Promising study on tamoxifen for Duchenne muscular dystrophy yields inconclusive results

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A Phase 3 clinical trial investigating the use of tamoxifen, an oestrogen receptor regulator, as an adjunct to corticosteroid therapy for Duchenne muscular dystrophy did not yield conclusive results.

Although tamoxifen was found to be safe and well-tolerated, there was no significant difference in the primary efficacy outcome, which measured changes in motor function over a 48-week period. Although there were indications of potentially slower disease progression in the tamoxifen group, these differences were not considered clinically or statistically significant.

As a result, the study does not currently support the recommendation of tamoxifen as a treatment option for boys with Duchenne muscular dystrophy in daily clinical practice.

The study included 82 ambulant boys with genetically confirmed diagnoses of Duchenne muscular dystrophy, and on stable corticosteroid treatment for over 6 months. One participant from the placebo group did not commence treatment, leaving a final intention-to-treat population of 40 individuals on tamoxifen and 38 on placebo.

The primary efficacy outcome, measured as the change from baseline to week 48 in scores on the D1 domain of the Motor Function Measure, did not exhibit a statistically significant difference between the tamoxifen and placebo groups. Tamoxifen showed a -3.05% change (95% CI -7.02 to 0.91), while the placebo group demonstrated a -6.15% change (95% CI -9.19 to -3.11), yielding a 2.90% difference (95% CI -3.02 to 8.82, P = 0.33).

The trial, which also assessed safety, reported only 2 severe adverse events: a participant receiving tamoxifen experienced a fall, while 1 on placebo had a panic attack. There were no reported deaths or life-threatening serious adverse events. The most common adverse events were viral infections.

The study authors concluded, “Currently, we cannot recommend the use of tamoxifen in daily clinical practice as a treatment option for boys with Duchenne muscular dystrophy due to insufficient clinical evidence.”

Henzi BC, Schmidt S, Nagy S, et al; North Star Consortium. Safety and efficacy of tamoxifen in boys with Duchenne muscular dystrophy (TAMDMD): a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial. Lancet Neurol. 2023;22(10):890-899. doi: 10.1016/S1474-4422(23)00285-5. PMID: 37739572.