Search

Background and purpose: Spinal muscular atrophy (SMA) is a genetic disorder caused by SMN1 gene mutations. Although studies on available disease‐modifying treatments have reported their efficacy and safety, long‐term natural history data are lacking for comparison. The aim of this prospective study was to report 4‐year changes on the Hammersmith Functional Motor Scale Expanded (HFMSE) in type II and III SMA in relation to several variables such as age, functional status and SMN2 copy number. Methods: The study involves retrospective analysis of prospectively collected data from international datasets (Belgium, Italy, Spain, USA, UK). HFMSE longitudinal changes were analyzed using linear mixed effect models, examining annualized HFMSE change and its association with variables such as age at baseline, sex, motor function, SMN2 copy number. Results: In SMA type II (n = 226), the 4‐year mean change was −2.20 points. The largest mean changes were observed in sitters aged 5–14 years and the lowest in those who lost the ability to sit unsupported. In SMA type III (n = 162), the 4‐year mean change was −2.75 points. The largest mean changes were in those aged 7–15 years, whilst the lowest were in those below 7 and in the SMA type IIIa subgroup over 15. Age and score at baseline were predictive of 4‐year changes. Conclusions: Our findings provide natural history reference data for comparison with long‐term follow‐up of clinical trials or real‐world data, highlighting the need to define patterns of changes in smaller SMA subgroups instead of reporting mean changes across an entire SMA cohort. [ABSTRACT FROM AUTHOR]

Background and purpose: At 12 months in the phase 2 TOPAZ study, treatment with apitegromab was associated with both an improved motor function in patients with Type 2 or 3 spinal muscular atrophy (SMA) and with a favorable safety profile. This manuscript reports the extended efficacy and safety in the nonambulatory group of the TOPAZ study at 36 months. Methods: Patients who completed the primary study (NCT03921528) could enroll in an open-label extension, during which patients received apitegromab 20 mg/kg by intravenous infusion every 4 weeks. Patients were assessed periodically via the Hammersmith Functional Motor Scale-Expanded (HFMSE), Revised Upper Limb Module (RULM), World Health Organization (WHO) motor development milestones, Pediatric Evaluation of Disability Inventory Computer Adaptive Test (PEDI-CAT) Daily Activities and Mobility domains, and Patient-Reported Outcomes Measurement Information System (PROMIS) Fatigue questionnaire. Results: Of the 58 patients enrolled in TOPAZ, 35 were nonambulatory (mean age 7.3 years). The mean change at 36 months in HFMSE score from baseline was +4.0 (standard deviation [SD]: 7.54), and + 2.4 (3.24) for RULM score (excluding n = 7 after scoliosis surgery). Caregiver-reported outcomes (PEDI-CAT and PROMIS Fatigue) showed improvements from baseline over 36 months. In addition, most patients (28/32) improved or maintained WHO motor milestones achieved at baseline. The most frequently reported treatment-emergent adverse events were pyrexia (48.6%), nasopharyngitis (45.7%), COVID-19 infection (40.0%), vomiting (40.0%), and upper respiratory tract infection (31.4%). Conclusion: The benefit of apitegromab treatment observed at 12 months was sustained at 36 months with no new safety findings. [ABSTRACT FROM AUTHOR]

Background and purpose: Spinal muscular atrophy (SMA) is a rare and progressive neuromuscular disorder with varying severity levels. The aim of the study was to calculate minimal clinically important difference (MCID), minimal detectable change (MDC), and values for the Hammersmith Functional Motor Scale Expanded (HFMSE) in an untreated international SMA cohort. Methods: The study employed two distinct methods. MDC was calculated using distribution‐based approaches to consider standard error of measurement and effect size change in a population of 321 patients (176 SMA II and 145 SMA III), allowing for stratification based on age and function. MCID was assessed using anchor‐based methods (receiver operating characteristic [ROC] curve analysis and standard error) on 76 patients (52 SMA II and 24 SMA III) for whom the 12‐month HFMSE could be anchored to a caregiver‐reported clinical perception questionnaire. Results: With both approaches, SMA type II and type III patients had different profiles. The MCID, using ROC analysis, identified optimal cutoff points of −2 for type II and −4 for type III patients, whereas using the standard error we found the optimal cutoff points to be 1.5 for improvement and −3.2 for deterioration. Furthermore, distribution‐based methods uncovered varying values across age and functional status subgroups within each SMA type. Conclusions: These results emphasize that the interpretation of a single MCID or MDC value obtained in large cohorts with different functional status needs to be made with caution, especially when these may be used to assess possible responses to new therapies. [ABSTRACT FROM AUTHOR]