Clopidogrel and Ticlopidine: P2Y₁₂ Adenosine Diphosphate-Receptor Antagonists for the Prevention of Atherothrombosis

ABSTRACT

Ticlopidine and clopidogrel belong to the same chemical family of thienopyridine adenosine diphosphate (ADP)-receptor antagonists. They have shown their efficacy as platelet antiaggregant and antithrombotic agents in many animal models, both ex vivo and in vivo. Although ticlopidine was discovered more than 30 years ago, it was only recently that the mechanism of action of ADP-receptor antagonists was characterized in detail. Ticlopidine and clopidogrel both behave in vivo as specific antagonists of P2Y₁₂, one of the ADP receptors on platelets. Metabolic steps that involve cytochrome P450-dependent pathways are required to generate the active metabolite responsible for this in vivo activity. The active moiety is a reactive thiol derivative that targets P2Y₁₂ on platelets. The interaction is irreversible, accounting for the observation that platelets are definitely antiaggregated, even if no active metabolite is detectable in plasma. The interaction is specific for P2Y₁₂; other purinoceptors such as P2Y₁ and P2Y₁₃ are spared. This results in inhibition of the binding of the P2Y₁₂ agonist 2-methylthio-ADP and the ADP-induced downregulation of adenylyl cyclase. Platelet aggregation is affected not only when triggered by ADP but also by aggregation inducers when used at concentrations requiring released ADP as an amplifier. The efficacy and safety of clopidogrel has been established in several large, randomized, controlled trials. The clopidogrel versus aspirin in patients at risk of ischaemic events (CAPRIE) trial demonstrated the superiority of clopidogrel over acetylsalicylic acid (ASA) in patients at risk of ischemic events, including ischemic stroke, myocardial infarction (MI), and peripheral arterial disease. The clopidogrel in unstable angina to prevent recurrent ischemic events (CURE) trial showed a sustained, incremental benefit when clopidogrel was added to standard therapy (including ASA) in patients with unstable angina and non-Q-wave MI. The clopidogrel for the reduction of events during observation (CREDO) trial demonstrated the benefit of continuing clopidogrel (plus ASA) for 12 months, as opposed to 1 month, after percutaneous coronary intervention. The proven efficacy of clopidogrel, coupled with its favorable safety and tolerability profile, has prompted its evaluation in an extensive, ongoing clinical trial program that will help to further characterize the benefit of clopidogrel in patients with a range of atherothrombotic profiles.

Antiplatelet agents - atherothrombosis - clopidogrel - platelets - ticlopidine

REFERENCES

• 1 Bhatt D L, Topol E J. Advances in antiplatelet therapy.  Nat Rev Drug Discov. 2003;  2 15-28
• 2 Hass W K, Easton J D, Adams Jr H P et al.. A randomized trial comparing ticlopidine hydrochloride with aspirin for the prevention of stroke in high-risk patients.  N Engl J Med. 1989;  321 501-507
• 3 Gent M, Blakeley J A, Easton J D et al.. The Canadian American ticlopidine study (CATS) in thromboembolic stroke.  Lancet. 1989;  1 1215-1220
• 4 Janzon L, Bergqvist D, Boberg J et al.. Prevention of myocardial infarction and stroke in patients with intermittent claudication; effects of ticlopidine. Results from STIMS, the Swedish ticlopidine multicentre study.  J Intern Med. 1990;  227 301-308
• 5 Final report on the aspirin component of the ongoing Physicians’ Health Study. Steering Committee of the Physicians’ Health Study Research Group.  N Engl J Med. 1989;  321 129-135
• 6 A randomised, blinded, trial of clopidogrel versus aspirin in patients at risk of ischaemic events (CAPRIE) . CAPRIE Steering Committee.  Lancet. 1996;  348 1329-1339
• 7 Yusuf S, Zhao F, Mehta S R et al.. Effects of clopidogrel in addition to aspirin in patients with acute coronary syndromes without ST-segment elevation.  N Engl J Med. 2001;  345 494-502
• 8 Panak E, Maffrand J P, Picard-Fraire C et al.. Ticlopidine: a promise for the prevention and treatment of thrombosis and its complications.  Haemostasis. 1983;  13 1-54
• 9 Maffrand J P, Defreyn G, Bernat A, Delebassee D, Tissinier A M. Reviewed pharmacology of ticlopidine.  Act Med Int - Angiologie. 1988;  5 (suppl 77) 6-13
• 10 Herbert J M, Frehel D, Vallee E et al.. Clopidogrel, a novel antiplatelet and antithrombotic agent.  Cardiovasc Drug Rev. 1993;  11 180-198
• 11 Herbert J M, Bernat A, Maffrand J P. Importance of platelets in experimental venous thrombosis in the rat.  Blood. 1992;  80 2281-2286
• 12 Savi P, Bernat A, Dumas A, Ait-Chek L, Herbert J M. Effect of aspirin and clopidogrel on platelet-dependent tissue factor expression in endothelial cells.  Thromb Res. 1994;  73 117-124
• 13 Hérault J P, Dol F, Gaich C, Bernat A, Herbert J M. Effect of clopidogrel on thrombin generation in platelet-rich plasma in the rat.  Thromb Haemost. 1999;  81 957-960
• 14 Leon C, Alex M, Klocke A et al.. Platelet ADP receptors contribute to the initiation of intravascular coagulation.  Blood. 2004;  103 594-600
• 15 Mazoyer E, Ripoll L, Boisseau M R, Drouet L. How does ticlopidine treatment lower plasma fibrinogen?.  Thromb Res. 1994;  75 361-370
• 16 Hayakawa M, Kuzuya F. Effects of ticlopidine on erythrocyte aggregation in thrombotic disorders.  Angiology. 1991;  42 747-753
• 17 de Loeril M, Bordet J C, Salen P et al.. Ticlopidine increases nitric oxide generation in heart-transplant recipients: a possible novel property of ticlopidine.  J Cardiovasc Pharmacol. 1998;  32 225-230
• 18 Arrebola M M, De la Cruz J P, Villalobos M A et al.. In vitro effects of clopidogrel on the platelet-subendothelium interaction, platelet thromboxane and endothelial prostacyclin production, and nitric oxide synthesis.  J Cardiovasc Pharmacol. 2004;  43 74-82
• 19 Herbert J M. Effects of ADP-receptor antagonism beyond traditional inhibition of platelet aggregation.  Expert Opin Investig Drugs. 2004;  13 457-460
• 20 Hermann A, Rauch B H, Braun M, Schrör K, Weber A-A. Platelet CD40 ligand (CD40L)-subcellular localization, regulation of expression, and inhibition by clopidogrel.  Platelets. 2001;  12 74-82
• 21 Klinkhardt U, Bauersachs R, Adams J et al.. Clopidogrel but not aspirin reduces P-selectin expression and formation of platelet-leukocyte aggregates in patients with atherosclerotic vascular disease.  Clin Pharmacol Ther. 2003;  73 232-241
• 22 Klinkhardt U, Graff J, Harder S. Clopidogrel, but not abciximab, reduces platelet leukocyte conjugates and P-selectin expression in a human ex vivo in vitro model.  Clin Pharmacol Ther. 2002;  71 176-185
• 23 Cimminiello C, Milani M, Uberti T, Arpaia G, Bonfardeci G. Effects of ticlopidine and indobufen on platelet aggregation induced by A23187 and adrenaline in the presence of different anticoagulants.  J Int Med Res. 1989;  17 514-520
• 24 Ashida S I, Abiko Y. Mode of action of ticlopidine in inhibition of platelet aggregation in the rat.  Thromb Haemost. 1979;  41 436-449
• 25 Bonne C, Battais E. Ticlopidine and adenylate cyclase.  Agents Actions Suppl. 1984;  15 88-96
• 26 Johnson M, Heywood J B. Possible mode of action of ticlopidine: a novel inhibitor of platelet aggregation.  Thromb Haemost. 1979;  42 367 (abst)
• 27 Gachet C, Stierlé A, Cazenave J P et al.. The thienopyridine PCR 4099 selectively inhibits ADP-induced platelet aggregation and fibrinogen binding without modifying the membrane glycoprotein IIb-IIIa complex in rat and in man.  Biochem Pharmacol. 1990;  40 229-238
• 28 Gachet C, Cazenave J P, Ohlmann P et al.. The thienopyridine ticlopidine selectively prevents the inhibitory effects of ADP but not of adrenaline on cAMP levels raised by stimulation of the adenylate cyclase of human platelets by PGE1.  Biochem Pharmacol. 1990;  40 2683-2687
• 29 Defreyn G, Gachet C, Savi P et al.. Ticlopidine and clopidogrel (SR 25990C) selectively neutralize ADP inhibition of PGE1-activated platelet adenylate cyclase in rats and rabbits.  Thromb Haemost. 1991;  65 186-190
• 30 Cattaneo M, Akkawat B, Lecchi A et al.. Ticlopidine selectively inhibits human platelet responses to adenosine diphosphate.  Thromb Haemost. 1991;  66 694-699
• 31 Wagner W R, Hubbell J A. ADP receptor antagonists and converting enzyme systems reduce platelet deposition onto collagen.  Thromb Haemost. 1992;  67 461-467
• 32 Cattaneo M, Canciani M T, Lecchi A et al.. Released adenosine diphosphate stabilizes thrombin-induced human platelet aggregates.  Blood. 1990;  75 1081-1086
• 33 Herbert J M. Clopidogrel and antiplatelet therapy.  Expert Opin Invest Drug. 1994;  3 449-455
• 34 Weber A A, Braun M, Hohlfeld T et al.. Recovery of platelet function after discontinuation of clopidogrel treatment in healthy volunteers.  Br J Clin Pharmacol. 2001;  52 333-336
• 35 Weber A A, Reimann S, Schrör K. Specific inhibition of ADP-induced platelet aggregation by clopidogrel in vitro.  Br J Pharmacol. 1999;  126 415-420
• 36 Abou-Khalil S, Abou-Khalil W H, Yunis A A. Mechanism of interaction of ticlopidine and its analogues with the energy-conserving mechanism in mitochondria.  Biochem Pharmacol. 1986;  35 1855-1859
• 37 Klein-Soyer C, Cazenave J P, Herbert J M, Maffrand J P. SR 25989 inhibits healing of a mechanical wound of confluent human saphenous vein endothelial cells which is modulated by standard heparin and growth factors.  J Cell Physiol. 1994;  160 316-322
• 38 Chen W H, Yin H L, Chang Y Y et al.. Antiplatelet drugs induce apoptosis in cultured cancer cells.  Kao Hsiung I Hsueh Ko Hsueh Tsa Chih. 1997;  13 589-597
• 39 Denninger M H, Necciari J, Serre-Lacroix E, Sissmann J. Clopidogrel antiplatelet activity is independent of age and presence of atherosclerosis.  Semin Thromb Hemost. 1999;  25(suppl 2) 41-45
• 40 Savi P, Herbert J M, Pflieger A M et al.. Importance of hepatic metabolism in the antiaggregating activity of the thienopyridine clopidogrel.  Biochem Pharmacol. 1992;  44 527-532
• 41 Savi P, Combalbert J, Gaich C et al.. The antiaggregating activity of clopidogrel is due to a metabolic activation by the hepatic cytochrome P450-1A.  Thromb Haemost. 1994;  72 313-317
• 42 Savi P, Heilmann E, Nurden P et al.. Clopidogrel: an antithrombotic drug acting on the ADP-dependent activation pathway of human platelets.  Clin Appl Thromb Hemost. 1996;  2 35-42
• 43 Di Perri T, Pasini F L, Frigerio C et al.. Pharmacodynamics of ticlopidine in man in relation to plasma and blood cell concentration.  Eur J Clin Pharmacol. 1991;  41 429-434
• 44 Pereillo J M, Maftough M, Andrieu A et al.. Structure and stereochemistry of the active metabolite of clopidogrel.  Drug Metab Dispos. 2002;  30 1288-1295
• 45 Savi P, Pereillo J M, Uzabiaga M F et al.. Identification and biological activity of the active metabolite of clopidogrel.  Thromb Haemost. 2000;  84 891-896
• 46 Easton J D. Clinical aspects of the use of clopidogrel, a new antiplatelet agent.  Semin Thromb Hemost. 1999;  25(suppl 2) 77-82
• 47 Havranek E, Weinberger J. Concomitant use of ACE inhibitors and antiplatelet therapies: clopidogrel versus aspirin.  J Hypertens. 1999;  17(suppl 3) S57 (abst)
• 48 Bhatt D L, Foody J, Hirsch A T et al.. Complementary, additive benefit of clopidogrel and lipid-lowering therapy in patients with atherothrombosis.  J Am Coll Cardiol. 2000;  35(suppl A) 326 (abst)
• 49 Lidell C, Svedberg L E, Lindell P et al.. Clopidogrel and warfarin: absence of interaction in patients receiving long-term anticoagulant therapy for non-valvular atrial fibrillation.  Thromb Haemost. 2003;  89 842-846
• 50 Lalé A, Herbert J M, Savi P. The antiaggregating effect of clopidogrel is not affected by N-acetyl L-cysteine.  Thromb Haemost. 2003;  90 839-843
• 51 Slugg P H, Much D R, Smith W B et al.. Cirrhosis does not affect the pharmacokinetics and pharmacodynamics of clopidogrel.  J Clin Pharmacol. 2000;  40 396-401
• 52 Lau W C, Waskell L A, Watkins P B et al.. Atorvastatin reduces the ability of clopidogrel to inhibit platelet aggregation: a new drug-drug interaction.  Circulation. 2003;  107 32-37
• 53 Saw J, Steinhubl S R, Berger P B et al.. Lack of adverse clopidogrel-atorvastatin clinical interaction from secondary analysis of a randomized, placebo-controlled clopidogrel trial.  Circulation. 2003;  108 921-924
• 54 Wienbergen H, Gitt A K, Schiele R et al.. Comparison of clinical benefits of clopidogrel therapy in patients with acute coronary syndromes taking atorvastatin versus other statin therapies.  Am J Cardiol. 2003;  92 285-288
• 55 Mills D CB, Puri R, Hu C J et al.. Clopidogrel inhibits the binding of ADP analogues to the receptor mediating inhibition of platelet adenylate cyclase.  Arterioscler Thromb. 1992;  12 430-436
• 56 Savi P, Laplace M C, Maffrand J P, Herbert J M. Binding of [³H]-2-methylthio-ADP to rat platelets-effect of clopidogrel and ticlopidine.  J Pharmacol Exp Ther. 1994;  269 772-777
• 57 Savi P, Laplace M C, Herbert J M. Evidence for the existence of two different ADP-binding sites on rat platelets.  Thromb Res. 1994;  76 157-169
• 58 Savi P, Beauverger P, Labouret C et al.. Role of P2Y1 purinocepter in ADP-induced platelet activation.  FEBS Lett. 1998;  422 291-295
• 59 Léon C, Vial C, Cazenave J P, Gachet C. Cloning and sequencing of a human cDNA encoding endothelial P2Y1 purinoceptor.  Gene. 1996;  171 295-297
• 60 Jin J, Daniel J L, Kunapuli S P. Molecular basis for ADP-induced platelet activation. II. The P2Y1 receptor mediates ADP-induced intracellular calcium mobilization and shape change in platelets.  J Biol Chem. 1998;  273 2030-2034
• 61 Derian C K, Friedman P A. Effects of ticlopidine ex vivo on platelet intracellular calcium mobilization.  Thromb Res. 1988;  50 65-76
• 62 Fabre J E, Nguyen M, Latour A et al.. Decreased platelet aggregation, increased bleeding time and resistance to thromboembolism in P2Y1-deficient mice.  Nat Med. 1999;  5 1199-1202
• 63 Léon C, Hechler B, Freund M et al.. Defective platelet aggregation and increased resistance to thrombosis in purinergic P2Y(1) receptor-null mice.  J Clin Invest. 1999;  104 1731-1737
• 64 Hollopeter G, Jantzen H M, Vincent D et al.. Identification of the platelet ADP receptor targeted by antithrombotic drugs.  Nature. 2001;  409 202-207
• 65 Savi P, Pereillo J M, Uzabiaga M F et al.. P2Y12, a new platelet ADP receptor, target of clopidogrel.  Biochem Biophys Res Commun. 2001;  283 379-383
• 66 Communi D, Gonzalez N S, Detheux M et al.. Identification of a novel human ADP receptor coupled to G(i).  J Biol Chem. 2001;  276 41479-41485
• 67 Marteau F, Le Poul E, Communi D et al.. Pharmacological characterization of the human P2Y13 receptor.  Mol Pharmacol. 2003;  64 104-112
• 68 Boeynaems J M, Communi D, Savi P, Herbert J M. P2Y receptors: in the middle of the road.  Trends Pharmacol Sci. 2000;  21 1-3
• 69 Savi P, Pflieger A M, Herbert J M. cAMP is not an important messenger for ADP-induced platelet aggregation.  Blood Coagul Fibrinolysis. 1996;  7 249-252
• 70 Weber A A, Hohlfeld T, Schrör K. cAMP is an important messenger for ADP-induced platelet aggregation.  Platelets. 1999;  10 238-241
• 71 Daniel J L, Dangelmaier C, Jin J, Kim Y B, Kunapali S P. Role of intracellular events in ADP-induced platelet aggregation.  Thromb Haemost. 1999;  82 1322-1326
• 72 Soulet C, Sauzeau V, Plantavid M et al.. Gi-dependent and -independent mechanisms downstream of the P2Y₁₂ ADP-receptor.  J Thromb Haemost. 2004;  2 135-146
• 73 Cattaneo M, Lecchi A, Randi A M, McGregor J L, Manucci P M. Identification of a new congenital defect of platelet function characterized by severe impairment of platelet responses to adenosine diphosphate.  Blood. 1992;  80 2787-2796
• 74 Nurden P, Savi P, Heilmann E et al.. An inherited bleeding disorder linked to a defective interaction between ADP and its receptor on platelets.  J Clin Invest. 1995;  95 1612-1622
• 75 Cattaneo M, Zighetti M L, Lombardi R et al.. Molecular bases of defective signal transduction in the platelet P2Y₁₂ receptor of a patient with congenital bleeding.  Proc Natl Acad Sci USA. 2003;  100 1978-1983
• 76 Jin J, Kunapuli S P. Coactivation of two different G protein-coupled receptors is essential for ADP-induced platelet aggregation.  Proc Natl Acad Sci USA. 1998;  95 8070-8074
• 77 Hechler B, Leon C, Vial C et al.. The P2Y1 receptor is necessary for adenosine 5′-diphosphate-induced platelet aggregation.  Blood. 1998;  92 152-159
• 78 Andre P, Delaney S M, LaRocca T et al.. P2Y12 regulates platelet adhesion/activation, thrombus growth, and thrombus stability in injured arteries.  J Clin Invest. 2003;  112 398-406
• 79 Humbert M, Nurden P, Bihour C et al.. Ultrastructural studies of platelet aggregates from human subjects receiving clopidogrel and from a patient with an inherited defect of an ADP-dependent pathway of platelet activation.  Arterioscler Thromb Vasc Biol. 1996;  16 1532-1543
• 80 Daniel J L, Dangelmaier C, Jin J et al.. Molecular basis for ADP-induced platelet activation. I. Evidence for three distinct ADP receptors on human platelets.  J Biol Chem. 1998;  273 2024-2029
• 81 Drouet L. Atherothrombosis as a systemic disease.  Cerebrovasc Dis. 2002;  13(suppl 1) 1-6
• 82 Antithrombotic Trialists’ Collaboration . Collaborative meta-analysis of randomised trials of antiplatelet therapy for prevention of death, myocardial infarction, and stroke in high risk patients.  BMJ. 2002;  324 71-86
• 83 Bhatt D L, Chew D P, Hirsch A T et al.. Superiority of clopidogrel versus aspirin in patients with prior cardiac surgery.  Circulation. 2001;  103 363-368
• 84 Bhatt D L, Marso S P, Hirsch A T et al.. Amplified benefit of clopidogrel versus aspirin in patients with diabetes mellitus.  Am J Cardiol. 2002;  90 625-628
• 85 Ringleb P A, Bhatt D L, Hirsch A T, Topol E J, Hacke W. Benefit of clopidogrel over aspirin is amplified in patients with a history of ischemic events.  Stroke. 2004;  35 528-532
• 86 Leon M B, Baim D S, Popma J J et al.. A clinical trial comparing three antithrombotic-drug regimens after coronary-artery stenting.  N Engl J Med. 1998;  339 1665-1671
• 87 Yusuf S, Mehta S R, Zhao F et al.. Early and late effects of clopidogrel in patients with acute coronary syndromes.  Circulation. 2003;  107 966-972
• 88 Budaj A, Yusuf S, Mehta S et al.. Benefit of clopidogrel in patients with acute coronary syndromes without ST-segment elevation in various risk groups.  Circulation. 2002;  106 1622-1626
• 89 Peters R JG, Mehta S R, Fox K AA et al.. Effects of aspirin dose when used alone or in combination with clopidogrel in patients with acute coronary syndromes. Observations from the clopidogrel in unstable angina to prevent recurrent events (CURE) study.  Circulation. 2003;  108 1682-1687
• 90 Mehta S R, Yusuf S, Peters R JG et al.. Effects of pretreatment with clopidogrel and aspirin followed by long-term therapy in patients undergoing percutaneous coronary intervention: the PCI-CURE study.  Lancet. 2001;  358 527-533
• 91 Steinhubl S R, Berger P B, Mann III J T et al.. Early and sustained dual oral antiplatelet therapy following percutaneous coronary intervention. A randomized controlled trial.  JAMA. 2002;  288 2411-2420
• 92 Bhatt D L, Kapadia S R, Bajzer C T et al.. Dual antiplatelet therapy with clopidogrel and aspirin after carotid artery stenting.  J Invasive Cardiol. 2001;  13 767-771
• 93 Teal P A. Recent clinical trial results with antiplatelet therapy: implications in stroke prevention.  Cerebrovasc Dis. 2004;  17(suppl 3) 6-10
• 94 Braunwald E, Antman E M, Beasley J W et al.. ACC/AHA 2002 guideline update for the management of patients with unstable angina and non-ST-segment elevation myocardial infarction: summary article: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on the Management of Patients with Unstable Angina).  J Am Coll Cardiol. 2002;  40 1366-1374
• 95 Bertrand M E, Simoons M L, Fox K AA et al.. Management of acute coronary syndromes in patients presenting without persistent ST-segment elevation.  Eur Heart J. 2002;  23 1809-1840
• 96 Diener H C, Bogousslavsky J, Brass L M et al.. Aspirin and elopiodgrel compared with clopidogrel alone after recent ischaamic stroke or translent ischeemic attack in high-risk patients (MATCH): randomised, double-blind placebo-controlled trial.  Lancet. 2004;  364 331-337
• 97 Markus H, Droste D, Kaps M et al.. Dual antiplatelet therapy with clopidogrel and aspirin in symptomatic carotid stenosis evaluated using Doppler embolic signal detectin; the multicenter CARESS study.  Circulation. 2005;  , in press
• 98 Hankey G J. Ongoing and planned trials of antiplatelet therapy in the acute and long-term management of patients with ischaemic brain syndromes: setting a new standard of care.  Cerebrovasc Dis. 2004;  17(suppl 3) 11-16
• 99 Bhatt D L, Topol E J. , on behalf of the Clopidogrel for High Atherothrombotic Risk and Ischemic Stabilization Management and Avoidance Executive Committee Clopidogrel added to aspirin versus aspirin alone in secondary prevention and high-risk primary prevention: rationale and design of the clopidogrel for high atherothrombotic risk and ischemic stabilization, management, and avoidance (CHARISMA) trial.  Am Heart J. 2004;  148 263-268
• 100 Jneid H, Bhatt D L. Advances in antiplatelet therapy.  Expert Opin Emerg Drugs. 2003;  8 349-363
• 101 Wald N J, Law M R. A strategy to reduce cardiovascular disease by more than 80%.  BMJ. 2003;  326 1419-1425