Seres Therapeutics, Inc. announced the publication of data analyses from the Company’s Phase 1b trial of SER-287 in patients with active mild-to-moderate ulcerative colitis (UC), most of whom were failing current therapies. The study results demonstrated that SER-287 administration was associated with positive impacts on clinical remission, endoscopic improvement, modulation of the gastrointestinal microbiome, and a favorable tolerability profile. The paper, titled “A Phase 1b Safety Study of SER-287, a Spore-Based Microbiome Therapeutic, For Active Mild-To-Moderate Ulcerative Colitis,” was published as the highlighted cover article in the January 2021 print edition of the leading journal Gastroenterology. The randomized, double-blind, placebo-controlled, multiple-dose, Phase 1b induction trial randomized 58 patients to one of four arms: daily SER-287 (preceded by short vancomycin conditioning regimen), weekly SER-287 (preceded by short vancomycin conditioning regimen), weekly SER-287 (preceded by placebo), and daily placebo (preceded by placebo). The highest efficacy was observed in the daily SER-287 arm of the study, with a remission rate of 40% compared to 0% in the placebo group. SER-287 engraftment was dose-dependent, durable for four weeks post-dosing, and associated with clinical remission across arms. An SER-287-associated benefit in endoscopic improvement was also observed. SER-287 engraftment, reflecting the germination and growth of drug bacteria, was associated with compositional and functional changes in the microbiome, including increased diversity of spore-forming Firmicutes implicated in colonic homeostasis, declines in non-spore forming species such as pro-inflammatory Enterobacteriaceae, and changes in the abundance of microbe-associated metabolites that impact epithelial barrier function and immune signaling. The SER-287 safety and tolerability profile were favorable, and study results demonstrated no imbalance in adverse events in patients treated with SER-287 compared to patients treated with placebo. There were no drug-related serious adverse events (SAEs) associated with SER-287. SER-287 is an oral, biologically-derived microbiome therapeutic candidate designed to have pharmacological effects on multiple pathways relevant to ulcerative colitis that can be modulated by the gastrointestinal microbiome. Seres has obtained FDA Fast Track designation for SER-287 in active mild-to-moderate UC. The SER-287 ECO-RESET induction study in patients with active mild-to-moderate UC remains ongoing. Seres has implemented a number of COVID-19-related mitigation strategies, and the study continues to enroll patients.