– Study results expected in the second half of 2017 –

CAMBRIDGE, MA, USA I June 5, 2017 I Seres Therapeutics, Inc. (NASDAQ:MCRB) today announced that it has completed enrollment for its ongoing SER-287 Phase 1b clinical study of 58 patients suffering from mild-to-moderate ulcerative colitis who are failing current therapies. SER-287 is the first microbiome therapeutic candidate to reach clinical‐stage development in a chronic inflammatory disease, and the first in an indication outside of infectious disease.

“The completion of enrollment in our SER-287 Phase 1b study marks an important step towards our goal of developing a novel microbiome-based approach to treat ulcerative colitis, a serious disease where many patients are not well managed by currently available therapies,” said Roger J. Pomerantz, M.D., President, Chief Executive Officer and Chairman of Seres. “We believe that SER-287 has the potential to offer ulcerative colitis patients a novel, non-immunosuppressive treatment option.”

Several encouraging proof-of-concept studies using repetitive fecal microbiota transplantation support the rationale for development of microbiome therapeutics in ulcerative colitis.1 The SER-287 Phase 1b study is a randomized, placebo-controlled, multiple-dose study in subjects with mild-to-moderate ulcerative colitis who are failing current therapies. The primary objectives of the study are to evaluate safety, tolerability and change in the microbiome at up to 8 weeks after dosing. Initial study results, including microbiome, clinical, and endoscopy data, are expected in the second half of 2017.

About SER-287

SER‐287 is a biologically sourced oral capsule developed using Seres’ proprietary microbiome therapeutics platform. The SER-287 Phase 1b study clinicaltrials.gov identifier is NCT02618187. In addition to SER-287, Seres’ pipeline in ulcerative colitis includes SER-301, a rationally designed, synthetic product comprised of in vitro cultured bacterial species for development in ulcerative colitis and other chronic gastrointestinal disorders with high unmet medical need.

About Ulcerative Colitis

Ulcerative colitis is a serious chronic condition affecting approximately 700,000 individuals in the United States. The disease results in inflammation of the colon and rectum and can cause debilitating symptoms, including abdominal pain, bowel urgency, and diarrhea. Severe cases of ulcerative colitis may result in surgical removal of the colon.

About Seres Therapeutics

Seres Therapeutics is a leading microbiome therapeutics platform company developing a novel class of biological drugs that are designed to treat disease by restoring the function of a dysbiotic microbiome, where the natural state of bacterial diversity and function is imbalanced. The company is planning to initiate the ECOSPOR III clinical study with its lead program, SER-109, in patients with multiply recurrent C. difficile infection. Seres’ second clinical candidate, SER-287, is being evaluated in a Phase 1b study in patients with mild-to-moderate ulcerative colitis. Seres is also developing SER-262, the first ever synthetic microbiome therapeutic candidate, in a Phase 1b study in patients with primary C. difficile infection. For more information, please visit www.serestherapeutics.com. Follow us on Twitter @SeresTx.

References

1. Moayyedi, P, et al., Gastroenterology. 2015; Paramsothy S. et al., The Lancet. 2017

SOURCE: Seres Therapeutics