PMID-38602181 – TAZPOWER Long-Term Elamipretide in Barth Syndrome
Thompson WR, Hornby B, Manuel R, Bradley E, Laux J, Carr J, Vernon HJ. A phase 2 open-label extension study of elamipretide in Barth syndrome: TAZPOWER. Genet Med. 2024;26(5):101098.
Quick Reference
| Property | Value |
|---|---|
| PMID | 38602181 |
| DOI | 10.1016/j.gim.2024.101098 |
| Year | 2024 |
| Journal | Genetics in Medicine |
| Study Type | Open-label extension of RCT |
| Evidence Level | II (Oxford CEBM) |
| Sample | n=10 patients with Barth syndrome, 168-week follow-up |
| Peptide(s) Studied | SS-31 |
Key Findings
- Long-term (168-week) open-label extension of the TAZPOWER trial demonstrated sustained clinical benefit of elamipretide in Barth syndrome
- Six-minute walk test (6MWT) improved by a mean of 96.1 meters at week 168, representing a clinically meaningful and sustained functional improvement
- Elamipretide was well-tolerated over the extended treatment period with no new safety signals emerging
- The magnitude of 6MWT improvement increased over time, suggesting continued benefit with long-term use rather than a plateau effect
- Cardiac function parameters showed stable or improved trajectories over the study duration
- These data provided key supporting evidence for the FDA regulatory pathway for elamipretide in Barth syndrome
Study Design
Phase 2 open-label extension (OLE) of the randomized, placebo-controlled TAZPOWER trial. 10 patients with genetically confirmed Barth syndrome who completed the double-blind phase continued on elamipretide (40 mg/day subcutaneous) for up to 168 weeks. Primary outcome was change in 6MWT distance from the original study baseline. Secondary outcomes included cardiac function (echocardiography), patient-reported outcomes, and safety/tolerability assessments at regular intervals.
Limitations
- Very small sample size (n=10), inherent to the ultra-rare disease population (Barth syndrome prevalence ~1 in 300,000-400,000)
- Open-label design introduces potential bias from patient and investigator expectations
- No concurrent placebo control arm in the extension phase
- All patients were male (Barth syndrome is X-linked), limiting sex-specific generalizability
- Results specific to Barth syndrome (tafazzin mutation, cardiolipin remodeling deficiency) may not fully translate to age-related mitochondrial dysfunction
Clinical Relevance
TAZPOWER is the pivotal long-term efficacy study for elamipretide in Barth syndrome and provides the strongest clinical evidence for sustained benefit of mitochondrial-targeted peptide therapy in humans. The 96.1-meter improvement on 6MWT at 168 weeks is substantial — for context, a 30-meter improvement is generally considered clinically meaningful. The sustained tolerability over 3+ years addresses long-term safety concerns. While Barth syndrome is a specific genetic condition, this study validates the broader principle that targeting cardiolipin with SS-31 can produce durable clinical improvements in mitochondrial disease, supporting its investigation in age-related mitochondrial dysfunction.
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#research #observational #evidence-level-II #ss-31 #mitochondrial