FDA review of apitegromab for SMA continues, minus one facility

Scholar Rock's biologics license application for apitegromab, an investigational muscle-targeted therapy for spinal muscular atrophy, remains on track for a September 30, 2026, decision after the company said it would proceed with only one of its two proposed manufacturing sites.¹

The FDA review of apitegromab, Scholar Rock's investigational anti-myostatin monoclonal antibody for spinal muscular atrophy (SMA), will move forward using only the company's second fill-finish manufacturing facility after a co-packaging partner's site received an unfavorable inspection outcome. The company said the Prescription Drug User Fee Act (PDUFA) action date of September 30, 2026, is unchanged.²

"We continue to be very pleased with our second fill-finish facility," David L. Hallal, board chair and CEO of Scholar Rock, said in a company statement, adding that the facility "has demonstrated a strong track record of compliance, including recent successful FDA and EMA inspections."

If approved, apitegromab would become the first muscle-directed therapy for SMA, a genetic neuromuscular disease marked by progressive motor neuron loss and muscle weakness.¹

Manufacturing shift behind the BLA update

Apitegromab's March 2026 BLA submission originally named 2 fill-finish facilities as independent supply pathways: Catalent Indiana LLC, now part of Novo Nordisk, and a second, undisclosed US-based site. On August 7, Scholar Rock said the FDA classified an April 2026 inspection of the Catalent Indiana facility as Official Action Indicated (OAI), a designation reserved for findings serious enough to warrant regulatory follow-up. The company will remove Catalent Indiana from the application and proceed solely with the second facility, under FDA guidance.¹

At a March 2026 Type C meeting, the company and FDA agreed on the data package needed for review of the second facility; it was submitted ahead of schedule and is under active review. Scholar Rock describes the site as a US-based facility in good standing with the FDA and EMA, with commercial vials already awaiting packaging and labeling. The company said it continues working with the EMA on including the facility in Europe's marketing application.³

Clinical rationale: the SAPPHIRE trial

Apitegromab's regulatory package rests on the phase 3 SAPPHIRE trial, a 52-week, placebo-controlled study at 48 sites in Europe and the US in patients aged 2 to 21 years with nonambulatory type 2 or type 3 SMA already receiving nusinersen or risdiplam. Among the 156 patients aged 2 to 12 years, combined apitegromab dose groups showed a mean HFMSE difference of 1.8 points versus placebo, a statistically significant and prespecified clinically meaningful margin. About 30% of apitegromab-treated patients achieved a 3-point or greater improvement, versus roughly 13% on placebo. Motor function improved with apitegromab and declined with placebo despite background SMN-targeted therapy in both arms, with a safety profile consistent across ages and no new safety signals. Results were published in The Lancet Neurology, with Thomas O. Crawford, MD, of Johns Hopkins University, as lead investigator.³

Disease burden and unmet need in SMA

SMA is a rare, autosomal recessive neuromuscular disorder caused by loss of the SMN1 gene, with an estimated incidence of roughly 1 in 10,000 live births. The 3 approved SMN-targeted therapies have transformed outcomes since 2016, but many patients continue to have measurable motor deficits despite treatment. Apitegromab instead selectively binds pro- and latent myostatin, a TGFβ-family protein regulating skeletal muscle mass. The FDA has granted it Fast Track, Orphan Drug, and Rare Pediatric Disease designations; the EMA has awarded PRIME and Orphan Medicinal Product status.⁴

Interpreting the update, and open questions

The disclosure is a manufacturing and supply-chain development, not a change to apitegromab's clinical data package; SAPPHIRE's efficacy and safety findings are unaffected. Whether the FDA's review of the second facility concludes favorably within the remaining window will determine whether the September 30 PDUFA date holds. Scholar Rock's characterization of "robust supply" and launch readiness should be weighed against the fact that the facility, though previously cleared for other products, has not yet completed the specific review tied to this BLA. The announcement does not specify what deficiencies prompted the OAI classification or quantify supply relative to anticipated demand, and the EMA timeline for the European application remains unset.

References

1. Scholar Rock, Inc. Scholar Rock announces FDA review of apitegromab Biologics License Application (BLA) for spinal muscular atrophy (SMA) to progress with second fill-finish facility; approval decision anticipated by September 30, 2026 action date. Published August 7, 2026. Accessed August 11, 2026. https://investors.scholarrock.com/news-releases/news-release-details/scholar-rock-announces-fda-review-apitegromab-biologics-license

2. Scholar Rock, Inc. About apitegromab. Press release, August 7, 2026. Accessed August 11, 2026. https://investors.scholarrock.com/news-releases/news-release-details/scholar-rock-announces-fda-review-apitegromab-biologics-license

3. Crawford TO, Servais L, Mercuri E, et al. Efficacy and safety of apitegromab in nonambulatory type 2 or type 3 spinal muscular atrophy (SAPPHIRE): a phase 3, double-blind, randomised, placebo-controlled trial. Lancet Neurol. 2025 Aug 13. doi:10.1016/S1474-4422(25)00225-X

4. Bertini E, et al. Pharmacological therapies of spinal muscular atrophy: a narrative review of preclinical, clinical-experimental, and real-world evidence. Accessed August 11, 2026. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10605203/