We are investigating apitegromab, a muscle-targeted therapy with the aim of improving motor function for people living with SMA who have been treated with certain existing SMA therapies. Scholar Rock is the first company to show clinical proof-of-concept for an investigational muscle-targeted therapy in SMA. We have reported positive topline data from our Phase 3 SAPPHIRE clinical trial.
Despite significant advances in SMA treatments, progressive muscle weakness continues to be a hallmark of the disease. Existing treatments do not directly address the muscular components, including muscle atrophy and weakness that can lead to deterioration in mobility, swallowing, and breathing and cause excess fatigue and exhaustion. Strong clinical and preclinical evidence indicates that apitegromab has the potential to improve motor function while minimizing adverse effects. If ongoing trials apitegromab is approved, it could open a number of potential benefits above existing SMA treatments – such as sustained or improved motor function intended to provide better quality of life for those living with SMA.
Apitegromab is a selective inhibitor of latent myostatin. Myostatin is a protein expressed primarily in skeletal muscle cells that regulates muscle mass. When myostatin is activated, it works with other growth factors and hormones to inhibit muscle growth. Unlike most myostatin inhibitors, apitegromab selectively targets the latent, or inactive, form of myostatin to block its activation in the muscle.
The TOPAZ Phase 2 proof-of-concept trial investigated apitegromab in patients with Type 2 and Type 3 SMA over a 12-month treatment period. The findings from TOPAZ informed the design of SAPPHIRE, a randomized, double-blind, placebo-controlled, phase 3 clinical trial to further investigate apitegromab in non-ambulatory people with Type 2 and Type 3 SMA. Scholar Rock reported positive topline data from the SAPPHIRE clinical trial. The study achieved its primary endpoint demonstrating a statistically significant and clinically meaningful improvement for apitegromab versus placebo in motor function as measured by the gold standard HFMSE in SMA patients on chronic dosing of standard of care therapies (either nusinersen or risdiplam).
The ONYX open-label, multi-center extension study remains ongoing. The study is evaluating the long-term safety and efficacy of apitegromab in patients who completed the TOPAZ or SAPPHIRE trials.
“Our hope is to help individuals with SMA and improve their motor function.”
Ryan Iarrobino
Senior Vice President,
Clinical Development & Operations
Myostatin: A Closer Look
Myostatin is a member of the TGFβ superfamily of growth factors. It is expressed primarily in skeletal muscle cells to inhibit muscle growth, and works in concert with other growth factors and hormones to maintain appropriate muscle mass. Vertebrates that lack the myostatin gene display increased muscle mass and strength but are otherwise healthy.
Clinical Trials
SAPPHIRE was a randomized, double-blind, placebo-controlled, phase 3 clinical trial designed to further investigate apitegromab in non-ambulatory people with Type 2 and Type 3 SMA
TOPAZ Phase 2 proof-of-concept trial assessed the safety and efficacy of apitegromab in later-onset Spinal Muscular Atrophy (SMA Type 2 and Type 3).
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