Tamoxifen Fails to Show Efficacy in Duchenne Patients in Phase 3 Trial

Patricia Inácio, PhD avatar

by Patricia Inácio, PhD |

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Tamoxifen, commonly used to treat breast cancer, failed to meet its primary goal — delaying disease progression — in a Phase 3 study evaluating its use in boys with Duchenne muscular dystrophy (DMD), preliminary data show.

Boys treated with tamoxifen and those given a placebo over 48 weeks in the TAM-DMD trial (NCT03354039) showed mild disease progression. A trend toward slower progression was seen in boys on tamoxifen, but early data indicated that group differences were not large enough to confirm effectiveness in delayed progression, Duchenne UK, which supported the study, said a press release.

Additional analyses are underway. Specifically, researchers want to assess the slower-than-expected disease progression in those on placebo, which contributed to the small differences between the two groups.

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Preliminary data from the trial and its follow-up open label extension (OLE) study confirmed that tamoxifen was safe and generally well tolerated.

Full results of the TAM-DMD clinical trial are expected to be published in a scientific journal next year.

A prior study in a mouse model of muscular dystrophy showed that tamoxifen and Evista (raloxifene) — also a breast cancer treatment — improved cardiac, respiratory, and skeletal muscle functions, and increased bone density.

The TAM-DMD trial was conducted at sites in France, Germany, the Netherlands, Spain, Switzerland, and the U.K. It enrolled 79 boys with DMD, ages 6.5 to 12, with the ability to walk and under stable treatment with glucocorticoids (group A).

A second group of up to 20 DMD boys, ages 10 to 16 but unable to walk and not under glucocorticoid treatment, were recruited to assess the therapy’s effectiveness in a broader population of patients (group B).

Participants were randomly assigned to 20 milligrams (mg) tamoxifen or a placebo once daily for 48 weeks (11 months).

The trial’s main goal was to assess if tamoxifen slowed disease progression in group A by at least 50%, as measured by the domain 1 (D1) of the motor function measure (MFM) scale. The D1 subscore measures standing position and transfers.

Patients who completed the trial were invited to participate in its OLE, where all are being given 20 mg of tamoxifen daily for 48 weeks.

The trial’s preliminary results — a lack of tamoxifen effectiveness as determined by the trial’s clinical team — have been given to all sites and participants, the release reported. Further discussions are underway to determine how these findings affect patients in the OLE study. Further decisions will be taken together with the participants and their families after reviewing all clinical information.

Patients and family members with additional questions should contact the trial sites directly, Duchenne UK stated.