The study also found broad tolerability, with 98% of patients remaining on the therapy after 12 months.
New real-world data from nearly 300 children and teenagers with spinal muscular atrophy (SMA) show Spinraza (nusinersen) can be beneficial for patients regardless of age or functional status.
The study authors came to this conclusion based on data collected in Poland following the country’s approval of nusinersen as a reimbursable therapy for SMA. The findings were published in European Journal of Pediatric Neurology.
Nusinersen is the first disease-modifying therapy approved to treat SMA, a neuromuscular disorder associated with the progressive loss of spinal motor neurons. People with SMA have an absence of survival of motor neuron (SMN) proteins; nusinersen is an antisense oligonucleotide that increases production of SMN.
The condition has several types, based on age of onset and impairment severity. The most common form is type 1, which appears in infants (before 6 months). Patients with type 1 SMA are never able to sit on their own and usually die before age 2.
Nusinersen was first approved by the FDA to treat SMA in 2016, followed the next year by an approval from the European Medicines Agency. In 2019, Poland’s National Healthcare Fund approved the therapy for reimbursement. Prior to that, patients in Poland only had access to the drug via an early access program.
The new report is based on 298 patients aged 0 to 18 years who participated in the Polish nusinersen treatment program between March 1 and September 20, 2019. These patients had an average age of disease onset of 6.9 years. Overall, 43.5% had symptoms consistent with SMA type 1, 23.3% of cases were classified as type 2, and 31.8% of cases were SMA type 3.
After 1 year, all but 6 patients were still taking nusinersen. Of those who stopped taking the therapy, 2 patients died, 3 switched to risdiplam (Evrysdi), and the final patient was lost to follow-up. Neither of the 2 deaths was considered to be related to treatment.
The patients were assessed using either the Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND) or the Hammersmith Functional Motor Scale Expanded (HFMSE), depending on their disease type. After 1 year, 87% of patients assessed using CHOP-INTEND had improved scores and 90% of those assessed by HFMSE improved.
The study investigators said their study provides an important picture of nusinersen’s efficacy, because the treatment program into which the patients were enrolled had wide inclusion criteria and standardized protocols and organization. They noted that previous clinical trials for nusinersen only included healthier and younger patients, thus limiting the generalizability of the results.
“We found that nusinersen treatment was beneficial for the children with SMA regardless of their age, baseline functional status, or number of SMN2 gene copies,” the authors noted.
Although the treatment led to a benefit regardless of age, the investigators said younger patients tended to have greater improvement within the cohort assessed by CHOP-INTEND; no such difference was noted in patients assessed by HFMSE.
The investigators said it was also notable that most patients who started nusinersen stayed on the therapy, noting this was likely an indication of nusinersin’s efficacy and tolerability, but also of the fact that there were no other therapies available. They said the retention rate will likely decrease over time, if and when more therapies are approved in Poland.
The authors added that a new newborn screening program for SMA has been launched in Poland, giving physicians the ability to more quickly identify—and treat—people with the disease.
“Therefore, in the near future, the results of nusinersen treatment in the whole cohort of SMA patients will likely be much better,” they concluded.
Kotulska K, Chmielewski D, Mazurkiewicz-Bełdzińska M, et al. Safety, tolerability, and efficacy of a widely available nusinersen program for Polish children with spinal muscular atrophy. Eur J Paediatr Neurol. 2022;39:103-109. doi:10.1016/j.ejpn.2022.06.001