Seres Therapeutics’ announcement last month that it was discontinuing its ECO-RESET Phase IIb clinical trial (NCT03759041) investigating SER-287 in patients with mild-to-moderate ulcerative colitis (UC) is likely to increase the scrutiny on other therapies targeting the microbiome and make funding more challenging, says GlobalData, a leading data and analytics company.

Chris Pilis, Immunology Analyst at GlobalData, explains: “This is Seres’ second trial termination of a microbiome-targeting drug in five years – the first being for a C. difficile microbiome therapeutic. These failures don’t help towards supporting what is a new and exciting area with high potential. Microbiome-targeting therapeutics is a growing field that has attracted increasing interest in the last decade, with the most explored area being the intestinal microflora. Nevertheless, this therapeutic space is still in its early days, and this latest result raises many questions concerning safety and efficacy.”

While key opinion leaders (KOLs) interviewed by GlobalData were enthusiastic about the prospect of microbiome treatments, they expressed reservations regarding the maintenance of these therapies and their poorly understood mechanisms of action.

Pilis continues: “As pricing potential can be impacted by indication, careful selection of an indication for a microbiome-targeting product’s initial launch will be essential to seeing the highest return on investment. SER-287 was expected to enter the US market in 2027. Its discontinuation clears the way for NuBiyota’s MET-2, which recently entered Phase IIa trials for UC.”

Seres’ CEO Eric Shaff stated that an analysis of the data collected during the trials will determine the company’s plans for SER-287. He did not exclude the potential of a re-trial. The company announced that, despite the discontinuation of SER-287, knowledge gained from these trials will have an important benefit for its SER-301 candidate, which is currently in Phase Ib in Australia and New Zealand for UC.

Pilis adds: “A re-trial has not yet been taken off the board, but, nonetheless, this withdrawal is an important setback beyond just losing a late-stage drug. Seres’ SER-301 candidate is under development in Australia and New Zealand, which are significantly smaller markets than the US.”