Apixaban is a highly selective, reversible inhibitor of Factor Xa with K_i of 0.08 nM and 0.17 nM in human and rabbit, respectively.

IC50: 0.08 nM (Human Factor Xa), 0.17 nM (Rabbit Factor Xa)

Apixaban exhibits a high degree of potency, selectivity, and efficacy on Factor Xa with K_i of 0.08 nM and 0.17 nM for Human Factor Xa and Rabbit Factor Xa, respectively^[1]. In vitro, Apixaban prolongs the clotting times of normal human plasma with the concentrations (EC2x) of 3.6 μM, 0.37 μM, 7.4 μM, and 0.4 μM, which are required respectively to double the prothrombin time (PT), modified prothrombin time (mPT), activated partial thromboplastin time (APTT) and HepTest. Besides, Apixaban shows the highest potency in human and rabbit plasma, but less potency in rat and dog plasma in both the PT and APTT assays^[2].

Apixaban shows the excellent pharmacokinetics with very low clearance (Cl: 0.02 L/kg/h), and low volume of distribution (Vdss: 0.2 L/kg) in the dogs. Besides, Apixaban also exhibits a moderate half-life (T1/2: 5.8 hours) and good oral bioavailability (F: 58%)^[1]. In the arteriovenous-shunt thrombosis (AVST), venous thrombosis (VT) and electrically mediated carotid arterial thrombosis (ECAT) rabbit models, Apixaban produces dose-dependent antithrombotic effects with EC₅₀ of 270 nM, 110 nM and 70 nM, respectively^[2]. Apixaban significantly inhibits factor Xa activity with IC₅₀ of 0.22 μM in rabbit ex vivo^[3]. In chimpanzee, Apixaban also shows small volume of distribution (Vdss: 0.17 L/kg), low systemic clearance (Cl: 0.018 L/kg/h), and good oral bioavailability (F: 59%)^[4].

• [1]. Pinto DJ, et al. Discovery of 1-(4-methoxyphenyl)-7-oxo-6-(4-(2-oxopiperidin-1-yl)phenyl)-4,5,6,7-tetrahydro-1H-pyrazolo[3,4-c]pyridine-3-carboxamide (apixaban, BMS-562247), a highly potent, selective, efficacious, and orally bioavailable inhibitor of blo

  [2]. Wong PC, et al. Apixaban, an oral, direct and highly selective factor Xa inhibitor: in vitro, antithrombotic and antihemostatic studies. J Thromb Haemost. 2008 May;6(5):820-9.

  [3]. Zhang D, et al. Metabolism, pharmacokinetics and pharmacodynamics of the factor Xa inhibitor apixaban in rabbits. J Thromb Thrombolysis. 2010 Jan;29(1):70-80.

  [4]. He K, et al. Preclinical pharmacokinetics and pharmacodynamics of apixaban, a potent and selective factor Xa inhibitor. Eur J Drug Metab Pharmacokinet. 2011 Sep;36(3):129-39.

Purified FXa is obtained after activation with Russell’s viper venom followed by affinity chromatography. The resulting FXa is > 95% pure as judged by sodium dodecylsulfate polyacrylamide gel electrophoresis. The substrate affinity values for FXa, expressed as the Michaelis-Menten-Henri constant (K_m), for human, rabbit, rat and dog FXa are determined using the chromogenic substrate S-2765, and are 36, 60, 240 and 70 μM, respectively. The substrate hydrolysis is monitored by measuring absorbance at 405 nm at 25°C for up to 30 min using a SpectraMax 384 Plus plate reader and SoftMax. FXa activity for each substrate and inhibitor concentration pair is determined in duplicate. The K_i values are calculated by non-linear least-squares fitting of the steady-state substrate hydrolysis rates to the equation for competitive inhibition (Equation 1) using GRAFIT, where v equals reactions velocity in OD min−1, Vmax equals maxiumum reaction velocity, S equals substrate concentration, and I equals inhibitor concentration. MCE has not independently confirmed the accuracy of these methods. They are for reference only.

Apixaban is formulated in vehicle (10%N,N-dimethylacetamide; 30% 1,2-propanediol; 60% water).

Briefly, male New Zealand White rabbits are anesthetized with ketamine (50 mg/kg i.m.) and xylazine (10 mg/kg i.m.), and their femoral artery, jugular vein and femoral vein are catheterized. These anesthetics are supplemented as needed. Thrombosis is induced by an arteriovenous (AV)-shunt device containing a silk thread. Blood flowed from the femoral artery via the AV shunt into the opposite femoral vein for 40 min. The shunt is then disconnected and the silk thread covered with thrombus is weighed. As apixaban has an oral bioavailability of < 5%="" in="" rabbits="" (unpublished="" result),="" it="" is="" administered="" intravenously="" for="" in="" vivo="" studies.="" to="" achieve="" a="" stable="" plasma="" level="" with="" minimum="" experimental="" variability,="" apixaban,="" fondaparinux="" or="" vehicle="" is="" given="" by="" a="" continuous="" intravenous="" infusion="" 1="" h="" prior="" to="" shunt="" placement.="" the="" infusion="" is="" continued="" throughout="" the="" experiment.="" warfarin="" or="" vehicle="" is="" dosed="" orally="" once="" daily="" for="" 4="" days.="" on="" the="" fourth="" day="" after="" the="" last="" oral="" dose="" of="" warfarin="" or="" vehicle,="" rabbits="" are="" anesthetized="" 1.5="" h="" later,="" and="" the="" treatment="" effect="" is="" evaluated="" about="" 2="" h="" postdose.="" arterial="" blood="" samples="" for="" the="" determination="" of="" clotting="" times="" or="" plasma="" levels="" are="" collected="" 20="" min="" after="" shunt="" placement.="" plasma="" levels="" of="" apixaban="" are="" measured="" by="" a="" specific="" and="" sensitive="" liquid="" chromatographic="" mass="" spectrometry="" method="" (lc/ms/ms).="" in="" rabbits="" treated="" with="" apixaban,="" fondaparinux="" or="" warfarin,="" the="" antithrombotic="" effects="" of="" these="" agents="" are="" expressed="" as="" percentage="" inhibition="" of="" thrombus="" formation="" based="" on="" the="" treated="" vs.="" the="" corresponding="" mean="" vehicle.="" the="">₅₀ value (dose that produced 50% inhibition of thrombus formation) is determined as described below. The apixaban group treatment consists of vehicle (10%N,N-dimethylacetamide; 30% 1,2-propanediol; 60% water) (n=4), and apixaban (mg/kg/h) at 0.03 (n=7), 0.1 (n=7), 0.3 (n=7), 1 (n=7), and 3 (n=3). The fondaparinux group treatment consists of vehicle (saline) (n=6), and fondaparinux (mg/kg/h1) at 0.01 (n=5), 0.03 (n=5), 0.1 (n=5), 0.3 (n=5), and 1 (n=5). The warfarin group treatment consists of vehicle (water) (n=6), and warfarin (mg/kg/day) at 0.1 (n=6), 0.3 (n=6), 1 (n=6), and 3 (n=6). MCE has not independently confirmed the accuracy of these methods. They are for reference only.

• [1]. Pinto DJ, et al. Discovery of 1-(4-methoxyphenyl)-7-oxo-6-(4-(2-oxopiperidin-1-yl)phenyl)-4,5,6,7-tetrahydro-1H-pyrazolo[3,4-c]pyridine-3-carboxamide (apixaban, BMS-562247), a highly potent, selective, efficacious, and orally bioavailable inhibitor of blo

  [2]. Wong PC, et al. Apixaban, an oral, direct and highly selective factor Xa inhibitor: in vitro, antithrombotic and antihemostatic studies. J Thromb Haemost. 2008 May;6(5):820-9.

  [3]. Zhang D, et al. Metabolism, pharmacokinetics and pharmacodynamics of the factor Xa inhibitor apixaban in rabbits. J Thromb Thrombolysis. 2010 Jan;29(1):70-80.

  [4]. He K, et al. Preclinical pharmacokinetics and pharmacodynamics of apixaban, a potent and selective factor Xa inhibitor. Eur J Drug Metab Pharmacokinet. 2011 Sep;36(3):129-39.

459.5

C₂₅H₂₅N₅O₄

503612-47-3

Room temperature in continental US; may vary elsewhere

DMSO: 14.25 mg/mL; H₂O：< 0.1="">

* "<1 mg/ml"="" means="" slightly="" soluble="" or="" insoluble.="" "≥"="" means="" soluble,="" but="" saturation="">