Seres Therapeutics, Inc.

What they do

Seres discovers and develops live biotherapeutic products (LBPs) designed to modulate host pathways via the microbiome. Its pipeline includes SER-155 for bloodstream infection prevention and irEC, SER-603 for inflammatory bowel disease, and earlier-stage candidates. The company previously developed and sold VOWST, the first FDA-approved orally administered microbiome biotherapeutic.

Revenue drivers

• License and royalty revenue from VOWST sale to Nestlé Health Science — Following the September 2024 sale of VOWST, Seres receives payments tied to the asset. Annual revenue was $789,000 in 2025 and quarterly revenue was $351,000–$736,000 in the last four reported quarters.
• Partnership and collaboration income — The company is actively seeking partners to fund development of SER-155 and other programs; no partnership revenue has been reported in the recent quarters.
• No approved commercial products currently — All revenue is derived from the VOWST sale and related arrangements; there are no marketed products generating product sales.

Recent performance

For the second quarter of 2026, revenue was $736,000, up from $438,000 in the prior quarter. Net income for 2025 was $5.7 million, a swing from a $113.7 million net loss in 2023. The company reported cash and equivalents of $15.6 million as of June 30, 2026. Operating cash flow was $1.1 million in 2025, compared to a $148.6 million outflow in 2024. Seres has substantial doubt about its ability to continue as a going concern, expecting to need additional funding after Q3 2026.

Strategy

Seres is prioritizing inflammatory and immune (I&I) indications, particularly SER-155 for irEC, which showed positive topline results from an investigator-sponsored trial. The company is engaging potential partners, including companies with ICI franchises, to fund development and is seeking capital to support SER-155 in allo-HCT and broader pipeline. It is also reducing facilities costs by terminating and restructuring leases to lower ongoing fixed costs. The SER-155 Phase 2 allo-HCT program is paused but ready to restart pending funding.

Risks

• Going concern risk — Seres has identified substantial doubt about its ability to continue as a going concern, with anticipated funding needs after Q3 2026 and limited cash of $15.6 million.
• Dependence on external financing — The company cannot consider the ability to obtain additional equity or partnership financing probable, which may limit its ability to advance programs.
• Clinical development risk — SER-155 is in early-stage trials and has not received regulatory approval for any indication; positive Phase 1b data may not predict later-stage success.
• Single-asset pipeline concentration — With SER-155 as the most advanced candidate, setbacks in this program would materially harm the company's prospects.

Outlook

Management plans to secure partnerships or other financing to advance SER-155 in irEC and allo-HCT, and to continue developing SER-603 for inflammatory bowel disease. The company is evaluating the clinical development pathway for irEC in consultation with key opinion leaders. Further lease terminations are expected to reduce annual fixed costs beginning in 2027, while maintaining operational infrastructure for the pipeline.