Quantitative high-performance liquid chromatographic method for pharmacokinetic studies of the potent mast cell inhibitor 4-(4 '-hydroxyphenyl)amino-6,7-dimethoxyquinazoline (WHI-P131)

The novel quinazoline derivative 4-(4'-hydroxyphenyl)amino-6,7-dimethoxyqui nazoline (WHI-P131) has recently been identified as a potent mast cell inhi bitor capable of preventing IgE/antigen induced cutaneous as well as system ic fatal anaphylaxis in mice. Here we describe a sensitive high-performance liquid chromatography (HPLC)-based quantitative detection method for measu rement of WHI-P131 levels in plasma as well as in target mast cells. The av erage extraction recovery for WHI-P131 was 88.4% for plasma and 75.7% for R BL-2H3 mast cell lysates. Good linearity (r>0.999) was observed throughout the concentration range of 0.1-20 mu M in plasma and 0.01-5 nmol in 5.10(6) cells (0.5-238 mu M per cell) for WHT-P131. Intra- and inter-assay variabi lities were <7% and the lowest detection limit of WHI-P131 was 0.05 mu M in plasma and 0.005 nmol in 5 million cells, respectively, at a signal-to-noi se ratio of similar to 2. The practical utility of this new HPLC method was confirmed in a pilot pharmacokinetic study in BALB/c mice as well as in a cellular drug uptake and disposition study in RBL-2H3 mast cells. After int raperitoneal administration of a non-toxic 40 mg/kg bolus dose of WHI-P131, the estimated maximum plasma concentration was 92.7 mu M, which is approxi mately 1-log higher than the effective in vitro mast cell inhibitory concen trations of WHI-P131, The drug absorption was rapid with an absorption half -life of only 2.9 min and the estimated time to reach the maximum plasma co ncentration was 8.3 min. WHI-P131 was cleared with an apparent systemic cle arance rate of 2586 ml/h/kg and an elimination half-life of 1.8 h. An intra cellular exposure level (AUC) of 55 mu M . h was obtained after in vitro tr eatment of RBL-2H3 mast cells with WHI-P131 at a 33.6 mu M final concentrat ion in culture medium. The availability of the described quantitative HPLC detection method for WHI-P131 provides the basis for further development of WHI-P131 as an anti-allergic drug through detailed pharmacodynamic studies in preclinical animal models. (C) 1999 Elsevier Science B.V. All rights re served.