FDA Grants Rare Pediatric Disease Designation to Scholar Rock SMA Therapy

Rare Daily Staff

The U.S. Food and Drug Administration has granted Rare Pediatric Disease designation to Scholar Rock for its experimental therapy SRK-015 to treat spinal muscular atrophy, a progressive, rare genetic disease that leads to motor function impairments.

Spinal muscular atrophy (SMA) is a severe, progressive neuromuscular disease that can be fatal. It is caused by a mutation of the survival motor neuron 1 (SMN1) gene, which leads to a deficiency of SMN protein. This protein is found throughout the body and is essential to the function of nerves that control muscles and movement. Without it, nerve cells cannot function correctly, leading to muscle weakness over time. Depending on the type of SMA, an individual’s physical strength and their ability to walk, eat or breathe can be significantly diminished or lost.

SRK-015 is a selective inhibitor of the activation of myostatin, a member of the TGFβ superfamily of growth factors that is expressed primarily by skeletal muscle cells, and the absence of its gene is associated with an increase in muscle mass and strength in multiple animal species. Scholar Rock believes the inhibition of the activation of myostatin with SRK-015 may promote a clinically meaningful increase in muscle strength.

A phase 2 clinical trial in patients with Type 2 and Type 3 SMA is on track to report 6-month interim efficacy and safety data in the fourth quarter of 2020. Top-line data for the 12-month treatment period are expected in the first half of 2021.

“This Rare Pediatric Disease designation, along with the previously granted Orphan Drug designation, highlights the FDA’s recognition of the unmet medical needs of patients with SMA,” said Yung Chyung, chief medical officer of Scholar Rock. “We continue to aim to establish SRK-015 as the potential first muscle-directed therapy to address motor function deficits that persist despite the availability of SMN upregulators.”

The FDA grants Rare Pediatric Disease designation for serious or life-threatening diseases with manifestations in individuals aged from birth to 18 years, including access to the FDA’s expedited review and approval process. The designation makes SRK-015 eligible for a Rare Pediatric Disease Priority Review voucher upon approval of the therapy by the FDA. There are no approved therapies for the condition.

The vouchers can be used to reduce the time of an FDA new drug approval review to six months from ten months. The vouchers are potentially lucrative because they are transferable. Most recently, Sarepta sold its priority review voucher to Vifor Pharma $111 million in February 2020.

Photo: Yung Chyung, chief medical officer of Scholar Rock

Sarepta sold its priority review voucher to Vifor Pharma $111 million in February 2020.