Objective: Examine the long-term safety and durability of intravenous or intrathecal onasemnogene abeparvovec in symptomatic and presymptomatic patients with spinal muscular atrophy (SMA) who enrolled into the LT-002 study (NCT04042025).
Background: Patients who received intravenous (STR1VE-US; STR1VE-EU; STR1VE-AP; SPR1NT) and intrathecal (STRONG) onasemnogene abeparvovec demonstrated improved survival and motor function versus natural history.
Methods: Long-term safety was assessed by medical history/record review, physical examination, laboratory evaluation, and pulmonary/cardiac assessments. Efficacy was assessed by developmental milestones and Hammersmith Functional Motor Scale Expanded (HFMSE).
Results: As of May 23, 2022, 81 patients (intravenous, n=63 [symptomatic, n=38; presymptomatic, n=25]; intrathecal, n=18) were enrolled in LT-002, with a mean (range) follow-up of 3.4 (1.0–4.3) and 3.6 (2.6–4.3) years for the intravenous and intrathecal cohorts, respectively. There were no deaths or treatment-emergent adverse events (TEAEs) resulting in discontinuation. The most frequently reported TEAEs were gastroenteritis, nasopharyngitis, pneumonia, respiratory distress, and viral infection. All patients survived and maintained developmental milestones with a mean (range) age at cutoff of 3.7 (2.4–4.7) and 5.3 (3.4–7.4) years for the intravenous and intrathecal cohorts, respectively. Only one patient required permanent ventilation. Twenty-seven patients achieved new developmental milestones (presymptomatic-intravenous, n=6; symptomatic-intravenous, n=16; intrathecal, n=5); more than half (n=16) did so without add-on therapy. Improvements in HFMSE were clinically significant (≥3 points; presymptomatic-intravenous, 81.25%; symptomatic-intravenous, 66.6%; intrathecal, 50%). No patients treated presymptomatically required ventilatory/nutritional support; few symptomatic patients required ventilatory (intravenous-symptomatic, 32%; intrathecal, 5.6%) or feeding (intravenous-symptomatic, 20%; intrathecal, 0%) support at cutoff. Most patients fed orally (intravenous, 95%; intrathecal, 100%). The majority (57/81) never received add-on therapy. Of those receiving add-on therapy, half did not achieve a new developmental milestone after initiation of add-on therapy.
Conclusions: Intravenous/intrathecal onasemnogene abeparvovec demonstrates consistent, substantial, and durable efficacy and no new safety signals in symptomatic and presymptomatic patients with SMA.