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Adherence, Persistence, and Safety of Risdiplam in Spinal Muscular Atrophy: A Population-Based Cohort Study
Maria Chovi-Trull1, Nancy C Ñungo-Garzón2,3, Karolina A Aragon-Gawinska2
1Pharmacy Department, Hospital Universitari i Politècnic La Fe, Valencia, Spain.
Introduction:
Spinal muscular atrophy (SMA) is a rare neuromuscular disorder caused by biallelic SMN1 variants, partially modulated by SMN2 copy number. Risdiplam, an oral SMN2 splicing modifier, has demonstrated efficacy in SMA. However, long-term adherence and persistence are key to sustaining benefit. We evaluated real-world adherence, persistence, and safety of risdiplam in a population-based cohort.
Methods:
This was a retrospective observational study including all genetically confirmed SMA type 1-3 patients treated with risdiplam in Spain between January 2020 and October 2025. Adherence was assessed using the proportion of days covered (PDC) from pharmacy dispensing records and the Morisky-Green questionnaire. Persistence was defined as time to permanent discontinuation or switch. Adverse events (AEs) were extracted from clinical records, and Kaplan-Meier analysis was used to estimate persistence probabilities.
Results:
Fifty-three patients were included (38 adults, 15 pediatric patients); 5.7% had SMA type 1, 52.8% type 2, and 41.5% type 3. One pediatric patient with SMA type 1 was presymptomatic at treatment initiation. Median age at risdiplam initiation was 29 years (interquartile range [IQR] 17-42), and 35.8% had prior nusinersen exposure. Adherence was high: median PDC was 100% (IQR 100-100) at 12 months and throughout follow-up; all patients assessed with the Morisky-Green questionnaire (35/53, 66%) were adherent. At 12 months, 92.5% (49/53) remained on treatment (Kaplan-Meier estimate 94.3%; 95% CI 88.3-100.0). Persistence at 24 and 36 months was 87.8% and 80.1%, respectively; later estimates should be interpreted cautiously because of the limited number of patients at risk. Median treatment duration was 28.1 months. Nine patients (17.0%) discontinued treatment. Treatment-related AEs occurred in 4/53 patients (7.5%), including one pediatric case of leukocytoclastic vasculitis requiring permanent discontinuation.
Conclusions:
In this real-world population-based cohort, risdiplam showed very high adherence, favorable short- to mid-term persistence, and a favorable safety profile, supporting the feasibility of oral therapy in both pediatric and adult patients with SMA.
