The US Food and Drug Administration (FDA) has recently given fast track designation to the experimental drug DYNE-251, intended to treat Duchenne muscular dystrophy (DMD) in patients with mutations attributed to exon 51 skipping, according to a press release.

DYNE-251 is a new drug candidate that binds to the transferrin receptor 1, which is highly expressed in skeletal muscle. Theoretically, the investigational drug should promote the production of a functional dystrophin protein by enabling exon skipping in the cellular nucleus.

The presence of functional dystrophin protein should, in turn, stop disease progression or even reverse it. The drug has already shown an acceptable safety profile and efficacy in improving cardiac and diaphragmatic function in animal models.

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The drug is currently being tested in the DELIVER trial. The phase 2 study is estimated to enroll 46 patients with a confirmed DMD mutation in the dystrophin gene due to exon deletion amenable to exon 51 skipping. All included patients must receive a stable corticosteroid for at least 12 weeks before the beginning of the trial.

Moreover, the trial will have 3 periods. The multiple ascending dose period is a randomized placebo-controlled period that will last 24 weeks, followed by a 24-week label extension. The last period will consist of a 96-week long-term extension.

The primary outcome measure will be the number of patients with treatment-emergent adverse effects and change from baseline dystrophin levels in muscle at week 25. Secondary outcome measures include baseline changes in creatinine kinase levels, time to rise in ambulatory patients, and predictive forced capacity.

“Duchenne is a fatal disease, and available therapies offer limited benefit. We are focused on driving toward meaningful clinical data in our DELIVER trial anticipated in the second half of 2023 and continuing to work closely with the DMD community and the FDA to advance a potentially transformative therapy,” said Wildon Farwell, MD, MPH, chief medical officer of Dyne.


Dyne therapeutics receives FDA fast track designation for DYNE-251 for the treatment of Duchenne muscular dystrophy. News release. Dyne Therapeutics; October 31, 2022.