SRK-105 is Scholar Rock’s lead product candidate, intended to improve muscle strength and motor function in SMA patients. The potential therapy selectively inhibits the activation of myostatin, a protein mainly produced in skeletal muscle cells that suppresses muscle growth.
Absence of the MSTN gene, which codes for myostatin, is associated with increased muscle mass and strength in animal models. Based on preclinical evidence from animal models, scientists at Scholar Rock believe that inhibiting the activation of myostatin will promote a similar, clinically meaningful effect.
Mice studies showed that SRK-105 can prevent additional atrophy in animals with muscle wasting and can improve muscle mass and function. Promising findings were also reported in studies with primates, where the investigational compound was able to increase animals’ lean body mass, particularly in a type of muscle fiber affected by SMA.
These preclinical studies support the company’s decision to advance into clinical testing in SMA patients.
According to Scholar Rock, SRK-105 may become the first muscle-targeting treatment to reverse or prevent muscle atrophy in patients with SMA. It could be used both as a stand-alone therapy and as a combination treatment with the current standard of care.
“We are very pleased that the FDA granted Orphan Drug Designation to SRK-015 for the treatment of patients suffering from SMA, and we appreciate that the agency’s decision came much earlier than anticipated,” Nagesh Mahanthappa, PhD, President and CEO of Scholar Rock, said in a press release.
“This designation is an important milestone in the development of our lead product candidate along the path towards a first-in-human Phase 1 clinical trial in the second quarter of 2018,” Mahanthappa added.
Orphan drugs are intended for the treatment, diagnosis or prevention of rare diseases affecting fewer than 200,000 people in the United States. The designation also can be granted for diseases affecting more than 200,000 people if there is no reasonable expectation that the company will be able to recover the costs of drug development and marketing.
The designation is granted if there is a medically plausible basis for using the treatment candidate. Orphan drug status provides incentives for product development, including tax credits for clinical trials, exemption from a prescription drug user fee, and access to protocol assistance from the FDA.
Companies may also benefit from seven years of market exclusivity if the drug is ultimately approved.