Gene therapy targeting hematopoietic cells: better not leave it to chance

Gene therapy targeting hematopoietic cells has arrived at a new stage of potency. While the potential for curing inherited disorders of the immune system has been demonstrated in clinical trials, we were also confronted with the first serious adverse events related to random insertion of foreign DNA into cellular chromosomes. As it is likely that the manifestation of severe side effects results from a multifactorial process, it will be of crucial importance to define the significance of the individual risk factors involved. The future of the field will depend on our ability to define risk classifications of clinical approaches, to continuously improve transgene technologies, and to introduce new concepts for targeted selection of transgenic cells. Interestingly, correction of genetic disorders by homologous gene repair in defined stem cell clones is on the horizon, but far from being available for clinical use.