Scholar Rock gets first drug approval as FDA okays Isembyld
Scholar Rock has won its first product approval, 14 years after it was founded, as the FDA gives a green light to its spinal muscular atrophy (SMA) therapy Isembyld.
Isembyld (apitegromab) has been cleared for adults and children aged 2 and over with SMA who are currently receiving an SMN2-targeted treatment, i.e. Biogen's antisense-based therapy Spinraza (nusinersen) and Roche's oral mRNA splicing modifier Evrysdi (risdiplam).
The approval comes a year after Scholar Rock's first attempt to persuade the FDA that Isembyld should be approved resulted in a complete response letter (CRL), sparked by unresolved compliance issues at a manufacturing plant operated by Novo Nordisk (now rebranded Novo).
Now, Scholar Rock has started to roll the myostatin inhibitor out in the US, saying it will be available in the coming days. A commercial price of the new therapy has not yet been released, but more details may be available on an investor call the company has scheduled for later today. Using placeholder pricing, analysts at BMO Capital Markets have forecast that Isembyld could reach peak global sales of $2.1 billion by 2030, according to a Reuters report.
The company is the "first and only muscle-targeted treatment" for children and adults with SMA in the US. Spinraza and Evrysdi, for example, prevent motor neuron loss in SMA, but do not directly address muscle.
SMA is a genetic disorder that can cause rapid and irreversible loss of motor neurons, affecting muscle functions, including breathing, swallowing, and basic movement. The condition is estimated to affect roughly 10,000 children and adults in the US.
Scholar Rock filed for approval of apitegromab based on the SAPPHIRE trial, which tested the drug in patients aged two to 12 who were already being treated with SMN2 drugs.
The drug showed a statistically significant and "clinically meaningful" 2.2-point improvement in motor function over placebo after 52 weeks of treatment, measured using the 33-point Hammersmith Functional Motor Scale Expanded (HFMSE), according to the Cambridge, Massachusetts biotech.
It will enter a market that has seen some major advances in recent years, including the approval of Novartis' gene therapies Zolgensma and Itvisma (both onasemnogene abeparvovec), which together offer a one-shot option for SMA patients in the same two-and-over age bracket.
"The approval of Isembyld as the first-ever treatment to directly target the muscular component of SMA is a significant turning point for adults and children who have been waiting for innovative therapeutic options to improve motor function," said Kenneth Hobby, president of the Cure SMA patient advocacy group.
"Such improvements are fundamental to maintaining independence and to enabling participation in important activities of daily living from self-care to work and social interactions," he added.
The FDA approval also earns Scholar Rock a rare paediatric disease priority review voucher, which can be used to reduce a future review from around 10 to six months and can be worth between $100 million and $200 million if sold to another company.
The company is also developing apitegromab for other indications, including SMA in the under-twos, facioscapulohumeral muscular dystrophy (FSHD), and skeletal muscle loss associated with weight-loss therapies.
