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Nature of the Business and Basis of Presentation

1.	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 microbiome therapeutics platform company developing a novel class of biological drugs, which are designed to restore health by repairing the function of a dysbiotic microbiome. The Company’s lead product candidate, SER-109, is intended to prevent further recurrences of Clostridium difficile infection (“CDI”), a debilitating infection of the colon, and, if approved by the FDA, could be a first-in-field drug. Using its microbiome therapeutics platform, the Company is developing additional product candidates to treat diseases where the microbiome is implicated, including SER-262, a synthetic microbiome therapeutic, to prevent an initial recurrence of primary CDI, SER-287 to treat inflammatory bowel disease, including ulcerative colitis, SER-301, a synthetic ulcerative colitis product candidate, and SER-155, a synthetic product candidate, to prevent mortality following allogeneic hematopoietic stem cell transplantation (allo-HSCT) due to infections and graft-versus-host disease. The Company is also using its microbiome therapeutics platform to conduct research on metabolic diseases, such as non-alcoholic steatohepatitis (NASH); inflammatory diseases, such as Crohn’s disease; rare liver disorders such as primary sclerosing cholangitis (PSC); and immuno-oncology treatments using checkpoint inhibitors.

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. Product candidates currently under development will require significant additional research and development efforts, including extensive pre-clinical and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure and extensive compliance-reporting capabilities.

The Company’s product candidates are in development. 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, that any products developed will obtain necessary government regulatory approval or that any approved products 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. 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.

Unaudited Interim Financial Information

The accompanying unaudited consolidated financial statements as of June 30, 2016 and for the three and six months ended June 30, 2016 and 2015 have been prepared by the Company, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”) for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. These consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2015 included in the Company’s annual report on Form 10-K for the fiscal year ended December 31, 2015, which was filed with the U.S. Securities and Exchange Commission on March 14, 2016.

The unaudited interim financial statements have been prepared on the same basis as the audited consolidated financial statements. The condensed consolidated balance sheet at December 31, 2015 was derived from audited annual financial statements, but does not contain all of the footnote disclosures from the annual financial statements. In the opinion of management, the accompanying unaudited interim consolidated financial statements contain all adjustments which are necessary for a fair statement of the Company’s financial position as of June 30, 2016 and consolidated results of operations for the three and six months ended June 30, 2016 and its cash flows for the six months ended June 30, 2016 and 2015. Such adjustments are of a normal and recurring nature. The results of operations for the three and six months ended June 30, 2016 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2016.

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2016

Summary of Significant Accounting Policies

2.Summary of Significant Accounting Policies

The significant accounting policies and estimates used in preparation of the condensed consolidated financial statements are described in the Company’s audited financial statements as of and for the year ended December 31, 2015, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K. During the three and six months ended June 30, 2016, the Company recorded revenue in connection with its collaboration agreement. See Note 9, “Collaboration Revenue,” for additional information.

Use of Estimates

The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, equity, revenue and expenses, and related disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, revenue recognition, the accrual of research and development expenses and the valuation of stock-based awards. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from the Company’s estimates.

Fair Value Measurements

Certain assets and liabilities are carried at fair value under 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. Certain cash equivalents or investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The carrying values of the Company’s accounts payable and accrued expenses approximate their fair value due to the short-term nature of these liabilities.

The following table presents information about the Company’s assets as of June 30, 2016 and December 31, 2015 that are measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values (note there were no liabilities measured at fair value on a recurring basis in either of the periods presented):

	Fair Value Measurements as of June 30, 2016 Using:
	Level 1		Level 2		Level 3		Not Subject to Leveling ⁽¹⁾		Total
Assets:
Cash Equivalents	$	—	$	9,971	$	—	$	7,359	$	17,330
Repurchase Agreements		—		5,500		—		—		5,500
Investments:
Commercial Paper	$	—	$	45,471	$	—	$	—	$	45,471
Certificates of Deposit		—		13,271		—		—		13,271
Corporate Bonds		—		84,728		—		—		84,728
Government Securities		—		51,101		—		—		51,101
Treasury Bonds		—		18,050		—		—		18,050
	$	—	$	228,092	$	—	$	7,359	$	235,451
⁽¹⁾ Certain cash equivalents and investments that are valued using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy.

	Fair Value Measurements as of December 31, 2015 Using:
	Level 1		Level 2		Level 3		Not Subject to Leveling ⁽¹⁾		Total
Assets:
Cash Equivalents	$	—	$	11,952	$	—	$	11,173	$	23,125
Repurchase Agreements		—		20,000		—		—		20,000
Investments:
Commercial Paper	$	—	$	64,820	$	—	$	—	$	64,820
Corporate Bonds		—		46,490		—		—		46,490
Government Securities		—		15,819		—		—		15,819
Treasury Bonds		—		4,020		—		—		4,020
	$	—	$	163,101	$	—	$	11,173	$	174,274
⁽¹⁾ Certain cash equivalents and investments that are valued using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy.

As of June 30, 2016, the Company’s cash equivalents, which were invested in money market funds, corporate bonds, and repurchase agreements with original maturities of less than 90 days from the date of purchase, were valued based on Level 2 inputs. Repurchase agreements are agreements with banks to repurchase notes that are collateralized by U.S. government securities.

As of December 31, 2015, the Company’s cash equivalents consisted of money market funds, corporate bonds, commercial paper, government securities and repurchase agreements with original maturities of less than 90 days from the date of purchase and were valued based on Level 2 inputs. Repurchase agreements are agreements with banks to repurchase notes that are collateralized by U.S. government securities.

The fair value of the Company’s investments, which consisted of commercial paper, certificates of deposit, corporate bonds, government securities and treasury bonds as of June 30, 2016 and December 31, 2015 were determined using Level 2 inputs. During the three and six months ended June 30, 2016 there were no transfers between Level 1, Level 2 and Level 3.

Revenue recognition

The Company currently generates its revenue through collaboration and license arrangements with strategic partners for the development and commercialization of product candidates.

The Company recognizes revenue in accordance with FASB ASC Topic 605, Revenue Recognition (“ASC 605”). Accordingly, revenue is recognized for each unit of accounting when all of the following criteria are met:

Persuasive evidence of an arrangement exists

Delivery has occurred or services have been rendered

The seller’s price to the buyer is fixed or determinable

Collectability is reasonably assured

Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s consolidated balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, current portion. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as long-term deferred revenue.

Collaboration revenue

In January 2016 the Company entered into a Collaboration and License Agreement (the “License Agreement”) with Nestec Ltd. (“NHS”), an affiliate of Nestlé Health Science US Holdings, Inc. In connection with the License Agreement, the Company received an upfront, non-refundable payment of $120,000. Other non-refundable payments to the Company under this arrangement may include: (i) payments for research and development services, (ii) payments for the supply of clinical product, (iii) payments for the supply of commercial product, (iv) payments based on the achievement of certain development, regulatory, commercial, and sales-based milestones and (v) royalties on product sales.

The Company evaluates multiple-element arrangements based on the guidance in FASB ASC Topic 605-25, Revenue Recognition-Multiple-Element Arrangements (“ASC 605-25”). Pursuant to this guidance, the Company identifies the deliverables included in the arrangement and determines: (1) whether the individual deliverables have value to the customer on a standalone basis and represent separate units of accounting or whether they must be accounted for as a combined unit of accounting; and (2) if the arrangement includes a general right of return relative to the delivered item. This evaluation requires management to make judgments about the individual deliverables and whether such deliverables are separable from the other aspects of the contractual relationship. Deliverables are considered separate units of accounting provided that: (i) the delivered item(s) has value to the customer on a standalone basis and (ii) if the arrangement includes a general right of return relative to the delivered item(s), delivery or performance of the undelivered item(s) is considered probable and substantially in the control of the Company. In assessing whether an item has standalone value, the Company considers factors such as the research, manufacturing and commercialization capabilities of the collaboration partner, the retention of any key rights by the Company, and the availability of the associated expertise in the general marketplace. In addition, the Company considers whether the collaboration partner can use the other deliverable(s) for their intended purpose without the receipt of the remaining element(s), whether the value of the deliverable is dependent on the undelivered item(s) and whether there are other vendors that can provide the undelivered element(s).

In situations where the Company has identified multiple units of accounting, the arrangement consideration that is fixed or determinable is allocated among the separate units of accounting using the relative selling price method. The Company determines the selling price of a unit of accounting following the hierarchy of evidence prescribed by ASC 605-25. Accordingly, the Company determines the estimated selling price for units of accounting within each arrangement using vendor-specific objective evidence (“VSOE”) of selling price, if available, third-party evidence (“TPE”) of selling price if VSOE is not available, or best estimate of selling price (“BESP”) if neither VSOE nor TPE is available.

Then, the applicable revenue recognition criteria in ASC 605-25 are applied to each of the separate units of accounting to determine the appropriate period and pattern of recognition. The Company recognizes arrangement consideration allocated to each unit of accounting when all of the revenue recognition criteria in ASC 605-25 are satisfied for that particular unit of accounting. The Company will recognize as revenue, upon delivery, arrangement consideration attributed to licenses that have standalone value from the other deliverables to be provided in an arrangement. For licenses that do not have standalone value from the other deliverables to be provided in an arrangement over the Company’s estimated performance period as the arrangement would be accounted for as a single unit of accounting.

The Company recognizes arrangement consideration allocated to each unit of accounting when all of the revenue recognition criteria in ASC 605-25 are satisfied for that particular unit of accounting. The Company will recognize as revenue arrangement consideration attributed to licenses that have standalone value from the other deliverables to be provided in an arrangement upon delivery. The Company will recognize as revenue arrangement consideration attributed to licenses that do not have standalone value from the other deliverables to be provided in an arrangement over the Company’s estimated performance period as the arrangement would be accounted for as a single unit of accounting.

If there is no discernible pattern of performance and/or objectively measurable performance measures do not exist, then the Company recognizes revenue under the arrangement for the single unit of accounting on a straight-line basis over the period the Company is expected to complete its performance obligations. Alternatively, if the pattern of performance in which the service is provided to the customer can be determined and objectively measurable performance measures exist, then the Company recognizes revenue under the arrangement using the proportional performance method. Revenue recognized is limited to the lesser of the cumulative amount of payments received or the cumulative amount of revenue earned, as determined using the straight-line method or proportional performance method, as applicable.

At the inception of an arrangement that includes milestone payments, the Company evaluates whether each milestone is substantive and at risk to both parties on the basis of the contingent nature of the milestone. This evaluation includes an assessment of whether: (i) the consideration is commensurate with either the Company’s performance to achieve the milestone or the enhancement of the value of the delivered item(s) as a result of a specific outcome resulting from the Company’s performance to achieve the milestone, (ii) the consideration relates solely to past performance and (iii) the consideration is reasonable relative to all of the deliverables and payment terms within the arrangement. The Company evaluates factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the respective milestone and the level of effort and investment required to achieve the respective milestone in making this assessment. There is considerable judgment involved in determining whether a milestone satisfies all of the criteria required to conclude that a milestone is substantive. The Company recognizes revenue associated with substantive milestones in accordance with FASB ASC Topic 605-28, Revenue Recognition-Milestone Method upon successful accomplishment of each milestone, assuming all other revenue recognition criteria are met. Milestones that are not considered substantive would be recognized as revenue over the remaining period of performance, assuming all other revenue recognition criteria are met.

The Company will recognize royalty revenue in the period of sale of the related product(s), based on the underlying contract terms, provided that the reported sales are reliably measurable and the Company has no remaining performance obligations, assuming all other revenue recognition criteria are met.

Refer to footnote 9 for further information related to the Company’s collaboration and license agreement with Nestec, Ltd.

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 warrants and unvested restricted stock. The Company applied the two-class method to calculate its basic and diluted net loss per share attributable to common stockholders for the three and six months ended June 30, 2015, as its convertible preferred stock and common stock are participating securities. 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 the three and six months ended June 30, 2015 and preferred stockholders do not participate in losses.

The Company’s restricted stock awards granted by the Company 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.

The following potential common shares, presented based on amounts outstanding at each period end, were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:

	Three and Six Months Ended June 30,
	2016		2015
Stock options to purchase common stock		5,612,389		4,809,621
Unvested restricted common stock		—		1,250
Warrants for the purchase of common stock		—		92,127
		5,612,389		4,902,998

Recently Issued Accounting Standards

In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606), which supersedes all existing revenue recognition requirements, including most industry-specific guidance. The new standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, which delayed the effective date of the new standard from January 1, 2017 to January 1, 2018. The FASB also agreed to allow entities to choose to adopt the standard as of the original effective date. In March 2016, the FASB issued ASU 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations, which clarifies the implementation guidance on principal versus agent considerations. In April 2016, the FASB issued ASU 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing, which clarifies how a company identifies promised goods or services and clarifies whether an entity’s promise to grant a license provides a customer with either a right to use the entity’s intellectual property (which is satisfied at a point in time) or a right to access the entity’s intellectual property (which is satisfied over time). In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients related to disclosures of remaining performance obligations, as well as other amendments to guidance on collectibility, non-cash consideration and the presentation of sales and other similar taxes collected from customers. We are currently evaluating the method of adoption and the potential impact that Topic 606 may have on our financial position and results of operations.

In May 2015, the FASB issued ASU 2015-07, Fair Value Measurement (Topic 820): Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent). The new standard removes the requirement to categorize within the fair value hierarchy all investments for which fair value is measured using the net asset value per share practical expedient. The new standard became effective for us on January 1, 2016. Refer to the Fair Value Measurements significant accounting policy for the impact of this change.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e. lessees and lessors). The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight line basis over the term of the lease, respectively. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases today. ASC 842 supersedes the previous leases standard, ASC 840 Leases. The standard is effective on January 1, 2019, with early adoption permitted. The Company is in the process of evaluating the impact of this new guidance.

In March 2016, the FASB issued ASU 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting, which amends the accounting for employee share-based payment transactions to require recognition of the tax effects resulting from the settlement of stock-based awards as income tax expense or benefit in the income statement in the reporting period in which they occur. In addition, the ASU requires that all tax-related cash flows resulting from share-based payments, including the excess tax benefits related to the settlement of stock-based awards, be classified as cash flows from operating activities in the statement of cash flows. The ASU also requires that cash paid by directly withholding shares for tax withholding purposes be classified as a financing activity in the statement of cash flows. In addition, the ASU also allows companies to make an accounting policy election to either estimate the number of awards that are expected to vest, consistent with current U.S. GAAP, or account for forfeitures when they occur. The new standard is effective for annual reporting periods beginning after December 15, 2016 with early adoption permitted. The Company is in the process of evaluating the impact of this new guidance.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The new standard changes the impairment model for most financial assets and certain other instruments. Under the new standard, entities holding financial assets and net investment in leases that are not accounted for at fair value through net income to be presented at the net amount expected to be collected. An allowance for credit losses will be a valuation account that will be deducted from the amortized cost basis of the financial asset to present the net carrying value at the amount expected to be collected on the financial asset. The new standard will be effective for the Company on January 1, 2020. The adoption of this standard is not expected to have a material impact on the Company’s financial position or results of operations.

Reclassifications

Certain amounts reported in the prior year financial statements have been reclassified for comparative purposes to conform with the presentation in the current year condensed consolidated financial statements.

Investments

6 Months Ended

Jun. 30, 2016

Investments Debt And Equity Securities [Abstract]

Property Plant And Equipment [Abstract]

3.	Investments

As of June 30, 2016 and December 31, 2015, the fair value of available-for-sale investments by type of security was as follows:

	June 30, 2016
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Investments:
Commercial Paper	$	45,413	$	58	$	—		$	45,471
Certificates of Deposit	$	13,271	$	—		—		$	13,271
Corporate Bonds		84,736		27		(35	)		84,728
Government Securities		51,088		16		(3	)		51,101
Treasury Bonds		18,029		21		—			18,050
	$	212,537	$	122	$	(38	)	$	212,621

	December 31, 2015
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Investments:
Commercial Paper	$	64,733	$	87	$	—		$	64,820
Corporate Bonds		46,538		—		(48	)		46,490
Government Securities		15,823		—		(4	)		15,819
Treasury Bonds		4,022		—		(2	)		4,020
	$	131,116	$	87	$	(54	)	$	131,149

Investments with original maturities of less than 90 days are included in cash and cash equivalents on the consolidated balance sheets and are not included in the table above. Investments with maturities of less than 12 months are considered current and those investments with maturities greater than 12 months are considered non-current.

As of December 31, 2015, the Company’s commercial paper, corporate bonds, government securities and treasury bonds had remaining maturities of less than 12 months.

- Definition

The entire disclosure for investments in certain debt and equity securities.

+ References + Details

Property and Equipment, Net

6 Months Ended

Jun. 30, 2016

Property and Equipment, Net

4.	Property and Equipment, Net

Property and equipment, net consisted of the following:

	June 30, 2016			December 31, 2015
Laboratory equipment	$	6,804		$	4,370
Computer equipment		971			408
Furniture and office equipment		788			285
Leasehold improvements		9,965			1,856
Construction in progress		10,692			1,843
		29,220			8,762
Less: Accumulated depreciation and amortization		(2,235	)		(1,011	)
	$	26,985		$	7,751

Construction in progress at June 30, 2016 was comprised primarily of leasehold improvements and laboratory equipment purchased in connection with the build-out of office and laboratory space at our new headquarters at 200 Sidney Street in Cambridge, Massachusetts.

Depreciation and amortization expense was $874, $1,260, $119 and $212 for the three and six months ended June 30, 2016 and 2015, respectively.

Accrued Expenses and Other Current Liabilities

6 Months Ended

Jun. 30, 2016

Payables And Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

5.	Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following:

	June 30, 2016		December 31, 2015
Development and manufacturing costs	$	3,258	$	1,436
Payroll and payroll-related costs		2,375		2,756
Professional fees		449		184
Facility		4,662		1,053
Other		121		94
	$	10,865	$	5,523

Preferred Stock Warrant Liability

6 Months Ended

Jun. 30, 2016

Class Of Stock Disclosures [Abstract]

Preferred Stock Warrant Liability

6.	Preferred Stock Warrant Liability

In September 2013, the Company issued a warrant to purchase 92,127 shares of Series A-2 convertible preferred stock in connection with its loan and security agreement. The warrant was immediately exercisable at an exercise price of $1.78 per share and has a contractual term of ten years from issuance. The fair value of the warrant at issuance was estimated to be $156 and was recorded as a debt discount and as a preferred stock warrant liability.

The Company classified the warrant to purchase shares of its Series A-2 convertible preferred stock as a liability on its consolidated balance sheets and subsequently re-measured to fair value at each balance sheet date. Changes in fair value of the warrant were recognized as a component of other income (expense), net, in the consolidated statement of operations and comprehensive loss.

In connection with the automatic conversion of the Company’s convertible preferred stock, which occurred upon the listing of the Company’s common stock on the NASDAQ on June 26, 2015, the preferred stock warrant became a warrant to purchase common stock. The Company performed the final mark to market adjustment on the preferred stock warrant using the fair value of the underlying common shares of $18.00 per share on June 26, 2015 and recorded the change in fair value in other income (expense), net in the consolidated statement of operations and comprehensive loss. The preferred stock warrant liability was then reclassified to additional paid-in-capital as it became a warrant to purchase common stock.

There was no balance related to the preferred stock warrant liability as of June 30, 2016 and December 31, 2015.

The Company recorded losses of $220 and $7 for the three and six months ended June 30, 2015 to reflect the change in fair value of this preferred stock warrant.

The following assumptions and inputs were used in determining the fair value of the preferred stock warrant liability valued using the Black-Scholes option-pricing model:

	Six Months Ended June 30,
	2015
Risk-free interest rate		2.40	%
Expected term (in years)		8.2
Expected volatility		91.2	%
Expected dividend yield		0	%
Fair value of Series A-2 convertible preferred stock	$	17.26

Preferred Stock

6 Months Ended

Jun. 30, 2016

Equity [Abstract]

Preferred Stock

7.	Preferred Stock

On July 1, 2015, in connection with the closing of the 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.

Stockholders’ Equity Common Stock

6 Months Ended

Jun. 30, 2016

Equity [Abstract]

Stockholders’ Equity Common Stock

8.	Stockholders’ Equity Common Stock

On July 1, 2015, the Company completed an IPO, and issued and sold 8,545,138 shares of common stock at a public offering price of $18.00 per share, resulting in net proceeds of approximately $139,267 after deducting underwriting discounts and commissions and other offering expenses totaling $3,748. The shares issued upon closing of the IPO included 1,114,583 shares of the Company’s common stock, which were sold to the underwriters pursuant to the full exercise of their option to purchase additional shares of common stock. Upon the listing of the Company’s common stock on the NASDAQ on June 26, 2015, all outstanding shares of the Company’s convertible preferred stock automatically converted into 22,866,987 shares of the Company’s common stock.

As of December 31, 2014, the Company’s Amended and Restated Certificate of Incorporation, as further amended, authorized the Company to issue 38,000,000 shares of common stock, $0.001 par value per share. On July 1, 2015, in connection with the closing of the IPO, the Company effected its Restated Certificate of Incorporation, which authorizes the Company to issue 200,000,000 shares of common stock, $0.001 par value per share.

Stock Options

The following table summarizes the Company’s stock option activity since December 31, 2015:

	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)
Outstanding as of December 31, 2015		5,026,246		$	8.01		8.70	$	136,945
Granted		1,418,625			28.05
Exercised		(777,138	)		1.21
Forfeited		(55,344	)		13.48
Outstanding as of June 30, 2016		5,612,389		$	13.96		8.41	$	88,441
Options exercisable as of June 30, 2016		1,793,436		$	6.00		7.52	$	41,438
Options vested and expected to vest as of June 30, 2016		5,491,857		$	13.85		8.40	$	87,103

The weighted average grant-date fair value of stock options granted during the three and six months ended June 30, 2016 was $20.64 and $19.87 per share, respectively.

The Company has granted performance-based stock options to certain employees. These stock options are exercisable only upon achievement of specified performance targets. As of June 30, 2016, none of these options were exercisable because none of the specified performance targets had been achieved. During the three months ended June 30, 2016, the Company has determined that the achievement of 60,000 of these specified performance targets is probable and has recorded expense of $212. The grant date fair value of these awards was $3.92 per share.

Stock-based Compensation Expense

The Company recorded stock-based compensation expense related to stock options and restricted common stock in the following expense categories of its consolidated statements of operations and comprehensive loss:

	Three Months Ended June 30,				Six Months Ended June 30,
	2016		2015		2016		2015
Research and development expenses	$	2,896	$	1,891	$	5,082	$	2,514
General and administrative expenses		1,821		1,182		3,539		1,886
	$	4,717	$	3,073	$	8,621	$	4,400

Collaboration Revenue

6 Months Ended

Jun. 30, 2016

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Collaboration Revenue

9.	Collaboration Revenue

Nestec Ltd.

In January 2016 the Company entered into a Collaboration and License Agreement with Nestec Ltd. (“NHS”), an affiliate of Nestlé Health Science US Holdings, Inc., a significant stockholder of the Company, for the development and commercialization of certain product candidates in development for the treatment and management of CDI and IBD, including ulcerative colitis and Crohn’s disease. The License Agreement will support the development of the Company’s portfolio of products for CDI and IBD in markets outside of the United States and Canada (“the Licensed Territory”). The Company has retained full commercial rights to its entire portfolio of product candidates with respect to the United States and Canada.

Under the License Agreement, the Company granted to NHS an exclusive, royalty-bearing license to develop and commercialize, in the Licensed Territory, certain products based on its microbiome technology that are being developed for the treatment of CDI and IBD, including SER-109, SER-262, SER-287 and SER-301, or, collectively, the NHS Collaboration Products. The License Agreement sets forth the Company’s and NHS’ respective obligations for development, commercialization, regulatory and manufacturing and supply activities for the NHS Collaboration Products with respect to the licensed fields and the Licensed Territory.

Under the License Agreement, the Company’s and NHS’ development activities will be governed by global and regional development plans, including the conduct of additional clinical studies. The Company has agreed to manufacture and supply NHS Collaboration Products to support development and commercialization of NHS Collaboration Products in the licensed fields and in the Licensed Territory. NHS will have the right to obligate the Company to transfer technology necessary to manufacture Collaboration Products in the event that the Company materially fails to meet its supply commitments to NHS under the commercial supply agreement. The Company has also agreed to use diligent efforts to develop NHS Collaboration Products under a global development plan and to obtain approval for such NHS Collaboration Products in the European Union, or EU.

In exchange for the license, NHS agreed to pay the Company an upfront cash payment of $120,000, which the Company received in February 2016. NHS also agreed to pay the Company tiered royalties, at percentages ranging from the high single digits to high teens, of net sales of NHS Collaboration Products in the Licensed Territory. The Company is eligible to receive up to $295,000 in development milestone payments, $365,000 in regulatory payments and up to an aggregate of $1,125,000 for the achievement of certain commercial milestones related to the sales of NHS Collaboration Products.

For the development of NHS Collaboration Products for IBD under a global development plan, the Company agreed to pay the costs of clinical trials of such products up to and including Phase 2 clinical trials, and 67% of the costs for Phase 3 and other clinical trials of such products, with NHS bearing the remaining 33% of such costs. For other clinical development of NHS Collaboration Products for IBD, the Company agreed to pay the costs of such activities to support approval in the United States and Canada, and NHS agreed to bear the cost of such activities to support approval of NHS Collaboration Products in the Licensed Territory.

With respect to development of NHS Collaboration Products for CDI under a global development plan, the Company agreed to pay all costs of an ongoing Phase 2 clinical trial for SER-109 and of Phase 3 clinical trials for SER-109. The Company agreed to bear all costs of conducting any Phase 1 or Phase 2 clinical trials under a global development plan for NHS Collaboration Products other than SER-109 for CDI. The Company agreed to pay 67% and NHS agreed to pay 33% of other costs of Phase 3 clinical trials conducted for NHS Collaboration Products other than SER-109 for CDI under a global development plan. For other clinical development of NHS Collaboration Products for CDI, the Company agreed to pay costs of such development activities to support approval in the United States and Canada, and NHS agreed to bear the cost of such activities to support approval of NHS Collaboration Products in the Licensed Territory.

The License Agreement continues in effect until terminated by either the Company or NHS on the following bases: (i) NHS may terminate the License Agreement in the event of serious safety issues related to any of the NHS Collaboration Products; (ii) the Company may terminate the License Agreement if NHS challenges the validity or enforceability of any of our licensed patents; and (iii) either the Company or NHS may terminate the License Agreement in the event of the other party’s uncured material breach or insolvency. Upon termination of the License Agreement, all licenses granted to NHS by the Company will terminate, and all rights in and to the NHS Collaboration Products in the Licensed Territory will revert to the Company. If the Company commits a material breach of the License Agreement, NHS may elect not to terminate the License Agreement but instead apply specified adjustments to its payment obligations and other terms and conditions of the License Agreement.

The License Agreement contains customary representations and warranties, intellectual property protection provisions, certain indemnification rights in favor of each party and customary confidentiality provisions and limitations of liability.

At the inception of the License Agreement, the Company identified the following deliverables: (i) a license to develop and commercialize the NHS Collaboration Products in the Licensed Territory, (ii) obligation to perform research and development services, (iii) participation on a joint steering committee (“JSC”), and (iv) manufacturing services to provide clinical supply to complete future clinical trials. The Company also identified a contingent deliverable, the obligation to perform manufacturing services to provide commercial supply if commercialization occurs, which is contingent upon regulatory approval. This contingent deliverable has been excluded from the initial allocation and will be treated as a separate unit of accounting when and if delivered.

The Company concluded that none of the four deliverables identified at the inception of the License Agreement has standalone value from the other undelivered elements. Accordingly, all deliverables represent a single unit of accounting.

All consideration received relating to the four identified deliverables that comprise the single unit of accounting will be recognized over the period of performance. The period of performance will be through the completion of development services for the NHS Collaboration Products which has been estimated to be ten years. The Company will periodically review and, if necessary, revise the estimated development period.

The Company will recognize revenue utilizing a time-based proportional performance model where revenue related to each payment is recognized over the ten year performance period. As of June 30, 2016, the only consideration that is fixed and determinable is the non-refundable upfront payment of $120,000 and $97 for the reimbursement of development services since the inception of the arrangement. For additional consideration that could be received for research and development services and/or manufacturing services for clinical supply, the Company will recognize a cumulative catch-up for the amount of time that has elapsed and spread the unrecognized portion over the remaining performance period.

Development and regulatory milestones that involve substantial effort on the Company’s part and the achievement of which are not considered probable at the inception of the License Agreement are considered substantive milestones, and will be recognized in their entirety in the period in which the milestone is achieved, assuming all other revenue recognition criteria are met. All commercial milestones will be recorded as revenue upon achievement of the milestone, assuming all other revenue recognition criteria are met.

Royalties will be recorded as revenue in the period they are earned assuming all other revenue recognition criteria are met.

During the three and six months ended June 30, 2016, the Company recognized $3,004 and $5,714, respectively, of related party revenue associated with the License Agreement. As of June 30, 2016, there was $114,383 of deferred revenue related to the License Agreement, which is classified as current or non-current in the consolidated balance sheets based on the Company’s estimate of revenue that will be recognized within the next twelve months. All costs associated with the License Agreement are recorded in research and development expense in the condensed consolidated statements of operations and comprehensive loss.

Income Taxes

6 Months Ended

Jun. 30, 2016

Income Tax Disclosure [Abstract]

Income Taxes

10.	Income Taxes

The Company did not provide for any income taxes for six month period ended June 30, 2016 or 2015.

The Company has evaluated the positive and negative evidence bearing upon the realizability of its U.S. net deferred tax assets. As required by the provisions of ASC 740, Income Taxes, management has determined that it is more-likely-than-not that the Company will not utilize the benefits of federal and state U.S. net deferred tax assets for financial reporting purposes. Accordingly, the net deferred tax assets are subject to a valuation allowance at June 30, 2016 and December 31, 2015.

As of June 30, 2016 and December 31, 2015, the Company had no accrued interest or tax penalties recorded. The Company files income tax returns in the U.S. and various state jurisdictions. The Company is no longer subject to U.S. federal income tax examinations by tax authorities for years before 2012. However, to the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated my still be adjusted upon examination by the Internal Revenue Service or state tax authorizes to the extent it is utilized in a future period. There are no currently ongoing or pending examinations in any jurisdictions.

Commitments and Contingencies

6 Months Ended

Jun. 30, 2016

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

11.	Commitments and Contingencies

Leases

The Company previously leased office and laboratory space with a lease term expiring in January 2018 and no extension periods. In May 2016, upon mutual agreement with the landlord, the Company accelerated the termination of the operating lease to June 30, 2016. Upon termination of the lease, the Company recorded a benefit to rent expense of $136 to write off amounts previously recorded as deferred rent. The outstanding security deposit of $119, which is secured by a cash collateralized letter of credit, will remain in place until 90 days after termination in accordance with the original lease.

On November 11, 2015, the Company entered into a non-cancelable property lease with BMR-Sidney Research Campus LLC (“BMR”) for 83,396 square feet of office, laboratory and pilot manufacturing space at 200 Sidney Street, Cambridge, Massachusetts. The lease term commenced in March 2016 and ends in November 2023. The Company has the option to extend the lease twice, each for a five-year period. The Company moved its corporate headquarters to this location in April 2016. BMR will contribute a total of $12,509 toward the cost of tenant improvements. BMR’s contribution toward the cost of tenant improvements is recorded as a lease incentive obligation on our consolidated balance sheet. The lease incentive obligation is amortized to our consolidated statement of operations as reductions to rent expense over the lease term. As of June 30, 2016, we have recorded a lease incentive obligation of $9,119.

During the three and six months ended June 30, 2016 and 2015, the Company recognized $787, $1,180, $354 and $540, respectively, of rental expense related to office and laboratory space.

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 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 June 30, 2016 or December 31, 2015.

Related Party Transactions

6 Months Ended

Jun. 30, 2016

Related Party Transactions

12.	Related Party Transactions

In October 2010, the Company entered into a services agreement with Flagship Ventures Management, Inc., an affiliate of one of its stockholders, Flagship Venture Funds, to provide general and administrative services to the Company, including the employer portions of employee health and dental benefit plans for Seres Therapeutics employees and consulting services. The Company made payments under the agreement of $1, $17, $131 and $249 during the three and six months ended June 30, 2016 and 2015, respectively. There were no amounts due to Flagship Ventures Management, Inc. related to the services agreement as of June 30, 2016 and December 31, 2015.

As described in Note 9, in January 2016 the Company entered into a License Agreement with NHS for the development and commercialization of certain product candidates in development for the treatment and management of CDI and IBD, including ulcerative colitis and Crohn’s disease. NHS is a related party since NHS is an affiliate of Nestlé Health Science, one of the Company’s significant stockholders. During the three and six months ended June 30, 2016, the Company recognized $3,004 and $5,714 of related party revenue associated with the License Agreement. As of June 30, 2016, there was $114,383 of deferred revenue related to the License Agreement, which is classified as current or non-current in the consolidated balance sheets. The Company has made no payments to NHS during the three and six months ended June 30, 2016. There is $97 due from NHS as of June 30, 2016 for the reimbursement of development costs.

401(k) Savings Plan

6 Months Ended

Jun. 30, 2016

Compensation And Retirement Disclosure [Abstract]

401(k) Savings Plan

13.	401(k) Savings Plan

The Company has a defined contribution savings plan under Section 401(k) of the Internal Revenue Code. 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 has 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 three and six months ended June 30, 2016, the Company recorded expense of $188 for accrued 401(k) match contributions.

Subsequent Events	6 Months Ended
Subsequent Events	Jun. 30, 2016
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events On August 2, 2016, the Company notified its Phase 3 SER-109 clinical research organization (“CRO”) partner that it intends to terminate its agreement with the CRO for work in connection with a planned global, pivotal Phase 3 trial for SER-109. The work performed to date under this agreement was tied to start-up activities of the planned trial. The Company has $690 of prepaid expense related to this agreement on its balance sheet as of June 30, 2016. The Company expects a portion of this amount to be recorded as research and development expense during the remainder of the year ending December 31, 2016.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2016

Recently Issued Accounting Standards

Use of Estimates

Fair Value Measurements

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

	Fair Value Measurements as of June 30, 2016 Using:
	Level 1		Level 2		Level 3		Not Subject to Leveling ⁽¹⁾		Total
Assets:
Cash Equivalents	$	—	$	9,971	$	—	$	7,359	$	17,330
Repurchase Agreements		—		5,500		—		—		5,500
Investments:
Commercial Paper	$	—	$	45,471	$	—	$	—	$	45,471
Certificates of Deposit		—		13,271		—		—		13,271
Corporate Bonds		—		84,728		—		—		84,728
Government Securities		—		51,101		—		—		51,101
Treasury Bonds		—		18,050		—		—		18,050
	$	—	$	228,092	$	—	$	7,359	$	235,451
⁽¹⁾ Certain cash equivalents and investments that are valued using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy.

	Fair Value Measurements as of December 31, 2015 Using:
	Level 1		Level 2		Level 3		Not Subject to Leveling ⁽¹⁾		Total
Assets:
Cash Equivalents	$	—	$	11,952	$	—	$	11,173	$	23,125
Repurchase Agreements		—		20,000		—		—		20,000
Investments:
Commercial Paper	$	—	$	64,820	$	—	$	—	$	64,820
Corporate Bonds		—		46,490		—		—		46,490
Government Securities		—		15,819		—		—		15,819
Treasury Bonds		—		4,020		—		—		4,020
	$	—	$	163,101	$	—	$	11,173	$	174,274
⁽¹⁾ Certain cash equivalents and investments that are valued using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy.

Revenue recognition

The Company currently generates its revenue through collaboration and license arrangements with strategic partners for the development and commercialization of product candidates.

Persuasive evidence of an arrangement exists

Delivery has occurred or services have been rendered

The seller’s price to the buyer is fixed or determinable

Collectability is reasonably assured

Collaboration revenue

Refer to footnote 9 for further information related to the Company’s collaboration and license agreement with Nestec, Ltd.

Net Loss per Share

	Three and Six Months Ended June 30,
	2016		2015
Stock options to purchase common stock		5,612,389		4,809,621
Unvested restricted common stock		—		1,250
Warrants for the purchase of common stock		—		92,127
		5,612,389		4,902,998

Reclassifications

Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2016

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

	Fair Value Measurements as of June 30, 2016 Using:
	Level 1		Level 2		Level 3		Not Subject to Leveling ⁽¹⁾		Total
Assets:
Cash Equivalents	$	—	$	9,971	$	—	$	7,359	$	17,330
Repurchase Agreements		—		5,500		—		—		5,500
Investments:
Commercial Paper	$	—	$	45,471	$	—	$	—	$	45,471
Certificates of Deposit		—		13,271		—		—		13,271
Corporate Bonds		—		84,728		—		—		84,728
Government Securities		—		51,101		—		—		51,101
Treasury Bonds		—		18,050		—		—		18,050
	$	—	$	228,092	$	—	$	7,359	$	235,451
⁽¹⁾ Certain cash equivalents and investments that are valued using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy.

	Fair Value Measurements as of December 31, 2015 Using:
	Level 1		Level 2		Level 3		Not Subject to Leveling ⁽¹⁾		Total
Assets:
Cash Equivalents	$	—	$	11,952	$	—	$	11,173	$	23,125
Repurchase Agreements		—		20,000		—		—		20,000
Investments:
Commercial Paper	$	—	$	64,820	$	—	$	—	$	64,820
Corporate Bonds		—		46,490		—		—		46,490
Government Securities		—		15,819		—		—		15,819
Treasury Bonds		—		4,020		—		—		4,020
	$	—	$	163,101	$	—	$	11,173	$	174,274
⁽¹⁾ Certain cash equivalents and investments that are valued using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy.

Summary of Potential Common Shares Excluded from Calculation of Diluted Net Loss per Share

	Three and Six Months Ended June 30,
	2016		2015
Stock options to purchase common stock		5,612,389		4,809,621
Unvested restricted common stock		—		1,250
Warrants for the purchase of common stock		—		92,127
		5,612,389		4,902,998

Investments (Tables)

6 Months Ended

Jun. 30, 2016

Investments Debt And Equity Securities [Abstract]

Schedule of Fair Value of Available-for-Sale Investments by Type of Security

As of June 30, 2016 and December 31, 2015, the fair value of available-for-sale investments by type of security was as follows:

	June 30, 2016
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Investments:
Commercial Paper	$	45,413	$	58	$	—		$	45,471
Certificates of Deposit	$	13,271	$	—		—		$	13,271
Corporate Bonds		84,736		27		(35	)		84,728
Government Securities		51,088		16		(3	)		51,101
Treasury Bonds		18,029		21		—			18,050
	$	212,537	$	122	$	(38	)	$	212,621

	December 31, 2015
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Investments:
Commercial Paper	$	64,733	$	87	$	—		$	64,820
Corporate Bonds		46,538		—		(48	)		46,490
Government Securities		15,823		—		(4	)		15,819
Treasury Bonds		4,022		—		(2	)		4,020
	$	131,116	$	87	$	(54	)	$	131,149

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Property and Equipment, Net (Tables)

6 Months Ended

Jun. 30, 2016

Property Plant And Equipment [Abstract]

Schedule of Property and Equipment, Net

Property and equipment, net consisted of the following:

	June 30, 2016			December 31, 2015
Laboratory equipment	$	6,804		$	4,370
Computer equipment		971			408
Furniture and office equipment		788			285
Leasehold improvements		9,965			1,856
Construction in progress		10,692			1,843
		29,220			8,762
Less: Accumulated depreciation and amortization		(2,235	)		(1,011	)
	$	26,985		$	7,751

Accrued Expenses and Other Current Liabilities (Tables)

6 Months Ended

Jun. 30, 2016

Payables And Accruals [Abstract]

Summary of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following:

	June 30, 2016		December 31, 2015
Development and manufacturing costs	$	3,258	$	1,436
Payroll and payroll-related costs		2,375		2,756
Professional fees		449		184
Facility		4,662		1,053
Other		121		94
	$	10,865	$	5,523

Preferred Stock Warrant Liability (Tables)

6 Months Ended

Jun. 30, 2016

Class Of Stock Disclosures [Abstract]

Summary of Assumptions and Inputs Used in Determining Fair Value of Preferred Stock Warrant Liability Valued Using Black-Scholes Option-Pricing Model

The following assumptions and inputs were used in determining the fair value of the preferred stock warrant liability valued using the Black-Scholes option-pricing model:

	Six Months Ended June 30,
	2015
Risk-free interest rate		2.40	%
Expected term (in years)		8.2
Expected volatility		91.2	%
Expected dividend yield		0	%
Fair value of Series A-2 convertible preferred stock	$	17.26

Stockholders’ Equity Common Stock (Tables)

6 Months Ended

Jun. 30, 2016

Equity [Abstract]

Summary of Stock Option Activity

The following table summarizes the Company’s stock option activity since December 31, 2015:

	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)
Outstanding as of December 31, 2015		5,026,246		$	8.01		8.70	$	136,945
Granted		1,418,625			28.05
Exercised		(777,138	)		1.21
Forfeited		(55,344	)		13.48
Outstanding as of June 30, 2016		5,612,389		$	13.96		8.41	$	88,441
Options exercisable as of June 30, 2016		1,793,436		$	6.00		7.52	$	41,438
Options vested and expected to vest as of June 30, 2016		5,491,857		$	13.85		8.40	$	87,103

Summary of Stock Based Compensation Expense

	Three Months Ended June 30,				Six Months Ended June 30,
	2016		2015		2016		2015
Research and development expenses	$	2,896	$	1,891	$	5,082	$	2,514
General and administrative expenses		1,821		1,182		3,539		1,886
	$	4,717	$	3,073	$	8,621	$	4,400

Nature of the Business and Basis of Presentation - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Entity incorporated year	Oct. 31, 2010
Entity incorporated state name	State of Delaware

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	1 Months Ended	6 Months Ended
	Feb. 29, 2016	Jun. 30, 2016	Dec. 31, 2015
Accounting Policies [Line Items]
Fair value of liabilities on recurring basis		$ 0	$ 0
Fair value, assets transfers from Level 1 to Level 2 measurement		0
Fair value, assets transfers from Level 2 to Level 1 measurement		0
Fair Value, assets transfers into (out of) Level 3 measurement		0
Nestlé Health Science [Member]
Accounting Policies [Line Items]
Upfront non-refundable payment	$ 120,000,000	$ 120,000,000

Summary of Significant Accounting Policies - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($)
$ in Thousands

Jun. 30, 2016

Dec. 31, 2015

Assets:

Cash Equivalents

$ 17,330

$ 23,125

Repurchase Agreements

5,500

20,000

Fair Value, Inputs, Level 2 [Member]

Total assets

235,451

174,274

Assets:

Cash Equivalents

9,971

11,952

Repurchase Agreements

5,500

20,000

Not Subject to Leveling [Member]

Total assets

228,092

163,101

Assets:

Cash Equivalents

^[1]

7,359

11,173

Commercial Paper [Member]

Total assets

^[1]

7,359

11,173

Commercial Paper [Member] | Fair Value, Inputs, Level 2 [Member]

45,471

64,820

Certificates of Deposit [Member]

45,471

64,820

Certificates of Deposit [Member] | Fair Value, Inputs, Level 2 [Member]

13,271

13,271

Corporate Bonds [Member]

Corporate Bonds [Member] | Fair Value, Inputs, Level 2 [Member]

84,728

46,490

Government Securities [Member]

84,728

46,490

Government Securities [Member] | Fair Value, Inputs, Level 2 [Member]

51,101

15,819

51,101

15,819

Treasury Bonds [Member]

Treasury Bonds [Member] | Fair Value, Inputs, Level 2 [Member]

18,050

4,020