Patients’ mean (range) ages at NEO1 enrollment were: Naïve: 44.8 (20-78) years; Switch: 46.7 (21-68) years. As of July, 2019, 17 patients (7 Naïve, 10 Switch) were participating in NEO-EXT and, due to sequential enrollment, had data available up to 5.5 years (2 discontinued for personal reasons). Here we focus on exploratory efficacy data up to Week 260. Forced vital capacity (FVC) % predicted was generally stable in both groups at Week 260 compared with baseline; mean±SD change from baseline for 5, 10, and 20 mg/kg, respectively: Naïve: −0.9±12.5; 13.0±not calculable (NC); 7.0±2.6 (Week 234); Switch: −6.5±2.7; −5.8±8.5; 0.2±4.9. Maximum inspiratory/expiratory pressures had similar trends. At Week 260, compared with baseline, 6-minute walk test (6MWT) distance (m) generally remained stable; mean±SD change from baseline for 5, 10, and 20 mg/kg, respectively: Naïve: −34.7±15.6; 2.0±NC; 53.5±41.7 (Week 234); Switch: −45.7±86.9; −11.7±83.5; −68.3±151.1. Generally, 6MWT improvement was observed in Naïve and Switch patients aged ≤50 years at study start. Avalglucosidase alfa was generally well-tolerated, and the safety profile observed in NEO-EXT was consistent with NEO1. One treatment-naïve patient discontinued NEO1 for a study drug-related serious adverse event (SAE; respiratory distress/chest discomfort); no deaths/life-threatening SAEs have occurred.

After up to 5.5 years of avalglucosidase alfa treatment, patients in both groups had sustained benefit on pulmonary function and 6MWT. Funding: Sanofi Genzyme.