Del-zota for Duchenne muscular dystrophy

Last updated Oct 10, 2025, by Margarida Maia, PhD
Fact-checked by José Lopes, PhD

What is del-zota for Duchenne muscular dystrophy?

Delpacibart zotadirsen (del-zota) is an investigational therapy for Duchenne muscular dystrophy (DMD) caused by mutations amenable to exon 44 skipping. It is being developed by Avidity Biosciences.

Duchenne is caused by a faulty DMD gene, which encodes dystrophin, a protein that protects muscles from wear and tear during movement. Without it, muscles become damaged over time.

Delivered as an intravenous, or into-the-vein, infusion, del-zota contains an antibody that targets muscle cells and a molecule called a phosphorodiamidate morpholino oligomer, or PMO, so that the protein-producing machinery in muscle cells skips over a portion of the DMD gene (exon 44) to produce a shorter but functional version of dystrophin. This is expected to protect muscles from damage and at least ease symptoms.

Therapy snapshot

How will del-zota be administered?

In adults and children with DMD, del-zota has been tested as an intravenous infusion at either 5 mg/kg or 10 mg/kg. The company has selected the lower dose, given every six weeks, for further clinical testing, and for a planned biologics license application seeking regulatory approval in the U.S.

Del-zota in clinical trials

After completing a Phase 1/2 clinical trial dubbed EXPLORE44 (NCT05670730), the company is continuing to test del-zota in an open-label extension called EXPLORE44-OLE (NCT06244082), which has enrolled 39 men and boys diagnosed with DMD.

• In the EXPLORE44 clinical trial, men and boys with DMD were randomly assigned to receive infusions of del-zota — 5 mg/kg every six weeks or 10mg/kg every eight weeks — or a placebo. Top-line results showed that production of dystrophin increased to about 25% of its normal levels with either low or high doses. Treatment also reduced levels of creatine kinase, a marker of damage to muscles, in the blood by more than 80%, a benefit sustained for up to 16 months, or nearly 1.5 years.
• In the ongoing EXPLORE44-OLE, patients who were being treated with the 10 mg/kg dose every eight weeks were switched to the lower dose of 5 mg/kg every six weeks. At about one year of follow-up, pooled data from the parent trial and the OLE showed benefits in multiple timed function tests and in the North Star Ambulatory Assessment of motor function relative to a natural history group of patients not treated with del-zota. Benefits were also reported in a measure of upper limb function regardless of the participants’ ability to walk.

Del-zota side effects

Most side effects reported with del-zota during clinical testing were mild or moderate in severity. The most common ones were:

• upper respiratory tract symptoms
• diarrhea
• falls
• back pain
• headache

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