Seres Therapeutics, Inc. (NASDAQ: MCRB) today announced that it has dosed the first patient in its Phase 1b trial evaluating SER-301 for the treatment of active mild-to-moderate ulcerative colitis (UC). SER-301 is an oral, rationally-designed microbiome therapeutic designed to dampen the aberrant gastrointestinal inflammation central to ulcerative colitis and induce clinical remission in patients suffering from active UC.

SER-301 is designed to modify the gastrointestinal microbiome and microbe-associated metabolites to modulate multiple pathways associated with ulcerative colitis. SER-301 is a consortium of bacteria designed using Seres’ reverse translational discovery platform that incorporates analysis of microbiome biomarkers from human clinical data and preclinical assessments using human cell-based assays and in vitro and in vivo disease models. SER-301 is designed to reduce induction of pro-inflammatory activity, improve epithelial barrier integrity and TNF-α driven inflammation in intestinal epithelial cells, and modulate UC-relevant anti-inflammatory, innate and adaptive immune pathways. The design of SER-301 incorporated learnings obtained through the Company’s prior SER-287 Phase 1b clinical study conducted in patients with ulcerative colitis. SER-287 Phase 1b study results demonstrated favorable pharmacodynamic changes, signals of clinical activity, and a favorable safety profile.

SER-301 was developed with innovative and novel manufacturing methods that do not require human donor material. It includes strains delivered in spore form and strains fermented in non-spore (vegetative) form. The product candidate is delivered using enterically-protected technology designed to release in the colon. GMP manufacturing technologies developed through the SER-301 program broaden the breadth of biology that can be incorporated into Seres’ microbiome therapeutics.

“Ulcerative colitis is a serious disease impacting approximately 700,000 individuals in the U.S. alone, and effective patient management can be challenging. Currently approved treatments are unable to induce disease remission in the large majority of patients, and many existing drugs are associated with a suboptimal safety profile,” said Matthew Henn, Ph.D., Executive Vice President and Chief Scientific Officer of Seres. “We believe that microbiome therapeutic approaches have the opportunity to address this condition in an entirely novel way which targets the underlying drivers of disease by modulating multiple disease-relevant pathways simultaneously, and with a favorable safety profile. We are pleased to have applied the deep scientific and clinical learnings obtained from our SER-287 and other clinical programs combined with our advanced microbiology and functional modeling capabilities to bring SER-301 into this Phase 1b study.”

The SER-301 Phase 1b study is being conducted in Australia and New Zealand in subjects with mild-to-moderate UC and is designed to include approximately 65 patients distributed across two cohorts. A first open-label cohort of 15 subjects will evaluate safety and pharmacokinetics (PK), as measured by bacterial engraftment. In the second cohort, 50 subjects will be randomized to receive either SER-301 or placebo, with a 3:2 randomization, respectively. The study utilizes an independent blinded central reader for the endoscopic component. The objectives for this cohort are to evaluate safety and PK, clinical remission, and other measures of drug pharmacology and efficacy as secondary endpoints.

Seres is entitled to receive a $10 million milestone payment associated with the clinical trial initiation from Nestlé Health Science, the Company’s ex-North American collaborative partner for this program.

About SER-301

SER-301 is an investigational, oral, rationally-designed, fermented microbiome therapeutic for the treatment of mild-to-moderate ulcerative colitis (UC). SER-301 is a consortium of multiple bacterial strains manufactured by fermenting each strain individually and then combining to form drug product. The composition includes strains formulated in spore form and strains fermented in non-spore, vegetative form. The product candidate is delivered using enterically-protected technology designed to release in the colon. SER-301 is designed to modify the microbiome and microbe-associated metabolites in the gastrointestinal tract to modulate pathways linked to gastrointestinal inflammation and to improve epithelial barrier integrity in patients with ulcerative colitis.