Developer tries again for US approval of SMA therapy apitegromab
With manufacturing issues resolved, Scholar Rock resubmits application to FDA
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- Scholar Rock has resubmitted its application for FDA approval of apitegromab as a treatment for children and adults with SMA in the U.S.
- Apitegromab is a muscle-strengthening agent, designed as an add-on treatment to existing therapies.
- A previous FDA rejection was due to manufacturing issues, now resolved; a decision is expected by late September, according to the developer.
Scholar Rock has resubmitted its application seeking approval in the U.S. of its muscle-strengthening agent apitegromab — rejected last year due to manufacturing issues — for the treatment of children and adults with spinal muscular atrophy (SMA).
The drug developer said it expects the U.S. Food and Drug Administration (FDA) to take as long as a month to accept the resubmitted biologics license application (BLA), then another six months to review it. A decision from the FDA should be expected in late September, according to the company.
Apitegromab is also under review in the European Union, with a decision expected this summer, per Scholar Rock.
“Our apitegromab BLA resubmission marks an important step forward in our mission to bring the world’s first muscle-targeted therapy to children and adults living with SMA,” David L. Hallal, chairman and CEO of Scholar Rock, said in a company press release, which noted that “updates to the apitegromab BLA for the resubmission were limited in scope.”
The FDA last year rejected Scholar Rock’s first application seeking approval of apitegromab as an add-on SMA treatment. At the time, the FDA did not note any issues specifically related to the experimental therapy, but concerns were raised during an inspection of Catalent Indiana, a third-party fill-finish facility. This type of facility is responsible for last steps of manufacturing medical products, such as making sure that medicines are sterile.
Since that rejection, Scholar Rock, Catalent Indiana, and the FDA have been working together to address the issues raised. According to Scholar Rock, the FDA has not noted any concerns with the proposed remediation plan.
In the meantime, Scholar Rock has also been working with a second U.S.-based fill-finish facility to strengthen its supply chain for apitegromab in anticipation of a global launch later this year. In line with FDA guidance, that second facility was also included in the newly submitted BLA.
“We continue to be encouraged by the FDA’s engagement and shared sense of urgency as we work relentlessly for the SMA community. As we execute our plans for both Catalent Indiana and our second fill-finish facility, we look forward to anticipated apitegromab approvals and launches in both the U.S. and Europe this year,” Hallal said.
Apitegromab designed as add-on therapy to aid muscle growth
SMA is a genetic disorder in which motor neurons, the nerve cells that control movement, sicken and die, most commonly due to low levels of a protein called SMN.
Several disease-modifying treatments can increase SMN protein levels, thereby preserving motor neuron health and slowing disease progression. But many SMA patients nonetheless continue to experience muscle weakness.
Apitegromab is designed to be an add-on to SMN-boosting therapies for SMA. It works by inhibiting myostatin, a protein that normally prevents unneeded muscle growth. By blocking this protein, the therapy aims to promote muscle growth and improve strength for people with SMA.
For now, apitegromab is administered intravenously, or by infusion into the bloodstream. Scholar Rock is also developing a version that can be given subcutaneously, or via under-the-skin injections, which is expected to be more convenient for patients.
The developer’s applications for apitegromab’s approval were based mainly on data from the now-completed Phase 3 SAPPHIRE clinical trial (NCT05156320). That trial enrolled 188 children and young adults with SMA type 2 or type 3, all of whom were receiving the SMN-targeted therapies Spinraza (nusinersen) or Evrysdi (risdiplam).
The results showed SAPPHIRE met its primary goal: Patients given apitegromab showed significant improvements in motor function compared with those on a placebo, with the greatest gains seen among participants who were younger and who started treatment earlier. The therapy was generally well tolerated, with no serious side effects reported.
While SAPPHIRE enrolled patients ages 2 to 21, a separate trial called OPAL (NCT07047144) is now testing the therapy in babies and toddlers up to age 2. That study is enrolling participants at sites in the U.S. and Europe.
