There has been some promising research into gene therapy for Duchenne Muscular Dystrophy, caused by mutation of DMD, coding for the protein dystrophin. This is a particularly large gene (2.5mb, containing 79 exons) which causes a problem in its delivery using a gene therapy vector.
Researchers at the University of Missouri have developed a “microgene” version of the DMD gene and used an adeno-associated virus to deliver it into the muscles of their dog model. The dogs began to show disease symptoms at 2-3 months old, when they were injected and they then showed normal development at 6-7 months old when the study ended.