Background
SMA is a progressive neuromuscular disease caused by deletion or mutation of the survival of motor neuron 1 (SMN1) gene. Risdiplam (EVRYSDI®) and nusinersen (SPINRAZA®) are two FDA-approved treatments for chronic use in pediatric and adult patients with SMA. Risdiplam is an at-home, once-daily, orally administered therapy, while nusinersen is administered intrathecally. In real-world studies of nusinersen, mean adherence rates and proportion of patients adherent over a ≈12-month follow-up period were 41%–67% and 72%–76%, respectively.
Objective
This retrospective study utilized real-world data to better understand risdiplam adherence and persistence over 12 months in patients with SMA.
Methods
Adherence and persistence were examined using a specialty pharmacy database that captures ≈98% of pharmacy claims for patients treated with risdiplam in the US. Patients with ≥2 prescription shipments of risdiplam and an ICD-9/10 diagnosis code for SMA from Aug 7, 2020–Sep 11, 2022, with ≥12 months of follow up from first shipment date, were included. Patient characteristics, including age, sex, diagnosis code, prescriber geographic region and primary payer, were collected. Adherence was calculated using the proportion of days covered (PDC) over a period of 12 months and adherent was defined as PDC ≥80%. Discontinuation was defined as a gap in supply ≥90 days.
Results
A total of 2,167 patients were included with a mean (SD) age at first risdiplam shipment of 23.1 (17.18) years. At 12 months, mean (SD) adherence rate was 87% (22%) and median (IQR) adherence rate was 97% (85%–100%). The proportion of patients adherent at 12 months was 80%. Highest adherence rates by age group were observed among those 3–5 years at 92%, followed by 6–17 years, 0–2 years and ≥18 years, at 87%, 87% and 86%, respectively. The majority of patients remained on treatment at 12 months. The mean (SD) and median (IQR) number of persistent days on treatment within a 12-month period was 330.4 (80.8) and 365 (365−365) days, respectively.
Conclusions
To our knowledge, this is the first study to evaluate real-world adherence and persistence with risdiplam in the US. These results demonstrate high adherence and continuous treatment with risdiplam among patients with SMA over the study period, which is essential in achieving preservation of function and improved clinical outcomes.