Page last updated: 3rd July 2020

Nusinersen was approved for the treatment of SMA because it was demonstrated to be effective through clinical trials that enrolled young patients with severe forms of the condition (see Nusinersen Trials and Updates).

There has not been a similar large-scale clinical trial of nusinersen in adults with SMA. Nevertheless, many smaller studies are beginning to emerge that are reporting positive responses to nusinersen treatment in some adults with SMA (See Other Published Summaries of Treatment Outcomes).

Dr James Sleigh our Scientific Research Correspondent discusses three recent scientific reports in which adults with SMA have received repeated injections of nusinersen into the fluid bathing the spinal cord and brain (i.e. intrathecal injections):

The first study by Veerapandiyn et al. , published in the scientific journal Muscle & Nerve and conducted in New York state, assessed the impact of nusinersen treatment in twelve SMA patients (one with Type 1, four with Type 2 and seven with Type 3). Patients were 12-52 years old (average of 22) at the first injection, and all had scoliosis (sideways curvature of the spine), which can make the drug administration more difficult. Assessments were conducted over an average duration of 17.4 months (range of 4-26 months) from the first injection.

Headaches and pain at the injection site were reported in a few instances (5-10% of injections), but these were deemed to be due to the procedure and not nusinersen, which was considered to be safe and generally well tolerated.

Assessment of muscle function by the Revised Upper Limb Module (RULM), six minute walk test (6MWT), and the time to complete a 30-foot walk, indicated that 6 out of 9 patients treated with nusinersen showed a stabilisation in their disease, while the remaining three patients showed an improvement. Subjective increases in endurance and fine hand movements/hand strength were also reported by 8 out of 12 patients, and improved bulbar muscle function (for speaking and swallowing) in 5 out of 12 patients.

In the second study by Jochmann et al., clinician scientists from Germany reported on the effects of nusinersen treatment in seven adult patients with SMA Type 2 or 3 (aged 20-68 years) at two, six and 10 months after the first injection. Published in the journal Therapeutic Advances in Neurological Disorders, the study assessed muscle function using the Hammersmith Functional Motor Scale Expanded (HFMSE), RULM and the 6MWT. Six of the seven patients received the full regimen of six nusinersen injections.

The intrathecal injections of nusinersen were again generally well tolerated by patients. Three patients displayed clinically meaningful improvements in RULM as early as two months after the initial dosing. Over the entire 10 month study, these three patients showed an average increase of +15.7 points in RULM from baseline. The mean change in score for all patients over this period was +7.7. The same three patients showed an average +9.3 point improvement in HFMSE, with an average improvement of +5 for all patients. Only one patient could perform the 6MWT – they walked 275 m at baseline, 327 m at six months, and 343 m at 14 months.

In addition to this, 6 out of 7 patients reported a stabilisation in their muscle function or a reduction in severity of their symptoms, which was corroborated by personal assistants and treating physical therapists.

The final study, by Osmanovic et al., which was published in the Journal of Neurology and again conducted in Germany, was designed to assess patient-reported outcomes of nusinersen administration in 24 patients with SMA Types 2-4 aged 19-65 years (average of 39). The expectations of patients before and during nusinersen treatment were also specifically evaluated, while HFMSE and RULM were used to assess muscle function.

Patients generally had high expectations of the effectiveness of nusinersen to improve muscle strength and stabilise their condition. 83% expected the treatment to be effective and had confidence in the treatment, with 91% not expecting it to be a cure. 22% of patients had worries about treatment and 26% reported that they were nervous about possible negative effects of treatment.

When asked about their experiences with nusinersen treatment, 13% of patients (3 out of 24) reported a stabilisation of the condition, while 75% reported improvements in strength, endurance and/or independence over the 10 month observation period. Increased muscle strength was more often reported in less severely affected patients (87% of SMA type 3/4 versus 33% of SMA Type 2). In contrast, three patients reported an overall worsening of their condition. An average increase in HFMSE of +1 and in the RULM of +0.5 was reported, but these are not considered to be clinically meaningful.

Although individually these three and similar small studies are not large enough to provide strong statistical evidence for the effectiveness of nusinersen in adults with SMA, together they continue to support the hypothesis that some adults with SMA can benefit from its use. Not all adult patients have shown clinically measurable improvements upon nusinersen administration, but patients generally report a benefit from the therapy despite the invasive injection method.

ln the future, longer observation periods after treatment and larger cohorts of patients are needed to provide more firm conclusions on the effectiveness of nusinersen in this patient population.