FDA greenlights first-ever Barth syndrome drug after decade-long push

Stealth BioTherapeutics' elamipretide, now branded as Forzinity, has received accelerated FDA approval, making it the first treatment for Barth syndrome, after a petition by 82 experts and pleas from families who were affected by the rare, life-limiting mitochondrial disease.

Why it matters: Elamipretide targets mitochondrial dysfunction, the core issue in Barth syndrome. Barth syndrome primarily affects young males and leads to severe muscle weakness, heart failure, and early death. Elamipretide improves mitochondrial function, offering significant quality-of-life gains such as improved mobility and stamina.

Backstory: Barth syndrome is a fatal genetic condition with no prior treatments affecting just 150 people in the U.S. Stealth BioTherapeutics began exploring elamipretide for Barth in 2014 after a nudge from the Barth Syndrome Foundation. After an initial FDA rejection in May, Stealth reapplied under the agency’s accelerated approval pathway. Approval came five months ahead of schedule, based on improved muscle strength metrics in older children.

Big picture: This decision signals a shift in FDA posture toward ultra-rare diseases, aligning with the agency’s new Rare Disease Evidence Principles. It may inspire similar expedited pathways for other conditions with tiny patient populations and limited clinical data.

Yes, but: The approval excludes the youngest and most vulnerable patients—those under 66 pounds, often under age 5—raising urgent access questions.

What´s next: Stealth will conduct a required post-approval trial to confirm clinical benefit beyond muscle strength.