Physiology and pharmacology of erythropoietin.

Human erythropoietin (Epo) is a 30.4 kDa glycoprotein hormone composed of a single 165 amino acid residues chain to which four glycans are attached. The kidneys are the primary sources of Epo, its synthesis is controlled by hypoxia-inducible transcription factors (HIFs). Epo is an essential factor for the viability and proliferation of erythrocytic progenitors. Whether Epo exerts cytoprotection outside the bone marrow still needs to be clarified. Epo deficiency is the primary cause of the anemia in chronic kidney disease (CKD). Treatment with recombinant human Epo (rhEpo, epoetin) can be beneficial not only in CKD but also for other indications, primarily anemia in cancer patients receiving chemotherapy. Considering unwanted events, the administration of rhEpo or its analogs may increase the incidence of thromboembolism. The expiry of the patents for the original epoetins has initiated the production of similar biological medicinal products ('biosimilars'). Furthermore, analogs (darbepoetin alfa, methoxy PEG-epoetin beta) with prolonged survival in circulation have been developed ('biobetter'). New erythropoiesis-stimulating agents are in clinical trials. These include compounds that augment erythropoiesis directly (e.g. Epo mimetic peptides or activin A binding protein) and chemicals that act indirectly by stimulating endogenous Epo synthesis (HIF stabilizers).