Entry into a Material Definitive Agreement.
Pursuant to the terms of the collaboration and license agreement between Seres Therapeutics, Inc. (the Company) and Nestec Ltd.
(NHS), dated January 9, 2016, the Company is entitled to receive a $20.0 million milestone payment from NHS following initiation of a SER-287 Phase 2 study and a $20.0 million
milestone payment from NHS following the initiation of a SER-287 Phase 3 study. On November 1, 2018 the Company entered into a letter agreement with NHS that modified the collaboration and license
agreement to address the current clinical plans for SER-287. The Company has designed a SER-287 Phase 2 study as a Phase 2b study that may potentially be a pivotal trial
and is awaiting feedback from the U.S. Food and Drug Administration on this study design. Pursuant to the letter agreement, the Company and NHS agreed that following initiation of the SER-287 Phase 2b study,
the Company is entitled to receive $40.0 million in milestone payments from NHS. The letter agreement also provides scenarios under which NHS reimbursement to the Company for certain Phase 3 development costs would be reduced or delayed
depending on the outcomes of the SER-287 Phase 2b study.