The levels of utrophin is very low in the diaphragms of old mdx mice with established fibrosis and a very high levels of collagen type I. Halofuginone did not affect utrophin synthesis in wild-type mice, which suggests that it probably does not affect utrophin synthesis directly and that the increase in utrophin levels is the result of fibrosis inhibition. The gene discussed is UTRN; the disease is fibrosis.