Primary Study Objective: To assess the efficacy of AT-GAA¹ co-administration on ambulatory function, as measured by the 6-minute walk test (6MWT), compared with alglucosidase alfa/placebo. 

Study Design
Randomized, double-blinded, global, multi-center study of AT-GAA co-administration in adult volunteers diagnosed with Late Onset Pompe Disease (LOPD) who have either received Enzyme Replacement Therapy (ERT) with alglucosidase alfa (i.e., ERT-experienced) or who have never received ERT (i.e., ERT-naïve) compared with alglucosidase alfa /placebo.

Study Duration
The study will consist of a screening period up to 30 days, a 12-month treatment period, and a 30-day safety follow-up period. The Screening Visit will occur over 2 days, with 6MWT and pulmonary function tests (PFTs) being repeated on the second day.

What happens to the study participants after the study ends?
It is expected that participants who complete this study will have the option to participate in an open-label extension study to receive AT-GAA under a separate protocol.

How many participants are being enrolled in the study and how many sites are being opened for the study execution?
The planned sample size is approximately 110 volunteers at up to approximately 90 sites globally.

What are the different steps in the study and will I need to stop taking the ERT before I enroll in the study? 

• You will need to contact a study center/site to set up a screening appointment.
• Enzyme replacement therapy-experienced participants will continue to take alglucosidase alfa during the screening period; treatment with alglucosidase alfa will then be replaced by study drug (AT-GAA or alglucosidase alfa/placebo) on the same schedule without interruption (i.e., every 2 weeks). The Screening Visit will occur over 2 days, with only the 6MWT being repeated on the second day.
• Eligible participants will be randomly assigned to receive AT-GAA or alglucosidase alfa/placebo. 
• Infusion visits will be scheduled every 2 weeks throughout the study; assessments (e.g. clinical laboratory tests) for initial safety monitoring will be performed at these visits for the first 6 weeks of the study.
• Study visits that include efficacy, safety, and other assessments will be scheduled approximately every 3 months and may occur over 2 days, provided all study assessments and procedures (with the exception of pharmacokinetic [PK] sample collection) are performed before administration of study drug.

What is Pompe Disease?

Pompe disease is an inherited lysosomal storage disorder that results from a deficiency in acid alpha-glucosidase (GAA) and is characterized by progressive accumulation of lysosomal glycogen primarily in cardiac and skeletal muscles. Enzyme replacement therapy (ERT) using recombinant human GAA (rhGAA) is the only approved treatment available for Pompe disease.

1. AT-GAA is an investigational treatment paradigm that consists of a ATB200, a recombinant human acid alpha-glucosidase (rhGAA) enzyme with optimized carbohydrate structures, particularly mannose-6 phosphate (M6P), designed to enhance uptake, co-administered with AT2221, a pharmacological chaperone.