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StocksMediumUpdated•Originally published 14 September 2026•Updated 14 September 2026•
2 min read

Scholar Rock Sets ISEMBYLD Price at $11,659 a Vial After FDA Approval

Key Facts

1The U.S. wholesale acquisition cost is $11,659 per single-use ISEMBYLD vial, while the company estimated a typical patient's net annual cost at about $310,000.
2The FDA approval covers adults and children aged 2 years and older who are receiving an SMN2-targeted treatment.
3The 10 mg/kg dose produced a 2.2-point HFMSE treatment difference, while 34.2% achieved at least a 3-point gain versus 13.5% on placebo.
4SRRK closed at $55.41 on September 11, 2026, within a daily range of $54.91 to $56.94.

Scholar Rock set the U.S. wholesale acquisition cost of a single-use vial of ISEMBYLD at $11,659 after the Food and Drug Administration approved the drug on September 11, 2026, for spinal muscular atrophy.

The company said the typical patient's net annual cost would be about $310,000, with the amount varying by weight and insurance coverage. A patient weighing 35 to 45 kilograms is expected to use approximately 3 vials every 4 weeks.

The approval covers adults and children aged 2 years and older who are already receiving an SMN2-targeted treatment. That condition is important: ISEMBYLD is an add-on to existing therapy, not an independently approved replacement for it.

ISEMBYLD, or apitegromab-mstn, is a fully human IgG4 monoclonal antibody that binds promyostatin and latent myostatin and inhibits myostatin activation. It therefore targets the muscular component of SMA directly, while SMN2-targeted therapies address motor-neuron survival.

Approval was based on the 52-week, randomized, double-blind, placebo-controlled SAPPHIRE trial, which enrolled 188 patients aged 2 to 21 years across 9 countries. Participants entered 3 groups receiving 10 mg/kg or 20 mg/kg of ISEMBYLD or placebo, with background SMN2 therapy continuing and infusions administered every 4 weeks.

In the main efficacy population of 103 patients aged 2 to 12 years, the recommended 10 mg/kg dose produced a 2.2-point treatment difference on the HFMSE motor-function scale after 1 year versus background therapy alone, with a nominal p=0.0121.

A gain of at least 3 HFMSE points was recorded in 34.2% of ISEMBYLD recipients versus 13.5% in the placebo group, an odds ratio of 3.8 with a nominal p=0.0125. Fractures occurred in 9% of patients receiving 10 mg/kg versus 2% on placebo, and the FDA warns of an increased risk of fractures, including serious fractures.

The U.S. commercial launch is underway, with the company saying product would be available to ship within days and that it is engaging insurers and other payers on access. SRRK closed at $55.41 on September 11, 2026, after trading between $54.91 and $56.94; the next execution markers are patient starts and coverage and reimbursement decisions, not a technical level inferred from a single session low.