If Duchenne muscular dystrophy (DMD) could be turned into something more resembling the Becker type of muscular dystrophy, that would be a considerable advance. DNA technology may make it possible. These two types of muscular dystrophy each result from mutations in the dystrophin gene (DMD) but whereas in the Duchenne type the open reading frame is disrupted, in the Becker type it is preserved. Antisense oligonucleotides might at least partially correct the defect. PRO051 is an oligoribonucleotide that induces skipping of exon 51 of the DMD, affecting about 13% of patients with Duchenne dystrophy. In 2007, it was reported that injection of PRO051 induced dystrophin production in patients with Duchenne dystrophy producing a situation similar to that of Becker dystrophy. Now (New England Journal of Medicine 2011;364:1513–22) a phase I–IIa study has been reported. The study included 12 patients with Duchenne dystrophy and relevant mutations (correctable by exon 51 skipping). Four possible doses of PRO051 (0.5, 2.0, 4.0 and 6.0 mg/kg) were each given by abdominal subcutaneous injection weekly for 5 weeks to three patients. Specific exon 51 skipping was detected at all doses except the lowest. Post-treatment muscle biopsies showed new dystrophin expression in 60%–100% of muscle fibres in ten of the 12 patients. The effect increased with increasing dosage. …