PTC Therapeutics terminates bid seeking FDA approval for rare muscle disease drug
PTC Therapeutics has been working back and forth with the FDA for more than a decade to find a way forward for a Duchenne muscular dystrophy drug with a spotty record in clinical trials. This effort has ended.
PTC announced after the close on Thursday that it had withdrawn its application for regulatory approval of the drug ataluren (trade name: Translarna). According to PTC, the regulator said based on its review to date, the data submitted are unlikely to show sufficient validity to support regulatory approval. The rare disease drug developer elaborated on this in a letter to the Duchenne community in the United States, saying there were differences in the interpretation of data submitted for the drug that could not be resolved.
“Despite multiple clinical studies demonstrating evidence of safety and efficacy, the FDA stated that they believe the data are insufficient to meet the threshold for approval,” the letter said. “Accordingly, PTC has made the difficult decision to withdraw the resubmitted New Drug Application for ataluren.”
The progressive muscle weakness in Duchenne results from an inherited deficiency of dystrophin, a protein critical for muscle function. So-called nonsense mutations in the gene encoding dystrophin prematurely stop production of the protein, resulting in a shortened and non-functional version of the protein. Translarna is a protein repair therapy discovered within PTC. The purpose of this orally administered small molecule is to enable the cell's protein-making machinery to read the premature stop signal and thereby form functional dystrophin. At least, that's how it should work.
Translarna failed in phase 2 testing. Nonetheless, PTC advanced Translarna to Phase 3. In 2015, PTC announced that the drug had failed this placebo-controlled study. Still, the company submitted its application to the FDA based on “all the data.” The FDA rejected PTC's application in 2017 and rejected the drugmaker's subsequent efforts to seek approval.
For a while, Translarna had better luck in Europe. In 2014, European regulators granted the drug a conditional marketing authorization, which needs to be renewed annually until sufficient data are available to support a standard marketing authorization. In 2023 and 2024, the PTC challenged negative opinions from the European Commission's Committee for Medicinal Products for Human Use, which concluded that the drug's benefits had not been proven and therefore the authorization should not be renewed. In March last year, the commission finally adopted the opinion and refused to renew the license.
Although Translarna is not yet available in the United States, a limited number of patients can obtain the drug under the FDA's expanded access program. PTC's letter said that in the coming weeks, the company will determine next steps for making the remaining doses available to patients currently receiving them.
Translarna is one of Duchenne's two PTC drugs. The company also markets Emflaza, which is approved in the United States but not yet in Europe. The way Emflaza works in Duchenne is unclear, but the drug is a corticosteroid that reduces inflammation. Translarna and PTC are PTC's top products, with combined revenue of $315.6 million through the first three quarters of 2025. But PTC faces financial challenges ahead. Translarna will provide marginal revenue from remaining markets where the drug is still available and where Emflaza has lost market exclusivity.
The second largest contributor to PTC's revenue is the new product Sephience. The drug was first approved in Europe and the United States last summer to treat the rare metabolic disease phenylketonuria. Sephience had revenue of $19.5 million in the third quarter of 2025. Kebilidi (European Upstaza), a gene therapy approved in 2024 to treat an ultra-rare enzyme deficiency, had revenue of $15.7 million in the first nine months of 2025.
As for PTC's pipeline, the company is still working to find a path forward for vantiquinone, a drug developed to target the rare neuromuscular disease Friedreich's ataxia. The FDA issued a full response letter last August regarding the drug. Although the small molecule failed in Phase 3 testing, PTC submitted a new drug application.
Photo by Flickr user Nimble Photography licensed under Creative Commons
