Radioimmunoassay method for DX-9065a, an anticoagulant agent. Development, evaluation and application to human plasma

Effects of DX-9065a, an inhibitor of factor Xa, on ellagic acid-induced plantar skin thrombosis assessed in tetrodotoxin- and N(omega)-nitro-L-arginine-treated rats

Effects of DX-9065a ((+)-2S-2-[4-[[(3S)-1-acetimidoyl-3-pyrrolidinyl]oxy]phenyl]-3-[7-amidino-2-naphthyl]propanoic acid hydrochloride pentahydrate), a dibasic propanoic acid and an inhibitor of factor Xa, were compared with those of argatroban, a low molecular weight thrombin inhibitor, on the ellagic acid-induced plantar skin thrombosis in the rats treated with tetrodotoxin and N(omega)-nitro-L-arginine. Plantar skin blood flow was measured with laser Doppler flow meters, and skin temperature of the hindlimb was monitored simultaneously. In order to induce thrombus in plantar skin vasculature, ellagic acid (300 microg, i.a.) was injected into a branch of femoral artery. The formation of thrombus in femoral and plantar vessels was assessed by light microscopy. Ellagic acid decreased plantar skin blood flow and skin temperature. Intravenous injections of DX-9065a (3 mg/kg) and argatroban (1-3 mg/kg) significantly inhibited the ellagic acid-induced disturbance of plantar skin blood flow and lowering skin temperature without affecting bleeding time. The oral administration of DX-9065a (30-100 mg/kg) significantly prevented the decrease in skin temperature induced by ellagic acid, but it partially inhibited the disturbance of plantar skin blood flow. DX-9065a and argatroban also prolonged prothrombin time in a dose-dependent manner. These results suggest that DX-9065a effectively prevented thrombosis produced by ellagic acid in the skin circulation without a risk of bleeding.

LC determination of YM466, a new factor Xa inhibitor, in rat and dog plasma

A specific method for the determination of YM466, a novel Factor Xa inhibitor, in rat and dog plasma was developed and validated. YM466 was extracted from plasma by solid-phase extraction and analyzed by UV-HPLC at an absorbance wavelength of 240 nm. The intra-day precision and accuracy ranged from 0.8 to 2.4% and 0.1 to 5.0% in rats, and from 1.6 to 2.4% and 0.0 to 4.1% in dogs, respectively. The lower limit of quantification was 10 ng/ml when 1 ml of plasma was used. No endogenous interference was observed in the plasma of rats and dogs.

Recent advances in clinical trials of the direct and indirect selective Factor Xa inhibitors

Over the years, pharmacological intervention to prevent undesired intravascular coagulation and the associated detrimental effects has been a clinical challenge. The first generation of anticoagulant agents, warfarin and unfractionated heparin (UFH), involve indirect mechanisms of inhibiting the coagulation cascade. Fractionated, or low-molecular weight, heparins (LMWHs) are more selective for coagulation Factor Xa (FXa) over thrombin (FIIa). LMWHs also utilise an indirect mechanism of inhibition and have improved pharmacokinetic, pharmacodynamic and therapeutic profiles over UFH. The success of LMWHs, along with the pivotal location of FXa in the coagulation cascade, has prompted interest in the discovery and development of selective FXa inhibitors. There are two general classes of FXa inhibitors in development, of which SR90107A/ORG31540, an antithrombin-III-dependent pentasaccharide and DX-9065a, a small molecule direct FXa inhibitor, have published clinical data. SR90107A/ORG31540 and DX-9065a offer safe, predictable pharmacokinetic and pharmacodynamic profiles when administered subcutaneously and intravenously, respectively, to healthy volunteers and appear to be progressing through clinical development. The purpose of this review is to compile and summarise the published Phase I and II clinical data for SR90107A/ORG31540 and DX-9065a.

Pharmacokinetics of the anticoagulant 14C-DX-9065a in the healthy male volunteer after a single intravenous dose

1. The plasma pharmacokinetics, excretion and metabolism of DX-9065a were studied in the healthy male Caucasian volunteer after a single intravenous dose of 10 mg 14C-labelled DX-9065a. 2. At the end of a 1 h infusion, the mean plasma concentration of total radioactivity was 380 ng ml(-1) (equivalent to unchanged DX-9065). Thereafter, it decreased in a bi-exponential manner and was below the detection limit by 48 h after dosing. The half-life for the distribution phase was 6.93 h. 3. The total radioactivity recovered in urine and faeces by 336 h post-dose was 83.8% of the administered dose, with excretion ongoing at the end of the 14-day collection. The major route of excretion was via urine, accounting for a mean of 77.6% of the administered radioactivity. The urinary excretion profile was biphasic, consisting of rapid (0-24 h) and slow (24-336 h) phases. A large renal clearance suggested that renal tubular secretion might contribute to the excretion of DX-9065 via urine. 4. No metabolite peaks in the radio-HPLC chromatograms of urine samples were detected, indicating that biotransformation of DX-9065 does not play a significant role in the elimination of DX-9065 in man.

DX-9065a, a specific factor Xa inhibitor, as a universal anticoagulant for blood collection tubes

DX-9065a is a direct and selective factor Xa inhibitor. We evaluated the usefulness of DX-9065a in anticoagulating specimens for routine laboratory tests. Results using blood anticoagulated with DX9065a corresponded well with results with blood treated with ethylendiamine tetraacetic acid (EDTA) in the complete blood count (CBC), including white blood cell (WBC) differential count and morphology of blood cells. Clinical chemistry results from DX-9065a-treated samples were similar to results obtained with serum specimens except for leucine aminopeptidase (LAP) and cholinesterase (Ch-E). Thus, DX-9065a may be a useful universal anticoagulant for laboratory medicine.

Tolerability, pharmacokinetics, and pharmacodynamics of DX-9065a, a new synthetic potent anticoagulant and specific factor Xa inhibitor, in healthy male volunteers

OBJECTIVE

The aim of this study was to assess the tolerability, pharmacokinetic and pharmacodynamic properties of DX-9065a, a novel low-molecule specific factor Xa inhibitor in healthy male volunteers.

METHODS

DX-9065a was intravenously administered to healthy male Japanese volunteers at doses of 0.625 to 30 mg. The drug concentrations in plasma and urine were measured and pharmacokinetic parameters were calculated. Coagulation time and bleeding time were also measured.

RESULTS

No serious adverse event was observed during or after administration of DX-9065a. The pharmacokinetics of DX-9065a in human subjects after intravenous dosing was linear. The simulated plasma concentrations of DX-9065 were well in accordance with the observed values. Though prolongation of coagulation times was dependent on plasma concentration of DX-9065, bleeding time did not increase even at the highest plasma concentration of 1640 ng/mL.

CONCLUSIONS

DX-9065a had a good correlation between linear pharmacokinetics and pharmacodynamics after intravenous administration in humans.

High-performance liquid chromatographic method for determination of DX-9065a, a novel anticoagulant, in human urine and feces using cation-exchange solid-phase extraction

A simple HPLC method for determination of DX-9065a in human urine and feces was developed. The drug was extracted by Bond Elut CBA, a cation-exchange solid-phase extraction cartridge. The extracted drug was analyzed by HPLC with UV detection at 242 nm. With this extraction procedure, no interfering peaks were observed. The method developed was validated and showed adequate precision and accuracy. This method was applied to human clinical samples obtained from healthy Japanese volunteers who had orally received the drug. Using this method, the excretion profile of the drug in human after oral administration was revealed for the first time.