Seres Therapeutics reports Phase 1b trial results for SER-155 treatment

Seres Therapeutics announced that Phase 1b trial results for its biotherapeutic candidate SER-155 were published in Nature Medicine on November 3, 2026, according to The Manila Times, GlobeNewswire, and Traders Union. The study examined allogeneic hematopoietic cell transplantation recipients to evaluate the effectiveness of the treatment. [1][2][3]

The Manila Times reported that the peer-reviewed publication showed a 77 percent relative risk reduction in bloodstream infections among patient recipients given SER-155 compared with a placebo. The trial also demonstrated significantly lower systemic antibiotic exposure in patients who received the treatment. [1]

Hematopoietic stem-cell transplantation involves transferring multipotent stem cells derived from peripheral blood, umbilical cord blood, or bone marrow to produce normal blood cells inside a patient. The trial translational data support SER-155 mechanisms of strengthening the mucosal epithelial barrier and reducing systemic inflammation, according to The Manila Times. [1][5]