In Vitro Dose Response to Different GPIIb/IIIa-Antagonists: Inter-Laboratory Comparison of Various Platelet Function Tests

• Published in: Thrombosis research Vol. 102; no. 1; pp. 39 - 48
• Main Authors: Harder, S, Klinkhardt, U, Graff, J, Westrup, D, Kirchmaier, C.M, Glusa, E, Mascelli, M.A, Marciniak, S.J, Just, A, Lösche, W, Breddin, H.K
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Ltd 01.04.2001; Elsevier Science
• Subjects: Abciximab; Aggregometry; Antibodies, Monoclonal - pharmacology; Biological and medical sciences; Blood. Blood coagulation. Reticuloendothelial system; Clinical Laboratory Techniques - standards; Clinical Laboratory Techniques - statistics & numerical data; Dose-Response Relationship, Drug; Eptifibatide; Fibrinogen; Flow cytometry; Flow Cytometry - methods; Flow Cytometry - standards; GPIIb/IIIa-antagonists; Humans; Immunoglobulin Fab Fragments - pharmacology; Medical sciences; Microspheres; Observer Variation; Peptides - pharmacology; Pharmacology. Drug treatments; Platelet Aggregation - drug effects; Platelet Function Tests - instrumentation; Platelet Function Tests - standards; Platelet Function Tests - statistics & numerical data; Platelet Glycoprotein GPIIb-IIIa Complex - antagonists & inhibitors; Platelet Glycoprotein GPIIb-IIIa Complex - immunology; Platelets; Aggregometry; Flow cytometry; GPIIb/IIIa-antagonists; Platelets; Aggregation; Human; Glycoprotein IIbIIIa; Platelet; Abciximab; Antagonist; Biological activity; Eptifibatide; Antiplatelet agent
• ISSN: 0049-3848; 1879-2472
• DOI: 10.1016/S0049-3848(01)00223-7

Aims: The aim of this study was to assess the inter- and intra-laboratory variation of the concentration–response to the GPIIb/IIIa-antagonists abciximab and eptifibatide on platelet aggregometry and to compare results with flow cytometric tests as well as the rapid platelet function analyser (RPFA). Methods: In five different laboratory sites, blood from three to five healthy donors was spiked with abciximab or eptifibatide, followed by the assessment of: (1) aggregometry (anticoagulant: sodium citrate 3.18% or hirudin 5 μg/ml); (2) flow cytometry (fibrinogen binding or PAC1-expression), or (3) RPFA. Dose–response curves were established on the basis of a sigmoidal I max-model [ I=( I max* C γ )/(IC 50 γ + C γ )]. Results: For citrated blood, aggregation induced by 20 μM ADP was blocked up to 100% by both GPIIb/IIIa-antagonists, IC 50 values varied between 0.11–0.22 μg/ml for eptifibatide and 1.25–2.3 μg/ml for abciximab. I max of the response to 5 μg/ml collagen ranged from 46% to 100%, and IC 50 values varied between 0.28–0.34 μg/ml for eptifibatide and 2.3–3.8 μg/ml for abciximab. In hirudinized blood, IC 50 values for eptifibatide were 1.5- to 3-fold higher than those obtained with citrated plasma. Inhibition of PAC1-expression by abciximab (IC 50 0.84 μg/ml) showed results similar those of the RPFA (approx. 1.0 μg/ml); larger differences between PAC1 and RPFA results were observed for eptifibatide. Based on aggregometry, eptifibatide concentrations for 80% inhibition varied from 0.27 to 0.55 μg/ml, and were considerably less when the RPFA was taken as basis (0.15 or 0.22 μg/ml). A similar pattern was observed for abciximab. Conclusions: We found quite a low inter- and intra-laboratory variation in the in vitro pharmacodynamic characterization of GPIIb/IIIa-antagonists by aggregometry, making results of these tests obtained from different laboratories during clinical trials at least comparable. The RPFA exhibits a higher sensitivity to inhibitory GPIIb/IIIa-effects, in keeping with the “real” inhibition of the activated receptor (PAC1) as assessed with more elaborate flow cytometry.