Seres Therapeutics presents expanded SER-155 biomarker data at ASCO meeting

Seres Therapeutics (MCRB) announced the Company will be presenting new exploratory biomarker data from its SER-155 Phase 1b study in a poster session at the 2025 American Society of Clinical Oncology, ASCO, Annual Meeting, taking place May 30 -June 3 in Chicago. The Company previously reported exploratory biomarker data from the SER-155 Phase 1b study showing evidence of improved intestinal epithelial barrier integrity and modulation of systemic inflammatory responses. The results are consistent with SER-155’s intended therapeutic mechanisms to reduce the risk of intestinal bacterial translocation-associated bloodstream infections and are supportive of the observed significant reduction in BSIs with SER-155 treatment. They also demonstrate the broader potential of live biotherapeutics to treat inflammatory and immune-mediated diseases. New biomarker data presented at ASCO build on these findings, focusing on the potential of SER-155 to promote immune reconstitution following allo-HSCT through the modulation of homeostatic cytokines and peripheral T-cell expansion. In post hoc analyses from the SER-155 Phase 1b study, significantly higher levels of the homeostatic cytokine IL-7 were observed both after the second course of SER-155 and at HSCT Day 100, as compared to placebo. Additionally, a higher frequency of CD4+ T cells was observed in peripheral blood at these same timepoints in the SER-155 arm. These findings support that SER-155 may play an important role in promoting T-cell populations, essential for immune reconstitution after allo-HSCT, reducing infection risk and improving clinical outcomes.