FDA launches new „Plausible Mechanism Framework“ to speed approvals for individualized therapies in ultra-rare diseases
The U.S. Food and Drug Administration (FDA) has released draft guidance introducing the Plausible Mechanism Framework, a novel regulatory pathway designed to accelerate the development and approval of highly personalized therapies for patients with ultra-rare genetic diseases. The framework, announced on February 23, 2026, allows sponsors to generate „substantial evidence“ of safety and effectiveness without traditional large-scale randomized controlled trials, which are often impossible due to extremely small patient populations (sometimes just one individual). The draft guidance, titled „Considerations for the Use of the Plausible Mechanism Framework to Develop Individualized Therapies that Target Specific Genetic Conditions with Known Biological Cause,“ focuses primarily on genome editing technologies (e.g., CRISPR-based approaches) and RNA-based therapies such as antisense oligonucleotides. It remains open to other tailored therapeutics that directly address a disease’s underlying molecular, genetic, or cellular cause. Key criteria for eligibility under the…

