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Tamoxifen breast cancer medication can help to at least slow down hereditary muscle disease that cannot be cured. Researchers at the University of Geneva reported with their colleagues that the drug extended the life of mice with disease.
Myotubular myopathy is a serious hereditary disease that affects one in 50,000 newborn boys. Genetic defects cause muscle atrophy. In particular, because of the weakness of the respiratory muscles, this rare disease usually causes death in the first two years of life.
Healing does not yet exist, but at least it can slow disease progression: Researchers from the University of Geneva and Strasbourg report promising results in animal experiments with tamoxifen.
Tamoxifen has been used for years in the treatment of breast cancer and has some interesting properties in terms of protecting muscle fibers, as announced by the University of Geneva. In previous studies, researchers have successfully tested the drug for its effect on more general muscle disease, Duchenne muscular dystrophy. This concerns one of 3500 boys; life expectancy is 30 years. Now clinical trials are underway.
Based on these promising results before, scientists around Leonardo Scapozza are now also testing the efficacy of tamoxifen in mouse models of myotubular myopathy. The results are reported in the journal "Nature Communications".
However, both diseases cause muscle weakness in different ways: In myotubular myopathy it does not have an enzyme called myotubularin. Without it, a protein called dynamin 2 accumulates, causing atrophy of the muscles. Tamoxifen starts with Dynamin 2.
Mice with the same symptoms as infants with myotubular myopathy live twice as long with the lowest dose tested, with the highest dose even seven times longer than untreated mice. The highest dose – equivalent to a mouse organism – used in breast cancer.
In addition, the drug slows progressive muscle paralysis or even makes it jam. Muscle strength also increases significantly by treatment.
The initial approach prevents paralysis
The researchers began treatment with tamoxifen when the first symptoms appeared in mice around three weeks old. A Canadian research group from Toronto started early, and the mice did not develop signs of paralysis, the University of Geneva wrote.
Meanwhile, there are also research efforts to treat serious hereditary diseases by means of gene therapy. Its effectiveness and safety, however, must be for years, speculates study author Olivier Dorchies from the University of Geneva.
Because tamoxifen has been approved for human use, and because clinical trials for Duchenne muscular dystrophy are underway, the researchers hope that treatment with tamoxifen will get faster approval in myotubular myopathy.