REGISTRIES AND CARE OF NEUROMUSCULAR DISORDERS: P.297Treatment responsive outcome measures in mouse models of neuromuscular disease

Abstract

Preclinical efficacy evaluations in mouse models of neuromuscular diseases are critical first steps for ensuring the success of therapeutic interventions in human clinical trials. Regulatory agencies such as the US FDA and EMA require robust and reliable preclinical data if animal models exist. We have tested 63 interventions (e.g. small molecules, biologics, exon-skipping and gene therapy) in mdx mice over the last 4 years. These preclinical studies were conducted with more than 2,600 mice, using a well characterized set of outcome measures; body weight and tissue weights, functional measures (grip strength, in vitro force contractions, treadmill exhaustion, voluntary wheel running, echocardiography, plethysmography), histological analyses (inflammation, central nucleation, degeneration, regeneration, fibrosis), serum CK, immunofluorescence and western blot for dystrophin expression. We used TREAT-NMD preclinical standard operating procedures for all applicable outcomes and each study was performed using appropriate blinding, randomization and statistical analysis. Treatment periods ranged from 2 weeks to 9 months depending on the nature of the intervention with an average sample size per group of n=14, and an average of 9 outcomes tested, yielding over a quarter million data points. Of the 63 interventions, only 32% showed statistically significant efficacy in 2 or more of the outcomes, indicating that 68% failed to show efficacy. Echocardiography, exhaustion assay, in vitro force contractions, western blot and immunofluorescence were consistently responsive to the efficacious interventions. Parameters such as histological measures, serum CK and voluntary wheel failed to show improvements in studies where other outcomes detected efficacy. Failure of some therapeutic interventions could be attributed to questionable therapeutic targets. Our data suggests that careful selection of appropriate endpoints is essential for all preclinical mouse efficacy trials.