(74) Longitudinal assessment of treatment costs in patients with spinal muscular atrophy receiving disease-modifying therapies

Background: : Spinal muscular atrophy (SMA), a rare neuromuscular disorder, was a leading genetic cause of infant mortality prior to the introduction of disease-modifying therapies (DMTs). Three DMTs are approved in the United States for SMA: nusinersen (initial approval 2016; intrathecal injection; 4 loading doses over 3 months followed by once every 4 months; all ages), risdiplam (initial approval 2020; once-daily oral solution/tablet; all ages), and onasemnogene abeparvovec-xioi (initial approval 2019; one-time intravenous infusion; patients aged < 2 years).

Objective: : Given their expected long-term use, we assessed real-world treatment costs (medication and administration) associated with nusinersen and risdiplam.

Methods: : Patients with SMA receiving nusinersen or risdiplam aged >/=2 years were identified from the 2016-2024 Komodo Health Research Database Plus. Dosing patterns and treatment costs were assessed each year separately for nusinersen (up to 5 years) and risdiplam (up to 4 years).

Results: : A total of 2743/1121 patients treated with nusinersen/risdiplam, respectively, were included, with the median(interquartile) age at 17(9,30)/23(10,36) years, close to half covered by Medicaid (42.5%/46.5%), followed by commercial plans (41.1%/31.5%) and Medicare (14.5%/20.6%). Median(interquartile) follow-up was 5.5 (3.7,6.7) years for nusinersen-treated patients and 1.1 (0.6,3.1) years for risdiplam-treated patients. Among nusinersen-treated patients, 2511 (91.5%) had evaluable data in year 2: 1683 (67.0%) maintained on treatment while others discontinued or switched to risdiplam; in year 5, 1905 (69.4%) had evaluable data and 753 (39.5%) maintained on nusinersen, with overall median 3 injections per year. Median annual treatment cost of nusinersen was $504,173 in year 1 and $438,788-$548,608 in years 2-5. Among patients treated with risdiplam, about half (544, 48.5%) discontinued in the first 3 months; in year 2, 556 (49.6%) had evaluable data: 413 (74.3%) maintained on risdiplam while others discontinued or switched to nusinersen; in year 4, 273 (24.4%) had evaluable data and 174 (63.7%) maintained on risdiplam. High discontinuation of risdiplam in year 1 resulted in a median annual risdiplam cost of $143,331 in year 1. Among those continuing risdiplam, median costs were $257,681-$289,340 in years 2-4.

Conclusions: : Among patients with SMA treated with nusinersen or risdiplam, low treatment persistence was observed. Patients who maintained on the respective therapies consistently incurred high treatment costs over time.

Sponsorship:: Novartis Pharmaceuticals Corporation