Fecal Microbiota-Based Therapies: Approved and Investigational Uses

Urgent safety note

This page gives no preparation or do-it-yourself instructions, and fecal transplant is not something to attempt at home. In 2020 FDA reported serious infections after a stool-bank product made with screened donors, and two patients who died after receiving product from the donor linked to some of those infections, although it was not known whether the infection contributed. [1] If you have repeated diarrhea after antibiotics, talk with a clinician; for a medical emergency in the US call 911.

What these therapies are

Fecal microbiota products are prepared from donated human stool and given to another person. FDA says they are thought to help restore the gut community, and that those used to prevent, treat or cure disease are biological products overseen by its biologics center. [2] Evidence labels: approved medicine, established, promising but limited, mixed, insufficient evidence.

Evidence for C. difficile

• Early randomized trial. In 2013, 16 people with recurrent CDI who got donor stool by tube had resolution in 13 after one infusion, compared with 4 of 13 on vancomycin alone. The trial stopped early after an interim analysis. [6] Label: established direction, small trial.
• Oral spores (VOWST). In a 182-person phase 3 trial of the investigational product SER-109, recurrence by 8 weeks was 12% with the product and 40% with placebo (relative risk 0.32). [7] A later open-label study of 263 people reported no treatment-related serious events and 8.7% recurrence at week 8. [8] A post hoc analysis found benefit across subgroups including comorbidities. [9]
• RBX2660 (REBYOTA). The phase 2b trial showed 56.8% and 55.6% success versus 43.2% with placebo, not statistically significant in the intention-to-treat analysis (p = 0.2) and significant in a per-protocol analysis. [10] The doses were given rectally. [11] FDA approval followed later; this page did not read the phase 3 results.
• Pooled comparison. A 2026 meta-analysis of 9 trials (759 people) found FMT more effective than antibiotics at resolving CDI (RR 1.51) and lowering recurrence (RR 0.38), with comparable adverse events. [12]

Other uses: still investigational

No other indication appears on FDA's approved list. [2]

• Ulcerative colitis. A 2026 meta-analysis of 16 randomized trials found higher clinical remission with donor FMT than control, dependent on delivery route, with no excess adverse events. [13] Label: promising but limited; not an approved indication in the US from the FDA pages read.
• Irritable bowel syndrome. A 2026 meta-analysis of 13 trials found very low-certainty evidence; the main analysis was not significant, though a per-protocol analysis was. [14] An earlier review of 12 trials found no significant difference. [15] Label: mixed.
• Cancer immunotherapy. In a 20-person single-arm trial in melanoma, FMT with anti-PD1 treatment gave a 65% response rate, and the authors called results hypothesis-generating. [16] Label: insufficient evidence (no control group).

Related guides

Probiotics vs Microbiota-Based Medicines, Microbiome-Targeted Medicines and Gut Microbiome Research.