The news of Spinraza’s (nusinersen) approval for Spinal Muscular Atrophy (SMA) in late December was a late end of the year gift that brought happiness to many.
Finally, the data of the drug’s demonstration of a statistically significant reduction in the risk of death or permanent ventilation in treated infants was presented at the British Pediatric Neurology Association (BPNA) annual conference in Cambridge.
Biogen ended their Phase 3 trial of Spinraza early after meeting its primary endpoint, so that all the patients involved in the study could participate in the open-label extension study.
The positive data continued in the open-label extension study as Spinraza met its primary endpoint, and demonstrated a 47% reduction in the risk of death or permanent ventilation
(P <0.01). 68% of the untreated infants in the study died or required permanent ventilation versus infants receiving treatment (39%).
Efficacy and Safety
The efficacy of Spinraza was demonstrated in a clinical trial in 121 patients with infantile-onset SMA who were diagnosed before 6 months of age and who were less than 7 months old at the time of their first dose.
Participants had their final study visit after the interim analysis (n=78) and had the opportunity to attend the six-month study visit assessment.
Patients were randomized to receive an injection of Spinraza, into the fluid surrounding the spinal cord, or undergo a mock procedure without drug injection (a skin prick). The trial assessed the percentage of patients with improvement in motor milestones, such as head control, sitting, ability to kick in supine position, rolling, crawling, standing and walking.
What is Spinal Muscular Atrophy?
SMA is a genetic condition that leads to a deficiency in the spinal motor neuron (SMN) protein as a result of mutations of the survival motor neuron 1 (SMN1) gene. The severity of SMA correlates with the amount of SMN protein. Generally, the muscles most affected are those near the shoulders, hips, thighs and upper back. Muscles used for breathing and swallowing may also be affected. Infants with Type I SMA produce very little SMN protein and have a life expectancy of less than two years. Children with Type II have greater amounts of SMN protein but still have a shortened lifespan and are never able to stand independently. Children with Type III have a normal lifespan but accumulate life-long physical disabilities as they grow.
Nusinersen is an antisense oligonucleotide (ASO) that is designed to alter the splicing of pre-mRNA from the SMN2 gene in order to increase production of fully functional SMN protein. Nusinersen is being investigated in Type I, II, and III SMA populations.