Trial Entry Criteria

How do I qualify? Study participant must meet all of the inclusion criteria and none of the exclusion criteria to participate in the study.

Inclusion Criteria:
  1. Male or female participants (ERT-naïve [have never received a dose of alglucosidase alfa] or ERT-experienced [have received at least 1 dose of alglucosidase alfa]), diagnosed with late-onset Pompe disease who are aged 12 to < 18 years at screening
  2. Participant's parent or legally authorized representative is willing and able to provide written informed consent and authorization for use and disclosure of personal health information or research-related health information, and participant provides assent, if applicable based on site and local regulations
  3. Participant must have a diagnosis of LOPD based on documentation of one of the following:
    1. Deficiency of GAA enzyme
    2. GAA genotyping
  4. If of reproductive potential, both male and female participants agree to use a highly effective method of contraception throughout the duration of the study and for up to 90 days after their last dose of the investigational treament, ATB200/AT2221
  5. Participant has a sitting Forced Vital Capacity (FVC) ≥ 30% of the predicted value for healthy adolescents (Global Lung Function Initiative [GLI]) at screening
  6. Participant performs two 6MWTs at screening that are valid, as determined by the clinical evaluator, and that meet all of the following criteria:
    1. Both screening values of 6-Minute Walk Distance (6MWD) are ≥ 75 meters
    2. Both screening values of 6MWD are ≤ 90% of the predicted value for healthy adolescents
    3. The lower value of 6MWD is within 20% of the higher value of 6MWD
Exclusion Criteria:
  1. Participant has received any investigational/experimental drug, biologic or device within 30 days or 5 half-lives of the therapy1 or treatment, whichever is longer, before screening
  2. Participant has received treatment with prohibited medications2 within 30 days of screening
  3. Participant has received any gene therapy at any time
  4. Participant has any intercurrent illness or condition at screening or baseline that may preclude the participant from fulfilling the protocol requirements or suggests to the investigator and/or the medical monitor that the potential participant may have an unacceptable risk by participating in this study
  5. Participant has a hypersensitivity to any of the excipients in ATB200, alglucosidase alfa, or AT2221
  6. Female participant is pregnant or breast-feeding at screening
  7. Participant requires the use of ventilation support for > 6 hours per day while awake




  1. None of these medications have a half-life that, when multiplied by 5, is longer than 30 days.
  2. Use of the following medications is prohibited during this study: miglitol (e.g. Glyset®), non-study miglustat (e.g. Zavesca®), Myozyme® or Lumizyme® after treatment with ATB200/AT2221 has begun, acarbose (e.g. Precose® or Glucobay®), voglibose (e.g. Volix®, Vocarb®, or Volibo®), any investigational/experimental drug.