Apitegromab Linked to Improved Outcomes for Those with Spinal Muscular Atrophy

  • The study included 58 individuals with SMA types 2 and 3 who were treated with IV apitegromab for 52 weeks.
  • At 36 months, treatment resulted in statistically significant improvements in motor function and mobility.

Earlier this month, Scholar Rock shared that treatment with apitegromab was linked to improved muscle strength and range of motion, while being safe and well-tolerated in those with spinal muscular atrophy types 2 and 3, according to a recent poster presentation*.

The study aimed to evaluate safety and efficacy of apitegromab, an investigational, fully human monoclonal antibody in nonambulatory children, adolescents and adults with SMA types 2 or 3, over 36 months.

The TOPAZ clinical trial is a 52-week, multicenter, phase 2 study conducted across 16 location in the United States and Europe. A total of 58 participants were divided into two treatment groups: administered either 2 mg/kg or 20 mg/kg IV apitegromab, alone (n = 11) or in combination with nusinersen (n = 47). Those who completed the initial study could enroll in three sequential extension periods of 52 weeks each, where all participants received 20 mg/kg apitegromab per month.

Efficacy analysis included the nonambulatory population from the TOPAZ study (n = 35) over 36 months, while safety analysis included all 58 individuals enrolled. Muscle function was measured by the Hammersmith Functonal Motor Scale-Expanded (HFMSE), Revised Upper Limb Module (RULM) and WHO motor development milestones. Daily activities and mobility were evaluated by the Pediatric Evaluation of Disability Inventory Computer Adaptive Test (PEDI-CAT) and self-reported or caregiver proxy of perceived fatigue was assessed using the PROMIS Fatigue questionnaire.

According to results, mean change in both HFMSE and RULM demonstrated sustained improvements (2.8 to 4; 0.6 to 2.4, respectively) measured from month 6 to month 36, while similar improvements were also found in both PEDI-CAT domain (1.3 to 2.2 in daily activities; 1.4 to 1 in mobility domain) and PROMIS perceived fatigue (1.4 to -4.6).

Data further showed improvement in WHO motor milestones, while results on patient-caregiver-reported outcomes were consistent with motor function improvements assessed by HFSME and RULM. Apitegromab’s safety profile was also consistent with prior research.

*Crawford TO, et al. Effect of apitegromab on motor function and patient-reported outcomes at 36 months in patients aged 2–21 years with spinal muscular atrophy. Presented at: Muscular Dystrophy Association Clinical & Scientific Conference; March 3-6, 2024; Orlando.

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