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Tamoxifen gets new use in Duchenne muscular dystrophy

Old drug improves muscle strength to near normal in dystrophic mice
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Tamoxifen is best known as AstraZeneca's ($AZN) now off-patent breast cancer drug, but in perhaps a rather surprising outcome, it also improves muscle strength in a mouse version of Duchenne muscular dystrophy.

In the muscle-wasting genetic disorder Duchenne muscular dystrophy, muscle is replaced by scar tissue. This leads to progressively weaker skeletal muscles and paralysis, breathing and heart problems, and eventually, death. Current drugs can improve symptoms but not change the course of the disease.

Mice with a form of the disease were given oral tamoxifen from 3 weeks of age for more than a year, at lower doses than used in breast cancer. They had improvements in their leg muscle strength and stamina, half the amount of scar tissue in their hearts, and less scar tissue and more muscle in their diaphragms. Their whole body strength was close to that of normal mice after a year, making them able to cling onto a wire. The results were published in the American Journal of Pathology.

Mouse muscle affected by the dystrophy has higher than normal levels of estrogen receptors and higher plasma creatine kinase activity. Tamoxifen normalizes the increased levels of the enzyme, and this could be through an estrogen receptor (ER) dependent mechanism.

It has been a busy couple of weeks for research into Duchenne muscular dystrophy. Stem cells have cut heart damage in mice with muscular dystrophy, and microdystrophin gene therapy has shown positive results in dogs, the first time this has been seen in a large mammal model. The work on tamoxifen could suggest a new use for this old drug, as well as new targets for research.

- read the press release
- see the abstract

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