The FDA placed clinical holds on two Regenxbio gene therapy studies after a patient in one trial developed cancer, prompting regulators to pause enrollment and dosing while safety investigations proceed. The holds affect programs aimed at rare diseases and cast uncertainty over near‑term approval timelines. Regenxbio and investigators are coordinating with the agency to analyze causality and amend protocols where needed; the regulatory action follows standard safety procedures when serious adverse events emerge in gene therapy studies. Coverage noted the hold alongside other recent trial suspensions that have amplified FDA scrutiny of viral‑vector programs.