Correction of Biochemical Abnormalities and Improved Muscle Function in a Phase I/II Clinical Trial of Clenbuterol in Pompe Disease

Abstract

This 52-week, phase I/II double-blind, randomized, placebo-controlled study investigated the novel use of clenbuterol in late-onset Pompe disease (LOPD) stably treated with ERT. Eleven of thirteen participants completed the study. No serious adverse events were related to clenbuterol, and transient minor adverse events included mild elevations of creatine kinase, muscle spasms, and tremors. At week 52, the 6-min walk test distance increased by a mean of 16 m (p = 0.08), or a mean of 3% of predicted performance (p = 0.03), and the maximum inspiratory pressure increased 8% (p = 0.003) for the clenbuterol group. The quick motor function test score improved by a mean of seven points (p = 0.007); and the gait, stairs, gower, chair test improved by a mean of two points (p = 0.004). Clenbuterol decreased glycogen content in the vastus lateralis by 50% at week 52. Transcriptome analysis revealed more normal muscle gene expression for 38 of 44 genes related to Pompe disease following clenbuterol. The placebo group demonstrated no significant changes over the course of the study. This study provides initial evidence for safety and efficacy of adjunctive clenbuterol in patients with LOPD (NCT01942590).

Keywords: acid alpha-glucosidase; enzyme replacement therapy; glycogen storage disease.

Copyright © 2018 The American Society of Gene and Cell Therapy. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Functional Testing Demonstrated Efficacy for the Clenbuterol Group Timeline for the study (A). Participants were enrolled and completed a baseline assessment prior to randomization to clenbuterol or placebo at week 6, dose increase at week 12, and returning for assessment at weeks 18 and 52. (B) Serum CK for clenbuterol group. Each line connects the data points for one research participant. Normal range, 30–220 U/L. One participant in the clenbuterol group was excluded at week 52 due to having stopped ERT several months earlier. 6MWT for clenbuterol group is shown in XY graphs depicting (C) predicted performance (data points for each participant), (D) predicted performance (mean ± SD), and (F) distance (mean ± SD). (E) 6MWT predicted performance and (G) distance for placebo group. Functional muscle testing for clenbuterol group is shown in XY graphs depicting (H) GSGC and (J) QMFT. Functional muscle testing for placebo group: (I) GCGS and (K) QMFT for placebo group (mean ± SD). Horizontal lines indicate the data points relevant to the adjacent p value.

Figure 2

Pulmonary Function Testing Revealed Improved Strength of Respiratory Muscles for Clenbuterol Group Pulmonary function testing for clenbuterol group is shown in XY graphs depicting (A) FEV1, (B) FVC, (C) MEP, and (D) MIP. Mean ± SD is shown. MIP for each individual in the clenbuterol group (E). One subject was excluded at week 52 due to having stopped ERT several months earlier. MIP for placebo, mean ± SD (F). MIP for each individual in the placebo group (G).

Figure 3

Muscle Effects from Clenbuterol Biochemical testing at baseline and week 52 for clenbuterol and placebo groups’ vastus lateralis muscle biopsies. (A) GAA activity. One participant from the clenbuterol group was excluded from the GAA assay due to having stopped ERT several months earlier. (B) Biochemical glycogen content. Mean ± SD are shown. (C) Histopathology revealed decreased (three patients) or stable (three patients) PAS-positive glycogen levels following clenbuterol administration; all four placebo patients with evaluable biopsy pairs demonstrated stable PAS-positive glycogen levels (high-resolution light microscopy, 1-micron epoxy resin sections, PAS-Richardsons stain, 400× magnification). Western blot quantification of (D) LAMP2 and CI-MPR in muscle biopsy samples and quantification of western blot signals. The lanes marked as + are from the post-randomization samples at week 52, whereas − indicates the baseline samples.

Figure 4

RNA-Seq Analyses of Differentially Expressed Genes and Pathway Analysis RNA-seq analyses of differentially expressed genes and pathway analysis. (A) Venn diagram showing that 44 overlapping genes significantly differ (by >2-fold; p 2 fold change) for specified comparisons. Red, upregulated genes; blue, downregulated genes. (C) Ingenuity pathway analysis of diseases and disorders. (D) Gene set enrichment analysis (GSEA) plots of Myofibil gene set from the whole transcriptome of Pompe versus normal (enrichment score, 0.705) and clenbuterol post versus pre (enrichment score, −0.652).