The U.S. Food and Drug Administration has rejected PTC Therapeutics’ application for vatiquinone, an experimental oral therapy for Friedreich’s ataxia, a rare, progressive neuromuscular disorder that affects roughly 25,000 people worldwide. In a Complete Response Letter issued on 19 August, the agency said the filing did not provide “substantial evidence of efficacy” and told the company it must conduct an additional well-controlled study before resubmitting the drug for review. Vatiquinone previously failed to meet its primary endpoint in a Phase III trial completed in 2023, although PTC cited positive results on a secondary measure when it sought approval. The company said it will request a meeting with the FDA to discuss potential next steps. The decision sent PTC shares down more than 5 percent in pre-market trading on Tuesday, though the stock later erased the loss and traded about 6 percent higher by mid-morning. Investors shifted focus to the company’s recently approved phenylketonuria drug, Sephience, and to management’s strategy for addressing the FDA’s concerns on vatiquinone. Biogen’s Skyclarys, cleared in early 2023, remains the only FDA-approved treatment for Friedreich’s ataxia in the United States, underscoring the unmet need the agency said must be demonstrated through further evidence before additional therapies can reach patients.