FDA names Biogen’s salanersen a breakthrough therapy for SMA
Third trial of new, more potent treatment expected to launch this month
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- Salanersen, a new Biogen treatment for SMA, was awarded breakthrough therapy status by the U.S. Food and Drug Administration.
- This potent therapy, similar to Spinraza, requires fewer doses (once yearly) and shows promise in improving motor function.
- Two late-stage clinical trials are now evaluating salanersen for SMA, with a third expected to launch this month.
The U.S. Food and Drug Administration (FDA) has granted breakthrough therapy designation to salanersen, a new, more potent Biogen treatment for spinal muscular atrophy (SMA) that’s now in late-stage testing.
The treatment candidate, being evaluated in two ongoing Phase 3 clinical trials, is similar to — but requires fewer doses than — Biogen’s Spinraza (nusinersen), the first approved therapy for SMA.
The FDA awards breakthrough status to experimental therapies designed to treat serious conditions, where early clinical evidence suggests the therapy may offer meaningful improvement over marketed treatments. Breakthrough designation aims to speed the development and review of treatments that may fill unmet medical needs.
“This designation reflects the FDA’s determination that salanersen has the potential to demonstrate substantial improvement over available therapies,” Stephanie Fradette, head of the rare neurology development unit at Biogen, said in a company press release announcing the new status.
The agency’s decision to grant this designation was based mainly on early data from a Phase 1b clinical trial (NCT05575011) that’s testing salanersen in children with SMA. The study enrolled youngsters who had previously received the one-time gene therapy Zolgensma (onasemnogene abeparvovec-xioi), but did not respond as well as was hoped.
2 late-stage trials of salanersen already underway
Findings from the ongoing study have suggested that salanersen may stabilize or even improve motor function in these children.
“The FDA’s designation of salanersen as a breakthrough therapy recognizes that there is continued unmet need in spinal muscular atrophy, and there is more that can be done for people impacted by the disease,” said Diana Castro, MD, founder and director of the Neurology Rare Disease Center in Flower Mound, Texas, who serves as principal investigator of one of the Phase 3 studies.
“In the Phase 1b study of salanersen, we saw unexpected improvements on exploratory endpoints in children previously dosed with gene therapy who gained critical functions, such as sitting and walking, after receiving salanersen,” Castro said.
SMA is caused primarily by mutations that result in low levels of working SMN protein, which is vital for the survival of motor neurons, the nerve cells that control movement. Not having enough SMN protein leads to the progressive loss of these nerve cells, and to disease symptoms such as muscle weakness and wasting.
Salanersen is designed to boost SMN levels, thereby preserving motor neuron health to slow disease progression. The therapy’s molecular mechanism is essentially identical to that of Biogen’s Spinraza, the first treatment proven to slow SMA progression and now widely approved for the disorder.
Like Spinraza, salanersen is delivered by injection into the spinal canal. However, the new therapy is engineered to be more potent and be dosed less frequently than the older one — specifically, once per year instead of three times, as is the regimen for Spinraza’s maintenance doses. A high-dose regimen of Spinraza requiring fewer loading doses was approved this year in the U.S.
In [an earlier] study of salanersen, we saw unexpected improvements on exploratory endpoints in children previously dosed with gene therapy who gained critical functions, such as sitting and walking, after receiving salanersen.
Kenneth Hobby, president of the advocacy group Cure SMA, said the new FDA status “reflects the FDA’s continued commitment to SMA and its recognition of the potential meaningful impact salanersen may offer.”
“It affirms what our SMA community has recently communicated to the agency: urgent, unmet needs remain, and promising therapies deserve a rapid path forward,” Hobby said.
Biogen is now sponsoring three Phase 3 clinical trials to further evaluate salanersen, with the ultimate goal of generating a dataset that can serve as the basis for seeking regulatory approvals.
The STELLAR-1 trial (NCT07221669), testing salanersen in presymptomatic babies with SMA, is already recruiting at two sites in the U.S. The SOLAR study (NCT07444476) is testing salanersen in SMA patients ages 15 to 60 who have either not been treated before or are currently on the oral therapy Evrysdi (risdiplam); that study is also already recruiting at a site in Virginia.
The third study, STELLAR-2 (NCT07444450), will test salanersen in infants with SMA who were given Zolgensma before developing disease symptoms. Enrollment is expected to start this month, Biogen said.
“We are excited about the potential of salanersen and eager to help advance the Phase 3 program,” Castro said.
