FMT as First-Line Therapy for Checkpoint-Inhibitor Colitis: Cell Reports Medicine | October 2026

What Did the Study Find?

This early-phase study evaluated first-line fecal microbiota transplantation (FMT) in 13 patients with cancer who developed grade ≥2 immune checkpoint inhibitor–mediated diarrhea and colitis (IMDC).

• Clinical response occurred in 10/13 patients (76.9%).
• Response was remarkably rapid, with symptom improvement after a median of only 1.5 days.
• Among initial responders, 80% maintained remission during a median follow-up of 6.5 months.
• Fecal calprotectin decreased from a median 416 to 146 μg/g.
• Endoscopic remission occurred in 33.3% of patients with baseline macroscopic inflammation, while histologic remission occurred in 18.1% with baseline histologic inflammation.
• FMT-related adverse events occurred in 23%, but all were grade 1 and transient.
• Importantly, 11/13 patients resumed cancer therapy, and 5 were able to restart immunotherapy.
• Microbiome analysis showed increased diversity in most sequenced responders and a shift toward a donor-like microbial profile.

Why Does It Matter?

Current IMDC treatment commonly relies on corticosteroids followed by biologic immunosuppression when necessary. A rapidly acting microbiome-directed treatment could potentially reduce immunosuppressive exposure while allowing patients to resume effective anticancer therapy sooner.

The study also provides biological support for the concept that checkpoint-inhibitor colitis is partly mediated by a modifiable gut microbiome–immune interaction.

GastroAGI Takeaway

FMT may be moving from rescue therapy toward an earlier treatment strategy for immune checkpoint inhibitor colitis.

A 76.9% response rate with median improvement within 1.5 days is impressive, particularly because most responders maintained remission and many patients subsequently restarted cancer treatment.

But this should not yet change standard first-line management. Only 13 patients were treated, there was no randomized control group, and clinical improvement was considerably greater than endoscopic or histologic remission.

The signal is exciting, not definitive: a randomized comparison of FMT versus corticosteroid-based therapy, ideally examining steroid exposure, biologic rescue, durable mucosal healing and ability to safely resume immunotherapy, is now the critical next step.