Only about 7% of US Duchenne patients eligible for Avidity drug under FDA review

Brecken, 12, who lives in a suburb of St. Paul, Minnesota, began receiving an experimental drug developed by Avidity Biosciences last winter, according to STAT News. Yannick, 13, of San Diego, has the same disease, Duchenne muscular dystrophy. STAT reported that Yannick is declining while Brecken is improving. Yannick's mother told him about a boy in Minnesota a few years ago, and the two now play Roblox or build virtual worlds on Minecraft together, according to STAT.

The medicine, called Del-zota, makes the cell's protein-building machinery "skip" part of the gene, called an exon, behind Duchenne, according to STAT. That allows patients to make a shortened but functional version of a protein essential for muscle survival. In trials, the drug appeared to virtually arrest the disease in some patients, STAT reported.

STAT reported that the approach is out of most patients' reach. In principle, "skipping" strategies could benefit about 70% of the 10,000 to 15,000 Duchenne boys and men in the U.S., according to STAT. But the medicines have to be targeted to a patient's specific mutation, and only about 7% of patients — roughly 900 Americans — are eligible for Del-zota, STAT reported.

Del-zota is now under review by the Food and Drug Administration, according to STAT. STAT also reported that Duchenne almost exclusively affects males. Yannick and his mother, Elena Etienne, and Brecken and his mother, Marit Siverston, were at the United Nations in 2025 for World Duchenne Awareness Day, according to STAT.