Drug Development

Microbiome pioneer Seres crushed as lead drug flops in PhII

One of the pioneers in the microbiome R&D world has slammed into a Phase II failure for its lead program. Seres Therapeutics $MCRB says that SER-109 flunked a mid-stage test for reducing the recurrence of Clostridium difficile infection.

SER-109 barely improved on the performance of a placebo in the study, with 44% in the microbiome drug arm seeing a recurrence of CDI, compared to 53% in the sugar pill group. That’s not nearly good enough to qualify as a significant improvement.

Seres’s stock was crushed, plummeting 78% in premarket trading and wiping out the lion’s share of its $1.4 billion market cap.

Seres is part of a group of startups that are working with a bugs-to-drugs strategy, using spores from a select group of bacteria to restore the proper microbial balance needed to maintain health and fight afflictions like CDI. The company raised more than $130 million before going public.

The setback is also bad news for Nestlé Health Science, which paid $120 million upfront to partner on CDI at the beginning of the year. The pact included some $2 billion in milestones for four programs, along with a commitment to help pay for late-stage development.

The Cambridge, MA-based company is one of several microbiome players to set up shop in Cambridge, MA. Not far from their base you can also find Vedanta and Synlogic, while out in San Francisco, Second Genome is promising to make its own microbial waves. Any doubts raised at one of these companies may well cast a pall over the emerging field.

Seres, though, is vowing to overcome the first big clinical blowup for experimental microbiome drugs.

Seres CEO Roger Pomerantz

Seres CEO Roger Pomerantz

“These are unexpected clinical results in view of the positive data in our prior investigator-sponsored Phase Ib trial, as well as in a wide range of supporting clinical and preclinical data,” noted Seres CEO Roger Pomerantz. “Specifically, the recurrence rates observed in the overall SER-109 treatment group, in the age stratified subgroups, and in the placebo groups are inconsistent with our expectations. Our priority is to complete a full review of the clinical results and microbiome data of the Phase 2 study and to compare it to data from the prior investigator sponsored Phase 1b. Based on this information and pending discussions with the FDA, we plan to make any necessary changes to our development plans for SER-109.”

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