High performance liquid chromatographic analysis and preclinical pharmacokinetics of the heteroarotinoid antitumor agent, SHetA2

Background: SHetA2 {[(4-nitrophenyl)amino][2,2,4,4-tetramethylthiochroman-6-yl)amino]methane-thione], NSC 726189} is a sulfur-containing heteroarotinoid, which selectively inhibits Cancer cell growth and induces Apoptosis without activation of nuclear retinoic acid receptors (RARs). The objective was to develop and validate a HPLC/UV method for the determination of SHetA2, and study the pharmacokinetics of SHetA2 in the mouse.

Methods: SHetA2 and the internal standard, methylated XK469 (MeXK469) were isolated from 0.2 ml of mouse plasma by solid phase extraction. The analytes were separated on a narrow-bore C18 column, with the mobile phase consisting of 60% acetonitrile in water at a flow rate of 0.2 ml/min. UV detection was set at 341 nm. Pharmacokinetic studies of SHetA2 were carried out in mice following i.v. bolus dose at 20 mg/kg and oral administrations at 20 and 60 mg/kg.

Results: The standard curves were linear between 25 and 2,500 nM and the lower limit of quantification (LLOQ) was 25 nM. The within-run coefficients of variation (CVs) were 11.1% at 10, 9.4% at 100, and 5.2% at 2,500 nM and the respective between-run CVs were 10.9, 3.1, and 1.5% (all n=5). The recovery was 85.8% for SHetA2 and 80.6% for MeXK469. Following i.v. bolus dose, plasma concentrations of approximately 10 microM were achieved at 5 min in mice and declined biexponentially with detectable levels at 60 h. The data were fitted with a two-compartment model, which gave a mean initial t1/2 of 40 min and terminal t1/2 of 11.4 h (n=6). The total body clearance was approximately 1.81 l/h/kg. The volume of distribution at steady state (Vdss) was 20.8 l/kg. Plasma protein binding was found to be 99.3-99.5% at low micromolar concentrations. Plasma concentration data for the i.v. and p.o. doses were also fitted interactively to a two-compartment deconvolution model. From this result, oral bioavailability values of 15% at 20 mg/kg and 19% at 60 mg/kg were obtained.

Conclusions: A highly sensitive HPLC/UV method for the quantification of SHetA2 in plasma has been developed to support pharmacokinetics of SHetA2 in the mouse. Pharmacokinetic behaviors of this drug appear to be favorable for future development.