Stealth Biotherapeutics announced Tuesday that the U.S. Food and Drug Administration (FDA) has missed its April 29 deadline to issue a decision on elamipretide, an experimental treatment for Barth syndrome. The agency has not yet established a new timeline for when the therapy might receive approval.
This marks the second delay in the review process for elamipretide. The FDA previously extended its review period in January to examine additional information submitted by Stealth following an October advisory committee meeting. At that time, the agency did not cite safety concerns or request additional clinical trials.
A Second Chance for Approval
Elamipretide's current review represents Stealth's second attempt at FDA approval. The company's initial application for primary mitochondrial myopathy was rejected in 2021 when regulators determined the drug's effectiveness had not been sufficiently demonstrated.
The company has since refocused its efforts on Barth syndrome, an ultra-rare genetic disorder that affects approximately 150 people in the United States. The condition, characterized by muscle weakness, heart failure, and reduced life expectancy, currently has no FDA-approved treatments.
Despite initial skepticism from the FDA regarding Stealth's clinical data, an advisory committee voted in favor of the drug's efficacy last October, setting the stage for potential approval. The application had been granted priority review status, intended to expedite the evaluation process for treatments addressing serious conditions with significant unmet needs.
Regulatory Delays Amid FDA Staffing Concerns
The missed deadline comes at a challenging time for the FDA, which recently announced thousands of layoffs. While the agency has maintained that its drug review divisions would not be affected by these cuts, Stealth's case joins at least two other companies—Novavax and Vanda Pharmaceuticals—that have reported unexpected delays in regulatory decisions.
Stealth CEO Reenie McCarthy expressed continued engagement with regulators, noting in the company's statement that the FDA has been working collaboratively with the biotech to "progress its review" and has recently initiated labeling discussions—typically a late-stage component of the approval process.
"We hope to gain more information about the new decision date in the coming days," McCarthy stated.
Patient Advocacy Response
The Barth Syndrome Foundation, representing patients affected by this rare condition, has expressed concern about the delay. Emily Mulligan, director of the non-profit organization, emphasized that the foundation is urging the FDA to "stay focused on completing this review" and provide a "clear new decision date."
For patients with Barth syndrome and their families, the regulatory delay extends the wait for what could potentially be the first approved therapy specifically targeting their condition. The disease typically manifests in infancy or early childhood and can lead to severe complications including heart failure, muscle weakness, growth delays, and compromised immune function.
Regulatory Context and Implications
The FDA's handling of elamipretide's review occurs against a backdrop of increasing scrutiny of the agency's review processes for rare disease treatments. While the FDA has tools like priority review and accelerated approval pathways designed to expedite the development of therapies for serious conditions with limited treatment options, the balance between speed and rigorous evaluation remains challenging.
Despite the current delay, the fact that the FDA has engaged in labeling discussions with Stealth suggests the review is progressing. Labeling negotiations typically occur in the final stages of the approval process when the agency has largely completed its efficacy and safety evaluations.
For Stealth Biotherapeutics, securing approval for elamipretide would represent a significant milestone after years of development and regulatory challenges. For the Barth syndrome community, it could provide the first FDA-approved therapeutic option for a condition that has historically had limited treatment alternatives beyond symptom management.
