This is an expanded access program (EAP) for eligible participants designed to provide access to ATB200/AT2221.

This program is being offered on a patient by patient basis and will require company, IRB/IEC and single patient IND approval.

Inclusion Criteria:

1. Subject must have a diagnosis of Pompe disease based on documentation of one of the following:

   1. deficiency of GAA enzyme
   2. GAA genotyping

2. Patient does not currently qualify for an Amicus sponsored on-going clinical trial or is declining on currently approved ERT (e.g. Myozyme)

3. The patient must be willing to receive treatment with ATB200/AT2221 via this program, which includes signing an authorization form for sharing clinical data with Amicus Therapeutics, and its agent Early Access Care LLC.

Exclusion Criteria:

1. Patient, whether male or female, is planning to conceive a child during the treatment program.
2. Patient has a hypersensitivity to any of the excipients in ATB200, alglucosidase alfa, or AT2221
3. Patient has a medical or any other extenuating condition or circumstance that may, in the opinion of the investigator, pose an undue safety risk to the subject or compromise his/her ability to comply with or adversely impact protocol requirements.
4. Patient has received any gene therapy at any time.
5. Concomitant use of miglitol (eg, Glyset), non-AT2221 form of miglustat (eg, Zavesca), acarbose (eg, Precose or Glucobay), voglibose (eg, Volix, Vocarb, or Volibo)