This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Quinn, M. Articles by Fitzgerald, D. Search for Related Content PubMed PubMed Citation Articles by Quinn, M. Articles by Fitzgerald, D. Pubmed/NCBI databases Compound via MeSH Substance via MeSH Related Collections Other Treatment Platelets Receptor pharmacology

(Circulation. 1999;99:2231-2238.)
© 1999 American Heart Association, Inc.

Clinical Investigation and Reports

Quantifying GPIIb/IIIa Receptor Binding Using 2 Monoclonal Antibodies

Discriminating Abciximab and Small Molecular Weight Antagonists

Martin Quinn, MB, BCh, BAO, MRCPI; Adele Deering; Maura Stewart, BSc; Dermot Cox, PhD; Brendan Foley, MD, MRCPI, FRCPC; Desmond Fitzgerald, MD, FRCPI

From the Centre for Cardiovascular Science (M.Q., A.D., M.S., D.C., D.F.), The Royal College of Surgeons, and St. James's Hospital (B.F.), Dublin, Ireland.

Correspondence to Dr Martin Quinn, The Centre for Cardiovascular Science, 123, St. Stephen's Green, Dublin 2, Ireland. E-mail mquinn{at}rcsi.ie

Background—Dosing of glycoprotein (GP) IIb/IIIa receptor antagonists is frequently based on the inhibition of platelet aggregation, which may be influenced by the agonist used or concurrent medications. Here we describe a monoclonal antibody-based technique to quantify total and ligand-occupied GPIIb/IIIa receptors.

Methods and Results—In vitro binding of monoclonal antibodies, LYP18 (Mab1) and 4F8 (Mab2), to the GPIIb/IIIa complex, was characterized using purified receptor and to platelets by flow cytometry. Patients undergoing coronary angioplasty received a single 20 mg dose of the oral GPIIb/IIIa antagonist, xemilofiban, or matching placebo, and antibody binding was compared with inhibition of platelet aggregation. Mab1 and Mab2 were bound to purified GPIIb/IIIa and to unoccupied, inactivated receptor on platelets. Mab2 identified the ß3 subunit, whereas Mab1 was complex-specific. Neither antibody interfered with the other's binding, suggesting that they identified distinct sites. Mab1 identified 53 300±5423 GPIIb/IIIa sites per platelet, whereas Mab2 identified 50 120±5066 sites per platelet. Mab1 binding was inhibited by abciximab in a dose dependent manner (IC₅₀, 0.85±0.1 µg/mL), whereas Mab2 binding was unaffected. In contrast, the 2 small molecular weight antagonists, SC-57101A (IC₅₀, 0.22±0.06 µmol/L) and eptifibatide (IC₅₀, 0.35±0.14 µmol/L) inhibited Mab2 but not Mab1 binding. In patients treated with xemilofiban, Mab1 binding was unaltered but Mab2 binding decreased from 37 930±2061 sites per platelet at baseline to 8318±870 sites per platelet 6 hours after dosing (P<0.0001). Platelet aggregation to adenosine diphosphate (20 µmol/L) fell to 3±3% of baseline in line with the inhibition of Mab2 binding (correlation coefficient 0.8, P<0.0001).

Conclusions—Mab1 and Mab2 bind to GPIIb/IIIa and are differentially displaced by abciximab and small molecular weight antagonists. These antibodies may be used to monitor receptor number and occupancy during administration of a GPIIb/IIIa antagonist.

Key Words: glycoproteins • platelet aggregation inhibitors • abciximab • thrombosis

This article has been cited by other articles:

				C. Patrono, C. Baigent, J. Hirsh, and G. Roth Antiplatelet Drugs: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition) Chest, June 1, 2008; 133(6_suppl): 199S - 233S. [Abstract] [Full Text] [PDF]

				C. Patrono, B. Coller, G. A. FitzGerald, J. Hirsh, and G. Roth Platelet-Active Drugs: The Relationships Among Dose, Effectiveness, and Side Effects: The Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy Chest, September 1, 2004; 126(3_suppl): 234S - 264S. [Abstract] [Full Text] [PDF]

				D. Larkin, D. Murphy, D. F. Reilly, M. Cahill, E. Sattler, P. Harriott, D. J. Cahill, and N. Moran ICln, a Novel Integrin {alpha}IIb{beta}3-Associated Protein, Functionally Regulates Platelet Activation J. Biol. Chem., June 25, 2004; 279(26): 27286 - 27293. [Abstract] [Full Text] [PDF]

				M. Schwarz, Y. Katagiri, M. Kotani, N. Bassler, C. Loeffler, C. Bode, and K. Peter Reversibility versus Persistence of GPIIb/IIIa Blocker-Induced Conformational Change of GPIIb/IIIa ({alpha}IIb{beta}3, CD41/CD61) J. Pharmacol. Exp. Ther., March 1, 2004; 308(3): 1002 - 1011. [Abstract] [Full Text] [PDF]

				D. E. Mager, M. A. Mascelli, N. S. Kleiman, D. J. Fitzgerald, and D. R. Abernethy Simultaneous Modeling of Abciximab Plasma Concentrations and ex Vivo Pharmacodynamics in Patients Undergoing Coronary Angioplasty J. Pharmacol. Exp. Ther., December 1, 2003; 307(3): 969 - 976. [Abstract] [Full Text] [PDF]

				D. Best, Y. A. Senis, G. E. Jarvis, H. J. Eagleton, D. J. Roberts, T. Saito, S. M. Jung, M. Moroi, P. Harrison, F. R. Green, et al. GPVI levels in platelets: relationship to platelet function at high shear Blood, October 15, 2003; 102(8): 2811 - 2818. [Abstract] [Full Text] [PDF]

				M. J. Quinn, T. V. Byzova, J. Qin, E. J. Topol, and E. F. Plow Integrin {alpha}IIb{beta}3 and Its Antagonism Arterioscler. Thromb. Vasc. Biol., June 1, 2003; 23(6): 945 - 952. [Abstract] [Full Text] [PDF]

				R. R. Hantgan, D. S. Lyles, T. C. Mallett, M. Rocco, C. Nagaswami, and J. W. Weisel Ligand Binding Promotes the Entropy-driven Oligomerization of Integrin alpha IIbbeta 3 J. Biol. Chem., January 24, 2003; 278(5): 3417 - 3426. [Abstract] [Full Text] [PDF]

				M. J. Quinn, R. T. Murphy, M. Dooley, J. B. Foley, and D. J. Fitzgerald Occupancy of the Internal and External Pools of Glycoprotein IIb/IIIa following Abciximab Bolus and Infusion J. Pharmacol. Exp. Ther., April 12, 2001; 297(2): 496 - 500. [Abstract] [Full Text]

				J. I. Osende, V. Fuster, E. I. Lev, D. Shimbo, U. Rauch, J. D. Marmur, M. Richard, D. Varon, and J. J. Badimon Testing Platelet Activation With a Shear-Dependent Platelet Function Test Versus Aggregation-Based Tests : Relevance for Monitoring Long-Term Glycoprotein IIb/IIIa Inhibition Circulation, March 20, 2001; 103(11): 1488 - 1491. [Abstract] [Full Text] [PDF]

				E. I. Lev, J. I. Osende, M. F. Richard, J. A. Robbins, J. A. Delfin, O. Rodriguez, S. K. Sharma, T. Jayasundera, J. J. Badimon, and J. D. Marmur Administration of abciximab to patients receiving tirofiban or eptifibatide: effect on platelet function J. Am. Coll. Cardiol., March 1, 2001; 37(3): 847 - 855. [Abstract] [Full Text] [PDF]

				R. Curtin and D.J. Fitzgerald A cold start for oral glycoprotein IIb/IIIa antagonists Eur. Heart J., December 2, 2000; 21(24): 1992 - 1994. [PDF]

				D. Cox, R. Smith, M. Quinn, P. Theroux, P. Crean, and D. J. Fitzgerald Evidence of platelet activation during treatment with a GPIIb/IIIa antagonist in patients presenting with acute coronary syndromes J. Am. Coll. Cardiol., November 1, 2000; 36(5): 1514 - 1519. [Abstract] [Full Text] [PDF]

				M. J. Quinn, D. Cox, J. B. Foley, and D. J. Fitzgerald Glycoprotein IIb/IIIa Receptor Number and Occupancy during Chronic Administration of an Oral Antagonist J. Pharmacol. Exp. Ther., November 1, 2000; 295(2): 670 - 676. [Abstract] [Full Text]

				S. R. Adderley and D. J. Fitzgerald Glycoprotein IIb/IIIa Antagonists Induce Apoptosis in Rat Cardiomyocytes by Caspase-3 Activation J. Biol. Chem., February 25, 2000; 275(8): 5760 - 5766. [Abstract] [Full Text] [PDF]

				J. B. Bussel, T. J. Kunicki, and A. D. Michelson Platelets: New Understanding of Platelet Glycoproteins and Their Role in Disease Hematology, January 1, 2000; 2000(1): 222 - 240. [Abstract] [Full Text] [PDF]