<p>Methoxy polyethylene glycol-epoetin beta is a chemically synthesized continuous erythropoietin receptor activator. Methoxy polyethylene glycol-epoetin beta differs from erythropoietin through integration of an amide bond between either the N-terminal amino group or the &epsilon; amino group of lysine, predominantly Lys52 and Lys45 and methoxy polyethylene glycol butanoic acid. This results in a molecular weight of approximately 60,000 daltons for methoxy polyethylene glycol-epoetin beta with the PEG-moiety having an approximate molecular weight of 30,000 daltons.<br />
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In contrast with erythropoietin, methoxy polyethylene glycol-epoetin beta shows a different activity at the receptor level characterized by a slower association to and faster dissociation from the receptor, a reduced specific activity in vitro with an increased activity in vivo, as well as an increased half-life. These differential pharmacological properties are relevant in order to achieve a once monthly dosing regimen with methoxy polyethylene glycol-epoetin beta in patients.<br />
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Methoxy polyethylene glycol-epoetin beta stimulates erythropoiesis by interaction with the erythropoietin receptor on progenitor cells in the bone marrow. As primary growth factor for erythroid development, the natural hormone erythropoietin is produced in the kidney and released into the bloodstream in response to hypoxia. In responding to hypoxia, the natural hormone erythropoietin interacts with erythroid progenitor cells to increase red cell production.</p>