The US Food and Drug Administration (FDA) has delayed its decision on Stealth BioTherapeutics’ new drug application (NDA) for elamipretide, a treatment for the ultra-rare disease Barth syndrome.
The Prescription Drug User Fee Act (PDUFA) action date has been extended by three months to 29 April 2025, following the submission of additional information by Stealth.
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Stealth stated that the FDA required more time to fully review the supplemental data, which was submitted in response to requests following the FDA’s Cardiovascular and Renal Drugs Advisory Committee (CRDAC) meeting in October 2024. At that meeting, the advisory panel voted 10-6 in favour of elamipretide’s approval. The FDA classified the new data as a major amendment to the NDA, which triggered the standard three-month extension.
Despite the delay, Stealth emphasised that the FDA has not raised any safety concerns or requested additional pre-market studies. In the announcement accompanying the extension, Stealth’s CEO Reenie McCarthy said: “We continue to work closely with the agency as it completes its review of the elamipretide NDA and are actively preparing to support broad access to this therapy for individuals living with Barth syndrome as quickly as possible following potential approval.”
It’s not the first time elamipretide’s development has faced regulatory challenges. The FDA rejected the company’s initial NDA in 2021, citing the lack of “an adequate and well-controlled trial that provides evidence of effectiveness”. That application was based on the SPIBA-001 study (NCT04689360), a Phase III trial incorporating data from prior studies and historical controls. The FDA expressed concerns about potential biases in the trial design, including selection bias and confounding bias, and questioned the methods used to analyse the results. Specifically, the trial compared data from a natural history cohort monitored in 2012 and 2019 with data from treated patients, which the FDA argued did not sufficiently address these biases.
The October 2024 AdCom meeting also faced difficulties. The panel discussed findings from the SPIBA-201 clinical trial (NCT03098797), which assessed the impact of elamipretide in 12 male patients over 12 weeks of daily treatment. The trial failed to meet the primary endpoint of improving walking distance.
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By GlobalDataDespite not meeting the efficacy endpoint, patients and physicians have strongly advocated for the drug’s approval.
During the AdCom meeting, testimonials highlighted the drug’s positive effects on weight gain, strength, and overall quality of life (QoL) for individuals with Barth syndrome. Jacob Wilson, a 24-year-old male with Barth syndrome told the panel the medicine “made him feel like a new person”. Ultimately, the committee decided to vote in favour of the drug, acknowledging “the devastating impact of Barth’s” and “the significant unmet medical need” in a document released in advance of the AdCom meeting.
The life-threatening disease – which causes symptoms such as cardiomyopathy and growth delays – has no cure, and no other therapies in late-stage clinical development, according to the Barth syndrome Foundation.
