Background: Avalglucosidase alfa (AVAL), a recombinant human GAA enzyme replacement therapy with increased mannose-6-phosphate content for increased cellular uptake compared with alglucosidase alfa (ALGLU), is approved in the United States for patients with late-onset Pompe disease (LOPD) aged ?1 year (Nexviazyme™, Sanofi Genzyme, Cambridge, MA).
Objectives: To report the safety and efficacy of AVAL in participants with LOPD in the extended treatment period (ETP) of Phase 3 COMET (NCT02782741) after a 49-week primary analysis period (PAP).
Methods: At PAP enrollment, participants were treatment-naïve (n=100; age 16–78 years). All 51 participants receiving AVAL 20 mg/kg every 2 weeks (qow) in the PAP continued this in the ETP (AVAL-arm). Of the 49 participants receiving ALGLU 20 mg/kg qow in the PAP, 44 entered the ETP and received AVAL 20 mg/kg qow (switch-arm).
Results: Changes (LS mean [SE]) from Week 0–97 in forced vital capacity % predicted were +2.65 (1.05) for AVAL-arm and +0.36 (1.12) for switch-arm participants and changes in 6-minute walk test distance (meters) were +18.60 (12.01) for AVAL-arm and +4.56 (12.44) for switch-arm participants. Similar trends occurred in other Week-97 outcomes. Treatment-emergent adverse events (AEs) in the ETP were seen in 49 (96%) AVAL-arm and 42 (95%) switch-arm participants. 5 participants discontinued treatment during the ETP by Week 97 for AEs (1 event each – treatment-related: ocular hyperemia, erythema, urticaria, respiratory distress; non-treatment related: acute myocardial infarction, pancreatic adenocarcinoma). In the ETP, 12 AVAL-arm and 10 switch-arm participants had treatment-emergent serious AEs (SAEs); 3 and 2 of them, respectively, had SAEs related to treatment. Switch-arm participants showed no safety- or immunogenicity-related concerns.
Conclusions: Results show sustained treatment effect and continued benefit with AVAL beyond the PAP, and stabilization of treatment effect after switching from ALGLU to AVAL over 97 weeks, supporting long-term maintenance of clinically meaningful outcomes with AVAL. Funding: Sanofi Genzyme.