Top FDA officials published a new regulatory roadmap to accelerate approval of individualized gene-editing treatments for ultra-rare diseases, building on the case of Baby KJ. The guidance — framed around a 'plausible mechanism' pathway — sets expectations for preclinical evidence, manufacturing controls, and clinical follow-up when randomized trials are infeasible. Authors and agency leaders emphasized safeguards for safety monitoring and long-term follow-up while enabling faster patient access. The perspective appeared in NEJM and was summarized in outlets covering implications for personalized gene medicines and rare-disease developers.