Isembyld (apitegromab-mstn) received FDA approval on September 11, 2026 for SMA in patients aged at least two receiving an SMN2-targeted treatment. Scholar Rock confirms first commercial U.S. infusions in October. Muscle preservation during weight loss remains investigational. FDA highlights fracture risk and possible fetal and reproductive harms.
1.9 kg less DXA lean mass lost with apitegromab added to tirzepatide (80% CI 1.2–2.7) · 24 weeks
EMBRAZE · Nature Medicine · Both groups received tirzepatide, titrated up to 15 mg weekly. The add-on was apitegromab 10 mg/kg every four weeks or placebo. · Adjusted least-squares means in treatment completers with evaluable DXA; baseline weight/lean mass, age and sex covariates. CIs are 80%, not 95%.
Limitations: Small phase 2 completer analysis; no multiplicity adjustment. DXA lean mass is not muscle function; exploratory function showed no notable difference. Eight weeks after stopping both drugs, the lean-mass difference narrowed to 0.9 kg.
Current status: Isembyld (apitegromab-mstn) received FDA approval on September 11, 2026 for SMA in patients aged at least two receiving an SMN2-targeted treatment. Scholar Rock confirms first commercial U.S. infusions in October. Muscle preservation during weight loss remains investigational. FDA highlights fracture risk and possible fetal and reproductive harms. Source
A fully human antibody that binds pro- and latent myostatin.
Uses, doses and availability depend on the formulation, indication and country. Study doses below describe research; they are not prescribing instructions.
The molecule
A fully human antibody that binds pro- and latent myostatin.
Structure not yet verified
Exact antibody structure not verified
A fully human antibody that binds pro- and latent myostatin.
Shown: Full monoclonal antibody
No exact apitegromab atomic model was verified. PDB 6UMX was checked but excluded: its Fab is 29H4-16, a high-affinity antibody variant with four CDR changes, not exact SRK-015.
A next milestone is not summarized for this therapy. This does not mean development has ended.
Development history3 selected milestones
Apitegromab · compound history across indications
This timeline includes selected body-composition publications and any separately sourced regulatory updates. It is not a complete development history; earlier clinical work and other indications may be missing.
Publication
EMBRAZE publication
Apitegromab for lean mass preservation during tirzepatide-induced weight loss: a randomized, double-blind, placebo-controlled phase 2 trial
Scholar Rock confirms first infusions in October 2026 after shipment to the specialty network. The approved use covers patients aged at least two receiving SMN2-targeted therapy.