Boys with Duchenne muscular dystrophy attend the opening for Sarepta Therapeutics' new global headquarters in Cambridge, Mass., in June 2014.

An experimental gene therapy for Duchenne muscular dystrophy, licensed to Sarepta Therapeutics, produced jaw-dropping increases in a crucial muscle protein normally missing in patients with the disease, according to preliminary clinical trial data released Tuesday.

The data were collected from just three boys, but the effect of the gene therapy — producing 38 percent of a truncated form of the normal dystrophin muscle protein — is profound enough to suggest it may halt or even reverse the effects of Duchenne in certain patients.