)	7 years
Risk-free interest rate	3.57%
Fair value of common stock price per share on the valuation date \| $ / shares	$ 5.32
Warrants exercise price \| $ / shares	$ 6.69
Tranche A Warrant [Member] \| Term Loan Facility [Member]
Debt Instrument [Line Items]
Debt instrument conversion warrants or options issued \| shares	647,589
Warrants exercise price \| $ / shares	$ 6.69
Tranche B Warrant [Member]
Debt Instrument [Line Items]
Debt instrument conversion warrants or options issued \| shares	264,922
Fair value of warrant liabilities deemed			0	276
Tranche C Warrant [Member]
Debt Instrument [Line Items]
Fair value of warrant liabilities deemed			$ 0	$ 270

Fair Value Measurements - Summary of Fair Value Hierarchy for Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrant liabilities	$ 0	$ 546
Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrant liabilities		546
Equity, Fair Value Disclosure [Abstract]
Total liabilities		546
Investments:
Total assets		81
Fair Value, Measurements, Recurring [Member] \| Money Market Funds [Member]
Cash Equivalents:
Cash equivalents		81
Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrant liabilities		0
Equity, Fair Value Disclosure [Abstract]
Total liabilities		0
Investments:
Total assets		81
Level 1 [Member] \| Fair Value, Measurements, Recurring [Member] \| Money Market Funds [Member]
Cash Equivalents:
Cash equivalents		81
Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrant liabilities		0
Equity, Fair Value Disclosure [Abstract]
Total liabilities		0
Investments:
Total assets		0
Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrant liabilities		546
Equity, Fair Value Disclosure [Abstract]
Total liabilities		546
Investments:
Total assets		$ 0

Leases - Schedule of Future Payments of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Leases [Abstract]
2025	$ 19,442
2026	19,983
2027	20,582
2028	20,862
2029	20,132
2030 and thereafter	36,850
Total future payments of operating lease liabilities	137,851
Less: imputed interest	(46,211)
Present value of operating lease liabilities	$ 91,640	$ 97,239

Leases - Summary of Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Operating lease costs	$ 19,514	$ 22,324	$ 8,830
Short-term lease costs	0	1,477	1,375
Variable lease costs	6,589	7,229	4,547
Sublease income	(2,708)	0	0
Total lease costs	$ 23,395	$ 31,030	$ 14,752

Discontinued Operations and TSA - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of VOWST business	$ 146,707	$ 0	$ 0
Stock-based compensation expense	20,971	34,101	25,482
Accounts receivable due from SPN - related party	2,068	0
Other (expense) income, net	(14,107)	134	(705)
Manufacturing services	3,532	0	0
Transition Services Agreement [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other (expense) income, net	6,292
Transition Services Agreement [Member] \| Passthrough Expenses [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other (expense) income, net	3,136
Transition Services Agreement [Member] \| NESA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Billed Contracts Receivable	3,724
Related party partial payments	1,656
Unbilled receivable	2,443
VOWST Business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of VOWST business	146,707	0	0
Capital expenditures	112	2,272	2,971
Depreciation	989	2,019	1,459
Non-cash operating lease costs	1,447	2,123	1,554
Collaboration loss sharing	0	5,158	1,004
Stock-based compensation expense	1,884	$ 2,773	$ 1,247
VOWST Business [Member] \| Transition Services Agreement [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of VOWST business	5,684
SPN [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Unbilled receivable	$ 2,683

Common Stock and Stock-Based Awards - Stock Based Compensation - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2024 USD ($)
Equity [Abstract]
Unrecognized stock-based compensation cost	$ 15,335
Weighted average period over which unrecognized compensation cost is expected to be recognized	3 years 8 months 12 days

Segment Reporting (Tables)

12 Months Ended

Dec. 31, 2024

Segment Reporting [Abstract]

The Company's reportable segment net income (loss) for the years ended December 31, 2024, 2023 and 2022, consisted of the following:


	Year Ended December 31,
	2024			2023			2022
Significant segment expenses:
Live biotherapeutics platform	$	29,006		$	43,342		$	34,764
SER-155		6,804			7,759			5,069
R&D personnel-related (including stock-based compensation)		28,689			65,251			68,059
G&A personnel-related (including stock-based compensation)		22,679			36,069			30,653
Professional fees		9,805			18,784			23,529
Facility-related and other		20,699			22,647			16,081
Other segment expense (income) (1)		8,089			(3,722	)		5,426
Net loss from continuing operations		(125,771	)		(190,130	)		(183,581	)
Net income (loss) from discontinued operations, net of tax (2)		125,907			76,406			(66,576	)
Net income (loss)	$	136		$	(113,724	)	$	(250,157	)

[2] See Note 3, Discontinued Operations and TSA, for further details.

Common Stock and Stock-Based Awards - Restricted Stock Units - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Nov. 30, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 20,971	$ 34,101	$ 25,482
Compensation cost		20,971	34,101	25,482
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value, vested		1,899	4,729	$ 1,809
Stock-based compensation expense	$ 1,255
Retention Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 655	$ 92
Service Based Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted		1,503,127	3,101,764	1,302,844
Stock option granted vesting period		4 years
Service Based Restricted Stock Units (RSUs) [Member] \| Share-Based Payment Arrangement, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights percentage		25.00%
Service Based Restricted Stock Units (RSUs) [Member] \| Share-Based Payment Arrangement, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights percentage		75.00%
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 8	$ 2,051
Performance Based Restricted Stock Units (PSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted		0	1,322,715	0
Weighted average grant-date fair value of stock options			$ 5.5
Stock-based compensation expense		$ 792	$ 4,293

Leases - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Operating Leased Assets [Line Items]
Existence of option to extend		true
Option to extend, description		Certain leases include one or more options to renew, exercisable at the Company’s sole discretion, with renewal terms that can extend the lease from approximately one year to ten years.
Impairment loss of leasehold improvements		$ 1,536
Lease payment over sublease term		10,400
Leases Payments		$ 17,330	$ 15,656	$ 7,809
Weighted average remaining lease term		6 years 11 months 23 days	7 years 11 months 12 days
Weighted average incremental borrowing rate		13.00%	13.00%
Cambridge Massachusetts [Member]
Operating Leased Assets [Line Items]
Impairment loss of leasehold improvements	$ 1,536
Impairment loss	3,267
Impairment loss	1,731
Cambridge Massachusetts [Member] \| General and Administrative Expenses [Member]
Operating Leased Assets [Line Items]
Impairment loss	540
Cambridge Massachusetts [Member] \| Research and Development Expenses [Member]
Operating Leased Assets [Line Items]
Impairment loss	$ 2,727
Maximum [Member]
Operating Leased Assets [Line Items]
Operating lease, remaining term		8 years
Lease renewal term (in years)		10 years
Minimum [Member]
Operating Leased Assets [Line Items]
Operating lease, remaining term		1 year
Lease renewal term (in years)		1 year

Income Taxes - Schedule of Reconciliation of U.S Federal Statutory Income Tax Rate to Company's Effective Income Tax Rate (Detail)

12 Months Ended

Dec. 31, 2024

Dec. 31, 2023

^[1]

Dec. 31, 2022

^[1]

Income Tax Disclosure [Abstract]

Federal statutory income tax rate

(21.00%)

Research and development tax credits

(1.80%)

(2.50%)

(4.20%)

State taxes, net of federal benefit

(3.60%)

(7.20%)

(3.90%)

Stock-based compensation

1.00%

0.80%

0.70%

Uncertain tax position reserves

0.40%

0.50%

6.30%

Other

(0.40%)

(0.10%)

0.20%

Change in deferred tax asset valuation allowance

25.40%

29.50%

21.90%

Effective income tax rate

0.00%

[1]	Prior period amounts have been retrospectively adjusted to reflect the effects of the Transaction.

Income Taxes - Schedule of Net Deferred Tax Assets (Detail) - USD ($)
$ in Thousands

Dec. 31, 2024

Dec. 31, 2023

Dec. 31, 2022

^[1]

Dec. 31, 2021

^[1]

Deferred tax assets:

Net operating loss carryforwards

$ 156,157

$ 142,506

Research and development tax credit carryforwards

54,648

52,843

Section 174 capitalized research and development expenses

53,600

55,572

Stock-based compensation expense

28,819

25,898

Lease liability

23,917

29,855

Deferred revenue

27,452

Accrued expenses

7,032

3,540

Section 163(j) limitation

5,599

3,741

Depreciation and amortization

953

398

Other

132

169

Total deferred tax assets

330,857

341,974

Deferred tax liabilities:

Depreciation and amortization

Right of use assets

(21,115)

(29,165)

Total deferred tax liabilities

(21,115)

(29,165)

Valuation allowance

(309,742)

^[1]

(312,809)

$ (277,370)

$ (220,114)

Net deferred tax assets

$ 0

[1]	Prior period amounts have been retrospectively adjusted to reflect the effects of the Transaction.

401(k) Savings Plan - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
	Jan. 01, 2016	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Retirement Benefits [Abstract]
Employer match of employee contributions	50.00%
Employee deferral subject to employer match	6.00%
Employer contribution expenses		$ 1,068	$ 2,003	$ 1,921

Fair Value Measurements - Schedule of Level 3 Inputs to Warrant Liabilities (Detail)	Dec. 31, 2023
Fair Value, Option, Quantitative Disclosures [Line Items]
Volatility	101.00%
Warrant [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Term (in years)	1 year 3 months 18 days

Property and Equipment, Net - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 64,730	$ 66,692
Less: Accumulated depreciation and amortization	(53,196)	(49,078)
Property and equipment, net	11,534	17,614
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	24,468	24,665
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,924	3,672
Furniture and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	4,523	4,752
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	30,954	32,489
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 861	$ 1,114

Discontinued Operations and TSA - Gain on Sale of the VOWST Business (Parenthetical) (Details) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2024	Dec. 31, 2024
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Upfront Payment		$ 15,000	$ 15,000
SPN [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Upfront Payment	$ 15,000
Upfront Payment	17,857		17,857
Upfront payment satisfaction fees	2,355	$ 2,355	2,355
VOWST Business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Upfront Payment	$ 100,000		$ 100,000

Common Stock and Stock-Based Awards - Summary of Estimated Fair Value of Employee Stock Options (Details)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Employees Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.70%	3.64%	1.67%
Expected term (in years)	6 years	6 years	6 years
Expected volatility	76.20%	107.20%	104.00%
Expected dividend yield	0.00%	0.00%	0.00%
Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	5.16%	5.01%	2.11%
Expected term (in years)	6 months	6 months	6 months
Expected volatility	118.30%	79.10%	99.00%
Expected dividend yield	0.00%	0.00%	0.00%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2024