After years of determined advocacy and scientific perseverance, Stealth BioTherapeutics has achieved a landmark victory with the FDA’s accelerated approval of elamipretide (now branded as Forzinity) the first-ever treatment for Barth syndrome. As reported by Biospace, this ultra-rare mitochondrial disorder, affecting only about 150 individuals in the U.S., primarily young boys, has finally met its first targeted therapy, offering a beacon of hope for families long left without options.
A Decade in the Making
The path to approval was anything but straightforward. After initially being rejected in May 2025, Stealth BioTherapeutics refiled their application under the FDA’s accelerated approval pathway, following regulatory advice and addressing prior concerns. The FDA’s green light, granted five months ahead of schedule, was based on data from the Phase II TAZPOWER trial, which showed promising improvements in knee muscle strength—an outcome closely linked to functional gains for patients.
Forzinity is indicated for those weighing at least 66 pounds, leaving out the youngest and often most severely affected children under five. Stealth has committed to maintaining expanded access for these children and to working with the FDA toward broader approval.
The Barth Community’s High Stakes
For the Barth syndrome community, the stakes could not have been higher. Barth syndrome, a genetic mitochondrial disorder, causes severe muscle weakness, heart failure, and often claims lives in early childhood. There were no approved treatments until now, and as Kate McCurdy, board chair at the Barth Syndrome Foundation, emphasized, many families have witnessed first-hand the life-changing effects of elamipretide through expanded access programs.
The journey began in 2014, when the Foundation recognized a scientific match between elamipretide’s mechanism and the core defect in Barth syndrome. Collaboration ensued, leading to years of trials and regulatory dialogue. Despite initial failures in clinical endpoints and regulatory hurdles, including a substantial staff reduction to keep the program alive, Stealth persisted, ultimately winning an adcomm vote and FDA approval.
Evidence and Advocacy
While Forzinity’s path was marked by debate, particularly around the adequacy of trial controls and the use of surrogate endpoints, the Barth community and clinicians rallied behind the therapy. A petition signed by 82 experts, including some who initially voted against approval, highlighted dramatic improvements in patients’ daily lives: walking stairs, attending school, and, in the case of the youngest, surviving and thriving against the odds.
Looking Forward
The FDA’s decision comes amid new agency principles for rare disease evidence, signaling a potential shift toward more flexible frameworks for ultra-rare conditions. While challenges remain, especially in approving the drug for younger children, Forzinity’s arrival is a milestone, both for Barth syndrome families and for the broader rare disease community.
Forzinity’s approval not only addresses an urgent, unmet medical need but also sets a precedent, fueling hope that other ultra-rare diseases will soon see similar breakthroughs.
