Two boys, Yannick in San Diego and Brecken in Minnesota, both live with Duchenne muscular dystrophy, a rare and fatal muscle-wasting disease. They bond over Minecraft and Roblox, rarely discussing their condition. But their mothers have noticed a stark difference: while Yannick declines, Brecken has been steadily improving since he began receiving an experimental drug from Avidity Biosciences last winter.
The medicine, called Del-zota, uses exon skipping to help cells produce a shortened but functional version of the muscle protein that Duchenne patients lack. In trials, the approach appeared to virtually arrest the disease in some patients. However, the therapy must be tailored to each patient's specific genetic mutation, limiting eligibility to roughly 7% of the 10,000 to 15,000 Duchenne patients in the U.S.—about 900 people.
In principle, exon-skipping strategies could benefit up to 70% of patients, but each drug targets a different exon. Del-zota is now under FDA review, and the gap between those who can access it and those who cannot has intensified calls from families and advocates for companies to move faster and broaden the reach of these promising treatments.