Effects of CYP3A4*1G and CYP3A5*3 polymorphisms on pharmacokinetics of tylerdipine hydrochloride in healthy Chinese subjects.

The aim of this analysis was to explore the influence of CYP3A4*1G and CYP3A5*3 polymorphisms on the pharmacokinetics of tylerdipine in healthy Chinese subjects. A total of 64 and 63 healthy Chinese subjects were included and identified as the genotypes of CYP3A4*1G and CYP3A5*3, respectively. Plasma samples were collected for up to 120 h post-dose to characterize the pharmacokinetic profile following single oral dose of the drug (5, 15, 20, 25 and 30 mg). Plasma levels were measured by a high-performance liquid chromatography-mass spectrometry (LC-MS/MS). The pharmacokinetic parameters were calculated using non-compartmental method. The maximum concentration (Cmax) and the area under the curve (AUC0-24 h) were all corrected by the dose given. In the wild-type group, the mean dose-corrected AUC0-24 h was 1.35-fold larger than in CYP3A4*1G carriers (p = .018). Among the three CYP3A5 genotypes, there showed significantly difference (p = .008) in the t1/2, but no significant difference was observed for the AUC0-24 h and Cmax. In subjects with the CYP3A5*3/*3 genotype, the mean t1/2 was 1.35-fold higher than in CYP3A5*1/*1 group (p = .007). And the t1/2 in CYP3A5*3 carriers also was 1.32-fold higher than in the wild-type group (p = .004). CYP3A4*1G and CYP3A5*3 polymorphisms may influence tylerdipine pharmacokinetic in healthy Chinese subjects.

A Randomized, Open-Label, Crossover Phase 1 Study to Evaluate the Effects of Food on the Pharmacokinetics of a Single Oral Dose of a 15-mg Tylerdipine Tablet in Healthy Chinese Male Volunteers.

Tylerdipine hydrochloride is a novel L-type and T-type dual calcium channel antagonist that has the potential effects of expanding blood vessels and lowering blood pressure. It is expected to reduce the side effect of ankle edema observed with other drugs in the same class. A randomized, open-label, crossover phase 1 study was performed to evaluate the effect of food on the bioavailability of tylerdipine. Fourteen healthy male volunteers were enrolled. The administration of tylerdipine after a high-fat meal increased the bioavailability of tylerdipine. In the fed state there was a 130% increase in the mean total systemic exposure (AUCinf ) and a 73% increase in the mean peak plasma concentration (Cmax ) compared with that in the fasting state. The geometric mean ratios (90% confidence interval) of Cmax and AUCinf were 2.54 (1.94, 3.33) and 1.75 (1.50, 2.04) for tylerdipine. The exposures of the 2 main metabolites M2 and M4 were increased by approximately 10% after a high-fat meal. The median time to peak plasma concentration of tylerdipine showed no difference between fasting and fed states.

Development and validation of two LC-MS/MS methods to assay urinary tylerdipine hydrochloride and its metabolites in healthy Chinese subjects.

For quantitative assaying tylerdipine hydrochloride, and its two primary metabolites (M2 and M4) in human urine, two sensitive and accurate LC-MS/MS methods were firstly developed and validated, where multiple reaction monitoring (MRM) was applied under positive electrospray ionization mode for tylerdipine and negative electrospray ionization mode for M2/M4, respectively. Urinary proteins were precipitated using acetonitrile, and deuterated isotopes of tylerdipine and M4 ([D5]­tylerdipine and [D6]-M4) were used as internal standards. Triton X-100, a good surfactant, was used to prevent the adsorption. An Agilent Poroshell 120 column was employed for chromatographic separation of the analytes with the mobile phases of 2 mM ammonium formate solution (containing 0.1% formic acid) and acetonitrile (45:55 for tylerdipine and 75:25 for the M2/M4, v/v). Flow rate was 0.3 mL/min. Calibration curves for tylerdipine, M2 and M4 in urine were linear over the ranges of 0.02-10 ng/mL, 2-1500 ng/mL and 0.5-200 ng/mL, respectively. The precision, accuracy, specificity and stability of two methods all evaluated and achieved the acceptable criteria. The LC-MS/MS methods were successfully applied to assay urinary excretion of tylerdipine and the metabolites in healthy Chinese subjects who orally received a single dose of 20 mg tylerdipine tablet. Generally, the urinary excretion of the two primary metabolites accounted for 11.7% of the total dose of tylerdipine in healthy Chinese subjects, while little tylerdipine was recovered in urine.

Quantitative GC-MS assay of citric acid from humans and db/db mice blood serum to assist the diagnosis of diabetic nephropathy.

The early diagnosis of diabetic nephropathy (DN) is rather challenging. Our previous study suggested that citric acid is a potential marker for the early diagnosis of diabetic nephropathy in db/db mice. For the first time, in this study, a surrogate analyte of 13C6-citric acid was employed to generate calibration curves for the quantitative measurement of the endogenous citric acid in the sera of db/db mice and diabetic nephropathy patients by GC/MS after the analytes were extracted, methoximated and trimethylsilylated. The constant response factor of 13C6-citric acid versus citric acid over the linear range indicated the identical ionization efficiency of these two compounds. The full validation assessments suggested that the method is sensitive, specific, reliable, reproducible and has acceptable parameters. Statistical analysis revealed cut-off citric acid concentrations of 29.24 µg/mL with a 95% confidence interval between 32.75 and 39.16 µg/mL in the diabetic nephropathy patients and 16.74 and 22.57 µg/mL in the normal controls. The areas under the receiver operating characteristic curves indicated accuracies of over 90% for the diagnoses of early diabetic nephropathy in both humans and db/db mice, which suggests that the serum citric acid level is potentially a biomarker that could assist in the diagnosis of diabetic nephropathy.