After a long regulatory road that included a complete response letter in May, Stealth Biotherapeutics Inc. finally got its Barth syndrome drug across the finish line, with the U.S. FDA granting accelerated approval to Forzinity (elamipretide HCl) to improve muscle strength in those with the ultra-rare pediatric mitochondrial cardioskeletal disease.
Developing a therapy for an ultra-rare condition has its challenges, including finding enough patients for clinical enrollment and convincing regulatory authorities that limited data prove the candidate is safe and effective. For that reason, Stealth Biotherapeutics Inc. has faced numerous roadblocks getting its mitochondria-targeting elamipretide across the finish line for Barth syndrome, a condition that affects about 230 to 250 males worldwide, including fewer than 150 in the U.S.
Stealth Biotherapeutics Inc., and, more importantly, patients with Barth syndrome, faced another disappointing delay April 29 when the U.S. FDA kicked its approval decision down the road for Stealth’s elamipretide.
“This was worse than our national election,” Eric Peterson said as he explained his vote Oct. 10 concluding that Stealth Biotherapeutics Inc.’s elamipretide is effective in treating Barth syndrome, an ultra-rare mitochondrial disease that currently affects 129 males in the U.S. Peterson, a vice provost, senior associate dean and professor at the University of Texas Southwestern Medical Center, was one of 10 members of the U.S. FDA’s Cardiovascular and Renal Drugs Advisory Committee (CRDAC) who came to that conclusion. Six others had a different opinion. Regardless of which way they voted, the panelists attested to how difficult the decision was.
Stealth Biotherapeutics Inc. had hoped the U.S. FDA would have approved its lead candidate, elamipretide, as the first treatment for Barth syndrome by now. Instead, it’s headed to a meet-up with the agency’s Cardiovascular and Renal Drugs Advisory Committee (CRDAC) Oct. 10. The discussion and vote at that meeting could be make-or-break for patients with the ultra-rare debilitating mitochondrial disease that has no approved therapies. “Barring support from CRDAC, the future of elamipretide for Barth syndrome in the U.S. is tenuous," Stealth CEO Reenie McCarthy told BioWorld.
Reneo Pharmaceuticals Inc.’s last patient visit Oct. 9 in the pivotal study with mavodelpar called Stride – due to yield top-line data in December 2023 – kept interest strong in primary mitochondrial myopathy (PMM), where parties are pursuing development bids by way of assorted strategies.
The U.S. development path for rare disease treatments is strewn with numerous challenges, not least of which are the regulatory hurdles. For companies developing promising candidates to treat ultra-rare diseases and the patients who are running out of time, the regulatory obstacles in the U.S. may seem almost insurmountable. And new concerns about drug development in general could make those barriers even higher.
