New anticoagulants: Monitoring or not Monitoring? Not Monitoring

Transcription

1 The 2 nd World Congress on CONTROVERSIES IN HEMATOLOGY (COHEM) Barcelona, Spain September 6 8, 2012 New anticoagulants: Monitoring or not Monitoring? Not Monitoring Anna Falanga, MD Immunohematology and Transfusion Medicine & Center of Hemostasis and Thrombosis, Ospedali Riuniti Bergamo, Italy

2 OLD ORAL ANTICOAGULANT DRUGS: Warfarin - slow onset (and offset) of action: requires bridging therapy with heparins. - unpredictable pharmacokinetics and pharmacodynamics - interacts with many other drugs - variability in relation to diet and comorbidities - variability in relation to genetic factors (CYP2C9 and VKORC1 polymorphisms) - narrow therapeutic range - need for laboratory monitoring

3 What are the characteristics of the ideal anticoagulants?

4 New Anticoagulants (NOACs) FONDAPARINUX RIVAROXABAN APIXABAN EDOXABAN Prothrombinase Xa, Va lipid DESIRUDIN ARGATROBAN BIVALIRUDIN (XIMELAGATRAN) Prothrombin Thrombin DABIGATRAN Platelet activation Fibrin formation Fibrinolysis inhibition Cellular effects

5 Main pharmacological characteristics of selected new oral anticoagulants Dabigatran Rivaroxaban Apixaban Edoxaban Target IIa Xa Xa Xa Hours to Cmax Prodrug Yes No No No CYP metabolism No Yes (CYP3A4/A5, CYP2J2) YES (CYP3A4, CYP1A2, CYP2J2) Efflux transporter P gp Yes Yes Yes Yes YES (CYP3A4) Bioavilability 7% 80% 66% >45% Protein binding 35% >90% 87% 55% Half life (Hours) Renal elimination 80% 66% 25% 35% Dosing Twice a day Once a day Twice a day Once a day Bid= twice daily; od= once daily; Tmax= time to peak plasma concentration

6 Comparative features of VKAs and NOACs VKAs Need for regular anticoagulation monitoring: food and drug interactions narrow therapeutic window inter and intra individual variability in dose response Delayed onset of action Long half life Mainly hepatic metabolism Available antidote Anticoagulant monitoring through INR NOACs Fixed dose regimen without need for routine monitoring: low potential for food and drug interaction wider therapeutic window predictable anticoagulant effect Rapid onset of action Short half life Mainly renal clearence No available antidote No standardized monitoring test INR: international normalized ratio, NOACs: novel oral anticoagulants, VKAs: vitamin K antagonist

7 Why monitoring drugs? Drug monitoring aims to optimize dosage regimens in order to increase efficacy and/or safety If the plasma concentration of a drug can be accurately anticipated from the dose applied and the patient s body weight, it does not usually require monitoring, even if its therapeutic window is narrow.

8 Why not monitoring NOACs? Not monitoring

9 Dabigatran: Predictable Pharmacokinetics After a Single Dose At Steady State Dose proportional increase in C max and AUC indicate linear pharmacokinetics over a wide range of doses Stangier J.: Clin Pharmacokinet 2008:47:

10 Reproducible PK Profile of Dabigatran PK profile is reproducible across a wide range of doses 1,2 1 Stangier et al. Br J Clin Pharmacol 2007:64: Stangier Clin Pharmacokinet 2008;47:

11 The oral direct thrombin inhibitor Dabigatran has: A predictable, linear PK/PD profile Quick onset and offset of action

12 Pharmacokinetics of Rivaroxaban Dose proportional and linear PK with no accumulation after multiple dosing Kubitza D., et al. Clin Pharmacol Ther 2005

13 Efficacy and safety No monitoring has been used in phase III clinical trials that established the efficacy and safety of the NOACs

14 Efficacy outcome Recurrent venous thromboembolism Event rate DABIGATRAN 2.4 % WARFARIN 2.1 % p< for non inferiority Schulman S et al. NEJM 2009; 361:

15 Efficacy outcome Recurrent venous thromboembolism p< for non inferiority Event rate RIVAROXABAN 2.1 % Enox- WARFARIN 3.0 % Safety outcome Major bleeding or clinically relevant nonmajor bleeding Event rate RIVAROXABAN 8.1 % Enox- WARFARIN 8.1 % P= 0.77 EINSTEIN investigators NEJM 2010; 363:

16 Effects of NOACs on Coagulation Assays

17 NOACs cause a significant prolongation of coagulation reactions producing misleading results in routine clotting assays Direct Thrombin Inhibitors Direct FXa Inhibitors PT in sec and INR APTT Thrombin Time (TT) No Fibrinogen (Clauss) No/ No D dimers No No These alterations do not correlate with the drug concentration, therefore these tests are not to be performed to determine the drug activity.

18 Effect of Dabigatran on APTT

19 Effects of Dabigatran on Coagulation Assays The time curves for aptt, PT (expressed as international normalised ratio [INR]), TT and ECT values parallel the plasma concentration time curve of dabigatran. The maximum effect of dabigatran on clotting parameters occurs at the same time as maximal plasma concentrations, indicating that thrombin inhibition by dabigatran is a direct effect linked to the central plasma compartment. Van Ryn J et al, Thrombs and Haemost 2010

20 Effects of Rivaroxaban on Coagulation Assays Harenberg J et al, Expert Rev. Hematol. 2012

21 Monitoring vs measuring the anticoagulant effects of the NOACs

22 Measurement of the anticoagulant activity after a therapeutic dose of rivaroxaban or dabigatran etexilate may be informative in cases of: Patients with low body weights or obese patients Pediatric Patients Renal or hepatic impairment Accidental or deliberate overdose To measure adherence To evaluate patients with hemorrhagic or thrombotic complication Before surgery However, in the absence of specific antidotes, a measured high activity merely allows us to approximate after which time the drug activity will vanish, according to its pharmacokinetic properties, which could have been calculated if the timing of administration and the exact dose are known.

23 Current problems with measuring these drugs No validated assays Each drug has unique effect Drug effect on clotting factors is transient Therapeutic ranges are uncertain

24 WHICH TEST? APTT Thrombin Time (TT) PT-INR Ecarin clotting time (ECT) Anti-Xa Thrombin Generation

25 DABIGATRAN Features Test APTT PT ECT TT Responsiveness Linearity Standardization Availability

26 RIVAROXABAN/APIXABAN Characteristics Test PT APTT HepTest DRVVT axa Responsiveness Linearity Standardization +/- -?? +/- Availability

27 For the time being, and only in case it is needed: ECT might be the choice for Dabigatran PT and/or axa might be the choice for Rivaroxaban/Apixaban

28 What the users of the new oral anticoagulants need to know The new direct Factor Xa and IIa inhibitors affect conventional clotting tests These effects are reagent dependent Do not routinely measure aptt or prothrombin time to detect over or underdose Use specific tests recommended (if available) to detect over or underdose, in particular in special patient populations However there is no need for routine monitoring.

29 NOACs do not need monitoring on a routine basis