Seres Therapeutics Pauses SER-155 Investment, Cuts Workforce by 30%

Seres Therapeutics announced that, following advancement of key startup activities for the SER-155 Phase 2 study in allo-HSCT, including the submission of a final protocol to the FDA, study site evaluation and qualification with its CRO, and manufacturing of Phase 2 study drug substance, Seres is pausing additional investment in that program and will shift its operational focus to high-value earlier-stage pipeline programs while continuing to seek funding for the SER-155 Phase 2 study. Seres also announced additional measures to reduce operating costs, including a workforce reduction of approximately 30%. As a result of these and other runway extension actions, and based on current operating plans, the Company expects to extend its cash runway through the third quarter of 2026, thereby providing additional opportunities to advance development of its live biotherapeutic programs for inflammatory and immune diseases, and pursue potential collaborations. The company said, "The SER-155 program has meaningfully advanced Seres' understanding of how microbes in the GI tract functionally modulate pathways at the mucosal barrier-immune interface associated with inflammatory and immune-related diseases. Accordingly, the Company's strategy moving forward will prioritize advancing its early-stage programs, including SER-603 that targets inflammatory and immune indications such as ulcerative colitis, Crohn's disease, and immune checkpoint related enterocolitis. Discussions are ongoing with counterparties related to potential collaborations in these areas." "Seres has taken extensive steps to prepare for a robust SER-155 Phase 2 study in allo-HSCT, including submission of a final protocol to the FDA, advancement of drug substance manufacturing, selection of a CRO and engagement with prospective study sites. As we shift our operational focus to our promising earlier-stage pipeline, we are now in a position to streamline our organization and cost structure," said Thomas DesRosier and Marella Thorell, co-CEOs of Seres. "These cost reduction initiatives and other actions are expected to extend our cash runway through the end of the third quarter of this year, supporting continued development of our programs for inflammatory and immune-related diseases, with targets validated by our previously reported preclinical and clinical datasets, and providing additional time to secure funding for our SER-155 Phase 2 study. In addition, as we pursue earlier stage programs with the greatest opportunity, such as those targeting inflammatory bowel disease, we are exploring collaborations to provide additional capital to the Company. We are very grateful for the many contributions of our departing team members."