BTI 322 (Anti-CD2 monoclonal antibody, monoclonal antibody Lo-CD2-a, Lo-CD2-a) is a rat IgG2b &kgr; anti-CD2 monoclonal antibody that binds specifically to the CD2 antigen receptor on T cells and NK cells, thereby suppressing their function. Currently, the drug is being codeveloped by BioTransplant and MedImmune after the 2 companies formed a strategic alliance to develop products for the prevention and treatment of organ transplant rejection.A phase I/II clinical trial has been completed for the prevention and treatment of acute kidney transplant rejection, and for the treatment of acute graft-versushost disease (GVHD), a potentially fatal complication that occurs when immune cells of the foreign graft initiate an inflammmatory reaction against tissues of the recipient. A multicentre, phase II clinical trial for the latter indication is evaluating the effects of BTI 322 in adult recipients, of allogenic bone marrow or stem cells, who have experienced acute GVHD and have not responded to corticosteroid treatment. BTI 322 is also undergoing development for the treatment of other autoimmune diseases.A humanised form of the product (MEDI 507), which is currently being prepared by MedImmune, is undergoing clinical trials for the prevention and treatment of acute kidney transplant rejection.BTI 322 is also a component of a new specific immune tolerance therapy which is being developed by BioTransplant for the transplantation of human organs with reduced chronic immune suppression (AlloMuneTM) and for the transplantation of porcine organs into humans (XenoMuneTM). Under the AlloMuneTMregimen, a 3-stage treatment being tested; transplant patients first receive BTI 322, then radiation treatment followed by bone marrow transplantation from the organ donor, before finally receiving the organ itself. The chimeric bone marrow created by the bone marrow transplantation educates the T cells in the thymus to accept tissue from both the host and the donor as ‘self’. MedImmune has no rights to the development or commercialisation of either AlloMuneTMor XenoMuneTMaccording to the agreement with BioTransplant.