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.