Prospects for gene therapy of haemophilia A and B

Haemophilia A and B are relatively rare, X-linked inherited bleeding disorders which are life-threatening to patients unless treated by regular injections of factors VIII or IX, respectively. Gene therapy offers the prospect of a cure for the disease, thus potentially freeing patients from the existing regimens of regular intravenous injection of proteins and the risks of infection by contaminating viruses. Although, in theory, gene therapy is very attractive to patients and clinicians, in practice, preclinical experiments in animal models suggests that it may be difficult to obtain adequate therapeutic levels of either factors VIII or IX for long periods of time in patients unless improved methods can be devised. Progress in the preclinical studies is more encouraging with haemophilia B than with haemophilia A. Clinical trials for haemophilia B patients have started in China.