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# Stealth Refiles NDA for Barth Syndrome Drug
- URL: https://www.fdaweb.com/stealth-refiles-nda-for-barth-syndrome-drug/
- Published: 2025-08-18T12:00:00.000Z
- Updated: 2026-09-14T15:19:19.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5159700

Stealth BioTherapeutics has resubmitted its NDA for elamipretide for treating Barth syndrome, a rare and life-threatening mitochondrial disease. The filing follows an FDA complete response letter (CRL) in May, which requested additional information but did not require new clinical efficacy data, according to the company. It says the submission now includes a minor safety update, confirmation that earlier manufacturing deficiencies were resolved, and details of proposed post-marketing commitments, including a trial to further validate elamipretide’s clinical benefit.

After extending its review and missing a 4/29 user fee review target date, FDA issued the CRL and proposed that company resubmit the NDA to seek accelerated approval for treating Barth syndrome. The company says it submitted data in the NDA showing that knee extensor muscle strength, which improved by over 45% in its Phase 2 TAZPOWER clinical trial, is significantly correlated with improvements on the six-minute walk test, an FDA-recognized indicator of clinical benefit.

“We appreciate FDA’s recognition of the seriousness of Barth syndrome and its commitment to review our NDA resubmission as quickly as possible,” the company says in a release. “With manufacturing concerns resolved and alignment on post-marketing trial design, we believe all issues raised in the CRL have now been addressed.”

Upon receiving Stealth’s filing, FDA will determine whether to classify the review as Class 1 (two months) or Class 2 (six months). While the agency has signaled a likely Class 2 designation, Stealth is pressing for a faster Class 1 review, arguing that no further inspection is necessary. This marks the company’s third NDA submission based on TAZPOWER data, nearly 19 months after the last priority review.

If approved, elamipretide would become the first FDA-approved therapy for Barth syndrome and the first marketed product for Stealth. The drug, a first-in-class mitochondrial-targeted therapeutic, is also being investigated for primary mitochondrial myopathy and dry age-related macular degeneration.

Barth syndrome is a rare, genetic mitochondrial disorder affecting an estimated 150 patients in the U.S., mostly males. It causes muscle weakness, severe fatigue, heart failure, and recurrent infections, with most deaths occurring in early childhood.