Scholar Rock secures first FDA approval for muscle-targeting rare disease drug

News FDA Scholar Rock secures first FDA approval for muscle-targeting rare disease drug September 14, 2026 | 2 min read | Tristan Manalac Twitter LinkedIn Facebook Email Print Scholar Rock’s spinal muscular atrophy drug, now to be called Isembyld, was originally rejected in September 2025, when the FDA cited compliance problems at a third-party manufacturer. Scholar Rock’s apitegromab has been cleared by the FDA for the treatment of spinal muscular atrophy—a key win for the company that culminates what has been a difficult regulatory path for the asset. The monoclonal antibody will be available to ship “in the coming days” under the brand name Isembyld.Isembyld is the first muscle-targeted therapy that improves motor function in patients with spinal muscular atrophy (SMA), Scholar Rock said in a news release on Friday afternoon.

The medicine is specifically indicated for patients two years and older who are also undergoing SMN2-targeted treatment. Friday’s approval came weeks earlier than the original target decision date of Sept. 30.SMA is a genetic illness characterized by the progressive weakening of muscles and is caused by mutations in genes that produce proteins crucial for the function of motor nerves.

There are other approved therapies for SMA, including Biogen’s antisense oligonucleotide Spinraza and Novartis’ gene therapy Zolgensma—but aside from Isembyld, none directly address the muscle loss in SMA, according to the FDA.The FDA’s approval grants Isembyld a “broad label,” analysts at BMO Capital Markets said in a Sunday evening note, pointing out that Isembyld isn’t limited to specific types of SMA or patients’ ambulatory status. “All in, broad labeling, differentiated efficacy, and visible physician demand reinforce [BMO’s] positive view” of Scholar Rock, the analysts wrote. Truist Securities agreed, contending that the label should translate to “broad uptake” of the drug.

The firm expects peak sales could hit $2.3 billion, though Scholar Rock hasn’t yet announced the product’s pricing.Data from the Phase 3 SAPPHIRE study supported Isembyld’s approval. Patients on the drug saw a 2.2-point improvement in a scale commonly used to quantify motor function—the trial’s primary endpoint—as compared to placebo. The most common side effects recorded in the study include vomiting, cough and upper respiratory tract infections.

Fractures occurred in 9% of patients receiving the lower Isembyld dose of 10 mg/kg dose, compared to 2% in placebo. Isembyld doesn’t carry a boxed warning.Friday’s verdict ends a difficult regulatory road for the drug. Scholar Rock first filed for approval in 2025, but that ended in a denial, with the FDA pointing to problems at a Catalent manufacturing site in Indiana.

The site is now owned by Novo Holdings, asset manager of Danish giant Novo, which bought out Catalent for $16.5 billion in 2024.This spring, Scholar Rock touted “significant progress” at the production plant, but just weeks later, the FDA gave the site an Official Action Indicated classification, for which the agency recommends regulatory or administrative actions. This classification prompted Scholar Rock last month to drop the location completely from its apitegromab application. Manufacturing Biotechs Secure Alternative Fill/Finish Capacity Amid Scrutiny of Novo Site Following FDA rejections, Regeneron and Scholar Rock are turning to other facilities to clear regulatory logjams created by quality problems at an ex-Catalent facility in Indiana.

Novo Nordisk, meanwhile, has been tight-lipped about whether its own FDA applications have been affected. December 2, 2025 · 6 min read · Nick Paul Taylor Read more Twitter LinkedIn Facebook Email Print Approvals Spinal muscular atrophy Rare diseases Manufacturing Tristan Manalac Tristan is BioSpace‘s senior staff writer. Based in Metro Manila, Tristan has more than eight years of experience writing about medicine, biotech and science.

He can be reached at tristan.manalac@biospace.com, tristan@tristanmanalac.com or on LinkedIn.