Pre-clinical studies in Mtm1 knockout mice (a model of XLMTM) demonstrated prolonged survival, increased motor function (including muscle strength), and improved muscle histopathology with tamoxifen treatment. Based on these data, and the known safety profile of the drug in humans, we hypothesize that tamoxifen treatment will be safe and will improve motor and respiratory function in XLMTM patients. This is a randomized, double-blinded, single crossover clinical trial to test this hypothesis and determine the safety and efficacy of tamoxifen in improving motor and respiratory function in MTM patients. Each subject will serve as his own control during the placebo phase of the study. As treatments for XLMTM are current not available, this study addresses a critical unmet need by testing a therapy that, if effective, may serve as a primary treatment, or in the future as an adjunct to other therapies in development.
This is a phase 1 / 2, randomized, double-blinded, single cross-over study, with a washout period between treatment regimens, to test the efficacy and safety of tamoxifen therapy to improve motor and respiratory function in males with XLMTM.