Isis Pharmaceuticals has opened a second phase 3 trial to test its antisense drug, ISIS-SMNRx, in children with spinal muscular atrophy (SMA) who are 2 to 12 years old, not able to walk, and experienced their first disease symptoms after 6 months of age. ISIS-SMNRx is designed to alter the splicing of a closely related gene (SMN2) to increase production of fully functional SMN protein. In August, Isis initiated a phase 3 trial of the same drug in SMA-affected infants age 7 months or younger. This trial is also open and enrolling.. In October, Isis announced promising results from phase 2 clinical studies of ISIS-SMNRx in infants and in children. On average, infants receiving the drug at either of two dosage levels survived longer and survived without requiring permanent ventilation than did untreated, SMA-affected infants in a recent natural history study. Infants and older children receiving ISIS-SMNRx showed increases in muscle function. The newly opened trial in SMA-affected children will include approximately 117 children who will be randomly assigned to receive injections of ISIS-SMNRx into the spinal fluid or to receive sham procedures, involving a needle prick of the skin in the area where an injection would have taken place.
