Newer anticoagulants

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Newer anticoagulants

  1. 1. Newer anti-coagulants<br />13.10.11<br />
  2. 2. Coagulation system<br />Available anticoagulants:<br />Heparin ,LMWH ,fondaparinux, Direct thrombin inhibitors, Warfarin<br />Limitations of established parenteral and oral anticoagulants<br />Potential advantages of the new agents<br />Pharmacology and clinical trial results with new anticoagulants<br />Conclusions and Future Directions<br />
  3. 3. Hemostatic system<br /> The major components of the hemostatic system are:<br />Vascular endothelium<br />Platelets<br />Coagulation system <br />Fibrinolytic system.<br />
  4. 4. Coagulation occurs through the action of discrete enzyme complexes, which are composed of a vitamin K–dependent enzyme and a nonenzyme cofactor. <br />
  5. 5. Intrinsic Pathway (APTT)<br /><ul><li>Factors VIII, IX, XI, and XII.
  6. 6. Activated on surface of exposed endothelium.
  7. 7. Complexes form on platelet phospholipids.</li></ul>Contact (Eg: with glass)<br />XII<br />XIIa<br />XIa<br />XI<br />IXa<br />IX<br />VIIIa<br />PL<br />Ca++<br />X<br />Xa<br />
  8. 8. Extrinsic Pathway<br />Extrinsic Pathway: (PT)<br /><ul><li>Factors VII, IX, X
  9. 9. Activated by Tissue phospholipids (Tissue Factor or Tissue thromboplastin) released into blood as a result of tissue damage. </li></ul>Tissue factor (TF)<br />VIIa- TF<br />VII<br />XIa<br />IX<br />IXa<br />VIIIa<br />Xa<br />X<br />
  10. 10.
  11. 11. Anticoagulants – historical development<br />Dabigatran<br />Rivaroxaban<br />Apixaban<br /> AZD0837<br />Oral<br />Spoiled sweet clover<br />Warfarin<br />clinical use<br />High / low dose<br />Warfarin / INR<br />Ximelagatran<br />clinical trials<br />Dicoumarol<br />discovered<br />Warfarin / Vitamin K<br />mechanism<br />Warfarin<br />clinical trials<br />1916<br />1924<br />1936<br />1940<br />1950s<br />2006<br />1970s<br />1976<br />1980s<br />1990s<br />2001<br />Heparin<br />clinical use<br />LMWH<br />discovered<br />Pentasaccharide<br />clinical trials<br />LMWH<br />clinical trials<br />Heparin<br />discovered<br />Continous heparin<br />infusion/<br />aPTT<br />Injection<br />
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  13. 13.
  14. 14. Features of an ideal anticoagulant<br />High efficacy to safety index<br />Predictable dose response<br />Administration by parenteral and oral routes<br />Rapid onset of action<br />Availability of a safe antidote<br />Freedom from side effects<br />Minimal interactions<br />
  15. 15. Heparin<br />ParenteralAnticoagulant<br />A sulfated polysaccharide<br />Most commercial heparin is derived from porcine intestinal mucosa <br />Polymer of alternating d-glucuronic acid and N-acetyl-d-glucosamine residues<br />
  16. 16. Mechanism of Action<br />Activates antithrombin and accelerates the rate at which it inhibits clotting enzymes, particularly thrombin and factor Xa<br />Heparin binds to the serpin via a unique pentasaccharide sequence found on one third of the chains of commercial heparin<br />
  17. 17. Mechanism of action of heparin, LMWH, and fondaparinux<br />
  18. 18. Side effects of heparin<br />Bleeding - the most common side effect<br />Thrombocytopenia<br />Osteoporosis<br />Elevated levels of transaminases.<br />
  19. 19. Pharmacokinetic and Biophysical Limitations of Heparin<br />
  20. 20. Low-Molecular-Weight Heparin<br />Consists of smaller fragments of heparin<br />LMWH is prepared from unfractionated heparin by controlled enzymatic or chemical depolymerization. <br />The mean molecular weight of LMWH is about 5000, one third the mean molecular weight of unfractionatedheparin<br />Shorter heparin chains bind less avidly to endothelial cells, macrophages, and heparin-binding plasma proteins<br />The clearance of LMWH is dose-independent and its plasma half-life is longer<br />Situations that may require LMWH monitoring include renal insufficiency , pregnancy and obesity<br />
  21. 21. Fondaparinux<br />A synthetic analogue of the antithrombin-binding pentasaccharidesequence<br />Fondaparinuxcatalyzes factor Xa inhibition by antithrombin and does not enhance the rate of thrombin inhibition<br />Recombinant activated factor VII reverses the anticoagulant effects of fondaparinux<br />
  22. 22. Comparison of the Features of Heparin, Low-Molecular-Weight Heparin, and Fondaparinux<br />
  23. 23. Advantages of Low-Molecular-Weight Heparin and Fondaparinux over Heparin<br />
  24. 24. Direct thrombin inhibitors<br />Hirudin<br />Recombinant proteins<br />Synthetic molecules<br /><ul><li>Derived from leech (Hirudo medicinalis)
  25. 25. Recombinant hirudin (MW 6979.5 Da)
  26. 26. Bivalirudin (MW 2180 Da)
  27. 27. Argatroban(MW 527 Da)
  28. 28. Melagatran
  29. 29. Dabigatran
  30. 30. AZD0837
  31. 31. Polypeptide (65 amino acids)
  32. 32. MW 7000 Da
  33. 33. Do not require a plasma cofactor
  34. 34. Bind directly to thrombin and block its interaction with its substrates</li></li></ul><li>Why thrombin is an excellent target?<br /><ul><li>Forms & stabilizes the clot
  35. 35. Furthers generation of thrombin
  36. 36. Stimulates thrombus- activated fibrinolysis inhibitor (TAFI) resulting in inhibition of fibrinolysis
  37. 37. Activates platelets</li></li></ul><li>Direct thrombin inhibitors – mechanism of action<br />Thrombin<br />Exosite 1(fibrin bindingsite)<br />Argatrobanormelagatran<br />Active site<br />
  38. 38. Direct thrombin inhibitors – mechanism of action<br />Thrombin<br />Hirudin and bivalirudin<br />Exosite 1(fibrin bindingsite)<br />Active site<br />
  39. 39. Parenteral Direct Thrombin Inhibitors<br />
  40. 40. Lepirudin and argatroban are approvedfor the treatment of patients with HIT<br />Bivalirudin is approved as an alternative to heparin in patients undergoing PCI, including those with HIT<br />
  41. 41. Limitations of Existing Parenteral Anticoagulants<br />The need for daily subcutaneous injection limits the long-term use of LMWH or fondaparinux. <br />Potential for accumulation in patients with renal impairment<br />The lack of an antidote<br />Risk of catheter thrombosis when these agents are used as the sole anticoagulant in patients undergoing PCI <br />
  42. 42. Dicoumarol<br />Phenprocoumon<br />Warfarin Sodium<br />Oral Anticoagulants - Vitamin K antagonists<br />Acenocoumarol<br />Anisindione<br />
  43. 43. Mechanism of Action<br />Some clotting factors need a carboxyl group added to their carboxyl-terminal glutamates after synthesis in the liver<br />This γ-carboxylation reaction requires reduced Vitamin K<br />Vitamin K epoxide is then converted back to its reduced form via the enzyme vitamin K epoxidereductase and NADH<br />The Vitamin K antagonists inhibit the action of the reductase enzyme<br />
  44. 44. Effect on Coagulation<br />Intrinsic pathway<br />Extrinsic pathway<br />XII<br />XIIa<br />VIIa<br />TF<br />XIa<br />XI<br />IXa<br />IX<br />VIIIa<br />Va<br />X<br />Xa<br />Common pathway<br />II (prothrombin)<br />IIa (thrombin)<br />XIII<br />XIIIa<br />Fibrinogen<br />Fibrin<br />Stabilized Fibrin<br /> Vitamin K dependent clotting factors:Factors II, VII, IX, and X<br />
  45. 45. Warfarin<br />Bioavailabilynearly complete; absorption dampered by food<br />Peak concentration 2 - 8 hr<br />Binds to albumin 99% of time<br />Can cross placental barrier<br />Racemic mixture: S form by CYP2C9; R by CYP1A2, minor pathway CYP2C19, and minor pathway CYP3A4<br />half-life: 25 - 60 hr; Excreted in urine and stool<br />Food-drug & drug-drug interactions: extensive!!<br />Toxicities: bleeding, fetal bone abnormalities, skin necrosis<br />
  46. 46. Problems with Warfarin<br />Food and drug interactions<br />Genetic variation in metabolism<br />narrow therapeutic window<br />slow onset of action<br />dosage adjustments & freq. monitor with INR<br />overlap with parenteral drugs<br />
  47. 47.
  48. 48. Comparison of Pharmacological Characteristics of AVE5026, Idrabiotaparinux, Otamixaban,and RB006<br />
  49. 49. AVE5026<br />Ultralow-molecular-weight heparin with a mean molecular weight of 2400<br />Primarily targets fXa<br />Given subcutaneously, the half-life is 16 to 20 hours, enabling once-daily administration. <br />Excreted renally<br />Anticoagulant effects are not neutralized by protaminesulfate<br />Phase III program comparing AVE5026 with enoxaparin for VTE prevention in 9000 patients undergoing hip, knee, or abdominal surgery and in 3200 cancer patients receiving chemotherapy is ongoing(SAVE-HIP2 , SAVE-ABDO, SAVE-KNEE , SAVE-HIP3 , SAVE-ONCO<br />
  50. 50. Idrabiotaparinux<br />Hypermethylated derivative of fondaparinux<br />Binds antithrombin with high affinity <br />Has a half-life of 130 hours; idrabiotaparinux is given subcutaneously on a once-weekly basis. <br />Excreted unchanged by the kidneys. <br />Differs from idraparinuxin that it contains a biotin moiety that enables reversal with intravenous avidin<br />
  51. 51. The Van Gogh deep vein thrombosis (DVT) trial compared 3 to 6 months of idraparinux with conventional anticoagulant therapy in 2904 patients with acute DVT.<br />At 3 months, the incidence of recurrent VTE (nonfatal or fatal) was similar in the 2 treatment groups<br />Idraparinuxwas associated with significantly fewer major plus clinically relevant nonmajor bleeds than conventional therapy<br />The AMADEUS trial compared idraparinux with a VKA for prevention of thromboembolism in patients with AF. <br />The trial was stopped early because of an excess of clinically relevant bleeds with idraparinux compared with a VKA<br />EQUINOX bioequivalence study suggested that idrabiotaparinux and idraparinux are similarly effective for DVT treatment<br />CASSIOPEA trial is comparing 3 to 6 months of idrabiotaparinux with conventional anticoagulation therapy for prevention of recurrent VTE<br />
  52. 52. Otamixaban<br />A parenteral direct fXainhibitor<br />Has a rapid onset of action<br />produces a predictable anticoagulant effect<br />Has a short half-life<br />25% of the drug is cleared by the kidneys.<br />These features render otamixaban an attractive candidate to replace heparin in patients with ACS<br />SEPIA-ACS 1(TIMI) 42, a phase II dose-finding study that compared 5 different doses of otamixabanwith the combination of heparin plus eptifibatide in 3241 patients with non–ST-segment elevation ACS<br />
  53. 53. RB006<br />An RNA aptamerthat targets factor IXa with high affinity and specificity, <br />When given intravenously, produces a rapid and dose-proportional anticoagulant effect <br />Immediately reversed by intravenous administration of RB007, the complementary oligonucleotide antidote.<br />RB006 is not cleared renally<br />does not appear to be immunogenic<br />has the potential to inhibit the activation of coagulation induced by exposure of blood to artificial surfaces, such as stents or cardiac bypass circuits<br />potential to replace heparin and protaminesulfate in patients undergoing cardiopulmonary bypass surgery. <br />May also be useful for patients at high risk of bleeding and for those with renal impairment<br />Phase II REVERSAL-PCI study, the efficacy and safety of RB006/RB007 are being compared with those of heparin in 26 patients undergoing elective PCI<br />
  54. 54.
  55. 55. Oral Thrombin Inhibitors<br />
  56. 56. DabigatranEtexilate<br />a prodrug of dabigatran, which reversibly inhibits the active site of thrombin<br />has an oral bioavailability of 6%<br />Plasma levels of dabigatran peak 2 hours after drug administration. <br />Dabigatranhas a half-life of 14 to 17 hours, which permits once- or twice-daily administration<br />80% of the drug is excreted unchanged by the kidneys<br />Coadministration of dabigatranetexilate and amiodarone, a weak P-gp inhibitor, increases dabigatran levels by 50% without significantly affecting those of amiodarone<br />
  57. 57. Dabigatranetexilatein VTE<br />Dabigatranetexilate is approved for VTE prevention after elective hip or knee arthroplasty. <br />220-mg dose of dabigatranetexilate is recommended for the majority of patients<br />150-mg dose is reserved for patients also taking amiodarone and for those at higher risk for bleeding<br />RECOVER-1 in acute VTE<br />dabigatranetexilateor warfarinfor 6 months after initial treatment with a parenteral anticoagulant.<br />recurrent symptomatic VTE and VTE-related death, were 2.4% and 2.1% in dabigatranand warfarin groups, respectively <br />Rates of major bleeding were 1.6% and 1.9% in the dabigatran and warfarin groups, respectively<br />
  58. 58. Dabigatranetexilate in AF<br />The RE-LY trial randomized 18 113 patients with AF and at least 1 additional risk factor for stroke to receive dabigatranetexilate (at doses of 110 or 150 mg twice daily) or warfarin<br />Dabigatran110 mg b.i.d. was non-inferior to VKA for the prevention of stroke and systemic embolism with lower rates of major bleeding<br />Dabigatran 150 mg b.i.d. was associated with lower rates of stroke and systemic embolism with similar rates of major haemorrhage, compared with VKA.<br />
  59. 59. Dabigatranetexilate in ACS<br />Dabigatranetexilate has also been evaluated in the phase II RE-DEEM study in ACS to determine whether it reduces the risk of recurrent ischemia when given in conjunction with antiplatelet drugs<br />
  60. 60. Oral fXa Inhibitors:Rivaroxaban, apixaban and edoxaban<br />
  61. 61. Rivaroxaban<br />An active compound with an oral bioavailability of 80%<br />Has a rapid onset of action and a half-life of 7 to11 hours.<br />Has a dual mode of elimination<br />concomitant administration of potent inhibitors or both P-gp and CYP3A4 is contraindicated<br />On the basis of the results of RECORD trials, rivaroxaban is approved for the prevention of VTE in patients undergoing elective hip or knee arthroplasty<br />
  62. 62. ROCKET AF<br />Primary Efficacy OutcomeStroke and non-CNS Embolism<br />Warfarin<br />Rivaroxaban<br />Cumulative event rate (%)<br />HR (95% CI): 0.79 (0.66, 0.96)<br />P-value Non-Inferiority: <0.001<br />Days from Randomization<br />No. at risk:<br />Rivaroxaban 6958 6211 5786 5468 4406 3407 2472 1496 634<br />Warfarin 7004 6327 5911 5542 4461 3478 2539 1538 655<br />Event Rates are per 100 patient-years<br />Based on Protocol Compliant on Treatment Population<br />
  63. 63. Summary ROCKET AF<br />Efficacy:<br />Rivaroxabanwas non-inferior to warfarin for prevention of stroke and non-CNS embolism.<br />Rivaroxaban was superior to warfarin while patients were taking study drug.<br />By intention-to-treat, rivaroxaban was non-inferior to warfarin but did not achieve superiority.<br />Safety:<br />Similar rates of bleeding and adverse events.<br />Less ICH and fatal bleeding with rivaroxaban.<br />Conclusion:<br />Rivaroxaban is a proven alternative to warfarin for moderate or high risk patients with AF.<br />
  64. 64.  Rivaroxaban in ACS<br /> phase-3  ATLAS-ACS 2 TIMI 51 clinical trial of  rivaroxaban ACS patients has met its primary efficacy end point<br />statistically significant reduction in the primary composite end point of cardiovascular death, MI, and stroke vs placebo. <br />significant increase in the primary safety end point: major bleeding events not associated with coronary artery bypass surgery<br />The ATLAS-ACS 2 TIMI 51 results will be presented as a late-breaking clinical trial at the American Heart Association 2011 Scientific Sessions in Orlando<br />
  65. 65. Apixaban<br />An active drug<br />absorbed rapidly<br />Maximal plasma concentrations are achieved 3 hours after oral administration.<br />half-life of 8 to14 hours. <br />eliminated via multiple pathways<br />Concomitant treatment with potent inhibitors of CYP3A4 is contraindicated<br />
  66. 66.  Pooled data from the ADVANCE clinical-trial program showed that apixaban is more effective than enoxaparin for the prevention of major VTEin patients undergoing hip- or knee-replacement surgery<br />
  67. 67. AVERROES<br />
  68. 68.
  69. 69. ARISTOTLE study<br />
  70. 70. ARISTOTLE study<br />
  71. 71. APPRAISE-2 ACS trial<br /> the phase 3 APPRAISE-2 trial of apixaban in high-risk patients with recent acute coronary syndrome discontinuedafter it became clear that the increase in bleeding risk in patients randomized to apixaban would not be offset by reductions in ischemic events<br />
  72. 72. Edoxaban<br />active drug <br />rapidly absorbed<br />half-life of 9 to 11 hours <br />dual mechanism of elimination<br />ENGAGE-AF-TIMI 48 trial is comparing 2 doses of edoxaban (30 or 60 mg once daily) with warfarin in 16 500 patients with AF<br />
  73. 73. Other oral fXa inhibitors under development include <br /><ul><li>betrixaban(15-hour half-life and extrarenal clearance)
  74. 74. YM150
  75. 75. TAK442</li></li></ul><li>Conclusions and Future Directions<br />the unmet needs for parenteral anticoagulants have diminished with LMWH and fondaparinux, <br />some problems persist.<br />severe renal impairment<br />The lack of an antidote<br />New synthetic parenteral anticoagulants that are <br />eliminated extrarenally<br />can be reversed readily and <br />do not cause thrombocytopenia<br /> may be advantageous<br />Anticoagulant aptamer/antidote pairs, such as RB007/RB008, possess all of these desirable features<br />
  76. 76. Conclusions and Future Directions<br />The favorableresults of the RE-LY trial are likely to revolutionize our approach to long-term anticoagulant therapy<br />The availability of simple, fixed-dose, unmonitored therapy should increase the use of anticoagulant therapy in patients with AF at risk for stroke<br />Streamlining oral therapy will increase the uptake of anticoagulant prophylaxis in patients with AF, thereby decreasing death and disability from stroke. <br />The search for replacements for VKAs appears to be nearing completion<br />
  77. 77. THANK YOU<br />
  78. 78.
  79. 79. Prothrombin Time: PT<br />PT reagent contains Calcium ions and Thromboplastin from brain tissue (Rabbit).<br />Thromboplastin (Tissue Factor) protein-lipid complex found in tissues outside blood vessels.<br />Measures the function of the Extrinsic Pathway. <br />Sensitive to Factors IV, V, VII, X.<br />Provided as a lyophilized reagent.<br />Used to monitor oral anticoagulant therapy (Warfarin / Coumadin).<br />
  80. 80. PT Reagent Calibration<br />Reagents are calibrated against standard PT reagent established by the WHO.<br />ISI = International Sensitivity Index.<br />ISI is assigned by the manufacturer for each lot of reagent using reference material traceable to WHO.<br />The lower the ISI the more sensitive the Reagent<br />ISI of 1.8 to 2.4 = Low sensitivity (North American Standard PT)<br />ISI of 1.4 to 1.8 = Average sensitivity <br />ISI 1.0 to 1.4 = High Sensitivity<br />
  81. 81. PT: INR Values<br />INR = International Normalised Ratio.<br />MNP = Mean Normal Plasma.<br />INR = (PT / MNP)ISI<br />An INR of 1.0 means that the patient PT is normal.<br />An INR greater then 1.0 means the clotting time is elevated.<br />
  82. 82. Performing a PT test<br />Pre-warm PT reagent and sample to 37 oC<br />Add 100 L sample to cuvette<br />Add 200 L of PT reagent to cuvette<br />Start timer<br />Record time to clot in seconds<br />Calculate INR<br />see product insert for PT<br />
  83. 83. Activated Partial Thromboplastin Time<br />APTT or PTT<br />Reagent contains phospholipids and a ‘surface activator’; (Ellagic Acid, Micronized Silica)<br />Calcium Chloride reagent added to start the reaction.<br />APTT reagent mimics the surface of a platelet.<br />Measures activity of clotting factors in the Intrinsic Pathway, factors VIII, IX, XI and XII<br />No WHO calibration standard<br />
  84. 84. Performing an APTT Test<br />Pre-warm Calcium Chloride reagent to 37 oC.<br />Add 100 L of sample to cuvette.<br />Add 100 L of APTT to cuvette and incubate for 3 minutes.<br />Add 100 L of Calcium Chloride reagent and start timer.<br />Record the time to clot in seconds.<br />See APTT product Insert<br />
  85. 85. Activated Clotting Time (ACT)<br />Clotting time of whole blood in the presence of silica based activator.<br />Normal clotting times = 90 to 170 sec.<br />Used to monitor heparin doses from 1 to 10 U/mL (APTT is sensitive to heparin at 0.2 to 1 U/mL).<br />Used with invasive procedures that require on-site adjustment of heparin and protamine dosage. (ex. Cardiopulmonary bypass surgery).<br />Not amenable for use with an optical instrument, too cloudy.<br />Also called HMT, Heparin Management Test<br />
  86. 86. Heparin monitoring<br />Variable anticoagulant response<br />Binds to plasma proteins; levels vary from patient to patient<br />Coagulation monitoring is essential to ensure the response is therapeutic<br />The aPTT, ACT or anti–factor Xa level is used to monitor heparin<br />
  87. 87. HIT<br />Heparin-induced thrombocytopenia (HIT) is an antibody-mediated process triggered by antibodies against neoantigens on PF4 that are exposed when heparin binds to this protein<br />
  88. 88. Features of Heparin-Induced Thrombocytopenia<br />

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