On September 3, 2025, the Food and Drug Administration (FDA) announced Rare Disease Evidence Principles (RDEP) with processes aimed at providing greater predictability and facilitating the development and review of drugs intended to treat rare diseases with very small patient populations and significant unmet medical needs driven by a known genetic defect. In conjunction with the agency’s announcement of the new processes jointly proposed by the Center for Drug Evaluation and Research (CDER) and Center for Biologics Evaluation and Research (CBER), the agency also unveiled additional information regarding eligibility and the potential for post-marketing requirements for those sponsors who participate in it.