Z-rostudirsen increases dystrophin levels in DMD

8 December 2025

A new medicine called z-rostudirsen (also known as DYNE-251) increased levels of dystrophin in people living with Duchenne muscular dystrophy (DMD), in an early clinical trial.

DMD is a genetic condition that stops the body from making enough of a protein called dystrophin, which helps keep muscles strong. Without dystrophin, muscles can become weaker over time, making everyday movement harder, and weakening the heart and lungs.

Z-rostudirsen is a type of treatment called exon-skipping. This means it hides a small part of the gene (called exon 51) so the body can make a shorter version of dystrophin that still works.

In the study, 32 people with DMD aged between four to 16 years took part. Some could still walk, and some could not. Of these, 24 participants received the treatment and 8 received the placebo (dummy drug). After six months of treatment with z-rostudirsen, participants produced on average 5.46% of the dystrophin level found in people without DMD.

The study was not designed to measure improvements in movement, but early results suggest z-rostudirsen might help slow progression affecting movement and lung function. People receiving z-rostudirsen were able to continue treatment after the trial ended, allowing researchers to collect more data. Early findings in a very small group who received z-rostudirsen for over 18 months suggest the benefits for movement and lung function may last.

The treatment has also been shown to be safe. The most common side effects are fever and headache.

These results are encouraging, but they need to be confirmed in a larger clinical trial. The company behind z-rostudirsen plans to start a phase 3 trial in 2026.

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