Human erythropoietin is an endogenous glycoprotein hormone that is the primary regulator of erythropoiesis through specific interaction with the erythropoietin receptor on the erythroid progenitor cells in the bone marrow. It acts as a mitosis-stimulating factor and differentiation hormone. The production of erythropoietin primarily occurs in and is regulated by the kidney in response to changes in tissue oxygenation. Production of endogenous erythropoietin is impaired in patients with chronic renal failure and the primary cause of their anaemia is erythropoietin deficiency. In patients with cancer receiving chemotherapy the aetiology of anaemia is multifactorial. In these patients, erythropoietin deficiency and a reduced response of erythroid progenitor cells to endogenous erythropoietin both contribute significantly towards their anaemia.
Epoetin theta is identical in its amino acid sequence and similar in its carbohydrate composition (glycosylation) to endogenous human erythropoietin.
The biological efficacy of epoetin theta has been demonstrated after intravenous and subcutaneous administration in various animal models in vivo (mice, rats, dogs). After administration of epoetin theta, the number of erythrocytes, the haematocrit values and reticulocyte counts increase.
The pharmacokinetics of epoetin theta have been examined in healthy volunteers, in patients with chronic renal failure and in cancer patients receiving chemotherapy. The pharmacokinetics of epoetin theta are independent of age or gender.
Following subcutaneous injection of 40 IU/kg body weight epoetin theta at three different sites (upper arm, abdomen, thigh) in healthy volunteers, similar plasma level profiles were observed. The extent of absorption (AUC) was slightly greater after injection in the abdomen in comparison to the other sites. The maximum concentration is reached after an average of 10 to 14 hours and the average terminal half-life ranges from approximately 22 to 41 hours.
Average bioavailability of epoetin theta after subcutaneous administration is approximately 31% compared with intravenous administration.
In pre-dialysis patients with chronic renal failure following subcutaneous injection of 40 IU/kg body weight, the protracted absorption results in a concentration plateau, whereby the maximum concentration is reached after an average of approximately 14 hours. The terminal half-life is higher than after intravenous administration, with an average of 25 hours after single dosing and 34 hours in steady state after repeated dosing three times weekly, without leading to an accumulation of epoetin theta.
In cancer patients receiving chemotherapy, after repeated subcutaneous administration of 20,000 IU epoetin theta once-weekly, the terminal half-life is 29 hours after the first dose and 28 hours in steady state. No accumulation of epoetin theta was observed.
In patients with chronic renal failure undergoing haemodialysis, the elimination half-life of epoetin theta is 6 hours after single dosing and 4 hours in steady state after repeated intravenous administration of 40 IU/kg body weight epoetin theta three times weekly. No accumulation of epoetin theta was observed. Following intravenous administration, the volume of distribution approximates to total blood volume.
Non-clinical data with epoetin theta reveal no special hazard for humans based on conventional studies of safety pharmacology and repeated dose toxicity.
Non-clinical data with other epoetins reveal no special hazard for humans based on conventional studies of genotoxicity and toxicity to reproduction.
In reproductive toxicity studies performed with other epoetins, effects interpreted as being secondary to decreased maternal body weight were observed at doses sufficiently in excess to the recommended human dose.
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