A phase I schedule dependency study of the aurora kinase inhibitor MSC1992371A in combination with gemcitabine in patients with solid tumors.

INTRODUCTION: MSC1992371A is an aurora kinase inhibitor with potential antitumor activity. METHODS: This trial established the maximum tolerated dose (MTD) and dose-limiting toxicities (DLTs) of oral MSC1992371A given before or after gemcitabine (1,000 mg/m(2)) in a 21-day cycle in patients with advanced malignancies. In schedule 1 (n = 31), gemcitabine was administered on days 1 and 8 followed by escalating doses of MSC1992371A on days 2 and 9. In schedule 2 (n = 35), MSC1992371A was given on days 1 and 8 followed by gemcitabine on days 2 and 9. Patients had a range of solid tumors, the most frequent of which was colorectal (n = 19). RESULTS: In both schedules, the 37 mg/m(2) dose level was defined as the MTD. The main DLT was grade 4 neutropenia. Adverse events consisted of neutropenia, thrombocytopenia, asthenia, fatigue, nausea, vomiting, anorexia, and diarrhea. Administration of MSC1992371A prior to gemcitabine had no effect on the metabolism or elimination of gemcitabine. Time to reach maximum plasma concentration and area under the plasma concentration-time curve for MSC1992371A increased proportionally with dose. Exploration of drug-target-related and tumor biomarkers did not identify predictors of biologic activity or response. Two patients (1 with lung carcinoma and 1 with hepatocellular carcinoma) had durable partial responses in schedule 2, and 5 patients had stable disease (SD) lasting 6 - 14 months. CONCLUSION: Oral MSC1992371A can be administered at a MTD of 37 mg/m(2) in combination with the standard 1,000 mg/m(2) dose of gemcitabine, but hematologic toxicity requires careful monitoring. Preliminary signs of efficacy were indicated by durable responses and SD.

Adenosine A1-receptor occupancy predicts A1-receptor antagonist effects of N-0861.

OBJECTIVE: To evaluate the relationship between dose of N-0861 ([+/-]N6-endo-norbornan-2-yl-9-methyladenine), N-0861 plasma concentrations, and antagonism of adenosine-induced slowing of atrioventricular nodal conduction and to evaluate A1-receptor occupancy by antagonist present in plasma of subjects after administration of N-0861 to determine A1-selectivity of these effects. METHODS: The study was conducted in patients undergoing a clinically indicated electrophysiology study to evaluate atrioventricular nodal conduction. Nineteen subjects were enrolled in the study and received adenosine (60 to 140 microg/kg) before or during a bolus dose and maintenance infusion of specific doses of N-0861. Adenosine-induced slowing of atrioventricular nodal conduction was determined by measuring A-H intervals on the intracardiac electrocardiograms. Plasma concentrations of N-0861 were determined with an HPLC method. A1-Receptor occupancy by antagonist present in plasma from identical time points was determined with use of a radioreceptor assay. RESULTS: A linear relationship was shown between plasma concentration and dose of N-0861. A-H interval lengthening by 60 microg/kg adenosine was reduced by administration of N-0861. A linear relationship was observed between A1 occupancy and N-0861 concentration and between occupancy and antagonism of adenosine-induced A-H prolongation. CONCLUSION: The results suggest that the effect of N-0861 on antagonism of adenosine-induced prolongation of A-H interval, at the doses used in this study, were the result of effects at the A1 receptor.

The behavioral sensitization induced by fencamfamine is not related to plasma drug levels

Fencamfamine (FCF) is a CNS stimulant that facilitates central dopaminergic transmission primarily though blockade of dopamine uptake. In the present study we evaluated the relationship between plasma FCF concentration and behavioral sensitization effect. Adult male Wistar rats (250-300 g) received FCF (10 mg/Kg, ip) or saline oince or daily for 10 consecutive days (N = 10 for each group). Blood samples were collected 30 min after injections and plasma FCF was measured by gas chromatography using an electron capture detector. FCF treatment enhanced sniffing duration (16.8 ñ 0.8 vs 26.6 ñ 0.9s) and decreased rearing behavior (8.2 ñ 0.8 vs 3.7 ñ 0.6s) when days 1 and 10 of drug administration were compared. Comparison of pair of means by the Student t-test did not show significant differences in plasma FCF concentration (390 ñ 40 vs 420 ñ 11 ng/ml) when blood samples were collected 30 min after acute FCF administration or after daily administration of 10 mg/Kg for 10 days. In conclusion, the behavioral sensitization to FCF could not be correlated with plasma drug levels, and changes in the activity of dopaminergic systems should be considered to explain the sensitization to the effect of FCF

Daily variation in plasma concentration of fencamfamine and striatal dopamine receptors in rats

Fencamfamine (FCF) is a psychostimulant drug classified as an indirect dopamine agonist. In the present study we evaluated the daily variation in plasma FCF concentration and in striatal dopamine receptors. Adult male Wistar rats (250-300 g) maintained on a 12-h light/12-h dark cycle (lights on at 07:00 h) were used. Rats received FCF (10.0 mg/kg, ip) at 09:00, 15:00, 21:00 or 03:00 h and blood samples were collected 30 (N = 6) or 60 (N = 6) min after the injections. Plasma FCF was measured by gas chromatography using an electron capture detector. Two-way ANOVA showed significant differences in FCF concentration when blood samples were collected 30 min after the injection, and the highest value was obtained following injection at 21:00 h. Moreover, at 15:00, 21:00 and 03:00 h, plasma FCF levels were significantly lower 60 min after injection when compared to the 30-min interval. Two other groups of rats (N = 6) were decapitated at 09:00 or 21:00 h and the striata were dissected for the binding assays. The Bmax for [3H]-spiroperidol binding to striatal membranes was higher at 21:00 h, without changes in affinity constant (Kd). In conclusion, plasma FCF levels and dopamine receptors undergo daily variation, a phenomenon that should be considered to explain the circadian time-dependent effects of FCF

Effects of N6-endonorbornan-2-yl-9-methyladenine, N0861, on negative chronotropic and vasodilatory actions of adenosine in the canine heart in vivo.

The pharmacology of N6-endonorbornan-2-yl-9-methyladenine (N0861), a new selective antagonist of adenosine at the A1 adenosine receptor subtype (A1-AdoR), was studied in vivo using a canine model. First, the pharmacokinetics of N0861 were determined in anesthetized dogs. The time-dependent decay of plasma levels of N0861 fitted a two-compartment polyexponential model with alpha-phase t1/2 = 3.80 min and beta-phase t1/2 = 80.55 min. Secondly, the effect of N0861 on the negative chronotropic and vasodilatory actions of adenosine in the canine heart were determined. N0861 attenuated the negative chronotropic action of adenosine (1-6 mumol/kg; rapid bolus into the right atrium) on sinus node pacemaker activity in a dose-dependent manner (pA2 = 4.23). For example, the maximal prolongation of sinus cycle length induced by 6 mumol/kg adenosine was 82 +/- 13% under baseline conditions and 57 +/- 10, 34 +/- 5 and 34 +/- 6% during infusion of N0861 at incremental rates leading to plasma levels of 7.75 +/- 1.02, 14.15 +/- 0.87, and 19.71 +/- 1.83 micrograms/mL, respectively. In contrast, N0861 did not inhibit but had a tendency to potentiate the vasodilatory action of adenosine (thought to be mediated by the A2 adenosine receptor subtype (A2-AdoR)) on the left anterior descending and circumflex coronary arteries. These data indicate that two different receptors, similar to the typical A1-AdoR and A2-AdoR, mediate the electrophysiologic and vasodilatory actions of adenosine in the canine heart, respectively, and that N0861 is a selective antagonist of adenosine at A1-AdoR in the canine heart in vivo.