Duchenne muscular dystrophy (DMD) is a progressive devastating disease that affects mainly boys, with an incidence of about 1:3,500 live births. The pathology of DMD is a result of non-repaired muscle damage that leads to muscle-tissue replacement by scar tissue, a process known as fibrosis. Currently, there is no effective treatment for the disease. The only therapy offered to these boys are steroids which slightly delayed the disease progression. The boys lose their ability to walk at around the age of 12, and die in the 4th decade of life from severe heart and lung problems.

In this study investigators will test the efficacy of Tamoxifen treatment in ambulatory DMD boys. Tamoxifen is a drug used for palliative treatment of breast cancer patients and has an outstanding safety profile. In addition, Tamoxifen was tested in the past in boys, for other pediatric indications, and showed an excellent safety with no side effects.

Tamoxifen is being tested in this study, as a therapy for DMD, for the following reasons:

(i) it was shown to have anti-fibrotic effect in multiple in-vivo systems; (ii) it assists in the repair of damaged muscles.

In other words, Tamoxifen is expected to have a synergistic effect on DMD patients, due to its dual mechanism of action. Indeed, Tamoxifen was shown to have significant beneficial effects in the mdx mouse model of DMD. Also, a small compassionate cohort of 3 boys, treated for 6 months with Tamoxifen, yielded very encouraging results.

Inclusion Criteria:

• Ambulatory

Exclusion Criteria:

• Non Ambulatory