In Development Pipeline & In-Development

Apitegromab

also known as: SRK-015

⚠ Monoclonal antibody — not a classical peptide. A Scholar Rock fully human IgG (~150 kDa) selective for pro-/latent myostatin (sparing mature myostatin in other tissues) — SAPPHIRE Phase 3 in spinal muscular atrophy read out positive in October 2024; BLA submission in 2025. Platform validation for myostatin biology beyond the muscle-sparing-in-obesity use case.

A fully human monoclonal antibody developed by Scholar Rock that selectively targets the pro- and latent forms of myostatin rather than the active mature ligand, preserving myostatin activity in non-target tissues; the SAPPHIRE Phase 3 trial in spinal muscular atrophy read out positive in October 2024 with a statistically significant improvement on the Hammersmith Functional Motor Scale Expanded, and a BLA has been prepared for FDA submission.

Mechanism of action

Binds the N-terminal prodomain of myostatin on its pro- and latent forms, preventing activation to the mature active ligand. Because the antibody does not bind the processed active myostatin already in circulation at physiological levels in other tissues, the mechanism is claimed to be more tissue-selective than mature-myostatin or receptor-level blockade, reducing off-target effects on other GDF/activin pathway members.

Primary uses

  • Spinal muscular atrophy (Phase 3 positive; BLA preparation)
  • Research interest in obesity muscle-sparing adjunct positioning

Typical dosing

10–20 mg/kg every 4 weeks (intravenous)

SAPPHIRE protocol dosed IV every 4 weeks as an adjunct to SMN-targeted therapy.

Regulatory status

Not yet approved. Scholar Rock announced positive SAPPHIRE Phase 3 results in spinal muscular atrophy in October 2024 (statistically significant improvement on HFMSE at week 52 in combination with SMN-targeted therapy) and prepared a BLA submission. If approved, apitegromab would be the first disease-modifying muscle-targeted therapy for SMA to act via the myostatin pathway.

References

  1. [manufacturer] Scholar Rock. "SAPPHIRE Phase 3 topline results for apitegromab in spinal muscular atrophy," corporate press release, October 2024.
  2. [clinical-trial] ClinicalTrials.gov identifier for the SAPPHIRE Phase 3 trial in SMA.

Related peptides

Bimagrumab

⚠ Monoclonal antibody — not a classical peptide. A first-in-class muscle-sparing antibody (fully human IgG1, ~150 kDa) against activin type II receptors. Combined with semaglutide in the BELIEVE Phase 2b trial (Nature Medicine, March 2026), it produced greater fat loss than semaglutide alone while preserving lean mass. Not approved; Lilly developer. Included here because it's widely discussed alongside peptides in the muscle-sparing and myostatin conversations.

Trevogrumab

⚠ Monoclonal antibody — not a classical peptide. A Regeneron anti-myostatin fully human IgG (~150 kDa) being tested as a muscle-sparing adjunct to GLP-1 therapy — CONVERGE combination program with semaglutide in obesity; earlier sarcopenia programs were deprioritized in favor of the obesity opportunity. Included here because it's widely discussed alongside peptides in muscle-sparing conversations.

Taldefgrobep alfa

A Biohaven (ex-BMS) myostatin-binding adnectin-Fc fusion — RESILIENT Phase 3 trial in spinal muscular atrophy missed its primary endpoint (December 2024); further development pivoted toward obesity and sarcopenia indications.
Disclaimer

This entry is for educational purposes only and does not constitute medical advice. Dosing information reflects published regulatory or research data and is not a recommendation. Many compounds described here are not approved for human use in the United States. Consult a licensed medical professional before considering any peptide therapy.