Overview
- A Boston Children’s Hospital open-label Phase I trial gave 15 highly peanut-allergic adults a one-time dose of 36 frozen, oral FMT capsules and found six participants showed sustained increases in the amount of peanut they could tolerate at the four-month endpoint.
- No allergic reactions tied to the capsules and no grade 3 or higher adverse events were reported, indicating the single-dose oral FMT was well tolerated in this small adult group.
- Responders displayed immune shifts linked to restored oral tolerance, including higher RORγt-positive regulatory T cell levels and lower type 2 helper T cell activity, and transferring responder microbiomes into allergy-prone mice protected those animals from peanut allergy.
- Analyses associated protection with increased colonization by Bacteroides species and higher bile acid metabolites, and removing a bile salt hydrolase gene from a candidate Bacteroides strain reduced protection in mice, implicating bacterial bile acid metabolism in tolerance.
- Investigators note the study’s limits—small size, open-label design, adult-only enrollment and a possible male-predominant response—and are moving toward larger, controlled trials using purified microbial formulations and combination tests with peanut oral immunotherapy to validate and refine the approach.