More companies are pushing to develop myostatin inhibitors. SRK-015 is another antibody that selectively inhibits myostatin. Phase 1 Trial of SRK-015, Potential SMA Therapy, Completes 1st Dosing, Scholar Rock Reports Scholar Rock announced it has completed dosing a first group of healthy volunteers in its Phase 1 clinical study of SRK-015, a spinal muscular atrophy(SMA) treatment candidate. SRK-105 selectively blocks the activation of myostatin, a growth factor produced primarily in skeletal muscle cells that helps to maintain a healthy muscle mass. Excessive activation of myostatin is associated with muscle atrophy. Prior trials of compounds targeting the mature form of myostatin found that they can affect other closely related growth factors, possibly causing side effects. In preclinical studies, SRK-105 prevented additional atrophy in mice with muscle wasting and increased healthy animals’ muscle mass and function. The company believes SRK-105 could become the first muscle-directed treatment to reverse or prevent additional muscle atrophy in SMA patients. “The initiation of this Phase 1 clinical trial of SRK-015 is a momentous milestone for Scholar Rock and we are one step closer to potentially bringing the first muscle-directed therapy to patients suffering from SMA,” Nagesh Mahanthappa, president and CEO at Scholar Rock, said in a press release. The company is based in Cambridge, Massachusetts. The placebo-controlled, double-blind Phase 1 study is assessing the safety, tolerability and pharmacological profile of single- and multiple-ascending doses of intravenous SRK-015 in healthy adult volunteers. If successful, Scholar Rock plans to open a Phase 2 study in early next year to test the efficacy and safety of SRK-015 in patients with later-onset SMA. The therapy will be assessed either as a stand-alone therapy or in combination with an approved SMN upregulator therapy as a background standard of care. The U.S. Food and Drug Administration granted SRK-015 orphan drug status for the treatment of muscle atrophy SMA, and in January 2018 Scholar Rock announced $47 million in new financing for the compound’s clinical testing. The Phase 1 trial is continuing to enroll healthy volunteers, but more information about the trial — including test location(s) was not available.