In this episode of PRIM&R's podcast, "Research Ethics Reimagined," we explore FDA's plausible mechanism pathway for ultra-rare genetic disorders with Holly Fernandez Lynch, Associate Professor of Medical Ethics at the University of Pennsylvania's Perelman School of Medicine. She discusses how this pathway enables personalized gene therapies for N-of-one or N-of-few diseases while raising important questions about regulatory process, evidence standards, and equitable access. Professor Fernandez Lynch also examines the remarkable case of baby KJ, who received a gene editor to treat his urea cycle disorder, and considers both the transformative potential and the procedural concerns surrounding FDA's approach.