Interim results of a phase 2 clinical trial to test multiple doses of the experimental drug ISIS-SMNRx in infants with spinal muscular atrophy (SMA) suggest that the drug is well-tolerated and may prolong ventilator-free survival. The drug is designed to increase the level of full-length, fully functional SMN. In the ongoing phase 2 trial, doses of either 6 mg or 12 mg are being administered intrathecally on days 1, 15 and 85 of the study. There are four infants in the 6-mg dosage group, all of whom have been in the study for more than six months and have received all three of their scheduled doses of ISIS-SMNRx. The infants are now approximately 9.6 to 16 months old, with an average age of 12.5 months. All four are alive and none has required permanent ventilation assistance. A recent study of the natural history of infants with SMA found that half had died or been put on permanent ventilation by about 10 months of age, suggesting that the four infants in the 6-mg group who have reached an average age of 12.5 months without permanent ventilation are doing better than the natural history studied would have predicted.Although early, these interim results, provide support for advancing ISIS-SMNRx into a phase 3 study in infants. The phase 2 study remains open to infants with SMA who are 210 days old or younger and meet study criteria.
