fibrinopeptide-a and bivalirudin

To characterize effects of bivalirudin compared with unfractionated heparin plus eptifibatide on inflammation, and thrombin generation and activity after percutaneous coronary intervention.. We measured the concentration in blood of fibrinopeptide A, prothrombin fragment 1+2, soluble CD40 ligand, interleukin 1 receptor antagonist, interleukin 6, and high sensitivity C-reactive protein in 63 patients treated with aspirin and clopidogrel and undergoing elective percutaneous coronary intervention, who were randomized to treatment with either bivalirudin (n=34) or unfractionated heparin plus eptifibatide (n=29).. Neither generation nor activity of thrombin increased 10 min after percutaneous coronary intervention in patients randomized to bivalirudin or unfractionated heparin plus eptifibatide. However, prothrombin fragment 1+2 increased modestly and comparably in both groups after 1 day. Inflammation, reflected by concentrations of interleukin 6 and high sensitivity C-reactive protein in blood, increased similarly 1 day after percutaneous coronary intervention in patients treated with either regimen. In a subset of patients (n=12 in each group) from whom blood was obtained 30 days after percutaneous coronary intervention, the concentration of high sensitivity C-reactive protein was lower in those who had been treated with bivalirudin (by 3.5 mg/l, P=0.002).. The early effects on inflammation and thrombin generation and activity are similar after treatment with bivalirudin alone compared with unfractionated heparin plus eptifibatide in patients treated with aspirin and clopidogrel who are undergoing percutaneous coronary intervention for symptoms of stable angina. The decreased concentration of high sensitivity C-reactive protein seen 30 days after percutaneous coronary intervention in those treated with bivalirudin is consistent with greater attenuation of inflammation that may have contributed to the trend toward reduced mortality 1 year later in those treated with bivalirudin in REPLACE-2.

Topics: Aged; Angioplasty, Balloon, Coronary; Anticoagulants; C-Reactive Protein; CD40 Ligand; Combined Modality Therapy; Coronary Artery Disease; Eptifibatide; Female; Fibrinopeptide A; Heparin; Hirudins; Humans; Interleukin-6; Male; Middle Aged; Peptide Fragments; Peptides; Platelet Aggregation Inhibitors; Protein Precursors; Prothrombin; Receptors, Interleukin-1; Recombinant Proteins; Thrombin; Treatment Outcome

Currently available antithrombotic therapy for unstable angina is unwieldy and occasionally ineffective. This study was designed to investigate the potential of Hirulog, a new synthetic specific antithrombin agent, for the management of this condition.. A total of 55 patients in the acute phase of unstable angina received intravenous Hirulog according to one of two protocols. In an acute dose-escalating study, 0.02, 0.05, 0.1, 0.25, and 0.5 mg.kg-1 x h-1, each for 30 minutes, were infused in 15 patients. Prolongation of activated partial thromboplastin time (aPTT) (r = .95), fibrinopeptide A inhibition (r = .96), and Hirulog plasma levels (r = .91) correlated closely with the dose infused, with significant changes compared with baseline appearing at doses of 0.25 mg.kg-1 x h-1 and higher. The purposes of the second protocol were to determine whether the anticoagulant and antithrombotic effects of the drug were sustained during a 72-hour infusion and to assess whether such treatment prevented the complications of unstable angina. Based on the initial study, we planned to give a dose of 0.25 mg.kg-1 x h-1 to each patient until 2 patients failed therapy, then successively higher doses until a 95% success rate was achieved or adverse effects intervened, increasing the dose after two failures had occurred at each level. Five patients received the 0.25-mg.kg-1 x h-1 dose and 14 the 0.5-mg.kg-1 x h-1 dose before two failures occurred. Failure was observed in only one of 21 patients at the dose of 1 mg.kg-1 x h-1. aPTT (+/- SEM) levels increased to 62 +/- 5, 76 +/- 2, and 98 +/- 3 seconds at the three doses, with minimal intraindividual variation, and Hirulog plasma levels to 1050, 2100, and 4200 mg/mL, respectively. Fibrinopeptide A plasma levels decreased at all doses but more consistently at the dose of 1 mg.kg-1 x h-1. The overall clinical success rate was 87.5%: 60% (3/5) at the low dose, 86% (12/14) at the intermediate dose, and 95% (20/21) at the high dose. No deaths, myocardial infarctions, or bleeding complications occurred.. In unstable angina patients, Hirulog infusions quickly and reproducibly yield stable, dose-dependent anticoagulant and antithrombotic effects with a favorable clinical efficacy profile.

Topics: Angina, Unstable; Dose-Response Relationship, Drug; Female; Fibrinopeptide A; Hirudin Therapy; Hirudins; Humans; Male; Middle Aged; Partial Thromboplastin Time; Peptide Fragments; Recombinant Proteins; Thrombin

To determine in vivo functional roles for thrombin's structural domains, we have compared the relative antithrombotic and antihemostatic effects of (i) catalytic-site antithrombin peptide, D-Phe-Pro-Arg; (ii) exosite antithrombin peptide, the C-terminal tyrosine-sulfated dodecapeptide of hirudin; and (iii) bifunctional antithrombin peptide, a 20-mer peptide combining catalytic-site antithrombin peptide and exosite antithrombin peptide with a polyglycyl linker. All three peptides inhibited thrombin-mediated platelet aggregation and fibrin formation in vitro. In vivo thrombus formation was measured in real time as 111In-labeled platelet deposition and 125I-labeled fibrin accumulation on thrombogenic segments incorporated into chronic exteriorized arteriovenous access shunts in baboons. Under low flow conditions, the continuous infusion of peptides reduced thrombus formation onto collagen-coated tubing by half at doses (ID50) and corresponding concentrations (IC50) of 800 nmol per kg per min and 400 nmol/ml for catalytic-site antithrombin peptide, greater than 1250 nmol per kg per min and greater than 1500 mumol/ml for exosite antithrombin peptide, and 50 nmol per kg per min and 25 nmol/ml for bifunctional antithrombin peptide. Under arterial flow conditions, systemically administered bifunctional antithrombin peptide decreased thrombus formation in a dose-dependent manner for segments of collagen-coated tubing or prosthetic vascular graft ID50 and IC50 values of 120 nmol per kg per min and 15 nmol/ml; this dose also produced intermediate inhibition of hemostatic function [bleeding time, 21 +/- 3 min vs. 4.5 +/- 0.5 min (baseline values); P less than 0.001; activated partial thromboplastin time, 285 +/- 13 sec vs. 31 +/- 3 sec (baseline), P less than 0.001]. In contrast, thrombus formation onto segments of endarterectomized aorta was potently decreased by bifunctional antithrombin peptide with an ID50 value of 2.4 nmol per kg per min and an IC50 value of 0.75 nmol/ml, a systemic dose that failed to affect hemostasis. Thus, inhibiting both thrombin's catalytic and exosite domains increases antithrombotic potency by several orders of magnitude over the inhibition of either domain alone, particularly at sites of deep arterial injury.

Topics: Amino Acid Sequence; Animals; beta-Thromboglobulin; Fibrinolytic Agents; Fibrinopeptide A; Hirudins; Male; Molecular Sequence Data; Papio; Peptide Fragments; Peptides; Platelet Factor 4; Recombinant Proteins; Thrombin

Hirudin and hirulog-1 [D-Phe-Pro-Arg-Pro-[Gly]4-desulphohirudin-(54-65)] abrogate the enzyme activities of alpha-thrombin by binding the enzyme simultaneously at its catalytic centre and fibrin(ogen)-recognition exosite. In contrast, hirugen [hirudin-(54-65)] binds alpha-thrombin solely at the fibrin(ogen)-recognition exosite, and competitively inhibits fibrinopeptide A release. To investigate the extent to which the fibrin(ogen)-recognition exosite is involved when alpha-thrombin catalyses the amplification reactions of coagulation, we compared the abilities of hirudin, hirulog-1 and hirugen to inhibit simultaneously Factor X, Factor V and prothrombin activation. Whereas 0.1 microM-hirudin and 0.1 microM-hirulog-1 (i.e. less than 10% of the concentration of prothrombin in plasma) inhibited Factor X, Factor V and prothrombin activation, 10 microM was the minimum concentration of hirugen to achieve a similar anticoagulant action. Concentrations of hirudin and hirulog-1 equimolar to and 5 times greater than those of alpha-thrombin respectively abrogated Factor V activation by exogenous alpha-thrombin. In contrast, a 500-fold molar excess of hirugen could not. The inability of hirugen to inhibit the activation of the three clotting factors effectively suggests that the fibrin(ogen)-recognition exosite does not play a mandatory role when thrombin activates Factor V.

Topics: Amino Acid Sequence; Animals; Binding Sites; Binding, Competitive; Blood Coagulation; Factor V; Factor X; Fibrinopeptide A; Hirudins; Humans; Molecular Sequence Data; Peptide Fragments; Prothrombin; Rabbits; Recombinant Proteins; Thrombin