In a paper published in December 2007 (see “Publications,” below), the investigators announced that intramuscular injection of PRO051 was not associated with any apparent adverse events in the four trial participants. Each participant showed specific skipping of the exon 51 portion of the dystrophin gene and had dystrophin protein properly located at the muscle-fiber membrane in 64 percent to 97 percent of muscle fibers in the injected area.

By causing specific skipping of exons (parts of a gene that carry the code for the final protein to be synthesized) during processing of the genetic material RNA, antisense compounds have recently been shown to correct the way in which cells “read” the dystrophin gene in DMD-affected cells in such a way that production of the needed dystrophin protein is restored.

Four patients with specific dystrophin mutations (gene flaws) and good response of their cells to PRO051 in a test tube will receive a dose of 0.8 milligrams of PRO051 injected into the tibialis anterior (front lower leg) muscle. A biopsy will be performed 28 days later. Safety, composition of the genetic material known as messenger RNA, and production of dystrophin protein will be assessed.

The main purpose of this trial is to see if there are any adverse events associated with the procedure. The investigators will also look at whether there is skipping of a part of the dystrophin gene known as exon 51 or production of dystrophin protein.

Participants may take corticosteroids.

• be between 8 and 16 years old
• have DMD with deletions in the dystrophin gene correctable by skipping of exon 51
• have no evidence of dystrophin on a previous diagnostic muscle biopsy
• have a tibialis anterior (front lower leg) muscle containing no more than 50 percent fat or scar tissue