His specific expertise and interests include virus-mediated gene transfer with a focus on target organs including the liver and bone marrow, both of which have immense promise as target organs for the treatment of genetic disease in children. His team became the first in Australia to treat a genetic disease (SCID-X1) by gene therapy and are recognised leaders in the establishment of this exciting field in Australia. Professor Alexander chaired the NHMRC Cellular Therapies Advisory Committee (CTAC). In addition, he helped establish the Australasian Gene Therapy Society, was elected as the inaugural president and was made a life member in 2009. His international recognition extends to positions as Chair of the International Committee of the American Society of Gene and Cell Therapy, Australasian Regional Editor of Current Gene Therapy and Associate Editor for Human Gene Therapy and The Journal of Gene Medicine.