One of the best Christmas presents ever given was last December 23rd
when the FDA approved Spinraza
(nusinersen) for the treatment of spinal muscular atrophy (SMA) based on interim analysis of a phase 3 study.
For the approval, the FDA looked at data from 82 of the 122 infants enrolled in the study and that was enough to convince them that the drug was effective. This week at the AAN Annual Meeting, results from all of the children in that study – the ENDEAR study — were presented and continued to show the remarkable effects this drug can have on this very vulnerable population.
Spinraza (nusinersen) in Early-Onset SMA
ENDEAR was a phase 3, randomized, double-blind, sham-procedure controlled 13-month study in which infants (< 7 months of age) with SMA were given intrathecal nusinersen (12-mg scaled equivalent dose), or sham-procedure. Primary endpoints included proportion of modified section 2 Hammersmith Infant Neurological Examination (HINE) motor milestone responders (more categories improving [≥2-point increase or maximal score in kicking ability, or ≥1-point increase in head control, rolling, sitting, crawling, standing, or walking] than worsening) and event-free survival (time to death or permanent ventilation).
At the end of the study, there was a significantly greater proportion of nusinersen-treated motor milestone responders versus sham-control (51% versus 0%; P
<.0001) demonstrating continued improvement over the previous interim analysis that led to the FDA approval (41% versus 0%; P<0.0001), and significantly greater nusinersen treatment benefit in event-free survival (hazard ratio=0.530; P
Nusinersen demonstrated a favorable safety profile and the study confirmed that the FDA approved drug is an effective treatment option for these infants.
Spinraza (nusinersen) in Later-Onset SMA
In addition to the ENDEAR study, the drug was tested in a phase 3 study involving children, aged 2-12 years of age with later-onset SMA. The CHERISH study is a phase 3, global, multicenter, randomized, double-blind, sham-procedure controlled study in which patients were given Nusinersen [ 4 intrathecal injections (totaling 12mg non-scaled)] and a sham procedure. Patients were monitored over 15 months, with a primary endpoint of change in Hammersmith Functional Motor Scale–Expanded (HFMSE) score at month 15.
Eugenio Mercuri, MD, of Catholic University and Centro Clinico Nemo in Rome presented
findings from the CHERISH trial during the Emerging Science session at the AAN meeting.
The study has shown that the efficacy trends of nusinersun in the later-onset SMA children are similar to that observed in early-onset SMA children—namely that the drug is effective. In the data, available, Dr. Mercuri noted that in more than 57% of the treated patients, HFMSE scores improved by 3 or more points at month 15, compared to about 20% of the controls. The trial reported a “favorable safety profile” with no withdrawals due to adverse events.
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 population.
Kuntz N, Farwell W, Zhong ZJ, et al. Nusinersen in Infants Diagnosed with Spinal Muscular Atrophy (SMA): Study Design and Initial Interim Efficacy and Safety Findings from the Phase 3 International ENDEAR Study. Presented at the AAN 2017 Annual Meeting; Boston, MA; April 22-28, 2017. Abstract 002.
Schneider E, Mignon L, Su J, et al. Nusinersen in Symptomatic Children with Later-onset Spinal Muscular Atrophy (SMA): Design of the Phase 3 CHERISH Study. Presented at the AAN 2017 Annual Meeting; Boston, MA; April 22-28, 2017. Abstract 184.
Mercuri E, Finkel R, Kirschner J, et al. Efficacy and safety of nusinersen in children with later-onset spinal muscular atrophy (SMA): interim results of the phase 3 CHERISH study. Presented at the AAN 2017 Annual Meeting; Boston, MA; April 22-28, 2017.