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Tamoxifen adjunct to corticosteroids shows no motor benefit in Duchenne muscular dystrophy extension studyDoes adding tamoxifen to standard treatment help boys with Duchenne muscular dystrophy?

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Key Takeaway
Interpret the lack of motor benefit for tamoxifen in DMD from this open-label extension cautiously.

This was a 48-week open-label extension of a phase 3 randomized controlled trial conducted at 10 centers across seven European countries. It included 66 boys with Duchenne muscular dystrophy who had participated in the prior TAMDMD trial, comparing early versus delayed initiation of tamoxifen 20 mg daily as an adjunct to corticosteroids.

The study's primary outcome was change in motor function. Results showed no significant difference between the early and delayed tamoxifen treatment groups. Secondary analyses found no evidence of a sustained effect of tamoxifen and no effect related to the timing of its initiation. Specific effect sizes, absolute numbers, and p-values or confidence intervals for these comparisons were not reported.

Regarding safety, no deaths or life-threatening serious adverse events occurred during the extension. The authors reported that tamoxifen continued to be well tolerated overall, though specific adverse event rates and discontinuation data were not provided. Key limitations include the open-label design, which introduces potential bias, and the absence of detailed statistical reporting for the null findings.

The authors conclude they cannot provide statistical or clinical evidence that prolonged tamoxifen treatment is effective in delaying DMD progression when used with corticosteroids. This extension study was not designed to establish causation, and its findings should be interpreted cautiously within the context of the prior parent trial's results.

When a child has Duchenne muscular dystrophy (DMD), a progressive muscle-wasting disease, families and doctors search for anything that might help preserve strength and mobility. A recent study followed 66 boys with DMD for 48 weeks to see if adding a daily dose of tamoxifen—a drug used for other conditions—to their standard steroid treatment could make a difference. The core finding was straightforward: there was no significant difference in motor function between boys who started tamoxifen early versus those who started it later. The researchers also found no evidence of a 'sustained effect' from the drug, meaning its use did not seem to slow the disease's progression over time.

It's important to understand what this study was and wasn't. This was an 'open-label extension' study, meaning everyone involved knew they were getting tamoxifen. This type of study is not as rigorous as a blinded trial where no one knows who is getting the real drug versus a placebo, so it's harder to draw firm conclusions about cause and effect. On the safety side, the report notes that tamoxifen was 'well tolerated overall' during the study period, with no deaths or life-threatening serious events reported among the participants.

The researchers themselves state they 'cannot provide statistical nor clinical evidence' that prolonged tamoxifen treatment is effective in delaying DMD progression. For now, this particular approach of adding tamoxifen to corticosteroids does not appear to be a promising path forward for treating the muscle weakness in DMD. The search for effective therapies continues.

What this means for you:
Adding tamoxifen to standard steroids did not improve motor function in boys with Duchenne muscular dystrophy.

Study Details

Study typeRct
Sample sizen = 66
EvidenceLevel 2
Follow-up11.1 mo
PublishedApr 2026
View Original Abstract ↓
Safety and efficacy of tamoxifen in boys with Duchenne muscular dystrophy was assessed in the double-blind, randomised, placebo-controlled, multicenter phase 3 trial (TAMDMD), which was followed by an 48 weeks open label extension study. The aim of the open label extension study was to investigate if earlier initiation of tamoxifen could reduce the progression of the disease compared to delayed initiation of tamoxifen. Of the initial TAMDMD trial participants, 66 patients were enrolled in the open label extension (OLE). The objective was to investigate the efficacy of prolonged treatment with tamoxifen 20 mg daily, adjunct to corticosteroids, in individuals with DMD over 48 weeks. We aimed to analyse the sustained effect and the timing effect of tamoxifen in patients with DMD on the basis of a set of motor function tests. The sustained effect corresponds to the treatment effect seen in the tamoxifen treatment arm of the RCT phase of the trial being sustained after all patients got the treatment in the OLE phase. The timing effect addresses if patients with earlier tamoxifen initiation show more favourable disease trajectory than patients with delayed tamoxifen initiation. This study was registered with ClinicalTrials.gov (NCT03354039). Between May 28th 2019 and July 28th 2021, 66 patients in 10 study centres in seven European countries could be enrolled into the OLE phase. Of those, 32 had previously been treated with tamoxifen and 34 had been assigned to placebo. The efficacy outcome defined as the change in the motor function did not differ significantly between the early tamoxifen treatment group and the delayed tamoxifen treatment group. There was neither a sustained nor a timing effect of tamoxifen. Overall tamoxifen was well tolerated. No deaths or life-threatening serious adverse events occurred. The OLE phase of the TAMDMD trial showed that treatment with tamoxifen continued to be well tolerated overall; however, there was neither a sustained nor a timing effect of tamoxifen treatment in patients with DMD. We cannot provide statistical nor clinical evidence that prolonged treatment with tamoxifen is effective in delaying disease progression in DMD when used as an adjunct to corticosteroids.
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