Pompe disease is a rare lysosomal disorder characterized by progressive loss of muscle and respiratory function due to acid α-glucosidase (GAA) deficiency, for which recombinant human GAA enzyme replacement therapy (ERT) is available. Here, we report the 24-month (mo) interim results from ATB200-02 (NCT02675465), a first-in-human, phase 1/2, open-label study assessing safety, tolerability, PK/PD, and efficacy of ATB200/AT2221, a next-generation ERT/chaperone regimen, in adults with Pompe disease. The study enrolled 22 patients: ERT-switch (n=11), ERT-switch nonambulatory (n=6), and ERT-naive (n=5). The 6-minute walk test improved in ambulatory ERT-switch patients (mean [SD], meters: Mo 6, +23.9 [52.2], n=10; Mo 12, +42.2 [46.5], n=10; Mo 24, +53.6 (36.4), n=8) and ERT-naive patients (n=5; Mo 6, +41.8 [29.4]; Mo 12, +63.1 [29.1]; Mo 21, +54.8 [34.7]). Other motor function tests were generally consistent with these results. Nonambulatory ERT-switch patients demonstrated increases in upper extremity strength per quantitative and manual muscle testing. Forced vital capacity increased in ERT-naive patients (n=5; mean, % predicted: Mo 6, +4.2; Mo 12, +4.5; Mo 21, +6.1) and was generally stable in ambulatory ERT-switch patients (Mo 6, -1.2, n=9; Mo 12, -3.0, n=9; Mo 24, -0.6, n=7). ATB200/AT2221 was associated with reductions in creatine kinase and urine Hex4. Improvements in patient-reported outcomes (Rasch-built Pompe-specific Activity Scale, Rotterdam Handicap Scale, Fatigue Severity Scale, Subject Global Impression of Change) were reported. The most common treatment-emergent adverse events were nasopharyngitis, fall, and abdominal pain. Six patients reported infusion-associated reactions. Data from this interim analysis show clinical benefits of ATB200/AT2221 in ERT-naive and ERT-experienced patients, suggesting that ATB200/AT2221 can be an effective and well-tolerated treatment for adults with Pompe disease. Updated data will be presented.