Scholar Rock hopes to one-up pharma titans with a muscle-building drug

Tiny startup Scholar Rock is pressing forward with an early-stage drug it believes can contend with a new class of treatments in development by some of the industry's biggest players, planning to enter the clinic next year with a muscle-building compound.

The company's lead asset, SRK-015, is designed to block the protein myostatin, which acts as a brake on muscle growth. Halting myostatin can potentially curb the debilitating atrophy that broadly affects about 17 million Americans, according to Scholar Rock, whether through age-related muscle-wasting or as an effect of other diseases.

Myostatin is already a well-understood target in biopharma, and Scholar Rock is years behind some well-funded contenders. Novartis ($NVS) is in Phase III with bimagrumab, a breakthrough-designated antibody slated for FDA filing next year, while GlaxoSmithKline ($GSK), Sanofi ($SNY), Eli Lilly ($LLY) and others trail with similar therapies.

But Scholar Rock believes SRK-015 has a chance to eventually become a best-in-class agent for building muscle, CEO Nagesh Mahanthappa said. The key is in the drug's mechanism of action.

Mahanthappa said the aforementioned Big Pharma therapies work in one of two ways: binding to mature myostatin proteins to quiet their activity, or targeting the receptors that bring them about to stop the process at its onset. But each of those approaches creates selectivity problems, he said, as myostatin shares many properties with other growth factors in the body, and the most common receptors also interact with at least 10 other proteins. That creates the risk of biological crosstalk that could both hamper efficacy and limit dosing, Mahanthappa said.

SRK-015, on the other hand, is engineered to target myostatin in its latent form, before it reaches final maturity. Doing so has the potential to create an efficacious treatment that can hit the same target without as much noise, Mahanthappa said, allowing SRK-015 to "effectively turn off the tap" on myostatin and thus promote muscle growth.

And in preclincal studies, the drug has done just that. At a medical congress in Switzerland this week, Scholar Rock is presenting results from animal trials in which SRK-015 successfully bonded to latent myostatin without getting stuck to its related growth factors, leading to a positive effect on muscle mass in healthy mice and preserving it in those with atrophy.

Now the company is gearing up to begin its first clinical trial in 2016, Mahanthappa said, expecting to report first-in-human data the following year. Scholar Rock is keeping its specific disease targets under wraps for now, with the CEO saying only that it is looking at "orphan and orphan-like" patient populations with the goal of moving quickly through the development process. Once it has established proof of concept in so-called primary myopathies, the company will likely look to larger indications in which muscle atrophy is secondary to a more common disease, he said.

To get there, Scholar Rock will eventually need to raise some more money. The company is now working off of a $20 million Series A closed in 2014 with the help of Polaris Partners, Arch Venture Partners, EcoR1 Capital and others. Mahanthappa declined to provide specifics on Scholar Rock's financing plans but said the company has so far found potential new investors to be receptive to its model.

Aside from its work in muscle atrophy, the company is collaborating with Johnson & Johnson ($JNJ) in oncology and immunology, targeting the same broad family of growth factors at play in SRK-015.

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