Determining SMA Treatment Adherence Rates in Real-World Clinical Setting

A majority of adults with spinal muscular atrophy (SMA) remained adherent to nusinersen therapy or effectively resumed treatment after a missed dose, according to results of a study published in the Journal of Neuromuscular Diseases.

Little data exists on adherence rates for SMA therapy, prompting authors to conduct a multisite retrospective chart review of 86 adults initiating nusinersen treatment across 9 US Muscular Dystrophy Association clinics between January 2017 and February 2019.

Included participants were aged ≥18 years, had a genetically confirmed diagnosis of 5q SMA, and had complete information on the date of nusinersen administration. Patients underwent follow-up from the initiation date through August 31, 2019, discontinuation, or lost to follow-up, whichever came first.

In terms of patient characteristics, 46 (53%) patients had SMA type III, 76 (86%) patients were nonambulatory at baseline, and 54 (63%) had a record of scoliosis.

After a mean (range) of 1.5 (0.3-2.2) years, participants had received a median (range) of 7 (401) doses. Of the 86 included patients, 79 (92%) remained adherent to nusinersen for the full period.

The majority of patients (58 [67%]) received all doses on time and overall, 454 of 493 total doses for the whole cohort were received on time. Most patients followed the regular dosing schedule throughout loading and maintenance dose periods.

“Median time from the previous dose was 14 days for doses 2 and 3, 31 days for dose 4, and 123 to 126 days for doses 5 through 8, which aligned well with the recommended dosing intervals,” said researchers.

Of 28 patients who received ≥1 dose either earlier or later than normal, 26 (93%) continued nusinersen treatment following the nonadherent dose, and 18 (64%) resumed nusinersen on time by shifting dosing schedules.

The 7 (8%) patients who discontinued treatment did so during the maintenance dose phase; however, authors noted reasons for discontinuation are unavailable as the information is not routinely recorded in medical charts. All patients who discontinued treatment were nonambulatory and 6 patients had scoliosis.

“Our findings on the low rates of discontinuation are consistent with studies conducted during a similar study period to examine nusinersen effectiveness and safety in adult patients treated with nusinersen,” said researchers.

For patients who missed doses, authors note in their discussion that the goal should be return to the original dosing schedule as soon as possible to ensure the most optimal exposure to nusinersen.

 “Recent studies on nusinersen adherence were based on US commercial insurance claims which often fail to capture all medications received by a patient,” authors noted. “This may produce erroneous findings when calculating patient adherence.”

With that in mind, this study contributes toward the real-world understanding of nusinersen adherence, but more research is needed to determine the short- and longer-term adherence, as well as its effect on patient outcomes.

Reference:
Elman L, Youn B, Proud CM, et al. Real-world adherence to nusinersen in adults with spinal muscular atrophy in the US: a multi-site chart review study. J Neuromuscul Dis. 2022;9(5):655-660. doi:10.3233/JND-210768