Erythropoietins continue to be the number one selling class of biological products (excluding vaccines), with total sales in 2005 estimated at $10.85 billion.

Erythropoietin (sometimes called EPO) is a glycoprotein hormone, produced mainly by the kidneys, that stimulates the production of red blood cells by stem cells in bone marrow.

Recombinant human erythropoietin has been used since 1989 to treat anemia. Because the kidneys are the primary source of erythropoietin, chronic renal disease often results in a deficiency of EPO and thus anemia. Anemia also foccurs in many cancer patients as an adverse side-effect of chemotherapy.

The leading recombinant human erythropoietins are: