SMA therapy stays on track for FDA decision after manufacturing change

Scholar Rock has successfully removed a manufacturing facility from its application to the U.S. Food and Drug Administration (FDA) seeking approval of apitegromab, an experimental muscle-strengthening treatment for spinal muscular atrophy (SMA).

The move follows an announcement earlier this month that the company planned to remove Catalent Indiana, part of Novo Nordisk, after the FDA classified it as Official Action Indicated (OAI), meaning significant problems were identified that may warrant regulatory action. Following FDA guidance, Scholar Rock proceeded with a second, U.S.-based fill-finish facility instead.

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FDA decision remains on track after manufacturing change

Scholar Rock continues to expect an FDA decision by Sept. 30. The company says it is prepared to launch apitegromab in the U.S. immediately if approved, with a supply of commercial vials produced at the alternate facility.

The manufacturing change is also reshaping apitegromab’s regulatory path in Europe. Scholar Rock has withdrawn its Marketing Authorisation Application (MAA) from review and plans to resubmit it using the alternate fill-finish facility.

“We are very pleased with the continued constructive and collaborative engagement we have with regulators both in the U.S. and Europe and look forward to commencing our US launch … pending FDA approval,” David L. Hallal, Scholar Rock’s board chair and CEO, said in a press release.

Meanwhile, regulators in Japan have agreed that no additional clinical studies are required to support Scholar Rock’s planned Japanese New Drug Application for apitegromab. Clinical studies involving Japanese patients are typically required to support such applications. However, recent guidelines allow certain rare disease medicines to be submitted without domestic clinical data under specific circumstances, including when a pivotal trial has already been successfully conducted outside Japan and recruiting enough local patients would be difficult because of the rarity of the disease. Scholar Rock plans to submit its Japanese application by year-end.

“In line with our ambition to serve patients with SMA in up to 50 countries around the world, we are also thrilled to announce that we now have alignment with [Japan’s Pharmaceuticals and Medical Devices Agency] in Japan to submit our apitegromab [application] for the treatment of children and adults with SMA by year end. Together, our regulatory advancements reinforce our commitment to act with urgency on behalf of the SMA community globally,” Hallal said.

Apitegromab takes a different approach to treating SMA

SMA is a genetic disease characterized by symptoms such as muscle weakness and wasting. While existing disease-modifying treatments target the underlying shortage of survival motor neuron (SMN) protein, which is essential for the health of nerve cells that control movement, apitegromab is being developed through a different approach. The antibody-based therapy is designed to selectively block the activation of myostatin, a protein that normally limits muscle growth.

By targeting the inactive, or pro- and latent, forms of myostatin before the protein becomes active, apitegromab is intended to improve muscle strength and improve motor function. Scholar Rock is developing it as a muscle-targeted treatment that could be used alongside SMN-targeting therapies.

The application seeking its approval is supported mainly by data from the Phase 3 clinical trial SAPPHIRE (NCT05156320), which enrolled 188 children and young adults with SMA type 2 or type 3, who were already taking Spinraza (nusinersen) or Evrysdi (risdiplam). After about a year, apitegromab improved motor function, with Hammersmith Functional Motor Scale Expanded (HFMSE) scores averaging 1.8 points higher than with a placebo.