Seres Therapeutics’ (NASDAQ:MCRB) Phase Ib SER-287 has drawn overall skeptical reviews from experts about its potential to change the microbiome of mild-to-moderate ulcerative colitis (UC) patients for clinical benefit. But any signal of microbial change in the trial’s patients would be welcome to help confirm SER-287 mechanism, they added.
Engraftment of new bacteria would be the ideal result, with the assistance of generic antibiotic vancomycin at the pretreatment phase, experts said. However, engraftment is hard because it is challenging to remake any person’s intestinal bacterial profile and probiotics like SER-287 are unlikely to lead to long-term change, experts said. It is unclear what new bacteria are being introduced by SER-287, some added.
This means SER-287 has a better shot as a maintenance therapy as any bacterial change is likely to be transient, experts added. Maintenance would lead to lower SER-287 dose, one expert noted.
However, UC being multifactorial and patient heterogeneity draws some maintenance success reservations, others noted. As seen in faecal microbial transplant (FMT), the ultimate probiotic example, some UC patients worsen and FMT does not lead to major benefit over placebo, some said.