Scholar Rock eyes Sept. 30 FDA decision on SMA drug apitegromab

Scholar Rock's apitegromab, the first muscle-targeted therapy for spinal muscular atrophy, faces a Sept. 30 FDA decision after the company pivoted to a second fill-finish facility to clear a manufacturing hurdle that had stalled its application.

"We are on the threshold of bringing the world's first muscle-targeted therapy to children and adults living with SMA," CEO David Hallal said on the company's second-quarter earnings call. "We are ready to launch apitegromab at any time prior to and including our September 30 PDUFA date."

The resubmitted biologics license application, filed March 30, includes two fill-finish facilities after the prior application drew a complete response letter over good manufacturing practice observations at Catalent Indiana's site, now owned by Novo Nordisk and classified as Official Action Indicated after an April inspection. Scholar Rock said the alternate facility's data package was submitted ahead of schedule and that it has more commercial vials ready from that site than from Catalent Indiana.

Approval would mark Scholar Rock's first commercial product, targeting an estimated 35,000 patients worldwide who have received an SMN-targeted therapy. The company ended the second quarter with $492 million in cash, cash equivalents and marketable securities, including $63 million in net proceeds from its at-the-market program.

A selective approach to myostatin

Apitegromab targets the latent, or inactive, form of myostatin, a protein that acts as the body's natural negative regulator of muscle growth. Prior myostatin-inhibition programs failed because targeting the mature protein or its receptor triggered off-target effects involving related proteins in the TGFβ superfamily, Hallal said.

The drug entered healthy-volunteer testing in 2018 and SMA development in 2019. Scholar Rock selected SMA because muscle is the principal organ affected by the disease, while existing treatments from Biogen's Spinraza, Roche's Evrysdi and Novartis' Zolgensma focus on improving survival motor neuron protein production and motor neuron health.

In the 188-patient Phase III SAPPHIRE trial, patients assigned to placebo lost motor function while those receiving apitegromab gained motor function despite background SMN-targeted therapy, Hallal said. The company is also running the Phase II OPAL study in infants and toddlers with SMA and initiated the 60-patient Phase II FORGE study in facioscapulohumeral muscular dystrophy, or FSHD.

Commercial readiness and the European path

Scholar Rock has built a U.S. commercial team led by executives Keith Woods and Rebecca McLeod, who previously led the launch of argenx's VYVGART. The company's Scholar Rock Supports program is designed to help SMA patients navigate access and reimbursement, though payer coverage processes could take time, including the eventual establishment of a drug-specific J-code for the every-four-week infusion schedule.

A survey of more than 30 key opinion leaders managing over 500 patients found that about 42 percent would call all eligible patients to offer apitegromab at approval, up from 23 percent a year earlier, Hallal said.

In Europe, the marketing authorization application initially listed only the Catalent Indiana facility. Scholar Rock is planning discussions with the European Medicines Agency on including the alternate facility, with potential options including withdrawing and resubmitting the application.

BMO Capital raised its price target on Scholar Rock to $76 from $70, noting confidence ahead of the apitegromab decision is shifting focus away from the Catalent concerns. Scholar Rock shares carry a Buy rating among analysts, and the company has an option to draw down an additional $150 million from its existing debt facility and plans to monetize a priority review voucher upon approval.

This article is for informational purposes only and does not constitute investment advice.