Demonstrating successful preclinical efficacy measures in mouse models of neuromuscular diseases is a critical step for ensuring the success of therapeutic interventions in human clinical trials. Regulatory agencies such as the US FDA, Health Canada, and EMA require convincing preclinical data before therapies can proceed to clinical trials. Since most outcome measures currently used are based on the lab or principal investigator’s expertise or capabilities, it is difficult for non-specialized labs to reliably reproduce the data. Therefore, there is a need for outcome measures that are easily standardized, and usable in a reliable, reproducible, and robust manner.
We have developed and standardized outcome measures that are robust using the dystrophin-deficient MDX mice and control animals and have tested over 180 interventions (e.g. small molecules, biologics, exon-skipping, and gene therapy) in MDX mice over the last 8 years. These preclinical studies were conducted with more than 4,400 mice, using a well-characterized set of outcome measures; body weight and tissue weights, functional measures (grip strength, in vitro, in vivo and in situ force, optical imaging, treadmill exhaustion, voluntary wheel running, echocardiography, plethysmography), histological analyses (inflammation, central nucleation, degeneration, regeneration, fibrosis), serum CK, immunofluorescence, RT-PCR, and western blot for dystrophin expression.
Based on the data collected, we have concluded that 1) we can successfully use non-invasive longitudinal functional measures (i.e. grip strength, voluntary wheel, treadmill exhaustion assay) to demonstrate drug efficacy in the MDX mice; 2) we can replace invasive, cumbersome, specialized techniques such as in vitro force with non-invasive, standardized, general techniques such as grip strength; and 3) we can replace using control (wild-type and diseased) animals with outcome data sets collected as part of natural history data, thereby fulfilling the 3R (replace, reduce and refine) principles of humane animal research.