The FDA placed clinical holds on two Regenxbio gene‑therapy studies after a participant developed cancer, raising fresh safety questions for adeno‑associated virus (AAV) and related viral vector programs. MedCity News reported the holds and framed them alongside other recent regulatory actions; the report notes one study patient’s malignancy prompted immediate trial suspension while agency investigators assess causality. The development removes near‑term clarity on approval timelines for the affected programs and could influence safety monitoring across the gene‑therapy sector. Sponsors running AAV or lentiviral programs should expect heightened FDA scrutiny, revised monitoring plans, and potential revisions to informed‑consent language. The holds echo broader regulatory caution seen in recent years where vector‑linked oncogenic signals have triggered pauses and additional long‑term follow‑up requirements.