ximelagatran and Blood-Coagulation-Disorders

Classic anticoagulant drugs, such as heparin and warfarin, are very effective. However, although in use for more than 50 years, they do have some clinical drawbacks. Heparin, now better termed unfractionated heparin, can only be used intravenously and its laboratory control is complicated. Warfarin is orally administered, but its therapeutic window is very narrow and patients need repeated laboratory tests. Moreover, both drugs are non-specific, as they inhibit the coagulation cascade at several steps. Pharmaceutic research has developed new drugs, some of which are already on the market, such as fondaparinux, a pentasaccharide that can interact with antithrombin, thus inhibiting factor Xa. This pentasaccharide is part of the parent heparin molecule and can be chemically synthesized, with the advantage of avoiding extractive compounds. Fondaparinux has a half-life compatible with once-a-day administration; modification of its structure (idraparinux) has led to more stable binding with antithrombin and to an increase in its half-life to allow once-a-week administration. Alternatives to oral anticoagulants have been developed following the study of some compounds like hirudin, which directly binds thrombin and blocks its catalytic site. One of these molecules, ximelagatran, is in advanced clinical development. Ximelagatran is converted into its active form, melagatran, in the circulation, and thrombin activity can be blocked by oral administration twice daily. There is no need for laboratory control and phase II and phase III studies are encouraging. The next few years should bring great changes to the treatment of patients with thromboembolic disorders.

Topics: Anticoagulants; Azetidines; Benzylamines; Blood Coagulation Disorders; Fondaparinux; Half-Life; Humans; Oligosaccharides; Polysaccharides

Patients with a recent myocardial infarction have an increased risk of recurrent ischaemic events. In the ESTEEM trial, the oral direct thrombin inhibitor ximelagatran reduced the risk of new ischaemic events when compared with placebo in aspirin treated post myocardial infarction patients. Ximelagatran persistently reduced markers of coagulation activity, i.e. prothrombin fragment 1 + 2 (F1 + 2) and D-dimer levels. The aim of this substudy was to evaluate the levels of these markers and activated thromboplastin time (APTT) in relation to new ischaemic events or bleeding.. In the substudy, 518 out of 1883 patients were included and within 14 days after a myocardial infarction randomized to ximelagatran or placebo for 6 months. The clinical endpoints death, myocardial infarction, severe recurrent ischaemia, ischaemic stroke, and bleeding were evaluated. The levels of F1 + 2, D-dimer, and APTT were analysed at randomization and in serial samples during the study. Ximelagatran treatment appeared to have a larger treatment effect in patients with F1 + 2 and D-dimer levels above the median at randomization with a reduction of ischaemic events from 18 to 9% (P = 0.03) for F1 + 2 and from 20 to 9% for D-dimer (P = 0.009). A reduction of D-dimer levels was found in 60% of the patients 1 week after randomization and these patients had less ischaemic events when compared with patients with unchanged or increased levels (P = 0.03) regardless of treatment. F1 + 2 and D-dimer levels were unrelated to bleeding risk. In the ximelagatran group, increased APTT was not related to ischaemic events but associated with a raised risk of bleeding.. A reduction of initially high coagulation activity, as measured by the D-dimer level, in patients with recent myocardial infarction identifies patients with a decreased risk of new ischaemic events, regardless whether the reduction occurs spontaneously or is induced by pharmacological means. Patients with higher initial coagulation activity seemed to benefit most from long-term treatment with ximelagatran.

Topics: Aged; Anticoagulants; Azetidines; Benzylamines; Blood Coagulation Disorders; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Humans; Male; Myocardial Infarction; Myocardial Ischemia; Partial Thromboplastin Time; Peptide Fragments; Protein Precursors; Prothrombin; Risk Factors; Thrombin