Rivaroxaban, an oral, direct factor Xa inhibitor, has a dual mode of elimination in humans, with two-thirds metabolized by the liver and one-third renally excreted unchanged. P-glycoprotein (P-gp) is known to be involved in the absorption, distribution, and excretion of drugs. To investigate whether rivaroxaban is a substrate of P-gp, the bidirectional flux of rivaroxaban across Caco-2, wild-type, and P-gp-overexpressing LLC-PK1 cells was investigated. Furthermore, the inhibitory effect of rivaroxaban toward P-gp was determined. Rivaroxaban exhibited high permeability and polarized transport across Caco-2 cells. Rivaroxaban was shown to be a substrate for, but not an inhibitor of, P-gp. Of a set of potential P-gp inhibitors, ketoconazole and ritonavir, but not clarithromycin or erythromycin, inhibited Pgp-mediated transport of rivaroxaban, with half-maximal inhibitory concentration values in the range of therapeutic plasma concentrations. These findings are in line with observed area under the plasma concentration-time curve increases in clinical drug-drug interaction studies indicating a possible involvement of P-gp in the distribution and excretion of rivaroxaban. In vivo studies in wild-type and P-gp double-knockout mice demonstrated that the impact of P-gp alone on the pharmacokinetics of rivaroxaban is minor. However, in P-gp double-knockout mice, a slight increase in brain concentrations and decreased excretion into the gastrointestinal tract were observed compared with wild-type mice. These studies also demonstrated that brain penetration of rivaroxaban is fairly low. In addition to P-gp, a further transport protein might be involved in the secretion of rivaroxaban.

The pharmacokinetics of BAY 59-7939 - a novel, oral, direct Factor Xa inhibitor - were investigated in rats and dogs in support of preclinical safety studies and clinical development. BAY 59-7939 was rapidly absorbed after oral dosing, with an absolute bioavailability of 57-66% in rats, and 60-86% in dogs. Plasma pharmacokinetics of BAY 59-7939 were linear across the investigated dose range (1-10 mg kg(-1) in rats, 0.3-3 mg kg(-1) in dogs). Plasma clearance was low: 0.4 l kg(-1) h(-1) in rats and 0.3 l kg(-1) h(-1) in dogs; volume of distribution (V(ss)) was moderate: 0.3 l kg(-1) in rats, and 0.4 l kg(-1) in dogs. The elimination half-life after oral administration was short in both species (0.9-2.3 h). Whole-body autoradiography showed moderate tissue affinity. No retention or small volume enrichments of BAY 59-7939-related radioactivity were observed. The plasma-protein binding of BAY 59-7939 was high, species dependent and fully reversible. BAY 59-7939 was rapidly excreted in rats and dogs, and was not irreversibly retained. A dual mode of excretion (biliary/faecal and renal) was observed. In summary, BAY 59-7939 had a favourable, predictable pharmacokinetic profile, with high oral bioavailability and a dual route of excretion.

BackgroundIncreased hypercoagulability has been reported with low doses of direct thrombin inhibitors but not with direct factor Xa inhibitors.ObjectivesTo compare the effects of rivaroxaban with those of melagatran and dabigatran on thrombin generation (TG) and tissue factor-induced hypercoagulability and to explore the possible involvement of the thrombin–thrombomodulin/activated protein C system.MethodsIn normal human plasma and in protein C-deficient plasma, TG was investigated in vitro in the presence and absence of recombinant human soluble thrombomodulin (rhs-TM). TG was determined by calibrated automated thrombography and an ELISA for prothrombin fragments 1+2 (F1+2). In an in vivo rat model, hypercoagulability was induced by tissue factor; levels of thrombin–antithrombin (TAT) and fibrinogen and the platelet count were determined.ResultsRivaroxaban inhibited TG in a concentration-dependent manner. In the absence of rhs-TM, melagatran and dabigatran also inhibited TG concentration dependently. However, in the presence of rhs-TM, lower concentrations of melagatran (119–474 nmol L–1) and dabigatran (68–545 nmol L−1) enhanced endogenous thrombin potential, peak TG, and F1+2 formation in normal plasma but not in protein C-deficient plasma. In vivo, rivaroxaban dose-dependently inhibited TAT generation, whereas melagatran showed a paradoxical effect, with an increase in TAT and a small decrease in fibrinogen and platelet count at lower doses.ConclusionLow concentrations of the direct thrombin inhibitors melagatran and dabigatran enhanced TG and hypercoagulability, possibly via inhibition of the protein C system. In contrast, rivaroxaban reduced TG and hypercoagulability under all conditions studied, suggesting that it does not suppress this negative-feedback system.

Rivaroxaban is an oral, direct Factor Xa (FXa) inhibitor that has been recommended for approval by the Committee for Medicinal Products for Human Use for the prevention of venous thromboembolism after elective hip and knee replacement, and is in advanced clinical development for the prevention and treatment of thromboembolic disorders. Because bleeding is a potential side-effect of accidental rivaroxaban overdose, we evaluated whether activated prothrombin complex concentrate (APCC, FEIBA®) and recombinant activated Factor VII (rFVIIa, NovoSeven®) administration could mitigate the antihemostatic effects of high-dose rivaroxaban in juvenile male baboons. Pharmacologic impairment of hemostasis (3- to 4-fold increase in prothrombin time [PT] from baseline and ≥2-fold increase in template bleeding time [BT]) was achieved by an intravenous (i.v.) bolus of rivaroxaban (0.6 mg/kg) followed by continuous infusion (0.6 mg/kg/h) for 60 minutes. At steady-state anticoagulation (30 minutes from bolus), one group of anticoagulated baboons (n=7) received APCC (50 U/kg, over 25 minutes). A second group (n=7) received an i.v. bolus dose of rFVIIa (210 μg/kg) 30 minutes after the start of anticoagulation. Reversal of the antihemostatic effects of supratherapeutic doses of rivaroxaban by APCC and rFVIIa was assessed by measurement of BT and clotting times. In the APCC group, high-dose rivaroxaban prolonged BT to 202% (95% CI±21%; p<0.001) of baseline and PT by 3-fold (Table). On completion of APCC infusion, BT returned to baseline and PT was reduced. In the rFVIIa group, rivaroxaban prolonged BT to 254% (95% CI±30%; p<0.05). Infusion of rFVIIa reduced BT by 34%, and PT was also shortened. Circulating thrombin–antithrombin complex (TAT) levels decreased during rivaroxaban infusion, and this decrease did not change significantly after rFVIIa bolus administration. However, APCC increased baseline plasma TAT levels, suggesting a systemic hypercoagulation. We conclude that administration of APCC or rVIIa can rapidly attenuate hemostasis impairment after rivaroxaban overdose in baboons, thus providing potential antidotes during bleeding emergencies. Table. The effect of activated prothrombin complex concentrate (APCC) and recombinant activated Factor VII (rFVIIa) on bleeding time (BT), prothrombin time (PT), and thrombin–antithrombin complex concentration (TAT) in baboons anticoagulated with high-dose rivaroxaban (n=7 each). Values are given as mean ± standard deviation Time BT (x-fold change from baseline) PT (x-fold change from baseline) TAT (μg/L) APCC Baseline 1.00 1.00 3.51±0.08 30 minutes after rivaroxaban 2.02±0.56 3.04±0.43 3.01±1.37 At end of APCC infusion 1.02±0.33 2.20±0.29 10.35±1.41 20 minutes after end of APCC infusion 1.65±0.94 2.28±0.29 n.d. rFVIIa Baseline 1.00 1.00 7.35±4.17 30 minutes after rivaroxaban 2.54±0.79 3.17±0.42 2.95±0.79 5 minutes after rFVIIa 1.68±0.80 2.38±0.41 2.58±0.52 30 minutes after rFVIIa 1.96±1.26 2.48±0.49 4.00±1.12

Rivaroxaban is an oral, direct factor Xa inhibitor for the management of thromboembolic disorders. Despite its short half-life, the ability to reverse rivaroxaban anticoagulation could be beneficial in life-threatening emergencies. The potential of prothrombin complex concentrate (PCC; Beriplex®), activated PCC (aPCC; FEIBA®) or recombinant activated factor VII (rFVIIa; NovoSeven®) to reverse rivaroxaban in rats and baboons was investigated. Anaesthetised rats pre-treated with intravenous rivaroxaban (2 mg/kg) received intravenous rFVIIa (100/400 μg/kg), PCC (25/50 U/kg) or aPCC (50/100 U/kg) after initiation of bleeding. Clotting times and bleeding times (BTs) were recorded. Rivaroxaban was administered as an intravenous 0.6 mg/kg bolus followed by continuous 0.6 mg/kg/hour infusion in baboons. Animals received intravenous aPCC 50 U/kg (2 U/kg/minute) or rFVIIa 210 μg/kg. BT and clotting parameters were measured. In rats pretreated with high-dose rivaroxaban, PCC 50 U/kg, aPCC 100 U/kg and rFVIIa 400 μg/kg significantly reduced BT vs rivaroxaban alone (5.4 ± 1.4-fold to 1.5 ± 0.4-fold [p<0.05]; 3.0 ± 0.4-fold to 1.4 ± 0.1-fold [p<0.001]; and 3.5 ± 0.7-fold to 1.7 ± 0.2-fold [p<0.01] vs baseline, respectively). In baboons pre-infused with rivaroxaban and then given aPCC, BT increased by 2.0 ± 0.2-fold and aPCC returned BT to baseline for the duration of its infusion. rFVIIa reduced BT from 2.5 ± 0.3-fold over baseline to 1.7 ± 0.3-fold over baseline. Prolongation of prothrombin time was reduced by PCC, aPCC and rFVIIa in both species. Rivaroxaban reduced thrombin-antithrombin levels; application of PCC and aPCC, but not rFVIIa, increased these levels. In conclusion, PCC, aPCC or rFVIIa have the potential to reverse the anticoagulant and anti-haemostatic effects of rivaroxaban.

In order to hyphenate ion pairing chromatography and MS detection we used several types of formates as volatile ion pairing reagents (IPRs) instead of common tetraalkylammonium salts, as these salts tend to precipitate in the ion source. The formates were prepared by mixing formic acid with the corresponding amine. Both tributyl- and trihexylammonium formate proved to be valuable IPRs for the separation of acidic compounds like nitrobenzoic acids, nitrobenzenesulfonic acids and nitrated phenols. Due to the weaker retention of the ion-pairs with trialkylammonium formates compared with tetraalkylammonium compounds, either less organic modifier or a higher concentration of the IPR had to be used. With negative atmospheric pressure chemical ionization mass spectrometry and electrospray ionization mass spectrometry it was possible to unambiguously identify several acidic oxidation products of 2,4,6-trinitrotoluene (TNT) in ammunition wastewater and soil extracts. 2-amino-4,6-dinitrobenzoic acid was often found to be the main metabolite of TNT in such water samples.

Aims This programme investigated topical regorafenib, a multikinase inhibitor, in patients with neovascular age‐related macular degeneration (nAMD). Methods Topical regorafenib was investigated in an open‐label, phase IIa/b study in which patients with choroidal neovascularization (CNV) secondary to nAMD received regorafenib (25 μl, 30 mg ml–1) three times a day for 12 weeks. The primary endpoint of the phase II/a/b study was mean change in best‐corrected visual acuity (BCVA) from baseline to weeks 4 and 12. Results In nAMD patients (N = 51), mean changes in BCVA were +1.2 [90% confidence interval (CI) –0.61, 2.97] and −2.4 (90% CI −4.18, −0.54) letters at weeks 4 and 12, respectively. Ocular treatment‐emergent adverse events (TEAEs) (study eye) were reported in 21 patients by week 12. There was one serious ocular TEAE (visual acuity reduced) that was not drug related. Twenty patients required rescue (intravitreal ranibizumab). Conclusions The programme was terminated after phase IIa ended because efficacy was lower than with current nAMD treatments. According to elaborate post hoc analyses, the most likely reason was insufficient exposure in the target compartment (back of the eye).

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