Efficacy of Switching Therapy From Alglucosidase Alfa to Avalglucosidase Alfa on Respiratory Function in Participants With Late‐Onset Pompe Disease: A Post Hoc Analysis From the <scp>COMET</scp> Trial

Pompe disease (PD) is a rare, autosomal recessive neuromuscular disorder caused by a deficiency in acid α-glucosidase. In the Phase 3 COMET trial (NCT02782741), respiratory function was examined in participants with late-onset PD randomized to receive enzyme replacement therapy with alglucosidase alfa (ALG; standard of care) or avalglucosidase alfa (AVA; intervention) in the primary analysis period (PAP). The open-label extended treatment period (ETP) provided long-term data on AVA treatment. This post hoc analysis evaluated respiratory outcomes in participants who received ALG in the PAP (Weeks 0-49) and switched to AVA in the ETP (Weeks 49-145). Participants were categorized according to improvement in upright forced vital capacity percent-predicted (FVC) at Week 49. Forty-four participants were included, of whom 20 (45.5%) had ΔFVC > 0% predicted at Week 49. Among ΔFVC > 0% predicted participants, FVC improved during the PAP (estimated slope [SE]: 4.0 (1.1) %/year, <i>p</i> < 0.01), and was maintained following switch to AVA in the ETP (0.1 (0.8) %/year, <i>p</i> = 0.86). For participants with ΔFVC ≤ 0% predicted during the PAP (<i>n</i> = 24; estimated slope [SE]: -3.4 (1.0) %/year, <i>p</i> < 0.01), FVC stabilized following switch to AVA (0.3 (0.7) %/year, <i>p</i> = 0.70). Slopes in measures of respiratory airflow and inspiratory/expiratory muscle strength were consistent with these findings. Similar results were observed using ΔFVC ≥ 3% predicted as a measure of clinically meaningful change. This analysis demonstrates clinically meaningful maintenance in measures of lung volume (FVC) and airflow (forced expiratory volume in 1 s) after switching therapy from ALG to AVA that persists for ≥ 2 years and is independent of prior outcomes with ALG.