The development of genomics-derived pharmaceuticals.

Messenger RNAs for the large majority of human genes are now available. Most of those contained in the Human Genome Sciences database are capable of producing functional proteins. We have sequenced the clones of approximately 8000 that are believed to be involved in cell signaling, and have produced small amounts of the corresponding proteins. These are being screened for biological activity; four have been entered into clinical trials, with one demonstrating clinical activity thus far.

Determination of a weight-adjusted dose of TNK-tissue plasminogen activator.

BACKGROUND: TNK-tissue plasminogen activator (TNK-tPA) is a potent new thrombolytic agent for treatment of acute myocardial infarction. TNK-tPA was evaluated in 4214 patients in two dose-ranging trials (Thrombolysis in Myocardial Infarction [TIMI] 10B and Assessment of the Safety and Efficacy of a New Thrombolytic Agent [ASSENT] I). This article describes the rationale for the weight-adjusted dosing regimen of TNK-tPA that was selected for evaluation in the large phase III clinical trial ASSENT II. METHODS: Weight-based analyses were conducted with data from both the angiographic TIMI 10B trial, which compared TNK-tPA in doses of 30 mg, 40 mg, and 50 mg with the accelerated regimen of tPA in 889 patients, and the ASSENT I trial, which evaluated the safety of TNK-tPA in doses of 30 mg, 40 mg, and 50 mg in 3301 patients. Graphic and statistical analytic methods were used to assess relationships between weight and efficacy or safety measurements. RESULTS: The plasma clearance, initial plasma concentrations, and plasma steady-state volume of distribution all increased with decreasing body weight (all P<.001). The corrected TIMI frame count decreased (flow was faster) (P =.001) and the TIMI grade 3 flow increased with an increasing weight-standardized dose of TNK-tPA (P<.008). Mortality was inversely related to dose, but this relationship was not statistically significant. There was no clear relationship between intracranial hemorrhage and dose and weight. Serious bleeding events increased with increasing weight-standardized dose (P<.02). CONCLUSIONS: On the basis of these analyses, a weight-adjusted dosing regimen was devised for TNK-tPA that included five dosing increments and was based on a target weight-standardized dose of 0.53 mg/kg.

Relation of coagulation parameters to patency and recurrent ischemia in the Thrombolysis in Myocardial Infarction (TIMI) Phase II Trial.

Current protocols for use of tissue-type plasminogen activator in acute myocardial infarction include heparin estimated by the activated partial thromboplastin time (aPTT). Recent reports indicate a risk of recurrent ischemic events with long aPTT values. Longer aPTT values in the Thrombolysis in Myocardial Infarction-II (TIMI II) Trial, obtained within the first 48 hours, were associated with patency at 18 to 48 hours and better left ventricular function at discharge (average 9.6 days), but also with emergency catheterizations within the first 48 hours and, weakly, with recurrent ischemia during the first 18 hours. A moderate decrease in fibrinogen, compared with a "small" decrease, was also associated with patency, but a "large" decrease was associated with hemorrhagic events. Patency was associated with higher fibrinogen values and higher plasminogen values at baseline. The aPTT results support frequent monitoring during the first 24 to 48 hours to ensure optimal clinical outcome. The coagulation factor results suggest that there may be an optimum window for fibrinogenolysis in this setting.

Lack of impact of early catheterization and fibrin specificity on bleeding complications after thrombolytic therapy. The TAMI Study Group.

OBJECTIVES: The aim of this study was to assess the hemorrhagic risk associated with fibrin-specific thrombolytic therapy and invasive procedures with acute myocardial infarction. BACKGROUND: Successful coronary artery reperfusion has important prognostic implications. Because immediate coronary angiography is the only method proved to differentiate early fibrinolytic success from failure, its use may be important for selected patients. METHODS: Five hundred seventy-five patients were evaluated with six combined thrombolytic and catheterization strategies. Patients were randomized to intravenous urokinase alone, recombinant tissue-type plasminogen activator (rt-PA) alone, or both; simultaneously they were randomized to an immediate versus a deferred catheterization strategy. Hemorrhagic events were assessed. The correlation of hemorrhage with clinical and hemostatic variables was evaluated. Prespecified transfusion criteria were employed. RESULTS: No difference in baseline characteristics or in hemorrhagic complications was noted among the three thrombolytic regimens. Although mild (< 250 ml) bleeding was more common in the group with immediate catheterization, no clinically significant difference among catheterization groups was seen in moderate to life-threatening hemorrhagic events. Most bleeding occurred at vascular access sites, yet severe and life-threatening hemorrhage occurred in < 1% of patients. Baseline and nadir fibrinogen levels, change in baseline fibrinogen levels and peak fibrin and fibrinogen degradation products did not correlate with bleeding risk. A clinical predisposition for bleeding was observed in women as well as older (> or = 65 years) and lighter (< or = 70 kg) patients. With prespecified transfusion criteria, only a minimal increase in blood product usage was noted with immediate catheterization. CONCLUSIONS: Immediate cardiac catheterization can be accomplished without a clinically significant difference in bleeding risk. Fibrin specificity offers no clear advantage in reducing hemorrhagic risk. Bleeding risk correlates best with baseline patient characteristics. Finally, the amount of blood transfused can be reduced with lower transfusion criteria.

Anticoagulant and fibrinolytic activities are promoted, not retarded, in vivo after thrombin generation in the presence of a monoclonal antibody that inhibits activation of protein C.

This study examines the assumption that both the anticoagulant and fibrinolytic activity that follow the generation of thrombin induced by infusion of factor Xa/PCPS are due to generation of activated protein C. Untreated controls or animals given unrelated antibody were compared with animals pretreated with a specific monoclonal antibody to protein C (HPC4). Compared with untreated controls excess HPC4 substantially reduced the level of protein C activation as observed by protein C immunoblotting and enzyme-linked immunosorbent assay for antitrypsin/activated protein C complexes. Despite this, the anticoagulant activity as reflected by the decline of factors Va and VIIIa levels (as observed by coagulation assays and by factor V immunoblotting) was significantly greater than controls. The fibrinolytic activity (as observed by assays of tissue plasminogen activator, D-Dimer, alpha 2-antiplasmin) also was significantly greater than controls. We conclude that neutralization of the protein C anticoagulant system while resulting in a significantly more intense coagulant response to Xa/PCPS does not preclude inactivation of factors Va and VIIIa and the full expression of the fibrinolytic response. We conclude further that after thrombin generation in vivo, protein C activation is not a prerequisite for the promotion of the fibrinolytic response previously observed, and that the inactivation of factors Va/VIIIa may be mediated by enzymes other than activated protein C. The reduction in alpha 2-antiplasmin levels in association with increased tissue plasminogen activator activity suggests that plasmin is a likely candidate.

Fibrinogen deposition and macrophage-associated fibrin formation in malignant and nonmalignant lymphoid tissue.

Nonmalignant lymphoid tissue and tissue from patients with nodular sclerosis, Hodgkin's disease, and large cell lymphocytic lymphoma was examined by immunohistochemical techniques for the occurrence in situ of components of coagulation and fibrinolysis reaction pathways. Staining for material interpreted as fibrinogen was observed in abundance in both malignant and reactive lymphoid tissue. Fibrin also occurred to a variable extent but focally in all tissues. Components of coagulation pathways, including tissue factor, factor VII, factor X, and factor XIII ("a" subunit), were restricted to tissue macrophages. Double-labeling techniques revealed fibrin in direct apposition to tissue macrophages. We conclude that fibrinogen and fibrin occur in both benign and malignant lymphoid tissue and that the transformation of fibrinogen to fibrin is attributable to macrophage-initiated thrombin formation. We postulate that both systemic and local hypercoagulability associated with these disorders may be attributable to macrophage activation resulting in expression of procoagulant activity.

Modulation of the fibrinolytic response of cultured human vascular endothelium by extracellularly generated oxygen radicals.

Clinical and experimental data indicate that activated oxygen species interfere with vascular endothelial cell function. Here, the impact of extracellular oxidant injury on the fibrinolytic response of cultured human umbilical vein endothelial (HUVE) cells was investigated at the protein and mRNA levels. Xanthine (50 microM) and xanthine oxidase (100 milliunits), which produces the superoxide anion radical (O2-) and hydrogen peroxide (H2O2), was used to sublethally injure HUVE cells. Following a 15-min exposure, washed cells were incubated for up to 24 h in serum-free culture medium. Tissue-type plasminogen activator (t-PA) antigen, plasminogen activator inhibitor-1 (PAI-1) antigen, and PAI-1 activity were determined in 1.25 ml of conditioned medium and t-PA and PAI-1 mRNA in the cell extracts of 2 x 10(6) HUVE cells. Control cells secreted 3.9 +/- 1.3 ng/ml (mean +/- S.D., n = 12) within 24 h. Treatment with xanthine/xanthine oxidase for 15 min induced a 2.8 +/- 0.4-fold increase (n = 12, p less than 0.05) of t-PA antigen secretion after 24 h. The t-PA antigen was recovered predominantly in complex with PAI-1. The oxidant injury caused a 3.0 +/- 0.8-fold increase (n = 9, p less than 0.05) in t-PA mRNA within 2 h. Total protein synthesis was unaltered by xanthine/xanthine oxidase. The oxidant scavengers superoxide dismutase and catalase, in combination, abolished the effect of xanthine/xanthine oxidase on t-PA secretion and t-PA mRNA synthesis. Xanthine/xanthine oxidase treatment of HUVE cells did not affect the PAI-1 secretion in conditioned medium nor the PAI-1 mRNA levels in cell extracts. Thus extracellular oxidant injury induces t-PA but not PAI-1 synthesis in HUVE cells.

Coexisting macrophage-associated fibrin formation and tumor cell urokinase in squamous cell and adenocarcinoma of the lung tissues.

Mechanisms of coagulation activation in situ were studied by means of immunohistochemical techniques applied to surgically resected primary adenocarcinomas and squamous cell carcinomas of the lung. Findings in these two histologic types were similar. Double-labeling techniques using macrophage-specific antibody together with antibody to either tissue factor, factor VII, factor X, or factor V revealed coincident staining for each of these coagulation factors on tumor-associated macrophages. Staining of tumor cells for these factors was rare and inconsistent. Both macrophages and fibroblasts in the tumor connective tissue stained for the a subunit of factor XIII. Fibrinogen was abundant throughout the tumor connective tissue, but staining for fibrin and D-dimer cross-linked sites of fibrin was restricted to areas adjacent to macrophages, indicating that thrombin was generated in association with tumor macrophages but not with tumor cells. By contrast, tumor cells stained diffusely for urokinase-type plasminogen activator and focally for thrombomodulin. These findings contrast with those reported previously for small cell carcinoma of the lung and suggest that coagulation activation in adenocarcinoma and squamous cell carcinoma of the lung may occur indirectly through activation of certain host cells such as macrophages. By contrast, tumor cell plasminogen activator may mediate certain aspects of the malignant phenotype in these tumor types.

Hemorrhagic events during therapy with recombinant tissue-type plasminogen activator, heparin, and aspirin for acute myocardial infarction. Results of the Thrombolysis in Myocardial Infarction (TIMI), Phase II Trial.

OBJECTIVES: To assess the effects of invasive procedures, hemostatic and clinical variables, the timing of beta-blocker therapy, and the doses of recombinant plasminogen activator (rt-PA) on hemorrhagic events. DESIGN: A multicenter, randomized, controlled trial. SETTING: Hospitals participating in the Thrombolysis in Myocardial Infarction, Phase II trial (TIMI II). INTERVENTIONS: Patients received rt-PA, heparin, and aspirin. The total dose of rt-PA was 150 mg for the first 520 patients and 100 mg for the remaining 2819 patients. Patients were randomly assigned to an invasive strategy (coronary arteriography with percutaneous angioplasty [if feasible] done routinely 18 to 48 hours after the start of thrombolytic therapy) or to a conservative strategy (coronary arteriography done for recurrent spontaneous or exercise-induced ischemia). Eligible patients were also randomly assigned to either immediate intravenous or deferred beta-blocker therapy. MEASUREMENTS: Patients were monitored for hemorrhagic events during hospitalization. MAIN RESULTS: In patients on the 100-mg rt-PA regimen, major and minor hemorrhagic events were more common among those assigned to the invasive than among those assigned to the conservative strategy (18.5% versus 12.8%, P less than 0.001). Major or minor hemorrhagic events were associated with the extent of fibrinogen breakdown, peak rt-PA levels, thrombocytopenia, prolongation of the activated partial thromboplastin time (APTT) to more than 90 seconds, weight of 70 kg or less, female gender, and physical signs of cardiac decompensation. Immediate intravenous beta-blocker therapy had no important effect on hemorrhagic events when compared with delayed beta-blocker therapy. Intracranial hemorrhages were more frequent among patients treated with the 150-mg rt-PA dose than with the 100-mg rt-PA dose (2.1% versus 0.5%, P less than 0.001). The extent of the plasmin-mediated hemostatic defect was also greater in patients receiving the 150-mg dose. CONCLUSIONS: Increased morbidity due to hemorrhagic complications is associated with an invasive management strategy in patients with acute myocardial infarction. Our findings show the complex interaction of several factors in the occurrence of hemorrhagic events during thrombolytic therapy.