This week, Stealth BioTherapeutics CEO Reenie McCarthy faced a seemingly insurmountable roadblock with the company’s drug for the ultra-rare, fatal mitochondrial disease Barth syndrome. FDA reviewers had extensively questioned the data supporting the drug’s efficacy. And the agency had already turned down Stealth once.
Instead, the advisory committee on Thursday voted 10-6 in support of the drug, following testimony from patients and their families, as well as doctors who had treated patients with it.
The result was a substantial win for the small, 50-person private company and its CEO. McCarthy joined Endpoints News via Zoom on Friday to discuss the surprise vote.
“We’ve had a lot of ups and downs along the way, and we really tried to keep progressing the program despite some of the disappointments because of the strong belief that we had a drug that was working for patients living with this terrible disease,” McCarthy said.
Barth syndrome affects about 130 American boys, and 80% don’t survive past 5 years of age. However, Stealth’s proposed indication for the drug is for 12 years and older, and the population in which the drug was studied was mostly older teenagers and children.
“That’s an FDA decision,” McCarthy said, noting there are about 20 to 25 boys on the drug through an expanded access program. “We certainly profiled some of our expanded access in our presentation, really to speak to the safety that we’ve seen in younger children.”
She said the company has had requests for the drug from 10 countries and a dozen US hospitals, noting patients and their families don’t pay for treatment under those expanded access efforts. The FDA has until Jan. 29, 2025, to make a final approval decision.
McCarthy declined to discuss potential pricing ahead of an elamipretide approval, and said the company plans to conduct a pharmacokinetic study in younger children to optimize dosing.
“You know what the price tags of drugs for super-rare diseases are,” McCarthy said. “We’re going to have to take that into consideration. But super-rare diseases are a little bit less of a problem from a payer perspective as well, because there’s a lot less patients affected by them.”
CDER Director Patrizia Cavazzoni, who typically doesn’t speak at advisory committee meetings, made a comment just prior to Thursday’s vote about regulatory flexibility and how the agency is evolving its work in ultra-rare indications.
McCarthy said it was the first time anyone in the FDA’s leadership had indicated that there might be some flexibility afforded to elamipretide.