THROMBOPOIETINS AND THROMBOPOIESIS - A CLINICAL PERSPECTIVE

Since the discovery of, thrombopoietin four years ago there has been m uch interest in the clinical use of this growth factor and its impact on platelet transfusions. Two recombinant thrombopoietin molecules are currently under intense clinical investigation. One is a full-length, glycosylated thrombopoietin (rHuTPO) and the other is a non-glycosyla ted, truncated thrombopoietin coupled to polyethylene glycol (PEG-rHuM GDF) Both bind to the thrombopoietin receptor, c-mpl, and stimulate me gakaryocyte growth and platelet production in vitro and in vivo. In ea rly clinical studies these ''Mpl ligands'' have been effective in redu cing thrombocytopenia after non-myeloablative but not after myeloablat ive chemotherapy. In transfusion medicine, they may serve to increase the yield of stem cell harvests, expand progenitor cells ex vivo and s timulate platelet apheresis donors. Their impact on platelet usage is still unclear but may be less than initially estimated.