piperidines and inogatran

To obtain more reliable and precise estimates of the effect of direct thrombin inhibitors in the management of acute coronary syndromes, including patients undergoing percutaneous coronary intervention, we undertook a meta-analysis based on individual patients' data from randomised trials comparing a direct thrombin inhibitor (hirudin, bivalirudin, argatroban, efegatran, or inogatran) with heparin.. We included trials that involved at least 200 patients. The primary efficacy outcome was death or myocardial infarction, and the primary safety outcome was major bleeding. Data from individual trials were combined by use of a modified Mantel-Haenszel method.. In 11 randomised trials, 35,970 patients were assigned up to 7 days' treatment with a direct thrombin inhibitor or heparin and followed up for at least 30 days. Compared with heparin, direct thrombin inhibitors were associated with a lower risk of death or myocardial infarction at the end of treatment (4.3% vs 5.1%; odds ratio 0.85 [95% CI 0.77-0.94]; p=0.001) and at 30 days (7.4% vs 8.2%; 0.91 [0.84-0.99]; p=0.02). This was due primarily to a reduction in myocardial infarctions (2.8% vs 3.5%; 0.80 [0.71-0.90]; p<0.001) with no apparent effect on deaths (1.9% vs 2.0%; 0.97 [0.83-1.13]; p=0.69). Subgroup analyses suggested a benefit of direct thrombin inhibitors on death or myocardial infarction in trials of both acute coronary syndromes and percutaneous coronary interventions. A reduction in death or myocardial infarction was seen with hirudin and bivalirudin but not with univalent agents. Compared with heparin, there was an increased risk of major bleeding with hirudin, but a reduction with bivalirudin. There was no excess in intracranial haemorrhage with direct thrombin inhibitors.. Direct thrombin inhibitors are superior to heparin for the prevention of death or myocardial infarction in patients with acute coronary syndromes. This information should prompt further clinical development of direct thrombin inhibitors for the management of arterial thrombosis.

Topics: Angina, Unstable; Antithrombins; Arginine; Glycine; Heparin; Hirudin Therapy; Hirudins; Humans; Myocardial Infarction; Oligopeptides; Peptide Fragments; Pipecolic Acids; Piperidines; Randomized Controlled Trials as Topic; Recombinant Proteins; Sulfonamides; Survival Rate; Thrombin

In addition to its pivotal role in blood coagulation, thrombin is one of the most important agonists for platelet recruitment and aggregation. Thrombin inhibitors impede thrombin-induced platelet aggregation but have no effect on aggregation induced by other agonists. A review is presented of selective thrombin inhibitors now in clinical investigation, some of which are also orally active.

Topics: Administration, Oral; Adult; Animals; Antithrombins; Arginine; Blood Platelets; Boron Compounds; Clinical Trials as Topic; Dogs; Drug Evaluation, Preclinical; Glycine; Hirudin Therapy; Hirudins; Humans; Naphthalenes; Oligopeptides; Peptide Fragments; Pipecolic Acids; Piperidines; Recombinant Proteins; Sulfonamides; Thrombin

Unstable coronary artery disease is in most cases associated with plaque rupture, activation of the coagulation system and subsequent intracoronary thrombus formation which may cause myocardial cell damage. The aim of the present analysis was to assess the relation between troponin T, markers of coagulation activity, i.e. prothrombin fragment 1+2, thrombin-antithrombin complex, soluble fibrin and D-dimer, and ischemic events, i.e. death, myocardial (re-)infarction or refractory angina. 320 patients with unstable coronary artery disease were randomized to 72 hours infusion with inogatran, a low molecular weight direct thrombin inhibitor, or unfractionated heparin. Patients with elevated troponin levels had higher levels of prothrombin fragment 1+2, soluble fibrin and D-dimer before, during, and at 24 hours after cessation of anticoagulant treatment. These troponin-positive patients tended to have worse short-term clinical outcome, without relation to markers of coagulation activity. Troponin-negative patients with unchanged or early increased thrombin generation during treatment had a cluster of ischemic events within 24 hours after cessation of the study drug. The 30-day ischemic event rate was 19 % in troponin-negative patients with unchanged or early increased prothrombin fragment 1+2, and 5.7 % in patients with decreased prothrombin fragment 1+2, p=0.006, and similarly 15 % in troponin-negative patients with unchanged or early increased thrombin-antithrombin complex and 4.5 % in patients with decreased thrombin-antithrombin complex, p=0.02. In conclusion, in unstable coronary artery disease a troponin elevation indicates higher risk and higher coagulation activity. However, among the troponin negative patients, with a lower risk and lower coagulation activity, a part of the patients seem to be non-responders to treatment with a thrombin inhibitor expressed as unchanged or raised coagulation activity and a raised risk of ischemic events early after cessation of treatment.

Topics: Adult; Aged; Biomarkers; Blood Coagulation; Coronary Artery Disease; Glycine; Heparin; Humans; Middle Aged; Myocardial Ischemia; Piperidines; Predictive Value of Tests; Risk Factors; Thrombin; Thrombophilia; Treatment Failure; Treatment Outcome; Troponin T

Unstable coronary artery disease (CAD) is a multifactorial disease involving both thrombotic and inflammatory processes. We have assessed the time-course and the influence of thrombin inhibitors on changes in fibrinogen and C-reactive protein levels, and their relation to myocardial ischaemia in unstable CAD.. Three hundred and twenty patients were randomized to 72 h infusion with three different doses of inogatran, a direct thrombin inhibitor, or unfractionated heparin. There were no significant differences between the treatment groups in fibrinogen or C-reactive protein levels. Overall, the fibrinogen levels were significantly increased in the first 24-96 h and still elevated at 30 days. The C-reactive protein levels showed a more pronounced increase during the first 24-96 h, but then markedly decreased over 30 days. Troponin-positive compared to troponin-negative patients had higher fibrinogen and C-reactive protein levels up to 96 h, although there was an increase compared to pre-treatment levels in both groups. A high fibrinogen level (pre-treatment top tertile) was associated with an increased rate of death or myocardial (re-)infarction at 30 days, 13% vs 5.6%, P=0.03, and increased long-term mortality. A high C-reactive protein level was related to increased 30-day mortality, 4% vs 0%, P=0.01.. Myocardial cell injury was related to a high degree of inflammation, only some of which is an acutephase response due to tissue damage. The rise in fibrinogen was sustained, which might reflect low grade inflammation with long-term risk of thrombosis. The transient elevation of C-reactive protein levels might indicate a propensity to a pronounced inflammatory response and is associated with increased mortality.

Topics: Adult; Aged; Aged, 80 and over; Antithrombins; C-Reactive Protein; Coronary Disease; Female; Fibrinogen; Follow-Up Studies; Glycine; Humans; Male; Middle Aged; Myocardial Infarction; Myocarditis; Piperidines; Survival Analysis; Troponin T

In the current study, we investigated molecular markers of coagulation activity, ie, prothrombin fragment 1+2 (F1+2), thrombin-antithrombin (TAT) complex, soluble fibrin (SF), and D-dimer, and their relation to death, myocardial infarction, and refractory angina during and after anticoagulant treatment in unstable coronary artery disease. Patients with unstable coronary artery disease (N=320) were randomized to a 72-hour infusion with either inogatran, a low-molecular-mass direct thrombin inhibitor, or unfractionated heparin. During the 30-day follow-up, a 40% lower event rate was seen in patients with high compared with low baseline levels of TAT or SF. High baseline levels of coagulation activity were correlated with a larger decrease during treatment. Patients with decreased compared with raised F1+2 or TAT levels after 6 hours of treatment had a 50% lower event rate at 30 days (F1+2, P=0.04; TAT, P=0.02). At the cessation of antithrombin treatment, there was a clustering of cardiac events that tended to be related to a rise in the levels of TAT and the other markers. During long-term follow-up (median, 29 months), there was a relation between higher baseline levels of D-dimer (P=0.003) and increased mortality. High baseline levels of molecular markers of coagulation activity might identify patients with a thrombotic condition (as the major cause of instability) who are good responders to anticoagulant therapy, with a larger decrease in coagulation activity during treatment and a decreased risk of ischemic events. However, this early benefit is lost during long-term follow-up when high baseline levels of coagulation activity are associated with a raised risk of early reactivation and increased mortality.

Topics: Adult; Aged; Angina, Unstable; Anticoagulants; Antithrombin III; Antithrombins; Biomarkers; Blood Coagulation; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Follow-Up Studies; Glycine; Heparin; Humans; Kinetics; Male; Middle Aged; Myocardial Infarction; Peptide Fragments; Peptide Hydrolases; Piperidines; Prothrombin; Random Allocation; Treatment Outcome

Patients with unstable coronary syndromes are a heterogeneous group with varying degrees of ischemia and prognosis. The present study compares the prognostic value of a standard electrocardiogram (ECG) obtained at admission to the hospital with the information from 24-hour continuous electrocardiographic monitoring obtained immediately after admission. The admission ECGs and 24 hours of vectorcardiographic (VCG) monitoring from 308 patients admitted with unstable coronary artery disease were analyzed centrally regarding standard electrocardiographic ST-T changes, ST-vector magnitude (ST-VM), and ST change vector magnitude episodes. End points were death, acute myocardial infarction, and refractory angina pectoris within a 30-day follow-up period. ST-VM episodes (> or = 50 microV for > or = 1 minute) during VCG monitoring was the only independent predictor of death or acute myocardial infarction by multivariate analysis. ST-VM episodes during vectorcardiography was associated with a relative risk of 12.7 for having a cardiac event, hypertension was associated with a relative risk of 1.7, and ST depression on the admission ECG was associated with a relative risk of 5.7. Patients with ST depression at admission had an event rate (death or acute myocardial infarction) of 17% at 30-day follow-up. Patients without ST depression could further be risk stratified by 24 hours of VCG monitoring into a subgroup with ST-VM episodes at similar (8%) risk and a subgroup without ST-VM episodes at low (1%) risk (p = 0.00005). Continuous VCG monitoring provides important information for evaluating patients with unstable coronary artery disease. It is recommended that patients not initially estimated at high risk based on the admission ECG are referred for 24 hours of VCG monitoring for further risk stratification.

Topics: Aged; Angina Pectoris; Angina, Unstable; Anticoagulants; Antithrombins; Coronary Disease; Electrocardiography; Electrocardiography, Ambulatory; Female; Follow-Up Studies; Glycine; Heparin; Humans; Hypertension; Male; Multivariate Analysis; Myocardial Infarction; Myocardial Ischemia; Patient Admission; Piperidines; Prognosis; Recurrence; Risk Assessment; Risk Factors; Survival Rate; Vectorcardiography

A multicentre study permits rapid recruitment of a large number of patients. However, there is a risk of heterogeneities in end-point evaluations, as complex definitions of criteria are interpreted by several local investigators from different hospitals. Reports discussing end-point evaluation are sparse. The TRIM trial was a multicentre trial of a thrombin inhibitor in patients with unstable angina or non-Q myocardial infarction. In this study, an independent end-point committee evaluated all the reported events of death, acute myocardial infarction and refractory angina pectoris in order to obtain uniform judgements of major end-points.. To describe the work of the end-point committee, to analyse its possible effect on the final study results and to discuss the impact on the design of future trials.. The end-point committee consisted of four members, one from each participating country. After the data were processed by the study monitors, completed case record forms and patient files for patients with reported end-points were mailed to the national member of the end-point committee for judgement. The end-point committee met regularly and made final decisions about the end-points. The work of the end-point committee was documented on a separate case record form.. The end-point committee assessed 246 events of death, acute myocardial infarction and refractory angina pectoris in 187 of the 1209 patients (15.5%) in the TRIM trial. Misinterpretation of the index event, an inclusion myocardial infarction, as an early cardiac event was found in 12 patients. After end-point committee judgements, the number of patients with acute myocardial infarction or refractory angina pectoris during 30 days of follow-up was reduced from 177 to 153 (13. 6% reduction). The classification of events was changed in 53 of 187 patients (28.3%) with death, acute myocardial infarction or refractory angina pectoris. The data assessed by the safety committee was significantly different from the final database after end-point committee judgements.. The end-point committee corrected misinterpretations in such a high proportion of cases that the final results differed significantly from the preliminary results delivered to the safety committee. End-point judgements by an end-point committee should be performed in multicentre clinical trials to improve the quality and reliability of study results.

Topics: Anticoagulants; Antithrombins; Coronary Disease; Data Collection; Double-Blind Method; Glycine; Heparin; Humans; Multicenter Studies as Topic; Outcome Assessment, Health Care; Piperidines; Randomized Controlled Trials as Topic; Survival Analysis

We investigated whether the addition of 24 h of continuous vectorcardiography ST segment monitoring (cVST) for an early (within 24 h of the latest episode of angina) determination of cardiac troponin T (cTnT) could provide additional prognostic information in patients with unstable coronary artery disease (UCAD), i.e., unstable angina and non-Q wave myocardial infarction.. Determination of cTnT at admission and cVST are individually reported to be valuable techniques for the risk assessment of patients with UCAD.. Two hundred and thirty-two patients suspected of UCAD were studied. Patients were followed for 30 days, and the occurrence of cardiac death or acute myocardial infarction (AMI) were registered.. One ST segment episode or more (relative risk [RR] 7.43, p = 0.012), a cTnT level > or = 0.20 microg/liter (RR 3.85, p = 0.036) or prestudy medication with calcium antagonists (RR 3.31, p = 0.041) were found to carry independent prognostic information after multivariate analysis of potential risk variables. By combining a cTnT determination and subsequent cVST for 24 h, subgroups of patients at high (25.8%) (n = 31), intermediate (3.1%) (n = 65) and low risk (1.7%) (n = 117) of death or AMI could be identified.. Twenty-four hours of cVST provides additional prognostic information to that of an early cTnT determination in patients suspected of having UCAD. The combination of biochemical and electrocardiographic methods provides powerful and accurate risk stratification in UCAD.

Topics: Adult; Aged; Aged, 80 and over; Angina, Unstable; Antithrombins; Coronary Disease; Death, Sudden, Cardiac; Dose-Response Relationship, Drug; Double-Blind Method; Drug Administration Schedule; Electrocardiography, Ambulatory; Female; Glycine; Humans; Male; Middle Aged; Myocardial Infarction; Patient Admission; Piperidines; Prognosis; Prospective Studies; Risk Assessment; Troponin T; Vectorcardiography

This study evaluated a novel specific thrombin inhibitor, inogatran, in comparison with unfractionated heparin, with regard to markers for coagulation activity in patients with unstable coronary artery disease.. In the Thrombin Inhibition In Myocardial Ischaemia (TRIM) study patients were randomized to one of three different doses of inogatran or to unfractionated heparin, given intravenously over 72 h. In a subpopulation of 320 patients, markers for coagulation activity were measured at baseline, during and after the study infusion. Prothrombin fragment 1 + 2, indicating thrombin generation, decreased in the low, medium and high dose inogatran groups and in the heparin group during the first 6 h of treatment by 12%, 15%, 21% and 26%, respectively. From 6 h to 72 h after the start of infusion the levels changed by -7%, -6%, -4% and +34%, respectively. The increase in the heparin group continued after the infusion was stopped. Thrombin-antithrombin complex, also indicating thrombin generation, decreased by 0%, 2%, 18% and 22%, respectively, during the first 6 h of treatment. During the same period soluble fibrin, an intermediate in fibrin formation, increased both in the low and medium inogatran group by 9%, while a decrease by 4% and 18%, respectively, was seen in the high dose inogatran group and in the heparin group. Fibrin dissolution, as measured by fibrin D-dimer, decreased during the first 24 h of treatment by 20%, 18%, 18% and 20%, respectively. The first 24 h after discontinuation of infusion, fibrin D-dimer increased by 6%, 23%, 25% and 44%, respectively. After 72 h, at the end of infusion, patients treated with inogatran, to a larger extent than those given heparin, had suffered from death, myocardial infarction or refractory angina pectoris. After 7 days this trend was less marked.. The more pronounced decrease in thrombin generation and fibrin turnover during the first 6 h of infusion, and the later increase in thrombin generation and fibrin turnover, in the heparin group, as compared to the inogatran groups, may be related to the lower clinical event rate during infusion with heparin compared with inogatran and the recurrence of ischaemic events, early after cessation of heparin infusion.

Topics: Aged; Angina, Unstable; Antithrombins; Biomarkers; Electrocardiography; Enzyme-Linked Immunosorbent Assay; Female; Fibrin; Fibrinolytic Agents; Follow-Up Studies; Glycine; Heparin; Humans; Infusions, Intravenous; Male; Middle Aged; Partial Thromboplastin Time; Piperidines; Prothrombin; Thrombin; Treatment Outcome

Aims Direct thrombin inhibitors have failed to prove superiority over unfractionated heparin in several clinical trials of unstable coronary artery disease. We have investigated the relationship between activated partial thromboplastin time levels and adverse clinical events, i.e. death, myocardial (re-)infarction or refractory angina. Methods and Results One thousand two hundred and nine patients with unstable coronary artery disease were randomized to 72 h infusion with inogatran, a low molecular mass direct thrombin inhibitor, or unfractionated heparin. During 30 days follow-up there was no significant difference between inogatran and unfractionated heparin treatment as regards clinical outcome. 11.6% of the 464 inogatran treated patients with activated partial thromboplastin time above the median at 6 h (44 s) had a clinical event in 7 days, and 6.6% of the 423 patients with activated partial thromboplastin time below the median (P=0.01). After 30 days the event rate was still 41% higher in the inogatran patients with activated partial thromboplastin time above the median (P=0.06). Activated partial thromboplastin time in quartiles indicated a direct relationship between higher activated partial thromboplastin time and worse outcome. In contrast, during heparin infusion there was a trend for improved clinical outcome with activated partial thromboplastin time above the median, but this benefit was lost after cessation of treatment.. Higher activated partial thromboplastin time levels during inogatran treatment are related to increased risk of death, myocardial infarction or refractory angina. This might, at least in part, be explained by differences in anticoagulant mechanisms between direct thrombin inhibitors and heparin, and further emphasizes the poorly defined optimal activated partial thromboplastin time range during treatment with direct thrombin inhibitors in unstable coronary artery disease.

Topics: Adult; Aged; Aged, 80 and over; Angina, Unstable; Antithrombins; Cause of Death; Coronary Disease; Dose-Response Relationship, Drug; Female; Glycine; Heparin; Humans; Infusions, Intravenous; Male; Middle Aged; Myocardial Infarction; Partial Thromboplastin Time; Piperidines; Survival Rate; Thrombin; Treatment Outcome

Thrombin has been suggested as one of the main pharmacologic targets in unstable coronary syndromes. Electrocardiographic signs of ischemia during continuous monitoring convey prognostic information in these patients. This study assessed the anti-ischemic and clinical effects of the novel low-molecular weight thrombin inhibitor inogatran in patients with unstable angina and non-Q-wave infarction without persistent ST-segment elevation on hospital admission. Within 24 hours of the last episode of chest pain, 324 patients were randomized to 72 hours of treatment with inogatran or heparin. Continuous ST-segment analysis with computerized vectorcardiography was used to monitor ischemia for 24 hours. The occurrence of cardiac events during the first 7 days were studied and compared with ischemic episodes during the initial 24 hours. The heparin-treated patients had less episodes of ischemia (ST vector magnitude [ST-VM]: 1 +/- 2.6 vs 2 +/- 4.5, p < 0.001 and ST change vector magnitude [STC-VM]: 3 +/- 4.7 vs 6 +/- 7.6, p < 0.001) than the patients receiving inogatran. This was paralleled by a lower incidence of the combined end point of death, nonfatal infarction, refractory or recurrent angina during the first 7 days for the heparin-treated patients (35%) compared with the inogatran-treated patients (50%) (p < 0.05). Patients who had episodes of ischemia in spite of anti-ischemic therapy were at increased risk of all events studied. Heparin is more effective than inogatran in suppressing myocardial ischemia and clinical events at short-term follow-up. Continuous ST-segment monitoring with vectorcardiography identifies nonresponders who are at an increased level of risk.

Topics: Adult; Aged; Aged, 80 and over; Angina, Unstable; Anticoagulants; Antithrombins; Double-Blind Method; Electrocardiography, Ambulatory; Female; Follow-Up Studies; Glycine; Heparin; Humans; Male; Middle Aged; Myocardial Ischemia; Piperidines; Prospective Studies; Recurrence; Thrombin; Vectorcardiography

Studies have demonstrated that troponin T is a strong independent indicator of a poor prognosis in patients with unstable coronary artery disease. Up to the present, no study has compared the prognostic value of troponin T with that of troponin I in the same cohort of patients.. Patients (n=516) suspected of having unstable coronary artery disease were investigated. Follow-up was done after 30 days, and the occurrences of cardiac death, acute myocardial infarction, refractory angina pectoris, and recurrent angina pectoris were registered. Elevated levels of troponin T (> or = 0.10 microg/L) were associated with an increased risk of cardiac death at 30 days compared with patients with normal levels, 3.2% versus 0.4% (P=.014). Troponin I values above the chosen cutoff (2.0 microg/L) were similarly found to be an indicator of increased risk of cardiac death, 3.2% versus 0.7% (P=.026). With regard to the composite end point of cardiac death/acute myocardial infarction, the troponins were strong independent indicators of adverse outcome.. In patients suspected of having unstable coronary artery disease, both troponin T and troponin I provide independent prognostic information with regard to cardiac death and acute myocardial infarction.

Topics: Adult; Aged; Antithrombins; Cohort Studies; Coronary Disease; Female; Glycine; Heparin; Humans; Male; Middle Aged; Multivariate Analysis; Myocardium; Outcome Assessment, Health Care; Piperidines; Prognosis; Prospective Studies; Troponin; Troponin I; Troponin T

Unstable coronary artery disease, i.e. unstable angina or non-Q wave myocardial infarction, is caused by rupture of atheromatous plaques initiating thrombus formation. Thrombin is thought to be pivotal in platelet activation and thrombus growth. The aim of the present study was to compare the effect of three different doses of a novel, low molecular weight, selective thrombin inhibitor (inogatran) with that of heparin in unstable coronary artery disease. The composite primary end-point was death, incidence of myocardial infarction, refractory angina or recurrent angina after 7 days. Secondary end-points were the same after 3 and 30 days, as were death and myocardial infarction with or without refractory angina on all three occasions.. Patients (n = 1209) admitted with suspected unstable angina, or non-Q wave myocardial infarction, were randomly assigned to double-blind treatment with inogatran or heparin bolus doses. This was followed by a 3 day infusion with a low (LDI), medium (MDI), or high (HDI) dose of inogatran, aiming at plasma concentrations of 0.15, 0.4 or 0.8 micromol.l-1, or heparin initiated at 1200 U.h-1.. Treatment with inogatran resulted in median activated partial thromboplastin times after 24 h of 36, 44 and 53 s in the low, medium and high dose inogatran groups, respectively, as compared to 54 s in the heparin group (ns). At the end of the infusion, after 3 days, heparin-treated patients had fewer composite events (29.5%) than inogatran-treated patients (LDI = 39.4%, MDI = 37.6%, HDI = 36.1%; P = 0.01). The event rate after 7 days with respect to the primary end-point, however, did not differ between the groups (heparin = 41.0%, LDI = 45.7% MDI = 45.9%, HDI = 45.5%; ns). Death and myocardial infarction occurred less frequently in the heparin group (0.7%) than in the three inogatran groups (LDI = 3.6%, MDI = 2.0%, HDI = 4.0%; P < 0.05) after 3 days. After 7 days, this difference was attenuated (heparin = 2.6% vs LDI = 4.0%, MDI = 4.3%, HDI = 6.7%; P = 0.10). After 30 days there were no significant differences in event rates between the four groups. Major bleeding occurred in 1.1% of the patients within 7 days, with no differences between the groups.. During study drug infusion the event rate was very low in the heparin group, and none of the inogatran dosages were better than heparin in preventing ischaemic events. Furthermore, there was no relationship between event rate and inogatran dosage. Thus, this study does not indicate that the efficacy of inogatran would improve with higher doses, despite a clear dose-effect as regards the prolongation of activated partial thromboplastin time. After cessation of heparin or inogatran there was an increase in event rates, suggestive of a rebound phenomenon.

Topics: Aged; Angina, Unstable; Antithrombins; Dose-Response Relationship, Drug; Double-Blind Method; Female; Glycine; Heparin; Humans; Male; Middle Aged; Myocardial Infarction; Partial Thromboplastin Time; Piperidines; Time Factors

The acute coronary syndromes of unstable angina and non-Q-wave infarction are initiated by coronary plaque rupture and subsequent thrombus formation. Thrombin is central to this response as it activates platelets and the coagulation system. In an open design study we assessed the tolerability and safety of the low molecular weight thrombin inhibitor, inogatran, for unstable angina or non-Q-wave infarction.. Thirty-seven patients, treated within 72 h of symptoms, were allocated consecutively to groups to receive a 4 h infusion with one of three doses of inogatran. Thrombin generation and activity were measured with plasma markers at baseline, after the 4 h treatment period and 4 h later. Ischaemia was monitored using continuous vectorcardiography during the 4 h of treatment and during the subsequent 4 h after inogatran infusion had been stopped, to detect any increase in ischaemic events after the period of treatment. In addition, 12 patients received inogatran as an infusion for 72 h.. Inogatran was tolerated well. There were no adverse haemodynamic effects or allergic reactions. Minor bleeding events were detected in 37% of the patients. The biochemical and vectorcardiographic findings indicated suppression of thrombin generation after the 4 h treatment period compared with baseline. During the first 4 h after inogatran treatment, thrombin activity and episodes of ischaemia were increased compared with during the treatment period.. Inogatran was tolerated well and was safe, but its discontinuation was followed by a reactivation of thrombin activity and ischaemia. Whether this reactivation represented a rebound phenomenon, or merely resulted from the discontinuation of an effective therapy, cannot be established from the present study.

Topics: Adult; Aged; Angina, Unstable; Antithrombins; Drug Tolerance; Female; Follow-Up Studies; Glycine; Hemodynamics; Humans; Infusions, Intravenous; Male; Middle Aged; Myocardial Infarction; Partial Thromboplastin Time; Piperidines; Recurrence; Thrombin; Vectorcardiography

Restenosis secondary to neointimal hyperplasia remains the major limiting factor after vascular interventions. Thrombin generated in high concentrations at the site of vascular injury plays a central role in thrombosis and hemostasis. Thrombin has also been implicated as a mitogen for smooth muscle cell proliferation that contributes to restenosis. This study was designed to determine the effects of a specific thrombin inhibitor on neointimal hyperplasia after balloon injury in a rat carotid artery model.. A total of 47 male Sprague-Dawley rats were divided into five groups. All groups underwent balloon injury of the left carotid artery. A specific thrombin inhibitor, inogatran, was given in four different regimens: low and high dose injections, short-term infusion for 3 h, and long-term infusion for 1 week. After 2 weeks the animals were killed and the carotid neointima/media area ratio and the luminal narrowing were calculated.. All treatments significantly reduced the neointimal hyperplasia. Inogatran given as a long-term infusion for 1 week had the lowest neointima/media ratio compared with the other groups. The percentage of lumen narrowing was also significantly lower in all treatment groups compared with the control group.. A specific direct thrombin inhibitor, inogatran, reduces neointimal hyperplasia after arterial injury in rats. A more prolonged administration of the thrombin inhibitor gave a further reduction of the neointimal hyperplasia. It seems that inhibition of thrombin activity is not only important early after injury, but also later. This could have clinical implications in the treatment of restenosis and needs to be further evaluated.

Topics: Animals; Antithrombins; Biomarkers; Disease Models, Animal; Glycine; Hyperplasia; Male; Models, Cardiovascular; Piperidines; Rats; Rats, Sprague-Dawley; Tunica Intima

The present study investigated the effect of the thrombin inhibitors antithrombin (AT) (with and without unfractionated heparin or low molecular weight heparin), hirudin, inogatran and melagatran on thrombin-thrombomodulin-mediated generation of activated protein C (APC), in solution and on endothelial cells. Sequential incubation with thrombin, thrombin inhibitors and protein C was followed by measurement of APC by an amidolytic assay. The approximate concentrations resulting in 50% inhibition of endothelial cell-mediated APC generation for AT, AT-unfractionated heparin, AT-low molecular weight heparin, hirudin, melagatran and inogatran were 200, 4, 9, 1, 8 and 60 nmol/l, respectively. The normal plasma level of AT is 2800 nmol/l and relevant therapeutic concentrations from clinical trials are 200 nmol/l for hirudin, 500 nmol/l for melagatran and 1000 nmol/l for inogatran. The present study indicates that clinically relevant concentrations of the tested thrombin inhibitors interfere with endothelial-mediated APC generation, which may offer an explanation for the lack of a dose-response effect in clinical trials with thrombin inhibitors.

Topics: Antithrombins; Azetidines; Benzylamines; Dose-Response Relationship, Drug; Endothelium, Vascular; Flow Cytometry; Glycine; Heparin; Hirudins; Humans; Piperidines; Protein C; Thrombin; Thrombomodulin

Thrombin-induced platelet activation involves cleavage of protease-activated receptors (PARs) 1 and 4, and interaction, via glycoprotein (Gp)Ibalpha, with the platelet GpIb/IX/V complex. This study investigated inhibition of platelet activation by thrombin inhibitors with different modes of action: two reversible direct thrombin inhibitors, melagatran and inogatran; hirudin, a tightly binding direct thrombin inhibitor; and two indirect thrombin inhibitors, heparin and dalteparin. Up-regulation of P-selectin (CD62P) and PAR-1 cleavage was measured in human whole blood, by flow cytometry. The thrombin concentration that induced 50% of maximum (EC50 ) PAR-1 cleavage was 0.028 nmol/l, while that of platelet activation (CD62P) was over two-fold higher (0.64 nmol/l). The EC50 of a PAR-1-independent component, defined as a further activating effect of thrombin on top of the maximum PAR-1-activating peptide (AP) effect, was 3.2 nmol/l. All anticoagulants were concentration-dependent inhibitors of thrombin-induced platelet activation and PAR-1 cleavage, but none inhibited PAR-1-AP or PAR-4-AP induced activation. Melagatran and inogatran were more potent inhibitors of CD62P up-regulation than of PAR-1 cleavage; conversely, hirudin, heparin and dalteparin were more potent inhibitors of PAR-1 cleavage.Thus, reversible direct thrombin inhibitors, such as melagatran, are potent inhibitors of thrombin-induced platelet activation, acting mainly by inhibition of a PAR-1-independent component.

Topics: Adult; Anticoagulants; Azetidines; Benzylamines; Dalteparin; Dose-Response Relationship, Drug; Flow Cytometry; Glycine; Heparin; Hirudins; Humans; Male; P-Selectin; Piperidines; Platelet Activation; Platelet Aggregation; Platelet Aggregation Inhibitors; Platelet Glycoprotein GPIb-IX Complex; Receptor, PAR-1; Receptors, Thrombin; Statistics as Topic; Thrombin

Clinical trials evaluating direct thrombin inhibitors in unstable coronary artery disease (CAD) have been disappointing. The hypothesis tested in the present study was that these agents may inhibit the anticoagulant effect of thrombin to a further extent than the procoagulant effect of thrombin.. We studied both reversible and irreversible thrombin inhibitors and compared the effects of each inhibitor on activated protein C (APC) generation vs. the effect on fibrinopeptide A (FPA) generation. A mixture of protein C, thrombin inhibitor, fibrinogen, fibrin polymerisation blocker and thrombin was incubated with thrombomodulin (TM)-expressing human saphenous vein endothelial cells (HSVECs). The inhibitors investigated were melagatran, inogatran, hirudin, hirugen, D-Phe-D-Pro-D-arginyl chloromethyl ketone (PPACK), and antithrombin (AT) alone or in combination with unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH).. All agents, except hirugen, inhibited APC and FPA generation in a dose-dependent manner. FPA inhibition/APC inhibition ratios, based on IC50 for inogatran, melagatran, hirudin, PPACK, AT, AT-UFH and AT-LMWH were 1.73, 0.85, 0.55, 2.1, 0.5, 0.65 and 3.1 respectively.. All agents, except hirugen, inhibited APC and FPA generation approximately to a similar extent. Thus, it can be inferred that the poor efficacy of thrombin inhibitors in recent clinical trials in patients with unstable CAD is unlikely to be a consequence of their effects on the protein C system.

Topics: Amino Acid Chloromethyl Ketones; Anticoagulants; Azetidines; Benzylamines; Clinical Trials as Topic; Coagulants; Coronary Artery Disease; Fibrinopeptide A; Glycine; Hirudins; Humans; Peptide Fragments; Piperidines; Protein C; Thrombin

LB-30057 (CI-1028) is a novel, orally bioavailable, direct thrombin inhibitor with a Ki of 0.38 nM against human thrombin. The effects of LB-30057 on thrombus formation and hemostasis were evaluated in a veno-venous shunt model of thrombosis in rabbits, and compared with inogatran, another direct inhibitor of thrombin. Each compound was studied at 5 or 6 different doses with 5 or 6 rabbits in each group. After administration as a bolus i.v. injection followed by continuous infusion, both LB-30057 and inogatran dose-dependently inhibited thrombus formation, which was measured as an increase in time to occlusion (TTO) and a decrease in thrombus weight. Both compounds also improved vena caval blood flow and reduced the overall incidence of thrombotic occlusion. LB-30057 significantly prolonged TTO from 23 +/- 4 min (before dose) to 110 +/- 10 min at the highest dose (0.7 mg/kg + 47 microg/kg/min) (p < 0.001), and reduced thrombus weight from 57 +/- 2 mg to 15 +/- 5 mg (p < 0.001). Occlusive thrombus formed in only one of six rabbits that received the highest dose of LB-30057 (vs. 13/13 in the control group, p < 0.01). At the dose that produced the maximum antithrombotic effect (0.7 mg/kg + 47 microg/kg/min), LB-30057 increased aPTT and bleeding time approximately 2-and 2.5-fold above baseline, respectively. On a gravimetric basis, LB-30057 and inogatran displayed comparable in vivo antithrombotic efficacy. When compared to equally effective anti thrombotic doses of inogatran, LB-30057 caused less prolongation in aPTT, had no effect on PT, and tended to have less of effect on bleeding time. These results indicate that LB-30057 is an effective antithrombotic compound and it appears to have a better benefit/risk profile than inogatran in this experimental model.

Topics: Animals; Benzamides; Bleeding Time; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Fibrinolytic Agents; Glycine; Hemostasis; Implants, Experimental; Injections; Piperidines; Rabbits; Regional Blood Flow; Thrombin; Thrombosis; Vena Cava, Superior

Oral thrombin inhibitors are under development as potential drugs for prophylaxis and treatment of thrombotic events. The effect of pretreatment with two direct thrombin inhibitors, melagatran and inogatran, was evaluated in a rat model of cerebral infarction. Ischaemic stroke was induced by photochemical reaction after an injection of Rose Bengal and focused posterior and to the right of the intersection of the coronal and sagittal sutures on the intact calvarium. A single oral dose of melagatran (30 micromol/kg) significantly reduced the volume of the cortical infarct by 53% (P<.05) compared with control. In addition, following intravenous inogatran (6 micromol/kg) or oral inogatran (100 micromol/kg), the volume of the cortical infarct decreased by 83% and 19%, respectively, compared with control. This study showed that experimental focal ischaemic infarction, elicited by photochemically induced endothelial cell damage, can be significantly reduced with melagatran and inogatran, direct thrombin inhibitors.

Topics: Administration, Oral; Animals; Antithrombins; Azetidines; Benzylamines; Brain Infarction; Cerebral Cortex; Drug Evaluation, Preclinical; Glycine; Hypertension; Injections, Intravenous; Light; Male; Photochemistry; Piperidines; Rats; Rats, Inbred SHR

The objective of the study was to investigate the mechanisms behind increased bioavailability of an enzymatically stable thrombin inhibitor, inogatran, after coadministration with a trypsin inhibitor, aprotinin.. Rat jejunum, ileum and colon segments were stripped and mounted in modified Ussing chambers, and the permeability to inogatran was determined both in the presence and absence of aprotinin. Inogatran and aprotinin were also coadministered intraduodenally to conscious rats. Competitive binding of inogatran to trypsin was studied using kinetic dialysis and was compared to aprotinin. The fraction of free (unbound) trypsin probe, in the absence of trypsin inhibitors was determined by performing experiments without pancreatine and without inhibitors, respectively.. A 3-fold increased permeability to inogatran in the presence of aprotinin was seen in vitro, in some cases correlated with changed barrier properties of the intestinal segments. The in vitro results were well correlated with the in vivo results. There was a 5-fold increase in the bioavailability of inogatran in the presence of aprotinin. The binding of a trypsin probe was inhibited by both the presence of inogatran and aprotinin. Aprotinin showed a several fold higher displacement than inogatran. The results indicate both an effect of aprotinin on the epithelial membrane and an inhibition of binding of the thrombin inhibitor to trypsin or other serine proteases in the gut.. The coadministration of aprotinin with enzymatically stable peptides, like thrombin inhibitors, may improve their absorption after oral administration. This suggests a new additional mechanism for intestinal absorption enhancement of peptide drugs.

Topics: Administration, Oral; Animals; Antithrombins; Aprotinin; Biological Availability; Chemistry, Pharmaceutical; Drug Stability; Glycine; Intestinal Absorption; Male; Piperidines; Rats; Rats, Sprague-Dawley; Trypsin Inhibitors

Topics: Antithrombins; Coronary Thrombosis; Drug Therapy, Combination; Glycine; Humans; Piperidines; Platelet Aggregation Inhibitors; Platelet Glycoprotein GPIIb-IIIa Complex; Thrombin; Treatment Outcome

In the treatment of unstable coronary artery disease, direct thrombin inhibitors have shown no or only limited benefit as compared with heparin, despite theoretical advantages. One explanation may be that the direct thrombin inhibitors to a greater extent than heparin have an inhibiting effect on the generation and activity of activated protein C. In the present study, this hypothesis was tested in an in vitro, "purified" system, where human protein C underwent activation to activated protein C by the thrombin-thrombomodulin complex. Direct thrombin inhibitors, inogatran and hirudin, unfractionated heparin+antithrombin, or dalteparin+antithrombin, were added to the system before activation to evaluate their inhibitory effect on the generation of activated protein C. At inhibitor concentrations well below the achieved plasma levels in major clinical trials, the thrombin-thrombomodulin-mediated activation of protein C was inhibited by all the studied inhibitors in a dose-dependent manner, but, contrary to our hypothesis, to a greater extent by unfractionated heparin+antithrombin and dalteparin+antithrombin than by the direct thrombin inhibitors, hirudin and inogatran. Despite difficulties to draw conclusions for the in vivo situation, the in vitro inhibition, by all studied inhibitors, of the generation of activated protein C, found in this study may be a possible explanation for ongoing cardiovascular events despite adequate treatment with thrombin inhibitors, in patients with unstable coronary artery disease. This inhibition of the generation of activated protein C may also contribute to the rebound in cardiovascular events after withdrawal of effective antithrombotic treatment.

Topics: Antithrombins; Dalteparin; Fibrinolytic Agents; Glycine; Heparin; Hirudins; Humans; Intercellular Signaling Peptides and Proteins; Peptides; Pilot Projects; Piperidines; Protein C; Thrombin; Thrombomodulin

Current clinical use of heparin as an antithrombotic agent is limited by suboptimal efficacy and safety considerations. Thrombin's central role in thrombosis makes it an attractive target to develop more effective and safer antithrombotic agents. BCH-2763 is a novel, potent (Ki: 0.11 nM), low molecular weight (1.51 kDa), bivalent direct thrombin inhibitor. The antithrombotic efficacy of BCH-2763 in vivo following i.v. bolus plus infusion in rats was compared in arterial and venous thrombosis models with two other bivalent direct thrombin inhibitors, r-hirudin and hirulog, with two catalytic site-directed thrombin inhibitors, inogatran and argatroban, and with heparin. In vivo efficacy was related to inhibition in vitro of fibrin clot formation, thrombin-induced aggregation of rat or human washed platelets and activity of free and plasma clot-bound thrombin. All the direct thrombin inhibitors were effective on both arterial and venous thrombosis at markedly lower fold aPTT increases than heparin. The antithrombotic doses of all inhibitors against venous thrombosis were less than against arterial thrombosis. The rank order of potency based on doses (mg/kg/h) required for full efficacy against arterial thrombosis was BCH-2763 (1.2) > inogatran (1.5) > r-hirudin (1.8) > hirulog (3.3) > argatroban (> 3.0); heparin required a markedly higher dose (5.7). In venous thrombosis the doses required for full efficacy were substantially lower for the bivalent (BCH-2763: 0.12; r-hirudin: 0.12; hirulog: 0.18) than for the catalytic site-directed (inogatran: 0.48; argatroban: 0.90) thrombin inhibitors; the dose required for heparin was 0.19. All the direct thrombin inhibitors caused similar shifts in aPTT at doses required to inhibit arterial thrombosis, but BCH-2763 inhibited venous thrombosis at lower aPTT fold increases. In vivo antithrombotic efficacy of direct thrombin inhibitors correlated with their inhibitory activity in vitro against fibrin clot formation and platelet aggregation. In contrast to heparin, all the direct thrombin inhibitors inhibited plasma clot-bound thrombin, but the relative IC50s did not correlate with their antithrombotic efficacy. In summary, direct thrombin inhibitors are more effective than heparin in inhibiting arterial and venous thrombosis in rats with less aPTT increases. BCH-2763 is effective at lower doses than the other direct thrombin inhibitors and for venous thrombosis at a smaller aPTT increase. BCH-2763 may offer an improved the

Topics: Animals; Anticoagulants; Arginine; Arteries; Glycine; Heparin; Hirudins; Humans; Infusions, Intravenous; Oligopeptides; Peptide Fragments; Pipecolic Acids; Piperidines; Rats; Rats, Sprague-Dawley; Recombinant Proteins; Sulfonamides; Thrombin; Thrombosis; Veins

Pharmacokinetics, excretion, and metabolism of inogatran, a low-molecular-weight thrombin inhibitor, were studied in the rat, dog, and cynomolgus monkey. After intravenous administration the half-life was short in all three animal species, due to a small volume of distribution and a relatively high clearance. At doses of 0.1-5 mumol kg-1, the mean residence time was about 10 min in the rat, 35 min in the dog, and 20 min in the cynomolgus monkey. The oral bioavailability of inogatran was incomplete, presumably due to a low membrane permeability, and dose dependent. The bioavailability was 4.8% at 20 mumol kg-1 and 32-51% at 500 mumol kg-1 in rats, 14% at 10 mumol kg-1 and 34-44% at 150 mumol kg-1 in dogs, and 2.1% at 1 mumol kg-1 in cynomolgus monkeys. The radioactivity excreted in urine and faeces was predominantly unchanged inogatran. After intravenous administration the percentage of the radioactivity recovered in faeces was about equal to or higher than the urinary recovery, which indicates biliary excretion of inogatran. After oral dosing, most of the dose was excreted in faeces, as expected from the estimates of oral bioavailability. The plasma protein binding of inogatran in rat, dog, and human plasma, was 20-28%. The blood-plasma concentration ratio was 0.39-0.56, indicating limited distribution into red blood cells.

Topics: Animals; Antithrombins; Area Under Curve; Biotransformation; Blood Proteins; Dogs; Female; Glycine; Half-Life; Humans; Macaca fascicularis; Male; Molecular Weight; Piperidines; Rats; Rats, Sprague-Dawley; Species Specificity

The aim of the present study was to develop a coronary thrombolysis model using the copper coil technique in closed-chest pigs. The first goal (protocol I) was to obtain a reproducible size of myocardial infarction by controlling the coronary occlusion period, a prerequisite for evaluation of myocardioprotective interventions. The second goal (protocol II) was to study if thrombin and platelet aggregation inhibitors influence the rate of thrombolysis, the degree of reocclusion, and the time of coronary patency when added to a thrombolytic regimen (recombinant tissue-type plasminogen activator, rt-PA). Coronary thrombosis was produced by insertion of a thrombogenic copper coil into the LAD of 40 anesthetized pigs. The animals were divided into six groups as follows: Protocol I, group 1: Open-chest, lysis initiated with intracoronary rt-PA (50 mg) concomitant with intravenous heparin and acetylsalicylic acid (ASA) (n=6). Group 2: Closed-chest, lysis initiated with intracoronary rt-PA concomitant with intravenous heparin and ASA (n=10). Protocol II, group 3: Closed-chest, lysis initiated with intravenous rt-PA (n=6). Group 4: Closed-chest, lysis initiated with intravenous rt-PA concomitant with heparin (n=6). Group 5: Closed-chest, lysis initiated with intravenous rt-PA concomitant with inogatran, a low molecular weight thrombin inhibitor (n=6). Group 6: Closed-chest, lysis initiated with intravenous rt-PA immediately after intravenous administration of ASA (n=6). Protocol 1; Reperfusion was achieved in all closed- and open-chest pigs. The time to thrombolysis was 5+/-1.6 and 6+/-3.0 min (mean+/-SD) for closed- and open-chest pigs, respectively. Reocclusions were rare (one in group 1). The size of the ischemic myocardial area was 21+/-11% of the left ventricular area in group 1 and 22+/-6% in group 2. The corresponding values for infarct size as a proportion of the ischemic area were 58+/-10% and 68+/-14%, respectively. The closed-chest model was subsequently used to study the effect of the thrombin and platelet aggregation inhibitors (inogatran, heparin, and ASA) as conjunctive agents to rt-PA-induced thrombolysis (groups 3-6). To mimic its clinical use, rt-PA was administered intravenously. Time to lysis after rt-PA only (group 3) was 33+/-24 min. Concomitant treatment with heparin (group 4), inogatran (group 5), and ASA (group 6) did not significantly influence time to lysis. All adjunctive compounds did, however, prolong the time to reocclusion, which oc. The described closed-chest pig model was feasible as regards the induction and lysis of a thrombus in the left coronary artery, giving reproducible areas of myocardial ischemia and infarction. This model was useful for the evaluation of pharmacological interventions in the thrombolysis process.

Topics: Animals; Antithrombins; Aspirin; Blood Flow Velocity; Coronary Thrombosis; Glycine; Hemodynamics; Heparin; Myocardial Ischemia; Piperidines; Reperfusion Injury; Swine; Thrombolytic Therapy

The thrombin inhibitors argatroban, efegatran, NAPAP, CH 1091, CH 248, inogatran and melagatran have been characterised with respect to their mechanism of binding to human alpha-thrombin. Stopped-flow spectrophotometry was used to follow thrombin-catalysed hydrolysis of the chromogenic substrate S-2238 in the presence of inhibitors. The rate of onset or decay of inhibition was evaluated using progress curve analysis. It was possible to obtain apparent association and dissociation rate constants from the dependence of the rates on the inhibitor concentrations. Inhibition constants calculated from the association and dissociation rate constants were in good agreement with those calculated from steady-state rates. The binding of 6 inhibitors was also monitored directly using stopped-flow spectrofluorimetry when two kinetic components were found with all inhibitors. The faster component accounted for the largest part of the change in the intrinsic fluorescence of thrombin induced by inhibitor binding and was dependent on the inhibitor concentration. The slower component was independent of the concentration of the inhibitor. The concentration dependence of the faster component was linear with the compounds argatroban, NAPAP, CH 1091 and melagatran and hyperbolic with the compounds CH 248 and inogatran. The values of the apparent second-order rate constants at pH 7.4 and 37 degrees C range from slow to rapid binding in the interval 16-78 x 10(6) M-1 s-1, which is somewhat higher than 1-34 x 10(6)M-1 s-1 obtained from progress curve analysis of the onset of inhibition. The present results support a mechanism that includes rearrangement of a weak initial thrombin-inhibitor complex towards a tighter complex. Moreover, at least one additional step is required in the mechanism. In this model, the rate-limiting step for the binding of the inhibitor at concentrations in the nanomolar range depends on the primary interaction between the inhibitor and native thrombin.

Topics: Antithrombins; Area Under Curve; Arginine; Azetidines; Benzylamines; Binding Sites; Dipeptides; Fluorescence; Glycine; Humans; Kinetics; Molecular Weight; Pipecolic Acids; Piperidines; Spectrometry, Fluorescence; Spectrophotometry; Sulfonamides; Thrombin

The thrombin inhibitor inogatran is a synthetic peptidomimetic with a molecular weight of 439 dalton. In vitro studies have shown that inogatran is a classical competitive inhibitor of the active site of thrombin with a Ki of 15 x 10(-9) mol/l. Inogatran doubles the thrombin clotting time in human plasma at 20 x 10(-9) mol/l, APTT at 1.2 x 10(-6) mol/l, and prothrombin time at 4 x 10(-6) mol/l. The effects on rat and dog plasma are similar although slightly weaker. IC50 for inhibition of thrombin-induced aggregation of human platelets is 17 x 10(-9) mol/l. Inogatran has no effect on platelet aggregation induced by ADP or collagen. Up to a concentration of 10 x 10(-6) mol/l inogatran does not inhibit t-PA-induced fibrinolysis as seen in an ECLT system. Inogatran has good selectivity for thrombin as compared to several other serine proteases occurring in the blood. It is concluded that the properties of inogatran in vitro make the compound suitable for further studies in animals and man.

Topics: Adenosine Diphosphate; Animals; Antithrombins; Collagen; Dogs; Fibrinolysis; Glycine; Humans; Kinetics; Male; Piperidines; Platelet Aggregation; Rats; Rats, Sprague-Dawley; Serine Endopeptidases; Thrombin; Thrombin Time

Topics: Angina, Unstable; Animals; Anticoagulants; Antithrombins; Clinical Trials as Topic; Dalteparin; Enoxaparin; Fibrinolytic Agents; Glycine; Heparin, Low-Molecular-Weight; Humans; In Vitro Techniques; Myocardial Infarction; Nadroparin; Piperidines; Thromboembolism

The relation between the antithrombotic effect in vivo, and the inhibition constant (Ki) and the association rate constant (k(on)) in vitro was investigated for eight different thrombin inhibitors. The carotid arteries of anaesthetized rats were exposed to FeCl3 for 1 h, and the thrombus size was determined from the amount of incorporated 125I-fibrinogen. The thrombin inhibitors were given intravenously, and complete concentration- and/or dose-response curves were constructed. Despite a 50,000-fold difference between the Ki-values comparable plasma concentrations of hirudin and melagatran were needed (0.14 and 0.12 micromol l(-1), respectively) to obtain a 50% antithrombotic effect (IC50) in vivo. In contrast, there was a comparable in vitro (Ki-value) and in vivo (IC50) potency ratio for melagatran and inogatran, respectively. These results can be explained by the concentration of thrombin in the thrombus and improved inhibition by the low-molecular-weight compounds. For all eight thrombin inhibitors tested, there was an inverse relationship between k(on)-values in vitro and the slope of the dose response curves in vivo. Inhibitors with k(on)-values of < 1 x 10(7) M(-1) s(-1) gave steep dose response curves with a Hill coefficient > 1. The association time for inhibition of thrombin for slow-binding inhibitors will be too long to give effective antithrombotic effects at low plasma concentrations, but at increasing concentrations the association time will decrease, resulting in a steeper dose-response curve and thereby a more narrow therapeutic interval.

Topics: Amino Acid Chloromethyl Ketones; Animals; Anticoagulants; Arginine; Azetidines; Benzylamines; Carotid Artery Thrombosis; Dose-Response Relationship, Drug; Fibrinolytic Agents; Glycine; Hemodynamics; Heparin; Hirudin Therapy; Hirudins; Kinetics; Male; Oligopeptides; Partial Thromboplastin Time; Peptide Fragments; Pipecolic Acids; Piperidines; Rats; Rats, Sprague-Dawley; Recombinant Proteins; Sulfonamides; Thrombin; Thrombin Time

A sensitive thrombosis model with a high reproducibility was developed in the rat, utilizing stasis of the caval vein and a standardized surgical trauma as the only thrombogenic stimuli. Since no procoagulant substances were used, the results of the present study might be relevant in a clinical situation. The antithrombotic effect of two recently synthesized low-molecular-weight thrombin inhibitors have been compared to dalteparin, (Fragmin) a low-molecular-weight heparin fragment. Each compound was studied at 8 different doses with 10 rats in each group. On a gravimetric basis, the thrombin inhibitor melagatran was twice as potent as dalteparin (ED50 16 and 33 microg/kg per h, respectively). The second thrombin inhibitor, inogatran, had an intermediate effect, with an ED50 of 24 microg/kg per h. No differences in antithrombotic effect were, however, found when the compounds were compared at anticoagulant equivalent doses (same APTT prolongation). A 50% reduction in the mean thrombus weight was obtained when APTT was prolonged to 1.2 to 1.3 times the pretreatment value.

Topics: Animals; Azetidines; Benzylamines; Dalteparin; Disease Models, Animal; Fibrinolytic Agents; Glycine; Heparin, Low-Molecular-Weight; Infusions, Intravenous; Injections, Intravenous; Male; Piperidines; Rats; Rats, Wistar; Thrombin; Thrombophlebitis; Vena Cava, Inferior

Topics: Acute Disease; Antithrombins; Coronary Disease; Glycine; Heparin; Hirudin Therapy; Humans; Piperidines; Syndrome

Coronary artery often reoccludes after therapy of acute myocardial infarction with recombinant tissue plasminogen activator rt-PA, most likely due to in situ thrombin generation during thrombolysis. Previous studies with high molecular weight thrombin inhibitors, such as hirudin, have shown variable improvement in the frequency of sustained thrombolysis. This study was conducted to examine the modulation of thrombolysis, indices of thrombin generation and activated partial thromboplastin time (APTT) by a novel low molecular weight direct thrombin inhibitor, inogatran. A stable occlusive intracoronary thrombus was created in 19 dogs. Nine dogs were given an intravenous bolus of saline (group A), and 5 dogs were given inogatran (group B) followed by rapid infusion of rt-PA (1 mg/kg over 20 min), whereas saline or inogatran was continuously infused for 2 hr. Five other dogs were given inogatran (bolus and continuous infusion) only after thrombolysis by rt-PA was obtained (group C). Time to reflow was similar in all dogs. None of the reperfused coronary arteries reoccluded in group B dogs (vs. 75% and 40% reocclusion rates in groups A and C, respectively, P < .02). Accordingly, the mean duration of reflow was > 120 min in group B dogs (vs. 39 +/- 7 and 44 +/- 14 min in group A and C dogs, respectively, P < .05). After infusion of inogatran, APTT was increased to 1.6 to 1.9 times the base-line value, and the changes in APTT were similar in group B and C dogs. Thrombin generation and activity, assessed by thrombin-antithrombin complex and fibrinopeptide A levels, increased in all dogs during thrombus formation. The increase in thrombin-antithrombin complex and fibrinopeptide A levels during thrombolysis was not evident in group B dogs. These data show that direct thrombin inhibition with inogatran, when initiated before rt-PA, results in sustained thrombolysis and only a modest increase in APTT. However, inogatran given after thrombolysis only partially prevents reocclusion because large amounts of thrombin generation occur during the early stages of thrombolysis.

Topics: Animals; Dogs; Female; Glycine; Hemodynamics; Male; Molecular Weight; Piperidines; Thrombin; Thrombosis; Tissue Plasminogen Activator

To characterize the antithrombotic activity of inogatran per se in a porcine model of copper-coil-induced coronary artery thrombosis and to compare its effect with that of heparin and ASA.. Forty-eight pigs were assigned to one of the following groups: (1) saline; (2) heparin, (a) 75 and (b) 150 IU/kg/h; (3) acetylsalicylic acid (ASA), 12.5 mg/kg; (4) ASA 12.5 mg/kg + inogatran, 0.06 mg/kg/h; (5) ASA 12.5 mg/kg + inogatran, 0.30 mg/kg/h; (6) inogatran, 0.30 mg/kg/h; (7) inogatran, 0.60 mg/kg/h; (8) inogatran, 1.5 mg/kg/h. Computerized vectorcardiography was applied to monitor coronary occlusion and reperfusion.. Cumulative time in which coronary arteries were patent, expressed as a percentage of the treatment time (i.e., 90 min) in heparin- and ASA-treated pigs, was 8 +/- 6 and 14 +/- 7%, respectively. This is not significantly different from placebo-treated pigs. Inogatran-treated pigs showed a dose-dependent antithrombotic effect, and the average patency rates were 34 +/- 39, 54 +/- 37 and 80 +/- 32%, in groups 6, 7 and 8, respectively. Combined treatment with inogatran and ASA did not significantly improve the antithrombotic effect. A partial antithrombotic effect of inogatran was maintained for, on average, at least 150 min after the end of treatment, as evidenced by patency rates of 31 +/- 43, 52 +/- 48 and 62% +/- 44, in groups 6, 7, and 8, respectively.. Inogatran inhibits the formation of arterial thrombosis more effectively than heparin or ASA. Inhibition of clot-bound thrombin and thrombin-induced platelet activation may be the mechanisms behind this effect. Our findings also suggest that a thrombus formed in the presence of inogatran is more susceptible to spontaneous endogenous fibrinolysis.

Topics: Animals; Aspirin; Coronary Thrombosis; Disease Models, Animal; Female; Glycine; Heparin; Male; Piperidines; Swine; Thrombin

Inogatran (MW 439 Da), a new, selective, active site inhibitor of thrombin, was evaluated in three rat models of thrombosis. In the venous thrombosis model, inogatran dose-dependently inhibited thrombus formation with a > 80% antithrombotic effect at a plasma concentration of 0.45 mumol l-1. In the arterial thrombosis model, inogatran dose-dependently inhibited thrombus formation, preserved vessel patency and the mean blood flow. Acetylsalicylic acid (ASA) potentiated the effects of low plasma concentrations of inogatran in the arterial thrombosis model. In the model of rt-PA-induced thrombolysis of a thrombus in the carotid artery, inogatran improved the patency time and the cumulative blood flow during the two hour thrombolysis period more than rt-PA alone. At high therapeutic plasma concentration of inogatran, there was only a moderate prolongation of bleeding time compared with the control value. It is concluded that inogatran is an effective antithrombotic agent both in the venous and arterial thrombosis models and also as adjuvant to rt-PA in the thrombolysis model.

Topics: Animals; Antithrombins; Arginine; Aspirin; Bleeding Time; Disease Models, Animal; Fibrinolytic Agents; Glycine; Heparin; Male; Molecular Weight; Pipecolic Acids; Piperidines; Platelet Aggregation Inhibitors; Rats; Rats, Sprague-Dawley; Sulfonamides; Thrombolytic Therapy; Thrombophlebitis; Thrombosis