Rare Daily Staff

The U.S. Food and Drug Administration granted Scholar Rock Fast Track designation for apitegromab, a selective inhibitor of myostatin activation for the treatment of patients with rare neuromuscular condition spinal muscular atrophy.

Spinal muscular atrophy (SMA) is a rare, and often fatal, genetic disorder that typically manifests in young children. An estimated 30,000 to 35,000 patients are afflicted with SMA in the United States and Europe. It is characterized by the loss of motor neurons, atrophy of the voluntary muscles of the limbs and trunk, and progressive muscle weakness. The underlying pathology of SMA is caused by insufficient production of the SMN (survival of motor neuron) protein, essential for the survival of motor neurons, and is encoded by two genes, SMN1 and SMN2. While there has been progress in the development of therapeutics that address the underlying SMA genetic defect, via SMN-dependent pathways, there continues to be a high unmet need for therapeutics that directly address muscle atrophy.

Apitegromab is a selective inhibitor of the activation of myostatin and is an investigational product candidate for the treatment of patients with SMA. Myostatin, a member of the TGFβ superfamily of growth factors, 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, including humans. Scholar Rock believes that inhibiting myostatin activation with apitegromab may promote a clinically meaningful improvement in motor function in patients with SMA.

Fast Track designation is intended to facilitate the development and expedite the review of drugs to treat serious conditions and get new drugs to patients earlier. Through Fast Track, Scholar Rock is eligible to submit a rolling Biologic License Application for apitegromab if relevant criteria are met. The designation is granted to experimental medicines that could fill an unmet medical need defined as providing a therapy where none exists or improving upon available therapies and is based on whether a drug will impact factors such as survival, day-to-day functioning, or if left untreated, progression to a more serious condition.

In addition to Fast Track designation, apitegromab had previously received Orphan Drug and Rare Pediatric Disease designations from the FDA and PRIME and Orphan Medicinal Product designations from the EMA for the treatment of SMA.

Tony Kingsley, president and CEO of Scholar Rock said apitegromab has the potential to be the first muscle-directed therapy for people with SMA. “We believe the recently announced top-line data from the TOPAZ phase 2 trial showed the transformative potential of apitegromab for patients with SMA,” he said.

Photo: Tony Kingsley, president and CEO of Scholar Rock

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