Building on previous positive results with mouse and dog models of X-linked myotubular myopathy (XLMTM)51,52, the efficacy of systemic intravenous AAV delivery of canine myotubularin (Mtm1) to dogs at 10 weeks of age (and already manifesting XLMTM) was assessed. This evidence concerns the gene MTM1 and X-linked myotubular myopathy.