Why FDA’s Plausible Mechanism Framework Matters For Ultra-Rare Disease Policy Peter J. Pitts June 8, 2026

https://www.healthaffairs.org/content/forefront/why-fda-s-plausible-mechanism-framework-matters-ultra-rare-disease-policy?utm_campaign=forefront&utm_medium=email&_hsenc=p2ANqtz-95-nW97T1x9NddRF4dD8VDz_mZRz_eXHlNTk8BK_GoxGc_m9D69jwRQjI_fONuRLVW1GgrOY7IB4gtWwRvY0s465qAYw&_hsmi=423554003&utm_source=hasu Ultra-rare diseases often lack patient populations large enough to support randomized controlled trials. The question is not whether to abandon rigorous standards, but how to apply them when the denominator collapses.