A Study to Assess the Long-term Safety and Efficacy of ATB200/AT2221 in Adult Subjects With Late-Onset Pompe Disease (LOPD)

Number of subjects with TEAE, TESAE, and TEAE leading to discontinuation during this long-term extension study

Motor function was measured using the 6-minute walk distance (meters)

Pulmonary function was measured by sitting % predicted forced vital capacity (FVC)

Strength was measured by manual muscle testing (MMT) using the Medical Research Council grading scale (0 to 5 points, with 5 indicating normal function). Change from baseline values >0 represent improvement.

Physical Function Short Form 20a (v2.0) consisted of 20 questions. The first 14 questions were each scored on a scale from 1 to 5 as follows: 1 = unable to do; 2 = with much difficulty; 3 = with some difficulty; 4 = with a little difficulty; 5 = without any difficulty; the next 6 questions were each scored on a scale from 1 to 5 as follows: 1 = cannot do; 2 = quite a lot; 3 = somewhat; 4 = very little; 5 = not at all. The total score was calculated by summing up scores (1 to 5) across all items. Total scores range from 20 to 100. A higher score represented a better outcome.

Fatigue Short Form 8a consisted of 6 questions, each scored on a scale from 1 to 5 as follows: 1 = not at all; 2 = a little bit; 3 = somewhat; 4 = quite a bit; 5 = very much; and 2 questions, each scored on a scale from 1 to 5 as follows: 1 = never; 2 = rarely; 3 = sometimes; 4 = often; 5 = always. The total score was calculated by summing up scores (1 to 5) across all items resulting in a total score range from 6 (minimum) to 30 (maximum). A lower score represented lower fatigue symptoms.

The GSGC consisted of a 10-meter walk for evaluation of gait, a 4-stair climb, Gowers' maneuver, and arising from a chair. Results of the GSGC included the time required to complete the individual tests, individual scores for each of the tests (1 to 7 points for each of gait, 4-stair climb, and Gowers' maneuver, and 1 to 6 points for arising from a chair), and a total score. GSGC total score was the sum of the component scores from the 4 functional tests. The total score ranged from a minimum of 4 points (normal performance) to a maximum of 27 points (worst performance).

The EuroQol 5 Dimensions 5 Levels (EQ-5D-5L) questionnaire comprises 5 dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. Each dimension has 5 levels: Level 1=no problems, Level 2=slight problems, Level 3=moderate problems, Level 4=severe problems, and Level 5=extreme problems. In this categorical assessment, subjects were asked to indicate their health state by ticking the box next to the most appropriate statement in each of the 5 dimensions.

Outcomes for change from baseline at Week 208 include 'no change', 'worsening' relative to baseline category, or 'improvement' relative to baseline category. Changes (worsening or improvement) are shown by magnitude of change (how many Levels) in each categorical assessment.

The Subject's Global Impression of Change overall physical well-being (question 1) is scored on a 7-point rating scale ranging from "very much worse" to "very much improved."

The Physician's Global Impression of Change (PGIC) is designed to record the physician's assessment of the subject's status, taking into account the subject's signs and symptoms and other neuromuscular symptoms, and signs relative to their status at the Baseline Visit. The PGIC is based on a single item that is scored on a 7-point rating scale ranging from 1 "very much worse" to 7 "very much improved."

Percent change from baseline to Week 208 in the levels of biomarker creatine kinase (CK)

Percent change from baseline to Week 208 in the levels of biomarker urine Hex4.

Immunogenicity was assessed by the number (%) of subjects with positive specific anti-cipaglucosidase antibodies at baseline and at Week 208