Darexaban (YM150) is a direct inhibitor of

factor Xa Coagulation factor X (), or Stuart factor, is an enzyme of the coagulation cascade, encoded in humans by ''F10'' gene. It is a serine endopeptidase (protease group S1, PA clan). Factor X is synthesized in the liver and requires vitamin K for ...

created by

Astellas Pharma is a Japanese multinational pharmaceutical company, formed on 1 April 2005 from the merger of and . Astellas is a member of the Mitsubishi UFJ Financial Group (MUFJ) keiretsu. History Early foundations Fujisawa Shoten was started in 1894 ...

. It is an experimental drug that acts as an

anticoagulant An anticoagulant, commonly known as a blood thinner, is a chemical substance that prevents or reduces the coagulation of blood, prolonging the clotting time. Some occur naturally in blood-eating animals, such as leeches and mosquitoes, which ...

and

antithrombotic An antithrombotic agent is a drug that reduces the formation of blood clots ( thrombi).http://cancerweb.ncl.ac.uk/cgi-bin/omd?antithrombotic Antithrombotics can be used therapeutically for prevention ( primary prevention, secondary prevention) or ...

to prevent venous thromboembolism after a major orthopaedic surgery, stroke in patients with

atrial fibrillation Atrial fibrillation (AF, AFib or A-fib) is an Heart arrhythmia, abnormal heart rhythm (arrhythmia) characterized by fibrillation, rapid and irregular beating of the Atrium (heart), atrial chambers of the heart. It often begins as short periods ...

and possibly ischemic events in

acute coronary syndrome Acute coronary syndrome (ACS) is a syndrome due to decreased blood flow in the coronary arteries such that part of the heart muscle is unable to function properly or dies. The most common symptom is centrally located pressure-like chest pain, ...

. It is used in form of the

maleate Maleic acid or ''cis''-butenedioic acid is an organic compound that is a dicarboxylic acid, a molecule with two carboxyl groups. Its chemical formula is HO2CCH=CHCO2H. Maleic acid is the ''cis'' isomer of butenedioic acid, whereas fumaric acid ...

. The development of darexaban was discontinued in September 2011.

Clinical uses

Atrial fibrillation

Atrial fibrillation Atrial fibrillation (AF, AFib or A-fib) is an Heart arrhythmia, abnormal heart rhythm (arrhythmia) characterized by fibrillation, rapid and irregular beating of the Atrium (heart), atrial chambers of the heart. It often begins as short periods ...

is an abnormal heart rhythm that causes a reduction in the

cardiac output In cardiac physiology, cardiac output (CO), also known as heart output and often denoted by the symbols Q, \dot Q, or \dot Q_ , edited by Catherine E. Williamson, Phillip Bennett is the volumetric flow rate of the heart's pumping output: tha ...

and blood flow to the brain. It also promotes the formation of blood clots in the atrial chambers of the heart. Atrial fibrillation is associated with an increased risk of

embolic stroke Stroke is a medical condition in which poor blood flow to a part of the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop ...

due to the increased risk of blood clot development. Oral anticoagulant drugs such as Darexaban decrease the incidence and severity of stroke in patients with atrial fibrillation by preventing the formation of blood clots.

Contraindictions

The RUBY-1 phase II trial results show that oral administration of darexaban in combination with the standard dual antiplatelet therapy used for

(ACS) patients caused a two- to four-fold increase in bleeding rates and no effect on ACS. Though there were no cases of fatal bleeding or intracranial haemorrhage, the results of this study questions the concept of adding an oral anticoagulant to standard of care dual antiplatelet therapy in order to prevent recurrent ischemic events after ACS. The development of darexaban was discontinued in September 2011.

Pharmacology

Mechanism of action

Factor Xa (FXa) is an essential blood coagulation factor that is responsible for the initiation of the coagulation cascade. FXa cleaves

prothrombin Prothrombin (coagulation factor II) is encoded in the human by the F2-gene. It is proteolytically cleaved during the clotting process by the prothrombinase enzyme complex to form thrombin. Thrombin (Factor IIa) (, fibrose, thrombase, throm ...

to its active form

thrombin Prothrombin (coagulation factor II) is encoded in the human by the F2-gene. It is proteolytically cleaved during the clotting process by the prothrombinase enzyme complex to form thrombin. Thrombin (Factor IIa) (, fibrose, thrombase, throm ...

, which then acts to convert soluble

fibrinogen Fibrinogen (coagulation factor I) is a glycoprotein protein complex, complex, produced in the liver, that circulates in the blood of all vertebrates. During tissue and vascular injury, it is converted Enzyme, enzymatically by thrombin to fibrin ...

to insoluble

fibrin Fibrin (also called Factor Ia) is a fibrous protein, fibrous, non-globular protein involved in the Coagulation, clotting of blood. It is formed by the action of the protease thrombin on fibrinogen, which causes it to polymerization, polymerize. ...

and to activate

platelet Platelets or thrombocytes () are a part of blood whose function (along with the coagulation#Coagulation factors, coagulation factors) is to react to bleeding from blood vessel injury by clumping to form a thrombus, blood clot. Platelets have no ...

s. Stabilization of the platelet aggregation by fibrin mesh ultimately leads to clot formation. Darexaban and darexaban glucuronide selectively and competitively inhibit FXa, suppressing prothrombin activity at the sites of blood clot (thrombus) formation. This leads to a decrease in blood clot formation in a dose dependent manner. Reducing blood clot formation will decrease blood flow blockages, thus possibly lowering the risk of

myocardial infarction A myocardial infarction (MI), commonly known as a heart attack, occurs when Ischemia, blood flow decreases or stops in one of the coronary arteries of the heart, causing infarction (tissue death) to the heart muscle. The most common symptom ...

unstable angina In dynamical systems instability means that some of the outputs or internal states increase with time, without bounds. Not all systems that are not stable are unstable; systems can also be marginally stable or exhibit limit cycle behavior ...

venous thrombosis Venous thrombosis is the blockage of a vein caused by a thrombus (blood clot). A common form of venous thrombosis is deep vein thrombosis (DVT), when a blood clot forms in the deep veins. If a thrombus breaks off ( embolizes) and flows to the lu ...

, and ischemic stroke.

Pharmacokinetics

Darexaban is rapidly absorbed and extensively metabolized in the liver to its active metabolite, darexaban

glucuronide A glucuronide, also known as glucuronoside, is any substance produced by linking glucuronic acid to another substance via a glycosidic bond. The glucuronides belong to the glycosides. Glucuronidation, the conversion of chemical compounds to glucu ...

(YM-222714) during first pass metabolism via

glucuronidation Glucuronidation is often involved in drug metabolism of substances such as drugs, pollutants, bilirubin, androgens, estrogens, mineralocorticoids, glucocorticoids, fatty acid derivatives, retinoids, and bile acids. These linkages involve gly ...

. The metabolism of darexaban also occurs in the small intestine but to a much lesser extent. Glucuronidation of darexaban occurs quickly, thus the half life of darexaban itself is short. However, the resultant darexaban glucuronide metabolite has a long half life of approximately 14–18 hours, reaching its maximum levels in the blood 1-1.5 hour post dose. As a result, darexaban glucuronide is the main determinant of the antithrombotic effects. Darexaban shows minimal interaction with food and is excreted through the kidneys (urine) and feces.

References

{{Antithrombotics Direct Xa inhibitors Benzamides Diazepanes Phenols Astellas Pharma