Prediction of a clinically effective dose of THY1773, a novel V1B receptor antagonist, based on preclinical data.

THY1773 is a novel arginine vasopressin 1B (V1B ) receptor antagonist that is under development as an oral drug for the treatment of major depressive disorder (MDD). Here we report our strategy to predict a clinically effective dose of THY1773 for MDD in the preclinical stage, and discuss the important insights gained by retrospective analysis of prediction accuracy. To predict human pharmacokinetic (PK) parameters, several extrapolation methods from animal or in vitro data to humans were investigated. The fu correction intercept method and two-species-based allometry were used to extrapolate clearance from rats and dogs to humans. The physiologically based pharmacokinetics (PBPK)/receptor occupancy (RO) model was developed by linking free plasma concentration with pituitary V1B RO by the Emax model. As a result, the predicted clinically effective dose of THY1773 associated with 50% V1B RO was low enough (10 mg/day, or at maximum 110 mg/day) to warrant entering phase 1 clinical trials. In the phase 1 single ascending dose study, TS-121 capsule (active ingredient: THY1773) showed favorable PKs for THY1773 as expected, and in the separately conducted phase 1 RO study using positron emission tomography, the observed pituitary V1B RO was comparable to our prediction. Retrospective analysis of the prediction accuracy suggested that the prediction methods considering plasma protein binding, and avoiding having to apply unknown scaling factors obtained in animals to humans, would lead to better prediction. Selecting mechanism-based methods with reasonable assumptions would be critical for the successful prediction of a clinically effective dose in the preclinical stage of drug development.

An enantiomeric quantitative LC-MS/MS method for tolvaptan and its monohydroxylates in human plasma using a reversed-phase separation procedure.

Racemic tolvaptan possessing an asymmetric carbon is metabolized to three pairs of monohydroxylate enantiomers of diol form with V2 receptor antagonistic activity via CYP3A. This study aimed to develop a simultaneous quantitative liquid chromatography-tandem mass spectrometry method for 5R- and 5S-tolvaptan and their monohydroxylate enantiomers in human plasma and to apply it to patient samples. Deproteinized plasma specimens were separated using a polysaccharide derivative chiral column in a reversed-phase elution mode. The mass spectrometer was run in positive ion electrospray ionization mode. The chromatographic peaks of tolvaptan monohydroxylate enantiomers were identified by the recombinant CYP3A4/5 digestion of 5R- and 5S-tolvaptan. The calibration curves ranged over the plasma concentrations of 0.25-125 ng/mL for 5R- and 5S-tolvaptan, 0.025-12.5 ng/mL for 4R5R- and 4S5S-diols, and 0.025-38.15 ng/mL for 4S5R-, 4R5S-, 3S5R-, and 3R5S-diols with a large variation. Their pre-treatment recovery rates and matrix factors in human plasma were 85.2-112.9 % and 86.9-113.1 %, respectively. The intra- and inter-day accuracy and imprecision were 92.3-113.8 % and 3.5-14.6 % for all analytes, respectively. The plasma concentration ranges of 5R- and 5S-tolvaptan, 4R5R-, 4S5S-, 4S5R-, 4R5S-, 3S5R-, and 3R5S-diols in heart failure patients with a 5-fold dilution procedure were 0.634-28.4, 2.37-131, 0.525-15.4, 0.0970-4.08, 6.82-108, 0.271-6.49, 0.394-4.18, and 4.81-39.8 ng/mL, respectively. In conclusion, the present method has an acceptable analytical performance level and can be helpful for characterization of the plasma 5R- and 5S-tolvaptan and their monohydroxylate enantiomers in heart failure patients.

Plasma concentration and efficacy of tolvaptan in cirrhotic patients with refractory ascites.

To investigate the relationship between the exposure and efficacy of tolvaptan, we measured pharmacokinetics of total drug at 7 days after repeated doses of 3.75 mg/day tolvaptan in 16 patients with hepatic edema. Nine patients (56.3%) were responders, which were defined as those with body weight reduction of >1.5 kg/week. Serum albumin levels were significantly lower in responders than in non-responders (P = 0.031). However, the pharmacokinetics varied greatly among individuals and was not relevant to the clinical response.

A rapid and sensitive LC-MS/MS-ESI method for the determination of tolvaptan and its two main metabolites in human plasma.

A liquid chromatography-tandem mass spectrometry (LC-MS) method to quantify tolvaptan and its two main metabolites and applied to human study was first developed and validated as a measure of compliance in clinical research. Because of the structure similarity of tolvaptan and its multiple metabolites, the method was optimized to obtain a chromatographic and MS separation of the endogenous interference and isotope ions as well as high analysis throughput. Tolvaptan, its two main metabolites and the internal standard were extracted from human serum (0.1mL) using solid-phase extraction, separated on a Waters nova-pak C18 column (150×3.9mm, 5µm) using isocratic elution with a mobile phase composed of acetonitrile, water and formic acid (65:35:0.25, v/v/v). The total run-time was shortened to 3.5min. The mass transition ranges under positive electrospray ionisation that were monitored for quantitation included m/z 449-252 for tolvaptan, m/z 479-252 for metabolite DM-4103, m/z 481-252 for metabolite DM-4107 and m/z 463-266 for the internal standard (IS). The limit of quantification in plasma for all three analytes was 1ng/mL. The method was validated over a linear range from 1 to 500ng/mL for all three analytes with acceptable inter- and intra-assay precision and accuracy. The stability of the analytes was determined to be suitable for routine laboratory practices. The method was successfully applied to samples taken from research volunteers who ingested a 15mg tolvaptan tablet.

Single-Dose Interaction Study of the Arginine Vasopressin Type 1B Receptor Antagonist ABT-436 and Alcohol in Moderate Alcohol Drinkers.

BACKGROUND: ABT-436, a potent and selective arginine vasopressin (AVP) type 1B receptor (V1B ) antagonist, has previously demonstrated basal hypothalamic-pituitary-adrenal (HPA) axis attenuation in man. A V1B antagonist is hypothesized as an alcohol-dependent treatment based on the role of the V1B receptor in stress regulation and the finding that stress is a trigger for relapse in alcoholics. A V1B antagonist has shown favorable effects in rat models of alcohol dependence. A single-dose clinical study was conducted to assess the potential for pharmacokinetic or pharmacodynamic interaction between ABT-436 and alcohol. METHODS: Twenty moderate alcohol drinkers each received the 4 possible combinations of a single 1,000 mg ABT-436 dose (or matching placebo) and a single 0.5 g/kg alcohol dose (or placebo for alcohol) in a double-blind, randomized, 4-period crossover study. Plasma ABT-436 and blood alcohol levels were measured to assess pharmacokinetic interactions. A computerized cognitive test battery (CDR System), Bond-Lader Visual Analog Scales scales, and a postural stability test were used to measure the effects of alcohol and the potential interaction with ABT-436. The pharmacologic effect of ABT-436 was assessed by measuring serum cortisol. RESULTS: Neither ABT-436 nor alcohol affected the blood levels of the other. Alcohol reduced performance on 2 of 5 CDR System composite variables (power of attention, p = 0.002; quality of secondary episodic memory, p < 0.001), and decreased postural stability (p = 0.043). ABT-436 did not exacerbate those deleterious effects. ABT-436 reduced serum cortisol (p < 0.001), and alcohol did not significantly diminish this expected effect on the HPA axis. CONCLUSIONS: No pharmacokinetic or pharmacodynamic interaction between ABT-436 and alcohol was observed.

Liquid chromatography-tandem mass spectrometry method for determining tolvaptan and its nine metabolites in rat serum: application to a pharmacokinetic study.

Tolvaptan is a competitive vasopressin V2-receptor antagonist that inhibits water reabsorption in the renal collecting ducts. A selective and sensitive liquid chromatography-tandem mass spectrometry method for determining tolvaptan and its nine metabolites in rat serum was developed and validated. An analogue of tolvaptan was used as an internal standard. Sample preparation involved protein precipitation following solid-phase extraction. Chromatographic separation was performed on a C18 reversed-phase column with a linear gradient elution. The flow rate was 0.25 mL/min, and total run time was 30 min. The analytes were detected by tandem mass spectrometry using an electrospray ionization interface in positive ion mode and multiple reaction monitoring. The calibration curve showed linearity over the concentration range from 5 to 1,000 ng/mL for each analyte. The lower limit of quantification using 0.1 mL of rat serum was 5 ng/mL for each analyte. Precision did not exceed 5.7 %, and accuracy as relative error were within ± 7.5 % for all analytes. The validated method was successfully applied to evaluate the pharmacokinetics of oral tolvaptan in rats, indicating the systemic exposure to tolvaptan in females eight times larger than that in males.