Laboratory determination of old and new targeted anticoagulant agents for prevention of bleeding and thrombotic events in cancer patients.

A two-fold prolongation of activated partial thromboplastin time (APTT) is established as therapeutic range for therapy with unfractionated heparin, hirudin and argatroban. The international normalized ratio (INR) of 2 to 3 is required to maintain anticoagulation in the therapeutic range of vitamin K antagonists. The therapeutic range of anti-factor Xa activity during therapy with low-molecular weight heparins and danaparoid are less well and of direct oral anticoagulants (DOAC) poorly defined. The relation of aPTT and INR values to thrombotic and bleeding events are well established despite a large variation of values in affected patients. The relation of coagulation values of the other anticoagulants to clinical events is open. The value of determination in cancer patients is higher because of the increased risk for thrombotic and bleeding events of this patient group. Several activities are currently undertaken to certify methods for in vitro diagnostic testing for DAOCs.

Cost-effectiveness of anticoagulation in patients with nonvalvular atrial fibrillation with edoxaban compared to warfarin in Germany.

We compared the cost-utility analysis for edoxaban at both doses with that of dabigatran at both doses, rivaroxaban, and apixaban (non vitamin K antagonist oral anticoagulants, NOAC) in a German population. Data of clinical outcome events were taken from edoxaban's ENGAGE-AF, dabigatran's RE-LY, rivaroxaban's ROCKET, and apixaban's ARISTOTLE trials. The base-case analyses of a 65-year-old person with a CHADS2 score >1 gained 0.17 and 0.21 quality-adjusted life years over warfarin for 30 mg od and 60 mg od edoxaban, respectively. The incremental cost-effectiveness ratio was 50.000 and 68.000 euro per quality-adjusted life years for the higher and lower dose of edoxaban (Monte Carlo simulation). These findings were also similar to those for apixaban and more cost-effective than the other NOAC regimens. The current market costs for direct oral anticoagulants are high in relation to the quality of life gained from a German public health care insurance perspective. The willingness-to-pay threshold was lowest for 60 mg edoxaban compared to all direct oral anticoagulants and for 30 mg edoxaban compared to dabigatran and rivaroxaban.

Determination of the anticoagulant effects of new oral anticoagulants: an unmet need.

Thromboembolic diseases require anticoagulation for their prevention and treatment. New oral anticoagulants, specifically direct factor Xa and thrombin inhibitors, were developed to overcome the limitations of conventional anticoagulants. Their benefit has been demonstrated using fixed doses without laboratory-guided dose adjustment for patients following elective knee and hip replacement, treatment of venous thromboembolism and prevention of embolic events in atrial fibrillation. These anticoagulants are excreted by glomerular filtration at a rate of between 25 and 80%. Thus, lower doses are required for patients with impaired renal function. Therefore, determination of the anticoagulant effects may be needed in other specific patient populations. Prothrombin time, activated partial thromboplastin time, prothrombin-induced clotting time, ecarin clotting time, hemoclot assay, other specific coagulation assays and chromogenic substrate are available to determine the effect of the anticoagulants. Standardization of methods, development of point-of-care tests and identification of patient groups is ongoing.

Development of idraparinux and idrabiotaparinux for anticoagulant therapy.

Idraparinux is an analogue of fondaparinux binding with high affinity to antithrombin. It was designed for weekly, rather than daily, administration, with an exceptionally long half-life. One potential problem with small heparin-like fragments of this type is the difficulty of neutralising excessive activity in the case of side-effects or overdose. The efficacy of idraparinux was was proven in clinical studies with patients suffering from venous thromboembolism (VTE) or atrial fibrillation. Due to major bleeding events during treatment for more than six months the development of idraparinux was stopped. Idrabiotaparinux has an attached biotin moiety at the non-reducing end unit, which allows its neutralisation with avidin, an egg-derived protein with low antigenicity. This compound is currently investigated in clinical trials for prevention of recurrent VTE in patients with acute pulmonary embolism. The future of idrabiotaparinux depends also on the safety and efficacy of avidin.

Current and future prospects for anticoagulant therapy: inhibitors of factor Xa and factor IIa.

Indirect systemic and direct oral factor Xa and direct oral factor IIa inhibitors with improved pharmacologic profiles compared with heparins and vitamin K antagonists are currently in clinical development. This overview focuses on the indirect antithrombin dependent pentasaccharide derivatives of idraparinux and on the most advanced oral direct inhibitors to factor Xa (rivaroxaban and apixaban) and IIa (dabigatran). Specifically, the results of dose-finding studies for the prevention of venous thromboembolism after elective orthopedic surgery, the results of dose-finding studies for treatment of acute venous thromboembolism including prolonged prophylaxis of recurrent events, and the designs of ongoing clinical trials are reviewed.