Apitegromab
Apitegromab (SRK-015)
Also known as: SRK-015
An antibody against latent myostatin, under FDA review for spinal muscular atrophy (decision due September 30, 2026) and shown to preserve 55% of the lean mass otherwise lost on tirzepatide.
Overview
Apitegromab binds the pro and latent forms of myostatin so it cannot be activated, releasing the brake on muscle growth. Scholar Rock filed it for spinal muscular atrophy; a 2025 complete response letter concerned a manufacturing site only, and the resubmission carries a September 2026 decision date. In the EMBRAZE Phase 2 in obesity, adding apitegromab to tirzepatide preserved 54.9% of lean mass (1.9 kg) and shifted the composition of weight lost to 85% fat and 15% lean, versus 70/30 on tirzepatide alone.
Mechanism of action
Monoclonal antibody that binds pro/latent myostatin and prevents its activation, increasing skeletal muscle mass.
Key studies & citations
- Human2025
Scholar Rock reports positive Phase 2 EMBRAZE results
Preserved 54.9% of lean mass on tirzepatide; weight lost was 85% fat.
Scholar Rock press release - Human2026
FDA review of apitegromab biologics license application
Decision expected September 30, 2026.
Scholar Rock press release
Frequently asked questions
Would apitegromab be the first myostatin drug approved?
Yes, if the FDA approves it for spinal muscular atrophy in 2026. Earlier myostatin programs failed in Duchenne and sarcopenia.
Can it be used with weight-loss drugs?
Only inside trials. The EMBRAZE data are Phase 2, and the obesity indication has no approval anywhere.