Over 7,500 individuals have been or are being treated with nusinersen (Spinraza; Biogen, Cambridge, MA). Across clinical trials and the real-world setting, there are now 7 years of data and experience showing that nusinersen has clinical efficacy and safety. In the NURTURE study (NCT02386553) in which presymptomatic infants likely to develop spinal muscular atrophy type one (SMA1) or type 2 (SMA2) were treated with nusinersen, children continue to develop and gain typical motor milestones. After 26 months of treatment, all infants could sit without support; 88% could walk with support and 77% could walk without support. These data support that early diagnosis of SMA1 and early treatment have efficacy and safety for treating SMA.
In the SHINE study (NCT02594124), which is the open-label extension of the pivotal ENDEAR trial (NCT02193074) of nusinersen, children also continue to achieve motor milestones. Children treated with nusinersen in SHINE and ENDEAR (n = 65) had an average 16.8-point increase on the Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP INTEND) score after nearly 3 years of treatment. Those who received sham-control in ENDEAR and then nusinersen in SHINE (n = 24) had an average increase in CHOP INTEND score of 8.2 points after more than 1.5 years of treatment. Participants who began treatment at an earlier age (≤ 5.42 months, n = 30) had an average 19.4-point improvement vs those treated at a later age who had an average 13.8 points improvement (>5.42 months, n = 21).
This work has also allowed the further study and better study of the disease, including work around a biomarker that may help us characterize disease progression in the future. People with SMA have elevated levels of phosphorylated neurofilament light-heavy chain (pNF-H), and in those treated with nusinersen, this is significantly reduced. The hope is that a biomarker like pNF-H in the future could be used to predict motor progression in people with SMA, and that this could be used to manage care.
This work is also helping to treat adults with SMA type 3 (SMA3), many of whom had discontinued care because of the lack of treatment. In a prospective study, outcomes for 34 adults with SMA were compared to outcomes for untreated adults. Of those who were treated, 90% reported improvements in strength, stamina, breathing strength, chewing/swallowing, jaw range of motion, voice strength, or muscle strength. Measures of ambulation (6-minute walk test [6MWT]), revised upper limb module [RULM], or CHOP INTEND scores) were measured for participants who were ambulatory, nonambulatory-strong, or nonambulatory-weak, respectively. On all measures, participants treated with nusinersen had improvement in these measures vs declines in participants who were untreated.
Wildon Farwell, MD, executive director of clinical development at Biogen said, “We are excited by the results we are seeing with nusinersen and committed to continuing our work to understand long-term efficacy and safety of nusinersen and the natural history of SMA. We are also continuing our work to develop new treatments for SMA. We encourage people with SMA and their families to have hope and talk with their health care professionals about how treatment may help them achieve their goals.”