Approximately 30% of HLA-identical related bone marrow graft recipients and up to 90% of patients receiving bone marrow from unrelated donors develop significant acute GvHD despite the use of prophylactic therapies such as cyclosporine and methotrexate. About half of these patients respond to initial treatment with steroids and require no further treatment. The remainder of these patients are either unresponsive to initial therapy or become steroid-resistant over time. The prognosis in these cases is poor and mortality for patients with steroid-resistant GvHD may be as high as 50%.

ECP is a technique in which peripheral white blood cells are exposed to a photoactivatable compound (UVADEX) administered extracorporeally and ultraviolet A light. After cells are reinfused into the patient, their function is altered, thereby activating mechanisms that allow for further regulation of specific lymphocyte populations. ECP has shown activity in several inflammatory and autoimmune diseases, including scleroderma, rheumatoid arthritis, transplantation rejection, acute and chronic GvHD.

In a previous single-center, open label, single-arm study of 56 patients receiving ECP treatment on two consecutive days and reduced-intensity bone-marrow conditioning prior to bone marrow transplantation from matched or partially matched human donors, the incidence of grade II-IV acute GvHD was less than 10%. This is in contrast to an expected incidence of approximately 40%.

The purpose of this study is to determine the role of ECP, administered pre-transplant, in preventing GvHD when used in conjunction with a standard myeloablative conditioning regimen.