Individualized Assessment of Exercise Capacity in Response to Acute and Long-Term Enzyme Replacement Therapy in Pediatric Pompe Disease

Background: Enzyme replacement therapy (ERT) with alglucosidase alfa improves the prospect of patients with infantile-onset Pompe disease (IOPD). However, a progressive decline has been reported. Objective quantification of the response to ERT when assessing newer strategies is warranted.

Methods: This combined retrospective-prospective study assessed the acute and long-term effects of ERT on exercise in IOPD patients. Evaluation included cardiopulmonary exercise testing (CPET), 6-min walking test (6MWT), spirometry, motor function test (GMFM-88) and enzyme blood levels.

Results: Thirty-four CPETs (17 pre- and 17 two days-post ERT) over variable follow-up periods were performed in four patients. Two days following ERT, blood enzyme levels increased (median, 1.22 and 10.15 μmol/L/h (p = 0.003)). However, FEV1, FVC and GMFM-88, the median 6MWD and the peak VO₂ were unchanged. Long-term evaluations showed stabilization in young patients but progressive deterioration in adolescents. Clinical deterioration was associated with more pronounced deterioration in peak VO₂ followed in the decreasing order by 6MWD, FVC and GMFM-88.

Conclusions: The peak VO₂ and 6MWD might serve as more sensitive markers to assess clinical deterioration. More studies are needed to clarify the sensitivity of the peak VO₂ and 6MWT for quantification of individualized response. This may be important when assessing newer strategies and formulations in IOPD.