A phase I clinical trial of the effect of belinostat on the pharmacokinetics and pharmacodynamics of warfarin

Belinostat is a potent small molecule inhibitor that exerts its antitumor effect through inhibition of histone deacetylase. The purpose of this study was to evaluate the pharmacokinetics and pharmacodynamics of warfarin (as a reference drug metabolized by CYP2C9) in the presence and absence of belinostat. We conducted a phase I, single-center, open-label, drug-drug interaction study between belinostat and warfarin. In part I, patients were given warfarin 5 mg orally (day-14 and 3) and belinostat 1000 mg/m(2) (days 1 through 5). Patients receiving benefit continued belinostat on days 1 through 5 every 21 days until disease progression, unacceptable toxicity, or per patient preference. A total of 18 patients were treated. With belinostat, the least-squared means for maximum concentration (C (max)), area under the curve(0-a), and area under the curve(0-t) of R-warfarin were slightly increased. However, for the more potent S-warfarin isomer, the same parameters were primarily contained within the pre-specified equivalence limits of 0.80 and 1.25, indicating there was no statistically significant interaction between S-warfarin and belinostat. The most common adverse events were nausea, vomiting, and fatigue. Three grade 3 adverse events (diarrhea 5.6 %, nausea 5.6 %, and vomiting 5.6 %) were thought to be treatment related. Progression-free survival ranged from 0.2 to 13.8 months in all patients. Belinostat did not significantly affect the pharmacokinetics and pharmacodynamics of warfarin, indicating no clinically relevant effect on the enzymatic activity of CYP2C9.