PT - JOURNAL ARTICLE AU - Jianyao Wang AU - Xiao Xian Li-Chan AU - Jim Atherton AU - Lin Deng AU - Robert Espina AU - Linning Yu AU - Peter Horwatt AU - Steven Ross AU - Susan Lockhead AU - Syed Ahmad AU - Appavu Chandrasekaran AU - Aram Oganesian AU - JoAnn Scatina AU - Abdul Mutlib AU - Rasmy Talaat TI - Characterization of HKI-272 Covalent Binding to Human Serum Albumin AID - 10.1124/dmd.110.032292 DP - 2010 Jul 01 TA - Drug Metabolism and Disposition PG - 1083--1093 VI - 38 IP - 7 4099 - http://dmd.aspetjournals.org/content/38/7/1083.short 4100 - http://dmd.aspetjournals.org/content/38/7/1083.full SO - Drug Metab Dispos2010 Jul 01; 38 AB - The study was initiated as an observation of incomplete extraction recovery of N-(4-(3-chloro-4-(2-pyridinylmethoxy)anilino)-3-cyano-7-ethoxy-6-quinolyl)-4-(dimethylamino)-2-butenamide (HKI-272) from human plasma. The objective of this study was to 1) identify the binding site(s) of HKI-272 to human plasma protein(s); 2) characterize the nature of the binding; and 3) evaluate the potential reversibility of the covalent binding. After incubation of [14C]HKI-272 with human plasma, the mixture was directly injected on liquid chromatography/mass spectrometry (LC/MS), and an intact molecular mass of HKI-272 human serum albumin (HSA) adduct was determined to be 66,999 Da, which is 556 Da (molecular mass of HKI-272) larger than the measured molecular mass of HSA (66,443 Da). For peptide mapping, the incubation mixture was separated with SDS-polyacrylamide gel electrophoresis followed by tryptic digestion combined with LC/tandem MS. A radioactive peptide fragment, LDELRDEGKASSAK [amino acid (AA) residue 182–195 of albumin], was confirmed to covalently bind to HKI-272. In addition, after HCl hydrolysis, a radioactive HKI-272-lysine adduct was identified by LC/MS. After combining the results of tryptic digestion and HCl hydrolysis, the AA residue of Lys190 of HSA was confirmed to covalently bind to HKI-272. A standard HKI-272-lysine was synthesized and characterized by NMR. The data showed that the adduct was formed via Michael addition with the ε-amine of lysine attacking to the β-carbon of the amide moiety of HKI-272. Furthermore, reversibility of the covalent binding of HKI-272 to HSA was shown when a gradual release of HKI-272 was observed from protein pellet of HKI-272-treated human plasma after resuspension in phosphate buffer, pH 7.4, at 37°C for 18 h. Copyright © 2010 by The American Society for Pharmacology and Experimental Therapeutics