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Investigation of the Pharmacokinetics of Romiplostim in Rodents with a Focus on the Clearance Mechanism.
MedLine Citation:
PMID:  21476045     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
PURPOSE: Romiplostim, a treatment for adults with immune thrombocytopenia (ITP), is a novel thrombopoietin mimetic agent with a similar mechanism of action as thrombopoietin with no sequence homology. Structurally, it is a peptibody containing thrombopoietin mimetic peptides and the Fc portion of human IgG(1). We investigated romiplostim pharmacokinetics in rodents with a focus on the clearance mechanism. METHODS: Studies with appropriate controls were conducted in four models: FcRn knockout mice, thrombocytopenic mice, splenectomized rats, and bilateral nephrectomized rats. Catabolic breakdown of romiplostim was investigated in normal rats. The primary analytical method determines the intact/active romiplostim concentration, and the secondary method determines the sum of romiplostim and its catabolic degradants. RESULTS: FcRn interaction results in prolonged exposure. Platelets are involved in the target-mediated elimination, a saturable process and more prominent at low dose. Splenectomy does not affect the romiplostim pharmacokinetics in rats, an observation not unexpected. Nephrectomy in rats results in a greater increase of romiplostim exposure at a higher romiplostim dose, a nonlinearity likely due to saturation of competing pathway. Catabolism plays a major role in romiplostim elimination. CONCLUSION: Romiplostim clearance involves multiple mechanisms, including a nonlinear pathway. Consequently, the relative contribution of different mechanisms appears to be dose dependent.
Authors:
Yow-Ming C Wang; Bethlyn Sloey; Teresa Wong; Prerna Khandelwal; Rebeca Melara; Yu-Nien Sun
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-4-8
Journal Detail:
Title:  Pharmaceutical research     Volume:  -     ISSN:  1573-904X     ISO Abbreviation:  -     Publication Date:  2011 Apr 
Date Detail:
Created Date:  2011-4-8     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8406521     Medline TA:  Pharm Res     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Pharmacokinetics and Drug Metabolism Department, Amgen Inc., One Amgen Center Drive, 28-3-B, Thousand Oaks, California, 91320, USA, wang.yowming@gmail.com.
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