A Phase I, Randomized, Single-Ascending-Dose, Multiple-Dose, and Food-Effect Trial of the Safety, Efficacy, and Pharmacokinetics of Topiroxostat in Healthy Chinese Participants

Background: As the structure of the human diet changes, the prevalence of hyperuricemia is increasing each year. Hyperuricemia and its comorbidities, such as gout, severely affect quality of life. Moreover, hyperuricemia causes renal impairment and is associated with chronic kidney disease. Topiroxostat, a selective xanthine oxidoreductase inhibitor, has been approved to treat hyperuricemia or gout in Japan. Topiroxostat has shown good tolerance and efficacy in the Japanese population. However, its pharmacokinetic (PK) characteristics, efficacy, and safety in the Chinese population remains unknown.Objective: This trial evaluated the PK profile, safety, efficacy, and food effects of Topiroxostat in healthy Chinese participants.Methods: The major endpoint was determination of the PK profile of Topiroxostat. Topiroxostat concentrations were detected with LC-MS/MS. PK parameters were calculated in Phoenix WinNonlin 8.1. Minor endpoints were safety and efficacy assessments. Assessment of adverse events and safety was performed by clinicians. Plasma uric acid concentration (ΔECmax and ΔAUEC) was determined as the pharmacodynamic index. This study consisted of three arms: single ascending dose (20, 40, and 80 mg, N = 10), multiple dose (80 mg BID, 7 days, N = 10), and food effects (40 mg single dose, fasting-fed cross-over design, N = 10).Results: In the single-ascending-dose arm, Topiroxostat showed rapid absorption and excretion, with Tmax <1.6 h and T1/2 2.49–3.72 h. Additionally, Topiroxostat showed a wide distribution, on the basis of moderate Vz/F (242.8–336.36 L). The main PK parameters Cmax, AUC0-t, and AUC0-C showed a linear relationship with dose (R2 = 0.5146, 0.8416, 0.8386, respectively). In the multiple-dose arm, no significant differences were observed in Cmin on days 3–6 (P = 0.265). No serious adverse events were observed. Regarding efficacy, plasma uric acid levels were controlled to low levels during multiple-dose administration. In the food-effects arm, the fed group showed a lower Cmax than the fasting group (316.00 ± 135.81 vs. 478.40 ± 175.42 ng/mL, P = 0.033) but demonstrated better efficacy (ΔECmax, P < 0.001; ΔAUEC, P < 0.001).Conclusions: Topiroxostat showed rapid absorption and a broad distribution in healthy Chinese adults. Additionally, it showed good safety and tolerance in the Chinese population. Moreover, the pharmacodynamic profile indicated that post cibum administration increased the efficacy of Topiroxostat.

Development of an In Vivo Predictive Dissolution Methodology of Topiroxostat Immediate-Release Tablet Using In Silico Simulation

The main objective of this study was to develop an in vivo predictive dissolution (IVPD) model for topiroxostat immediate-release (IR) formulation by the combination of mechanistic absorption model (MAM) deconvolution method with time shifting factor (TSF) adjustment. The in vitro dissolution profiles in different biorelevant dissolution media containing different concentrations of sodium lauryl sulfate (SLS) were obtained from dissolution testing with the paddle method of the US Pharmacopeia, while the human pharmacokinetic profile was taken from the published experimental results. The GastroPlus™ software was used to observe the linear relationship between in vitro drug dissolution and in vivo absorption. The pharmacokinetic profile of topiroxostat IR tablet was first deconvoluted through the MAM method to obtain the fraction absorbed in vivo. Next, Levy plot was constructed to estimate the TSF, and the time scale for both processes of dissolution and absorption was then adjusted to be superimposable. The IVPD modelling was subsequently established with data between in vitro dissolution profiles and fraction absorbed in vivo. Finally, the dissolution profiles of topiroxostat IR tablet were translated into a pharmacokinetic curve in terms of convolution method. The comparison between translated and observed pharmacokinetic data will validate the performance of the developed IVPD model. This new linear IVPD model with high predictive power for the tablet can predict the in vivo pharmacokinetic differences through in vitro dissolution data, and it can be utilized as a risk-control tool for the formulation development of the topiroxostat IR tablet and the quality control of product batches.

Multicenter, Open-Label Study of Long-Term Topiroxostat (FYX-051) Administration in Japanese Hyperuricemic Patients with or Without Gout

Background and Objectives

Topiroxostat—a novel selective xanthine oxidoreductase inhibitor—has been reported to reduce serum urate levels. The purpose of this study was to assess the efficacy and safety of long-term topiroxostat administration in Japanese hyperuricemic patients with or without gout.

Methods

This multicenter, open-label study evaluated the efficacy and safety of long-term twice-daily oral topiroxostat administration in patients with or  without gout. The initial topiroxostat dosage was 40–80 mg/day, and the maintenance dosage was 120 mg/day, which was increased to 240 mg/day at 40 mg increments if the serum urate level exceeded 6.0 mg/dL.

Results

Serum urate level, which was the primary endpoint, decreased stably over time and showed significant reduction on the final visit (38.44% ± 13.34%) compared with that at the baseline. Both urinary albumin/creatinine ratio and mean blood pressure significantly improved. The overall incidence rate of adverse drug reactions to topiroxostat was 67.8%; on the final visit, the rate of adverse drug reactions was 66.7% with 120 mg/day, 72.2% with 160 mg/day, 53.8% with ≥ 200 mg/day, and 100% with the other dosages. On the final visit, the incidence of gouty arthritis, for which a causal relationship with topiroxostat could not be ruled out, was 4.1% overall, 4.8% with 120 mg/day, 0% with 160 mg/day, and 7.7% with ≥ 200 mg/day.

Conclusions

We verified the efficacy and safety of 58-week oral topiroxostat administration at stepwise increments to up to 240 mg/day.

Study Registration

JAPIC CTI-101068.

Protective Effects of Topiroxostat on an Ischemia-Reperfusion Model of Rat Hearts

BACKGROUND

Ischemia/reperfusion (I/R) injury triggers cardiac dysfunctions via creating reactive oxygen species (ROS). Because xanthine oxidase (XO) is one of the major enzymes that generate ROS, inhibition of XO is expected to suppress ROS-induced I/R injury. However, it remains unclear whether XO inhibition really yields cardioprotection during I/R. The protective effects of the XO inhibitors, topiroxostat and allopurinol, on cardiac I/R injury were evaluated.Methods and Results:Using isolated rat hearts, ventricular functions, occurrence of arrhythmias, XO activities and thiobarbituric acid reactive substances (TBARS) productions and myocardial levels of adenine nucleotides before and after I/R, and cardiomyocyte death markers during reperfusion, were evaluated. Topiroxostat prevented left ventricular dysfunctions and facilitated recovery from arrhythmias during I/R. Allopurinol and the antioxidant, N-acetylcysteine (NAC), exhibited similar effects at higher concentrations. Topiroxostat inhibited myocardial XO activities and TBARS productions after I/R. I/R decreased myocardial levels of ATP, ADP and AMP, but increased that of xanthine. While topiroxostat, allopurinol or NAC did not change myocardial levels of ATP, ADP or AMP after I/R, all of the agents decreased the level of xanthine. They also decreased releases of CPK and LDH during reperfusion.

CONCLUSIONS

Topiroxostat showed protective effects against I/R injury with higher potency than allopurinol or NAC. It dramatically inhibited XO activity and TBARS production, suggesting suppression of ROS generation.

Why Can dl-Sotalol Prolong the QT Interval In Vivo Despite Its Weak Inhibitory Effect on hERG K(+) Channels In Vitro? Electrophysiological and Pharmacokinetic Analysis with the Halothane-Anesthetized Guinea Pig Model

In order to bridge the gap of action of dl-sotalol between the human ether-a-go-go-related gene (hERG) K(+) channel inhibition in vitro and QT-interval prolongation in vivo, its electropharmacological effect and pharmacokinetic property were simultaneously studied in comparison with those of 10 drugs having potential to prolong the QT interval (positive drugs: bepridil, haloperidol, dl-sotalol, terfenadine, thioridazine, moxifloxacin, pimozide, sparfloxacin, diphenhydramine, imipramine and ketoconazole) and four drugs lacking such property (negative drugs: enalapril, phenytoin, propranolol or verapamil) with the halothane-anesthetized guinea pig model. A dose of each drug that caused 10 % prolongation of Fridericia-corrected QT interval (QTcF) was calculated, which was compared with respective known hERG K(+) IC50 value and currently obtained heart/plasma concentration ratio. Each positive drug prolonged the QTcF in a dose-related manner, whereas such effect was not observed by the negative drugs. Drugs with more potent hERG K(+) channel inhibition showed higher heart/plasma concentration ratio, resulting in more potent QTcF prolongation in vivo. The potency of dl-sotalol for QTcF prolongation was flat middle, although its hERG K(+) channel inhibitory property as well as heart/plasma concentration ratio was the smallest among the positive drugs, which may be partly explained by its lack of binding to plasma protein.

Moxifloxacin-induced QTc interval prolongations in healthy male Japanese and Caucasian volunteers: a direct comparison in a thorough QT study

AIM

We investigated whether moxifloxacin-induced QTc prolongations in Japanese and Caucasian healthy male volunteers were significantly different.

METHODS

A two period, randomized, crossover, ICH-E14-compliant thorough QT (TQT) study compared placebo-corrected changes in QTc interval from baseline (ΔΔQTc F) and concentration-effect relationships following administration of placebo and 400 mg moxifloxacin to 40 healthy male volunteers from each ethnic population. The point estimates of ΔΔQTc F for each population, and the difference between the two, were calculated at a geometric mean Cmax of moxifloxacin using a linear mixed effects model. The concentration-effect slopes of the two populations were also compared. Equivalence was concluded if the two-sided 90% confidence interval of the difference in ΔΔQTc F was contained within -5 ms to +5 ms limits and the ratio of the slopes was between 0.5 and 2.

RESULTS

There were no statistically significant differences between the two populations studied, Japanese vs. Caucasians, respectively, for moxifloxacin Cmax (3.27 ± 0.6 vs. 2.98 ± 0.7 µg ml(-1) ), ΔΔQTc F (9.63 ± 1.15 vs. 11.46 ± 1.19 ms at Cmax of 3.07 µg ml(-1) ) and concentration-response slopes (2.58 ± 0.62 vs. 2.34 ± 0.64 ms per µg ml(-1) ). The difference in the two ΔΔQTc F of -1.8 (90% CI -4.6, 0.9) and the ratio of the two slopes (1.1; 90% CI 0.63, 1.82) were within pre-specified equivalence limits.

CONCLUSIONS

Moxifloxacin-induced QTc prolongations did not differ significantly between the Japanese and Caucasian subjects. However, before our findings are more widely generalized, further studies in other populations and with other QT-prolonging drugs are needed to clarify whether inter-ethnic differences in QT sensitivity exist and whether ethnicity of the study population may affect the outcome of a TQT study.