Determination of a novel phosphodiesterase4 inhibitor, 3-[1-(3cyclopropylmethoxy-4-difluoromethoxybenzyl)-1H-pyrazol-3-yl]-benzoic acid (PDE-423) in rat plasma using liquid chromatography-tandem mass spectrometry.

A method for determining a novel phosphodiesterase-4 inhibitor, 3-[1-(3cyclopropylmethoxy-4-difluoromethoxybenzyl)-1H-pyrazol-3-yl]-benzoic acid (PDE-423), in rat plasma was developed and validated using liquid chromatography-tandem mass spectrometry for further pharmacokinetic study for development as a novel anti-asthmatic drug. PDE-423 in the concentration range of 0.02-10 µg/mL was linear with a correlation coefficient of >0.99, and the mean intra- and inter-assay precisions of the assay were 7.50 and 3.86%, respectively. The validated method was used successfully for a pharmacokinetic study of PDE-423 in rats.

Preclinical pharmacokinetic characterization of 2-(4-(4-(5-(2-phenyl-5-(trifluoromethyl)oxazole-4-carboxamido)-1H-benzo[d]imidazol-2-yl)phenyl)cyclohexyl) acetic acid, a novel DGAT-1 inhibitor.

1. A novel diacylglyceride acyltransferase-1 (DGAT-1) inhibitor, 2-(4-(4-(5-(2-phenyl-5-(trifluoromethyl) oxazole-4-carboxamido)-1H-benzo[d]imidazol-2-yl)phenyl)cyclohexyl) acetic acid (KR-69232), was synthesized for a potential therapeutic use against several metabolic disorders, such as obesity, insulin resistance, and type II diabetes, characterized by excessive triglycerides (TGs) in the blood. 2. The half-lives against phase I metabolism were measured as 75.3 ± 20.9 min and over 120 min in rat and human liver microsomes, respectively. In Caco-2 cell monolayers, extremely low permeability (<0.13 × 10⁻6cm/s) was seen in the absorptive direction, predicting limited intestinal absorption of KR-69232. This compound was highly bound to rat and human plasma proteins (>99.8%). 3. With the intravenous administration of KR-69232 in rats (1, 2, and 5 mg/kg), non-linear kinetics were observed at the highest dose, with significantly higher systemic clearance, higher volume of distribution, and lower dose-normalized AUC. Following oral administration, it exhibited low bioavailability (<10%) and was absorbed slowly (T(max), 3.8-5.2 h) over the dose range. We also confirmed that considerable KR-69232 remained in the intestine at T(max), demonstrating its limited absorption into the systemic circulation.

Pharmacokinetic characterization of the novel TAZ modulator TM-25659 using a multicompartment kinetic model in rats and a possibility of its drug-drug interactions in humans.

This study evaluated the pharmacokinetics of the novel TAZ modulator TM-25659 in rats following intravenous and oral administration at dose ranges of 0.5-5 mg/kg and 2-10 mg/kg, respectively. Plasma protein binding, plasma stability, liver microsomal stability, CYP inhibition, and transport in Caco-2 cells were also evaluated. After intravenous injection, systemic clearance, steady-state volumes of distribution, and half-life were dose-independent, with values ranging from 0.434-0.890 mL · h(-1) · kg(-1), 2.02-4.22 mL/kg, and 4.60-7.40 h, respectively. Mean absolute oral bioavailability was 50.9% and was not dose dependent. Recovery of TM-25659 was 43.6% in bile and <1% in urine. In pharmacokinetic modeling studies, the three-compartment (3C) model was appropriate for understanding these parameters in rats. TM-25659 was stable in plasma. Plasma protein binding was approximately 99.2%, and was concentration-independent. TM-25659 showed high permeation of Caco-2 cells and did not appear to inhibit CYP450. TM-25659 was metabolized in phase I and II steps in rat liver microsomes. In conclusion, the pharmacokinetics of TM-25659 was characterized for intravenous and oral administration at doses of 0.5-5 and 2-10 mg/kg, respectively. TM-25659 was eliminated primarily by hepatic metabolism and urinary excretion.

Discovery of a Novel Highly Selective Histamine H4 Receptor Antagonist for the Treatment of Atopic Dermatitis.

The histamine H4 receptor (H4R), a member of the G-protein coupled receptor family, has been considered as a potential therapeutic target for treating atopic dermatitis (AD). A large number of H4R antagonists have been disclosed, but no efficient agents controlling both pruritus and inflammation in AD have been developed yet. Here, we have discovered a novel class of orally available H4R antagonists showing strong anti-itching and anti-inflammation activity as well as excellent selectivity against off-targets. A pharmacophore-based virtual screening system constructed in-house successfully identified initial hit compound 9, and the subsequent homology model-guided optimization efficiently led us to discover pyrido[2,3- e]tetrazolo[1,5- a]pyrazine analogue 48 as a novel chemotype of a potent and highly selective H4R antagonist. Importantly, orally administered compound 48 exhibits remarkable efficacy on antipruritus and anti-inflammation with a favorable pharmacokinetic (PK) profile in several mouse models of AD. Thus, these data strongly suggest that our compound 48 is a promising clinical candidate for treatment of AD.

P-Glycoprotein, not BCRP, Limits the Brain Uptake of [(18)F]Mefway in Rodent Brain.

PURPOSE: The aim of this study was to determine whether the brain uptake of [(18)F]Mefway is influenced by the action of P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp) in rodents. PROCEDURES: [(18)F]Mefway was applied to rats pharmacologically inhibited with tariquidar (TQD) and to genetically disrupted mice. RESULTS: Pretreatment of TQD results in 160% higher hippocampal uptake compared with control rats. In genetically disrupted mice, a maximal brain uptake value of 3.2 SUV in the triple knockout mice (tKO, Mdr1a/b((-/-))Bcrp1((-/-))) was comparable to that of the double knockout mice (dKO, Mdr1a/b((-/-))) and 2-fold those of the wild-type and Bcrp1((-/-)) knockout mice. The differences of binding values were statistically insignificant between control and experimental groups. The brain-to-plasma ratios for tKO mice were also two to five times higher than those for other groups. CONCLUSIONS: [(18)F]Mefway is modulated by P-gp, and not by Bcrp in rodents.