Gloria Y. Kwei

Lymphatic uptake of MK-386, a sterol 5α-reductase inhibitor, from aqueous and lipid formulations

Abstract 4,7- β -Dimethyl-4-aza-5 α -cholestan-3-one (MK-386) is a specific inhibitor of type-1 5 α -reductase, with over 10 4 -fold greater solubility in lipid-type vehicles than in water. The absorption of orally administered MK-386 was investigated with three formulations to test the possibility that formulation can influence the absorption by altering the relative lymph/blood partitioning of MK-386. Drug concentrations in mesenteric lymph or in portal plasma were determined after administration of a 5 mg/kg dose in aqueous suspension, a mono-diglyceride/polysorbate 80 (MDG/PS80) vehicle or a soybean oil solution to conscious rats. Lymph volume collected over a 6 h period was in the order aqueous suspension>MDG/PS 80>soybean oil-dosed animals. Total mass of MK-386 collected in lymph also followed this trend. MK-386 radioactivity equivalents from all formulations were as much as 80-fold greater in lymph compared with portal plasma, and radioactivity was exclusively associated with parent drug in lymph. Traces of metabolites, but virtually no MK-386, were detected in portal plasma. Distribution of MK-386 into lymph was insignificant after intravenous administration. The results demonstrate that systemic availability of orally administered MK-386 was due to lymphatic, not portal blood transport, and the rate of transport determined in this model was influenced by formulation.

Identification of Novel Metabolites of Colchicine in Rat Bile Facilitated by Enhanced Online Radiometric Detection

Three novel conjugation metabolites of colchicine were identified in rat bile facilitated by enhanced on-line liquid chromatography-accurate radioisotope counting. The known 2- and 3-demethylcolchicines (DMCs) underwent O-sulfate conjugation in addition to the previously described O-glucuronidation. 2-DMC was preferably O-glucuronidated, whereas 3-DMC predominantly yielded O-sulfation conjugates, indicating phase II conjugation regiopreferences. Moreover, M1 was identified as a novel glutathione conjugate and a possible biotransformation pathway for its formation was proposed. The known 2-DMC (M6), 3-DMC (M7), 2-DMC glucuronide (M4), and novel 3-DMC sulfate (M3) were confirmed as the major metabolites. Radiometric data were acquired by the XFlow liquid chromatography-accurate radioisotope counting (XFlow LC-ARC) system, a novel technology for dynamic control of both on-column and postcolumn high-performance liquid chromatography flow rates to maximize sensitivity and resolution of radiochromatograms. A comparative evaluation was also performed between the XFlow LC-ARC system and a conventional flow radiometric detection system using bile samples from an in vivo disposition study of colchicine in male Sprague-Dawley rats. Results demonstrated a 20-fold sensitivity improvement of the XFlow LC-ARC system in comparison with radioactivity detection by conventional flow scintillation analyzers. The dynamic flow mode also provided the best chromatographic resolution. Unambiguous metabolite identification was performed by high-resolution mass spectrometry and nuclear magnetic resonance analysis.

Lead optimization of 4,4-biaryl piperidine amides as γ-secretase inhibitors.

Alzheimers disease is a major unmet medical need with pathology characterized by extracellular proteinaceous plaques comprised primarily of β-amyloid. γ-Secretase is a critical enzyme in the cellular pathway responsible for the formation of a range of β-amyloid peptides; one of which, Aβ42, is believed to be responsible for the neuropathological features of the disease. Herein, we report 4,4 disubstituted piperidine γ-secretase inhibitors that were optimized for in vitro cellular potency and pharmacokinetic properties in vivo. Key agents were further characterized for their ability to lower cerebral Aβ42 production in an APP-YAC mouse model. This structural series generally suffered from sub-optimal pharmacokinetics but hypothesis driven lead optimization enabled the discovery of γ-secretase inhibitors capable of lowering cerebral Aβ42 production in mice.