Muscular dystrophy therapy is available, but only to a fortunate few

There’s a boy like you in Minnesota, Yannick’s mom told him a few years ago. He has the same disease. He has the same kind of smile. Maybe you could talk?

They clicked. After school and on weekends, the two boys boot up their computers, Yannick in San Diego and Brecken in a suburb of St. Paul, Minn. They play Roblox or build virtual worlds on Minecraft: a zoo, for example, like the real-world one 13-year-old Yannick wants to build when he grows up, full of lions, tigers, and giraffes. 

They seldom talk about Duchenne muscular dystrophy, the rare fatal muscle-wasting disease they live with. But lately it’s all their moms can talk about. In stolen phone calls on the way to coffee or back from school, they compare the two boys: how quickly Yannick is declining and how steadily Brecken is — shockingly — improving.

Last winter, Brecken, 12, started receiving an experimental drug developed by Avidity Biosciences. The medicine makes the cell’s protein-building machinery “skip” part of the gene, called an exon, behind Duchenne, allowing patients to make a shortened but functional version of a protein essential for muscle survival. In trials, it appeared to virtually arrest the disease in some patients. 

The approach, however, 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. (The disease almost exclusively affects males.) But the medicines have to be targeted to a patient’s specific mutation. Only about 7% of patients — or roughly 900 Americans — are eligible for Avidity’s drug, called Del-zota, which is now under Food and Drug Administration review.