Motor Responses in Pediatric Pompe Disease in the ADVANCE Participant Cohort.

Background: ADVANCE (NCT01526785) presented an opportunity to obtain a more nuanced understanding of motor function changes in treatment-experienced children with Pompe disease receiving 4000L-production-scale alglucosidase alfa for 52 weeks.

Objective: To estimate minimal detectable change (MDC) and effect size on Gross Motor Function Measure-88 (GMFM-88) after 52 weeks of 4000L alglucosidase alfa (complete data N =  90).

Methods: The GMFM-88 mean total % score changes, MDC, and effect size were analyzed post hoc by Pompe Motor Function Level at enrollment, age groups at enrollment, and fraction of life on pre-study 160L-production-scale alglucosidase alfa.

Results: Overall, participants aged < 2 years surpassed MDC at Week 52 (change [mean±standard deviation] 21.1±14.1, MDC range 5.7-13.3, effect size 1.1), whereas participants aged≥2 years did not attain this (change -0.9±15.3, MDC range 10.8-25.2, effect size -0.03). In participants aged < 2 years, improvements surpassed the MDC for walkers (change 17.1±13.3, MDC range 3.0-6.9, effect size 1.7), supported standers (change 35.2±18.0, MDC range 5.9-13.7, effect size 1.8) and sitters (change 24.1±12.1, MDC range 2.6-6.2, effect size 2.7). Age-independent MDC ranges were only attained by walkers (change 7.7±12.3, MDC range 6.4-15.0, effect size 0.4) and sitters (change 9.9±17.2, MDC range 3.3-7.7, effect size 0.9).

Conclusions: These first GMFM-88 minimal-detectable-change estimates for alglucosidase alfa-treated Pompe disease offer utility for monitoring motor skills.

Trial Registration: ClinicalTrials.gov; NCT01526785; Registered 6 February 2012; https://clinicaltrials.gov/ct2/show/NCT01526785.