<p>Myocardial infarction (MI) is often caused by a disruption of an atherosclerotic plaque with activation of coagulation, platelets and inflammation. The aims were; to investigate whether the oral direct thrombin inhibitor, ximelagatran affected markers for coagulation, platelet and inflammation in a patient cohort with recent MI and if the coagulation markers could identify patients with increased risk of new ischemic events; to evaluate some of the mechanisms involved in formation of platelet-monocyte aggregates (PMAs). </p><p>In a biomarker substudy patients with recent MI were randomized to 24-60 mg of ximelagatran or placebo for six months. There was a persistent dose-independent reduction of coagulation markers (F1+2, D-dimer) by ximelagatran treatment. 60 % reduced their D-dimer levels after one week and that group had less ischemic events during treatment. There was an early increase of the platelet activation marker and ximelagatran in higher doses attenuated these increased levels. Both in vivo and in vitro the direct thrombin inhibitor diminished procoagulant activity and tissue factor (TF) presenting microparticles. In contrast, the inflammatory markers increased after six months of ximelagatran treatment. The PMA-levels were elevated for long-term after MI. In vitro thrombin inhibition diminished formation of PMAs. Formation of PMAs in stimulated whole blood was P-selectin dependent and induced TF expression through phosphorylation of the Src-family member Lyn in monocytes.</p><p>Addition of an oral direct thrombin inhibitor reduces coagulation and platelet activation markers for long-term after a MI together with reduced procoagulant activity which may contribute to the clinical benefit of the drug. Early reduction of D-dimer levels seems to be suitable to identify patients with reduced risk of new ischemic events independent of antithrombotic treatment. Circulating PMAs persist after a MI connecting coagulation to inflammation. Within these aggregates P-selectin induces TF, the main initiator of coagulation, partly through phosphorylation of Lyn.</p>

The occurrence of thrombosis in several pathophysiological conditions creates a huge need for anticoagulation therapy. Thrombin and factor Xa have been prime targets for regulation of clotting through the direct and indirect mechanism of inhibition. This work investigates chemo-enzymatically prepared oligomers of 4-hydroxycinnamic acids (DHPs) as potential anticoagulants. Oligomers were prepared through peroxidase-catalyzed oxidative coupling of 4-hydroxycinnamic acids. The products resulting from this reaction are called CDs, FDs and SDs. Structurally, these sulfated DHPs are unique and do not resemble any of the anticoagulants known in the literature.DHP oligomers were found to increase clotting times at concentrations comparable to heparin. Studies in blood and plasma show that DHPs possess an anticoagulation profile similar to enoxaparin. To understand the mechanism of action of DHPs, we studied the inhibition of thrombin, FXa, FIXa, and FVIIa in the presence and absence of antithrombin. CDs and FDs display a preference for direct inhibition of thrombin and FXa, and exhibit a high level of specificity over FIXa and FVIIa. In the presence of AT, CDs and FDs displayed weaker inhibition of FXa and thrombin suggesting that binding to AT is a competitive side reaction. SDs exhibited potent inhibition of FXa and thrombin in the absence of antithrombin, but was inactive against FIXa and FVIIa representing the best selectivity among the DHPs. For SDs, inhibition of all the pro-coagulant enzymes favored the antithrombin dependent pathway. Binding studies were performed to determine how CDs directly inhibits thrombin. Competitive binding studies suggest that CDs interacts with exosite II and disrupts the catalytic triad of thrombin. These results indicate that the preferred mechanism of CDs action is exosite II mediated allosteric disruption of thrombin. CDs appears to be the first exosite II mediated DTI and this represents a novel mechanism of inhibitor function. The inhibition characteristics of DHPs are unique and radically different in structure from all the current clinically used anticoagulants. To the best of our knowledge this dual mechanism of anticoagulation and unique binding mode has not been described as yet in literature and represents a novel strategy that our laboratory has discovered.

<p>In patients with unstable coronary artery disease, this study evaluated the degree of inflammation and coagulation activity, relations to myocardial cell damage, prognosis, and influences of randomisation to 72 h infusion with three different doses of inogatran, a direct thrombin inhibitor (n=904), or unfractionated heparin (n=305). </p><p>Anticoagulant treatment effects were evaluated with aPT time. In inogatran treated patients with aPT times ≥ 44 s (median), the 7-days event rate - death, myocardial infarction or refractory angina – was 11.6 %, compared to 6.6 % with aPT times < 44 s (p=0.01). Higher aPT times was related to improved outcome during heparin treatment.</p><p>Markers of inflammation, i.e. fibrinogen and C-reactive protein (CRP), and coagulation, i.e. prothrombin fragment 1+2 (F1+2), thrombin-antithrombin complex (TAT), soluble fibrin (SF) and D-dimer were analysed in serial samples (n=320). High fibrinogen, F1+2 and D-dimer levels persisted at 30 days. Patients with myocardial damage, detected by elevated troponin, had higher levels of all markers except TAT.</p><p>Ischemic events occurred at 30 days in 17 % of patients with high (pre-treatment top tertile) and 8.5 % of patients with lower fibrinogen levels (p=0.03), while high CRP levels only were related to increased mortality. At 30 days, patients with high compared to low pre-treatment levels of TAT or SF had 40 % lower event rate. Patients with early decreased compared to raised F1+2 or TAT levels during treatment had 50 % lower 30-days event rate (p<0.05). </p><p>Conclusions: The aPT time is an inappropriate indicator of antithrombotic efficacy. The raise in fibrinogen in the acute phase is sustained, and indicates risk of thrombosis and new ischemic events. The pronounced CRP elevation is transient, but associated with increased mortality. Higher coagulation activity may identify patients with a thrombotic condition as the major cause of instability, who are best responders to anticoagulant therapy. However, reactivation of coagulation activity with raised risk of ischemic events is a concern at cessation of treatment.</p>

Myocardial infarction (MI) is often caused by a disruption of an atherosclerotic plaque with activation of coagulation, platelets and inflammation. The aims were; to investigate whether the oral direct thrombin inhibitor, ximelagatran affected markers for coagulation, platelet and inflammation in a patient cohort with recent MI and if the coagulation markers could identify patients with increased risk of new ischemic events; to evaluate some of the mechanisms involved in formation of platelet-monocyte aggregates (PMAs). In a biomarker substudy patients with recent MI were randomized to 24-60 mg of ximelagatran or placebo for six months. There was a persistent dose-independent reduction of coagulation markers (F1+2, D-dimer) by ximelagatran treatment. 60 % reduced their D-dimer levels after one week and that group had less ischemic events during treatment. There was an early increase of the platelet activation marker and ximelagatran in higher doses attenuated these increased levels. Both in vivo and in vitro the direct thrombin inhibitor diminished procoagulant activity and tissue factor (TF) presenting microparticles. In contrast, the inflammatory markers increased after six months of ximelagatran treatment. The PMA-levels were elevated for long-term after MI. In vitro thrombin inhibition diminished formation of PMAs. Formation of PMAs in stimulated whole blood was P-selectin dependent and induced TF expression through phosphorylation of the Src-family member Lyn in monocytes. Addition of an oral direct thrombin inhibitor reduces coagulation and platelet activation markers for long-term after a MI together with reduced procoagulant activity which may contribute to the clinical benefit of the drug. Early reduction of D-dimer levels seems to be suitable to identify patients with reduced risk of new ischemic events independent of antithrombotic treatment. Circulating PMAs persist after a MI connecting coagulation to inflammation. Within these aggregates P-selectin induces TF, the main initiator of coagulation, partly through phosphorylation of Lyn.

In patients with unstable coronary artery disease, this study evaluated the degree of inflammation and coagulation activity, relations to myocardial cell damage, prognosis, and influences of randomisation to 72 h infusion with three different doses of inogatran, a direct thrombin inhibitor (n=904), or unfractionated heparin (n=305). Anticoagulant treatment effects were evaluated with aPT time. In inogatran treated patients with aPT times ≥ 44 s (median), the 7-days event rate - death, myocardial infarction or refractory angina – was 11.6 %, compared to 6.6 % with aPT times &lt; 44 s (p=0.01). Higher aPT times was related to improved outcome during heparin treatment. Markers of inflammation, i.e. fibrinogen and C-reactive protein (CRP), and coagulation, i.e. prothrombin fragment 1+2 (F1+2), thrombin-antithrombin complex (TAT), soluble fibrin (SF) and D-dimer were analysed in serial samples (n=320). High fibrinogen, F1+2 and D-dimer levels persisted at 30 days. Patients with myocardial damage, detected by elevated troponin, had higher levels of all markers except TAT. Ischemic events occurred at 30 days in 17 % of patients with high (pre-treatment top tertile) and 8.5 % of patients with lower fibrinogen levels (p=0.03), while high CRP levels only were related to increased mortality. At 30 days, patients with high compared to low pre-treatment levels of TAT or SF had 40 % lower event rate. Patients with early decreased compared to raised F1+2 or TAT levels during treatment had 50 % lower 30-days event rate (p&lt;0.05). Conclusions: The aPT time is an inappropriate indicator of antithrombotic efficacy. The raise in fibrinogen in the acute phase is sustained, and indicates risk of thrombosis and new ischemic events. The pronounced CRP elevation is transient, but associated with increased mortality. Higher coagulation activity may identify patients with a thrombotic condition as the major cause of instability, who are best responders to anticoagulant therapy. However, reactivation of coagulation activity with raised risk of ischemic events is a concern at cessation of treatment.