Seres Therapeutics Pauses SER-155 Phase 2 Study, Cuts 30% Workforce to Extend Runway
Seres Therapeutics paused its Phase 2 SER-155 allo-HSCT study and cut about 30% of its workforce to extend its cash runway through Q3 2026. The company will shift operational focus to early-stage inflammatory and immune live biotherapeutics while supporting an irEC trial read-out expected in early Q2 2026.
1. SER-155 Phase 2 Protocol Finalized and Paused
Seres Therapeutics finalized the protocol for its Phase 2 SER-155 study in allo-HSCT patients but has paused further investment while seeking external funding to support the trial’s progression.
2. Workforce Reduction Extends Cash Runway
The company announced a roughly 30% workforce reduction, extending its cash runway through the third quarter of 2026 versus prior projections through Q2 2026 based on a $47.6 million cash balance.
3. Strategic Pivot to Early-Stage Programs
Seres will concentrate on advancing high-value early-stage live biotherapeutic candidates, including SER-603 for ulcerative colitis, Crohn’s disease and irEC, and is in discussions with potential collaborators.
4. Upcoming irEC Study Read-Out
The fully enrolled Investigator-sponsored SER-155 trial in immune checkpoint-related enterocolitis (irEC) remains on track for data read-out in early Q2 2026, with Seres providing support for the analysis.