Topline results from the phase IIb ECO-RESET study

“While these outcomes were not what we, nor the UC community, were hoping for, we remain committed to leading the creation of a new class of medicines designed to impact how diseases like ulcerative colitis are treated. As with SER-109, we will again follow the science and the data, conduct a rigorous scientific analysis, and determine the optimal path forward for our UC franchise,” said Eric Shaff, Chief Executive Officer at Seres. “We are well resourced and continue to prepare for SER-109 commercialization, in collaboration with Nestlé Health Science, and we are excited about advancing the development of our SER-301 and SER-155 investigational candidates as well as our earlier stage pipeline.”

The primary objective of the induction portion of the Phase IIb study was to evaluate the safety and efficacy of SER 287, after 10 weeks of induction dosing (following vancomycin pre-conditioning) in achieving clinical remission in participants with mild-to-moderate UC. The trial was a randomized, placebo controlled, double blind, parallel group multicenter study which enrolled 203 UC patients in 104 sites throughout the U.S. and Canada. Dosing was explored in two SER 287 cohorts (full induction dose and step-down induction dose) or placebo (randomized 1:1:1). Clinical remission was analyzed and defined by a 3-component modified Mayo Score. No meaningful clinical differences and no statistical significance were observed in absolute clinical remission rates among the three treatment arms (10.3% for the full induction dose, n=68 and 10.6% for the step-down induction dose, n=66 versus 11.6% for placebo, n=69). There were also no meaningful differences observed across the three treatment groups for endoscopic improvement, endoscopic remission or symptomatic remission.

“While the efficacy results in this trial did not meet the pre-defined threshold, we believe this data-rich study, including microbiome analyses expected in the second half of 2021, will provide valuable insights to inform continued development of our pipeline, including SER-301, our next generation investigational candidate for UC,” said Lisa von Moltke, M.D., Chief Medical Officer at Seres. “We are grateful for everyone who made this study possible, including the study investigators, and in particular, the patients and their families."