title: In vitro protein binding of liraglutide in human plasma determined by reiterated stepwise equilibrium dialysis.
abstract: Liraglutide is a human glucagon-like peptide-1 (GLP-1) analogue approved for the treatment of type 2 diabetes. It is based on human GLP-1 with the addition of a 16-carbon fatty acid, which facilitates binding to plasma proteins, thus prolonging the elimination half-life and allowing once-daily administration. It has not been possible to quantify liraglutide protein binding by ultrafiltration (the usual method of choice), as the lipophilic molecule becomes trapped in the filter membrane. Therefore, the aim of this study was to develop a methodology that could determine the extent of liraglutide binding to plasma proteins in vitro. We report here the details of a novel reiterated stepwise equilibrium dialysis assay that has successfully been used to quantify liraglutide plasma protein binding. The assay allowed quantification of liraglutide binding to proteins in purified plasma protein solutions and human plasma samples and was effective at plasma dilutions as low as 5%. At a clinically relevant liraglutide concentration (10(4) pM), greater than 98.9% of liraglutide was bound to protein. Specific binding to human serum albumin and α1-acid glycoprotein was 99.4% and 99.3%, respectively. The novel methodology described herein could have an application in the quantification of plasma protein binding of other highly lipophilic drug molecules.
authors.affiliation: Department of Diabetes Pharmacology PK/PD, Novo Nordisk A/S, Måløv DK-2760, Denmark. anp@novonordisk.com
authors.forename: Anne
authors.initials: A
authors.lastname: Plum
authors.forename: Lisbeth Bjerring
authors.initials: LB
authors.lastname: Jensen
authors.forename: Jesper Bøggild
authors.initials: JB
authors.lastname: Kristensen
mesh_terms: D001798:Blood Proteins / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy; D003956:Dialysis / Q000295:instrumentation*; D004867:Equipment Design; D052216:Glucagon-Like Peptide 1 / Q000031:analogs & derivatives* / Q000378:metabolism; D006801:Humans; D007004:Hypoglycemic Agents / Q000378:metabolism*; D000069450:Liraglutide; D011485:Protein Binding
chemical_list: D001798:Blood Proteins; D007004:Hypoglycemic Agents; D000069450:Liraglutide; D052216:Glucagon-Like Peptide 1
keywords: acylated peptides; equilibrium dialysis; human serum albumin; in vitro method; insulin detemir; liraglutide; plasma proteins; protein binding; type 2 diabetes mellitus