PTC Therapeutics withdrew its US filing for Translarna (ataluren) for nonsense‑mutation Duchenne muscular dystrophy after the FDA signaled that the submitted data were unlikely to meet the agency’s standard for substantial evidence of effectiveness. The move follows a negative regulatory decision in Europe and closes a multi‑decade development program. PTC framed the withdrawal as a pragmatic response to the agency’s feedback; regulators cited data limitations rather than safety concerns. The episode underscores the difficulty of obtaining approvals for therapies relying on surrogate or complex endpoints and may affect future strategy for drugs in rare genetic disorders.