Dabigatran versus enoxaparin for prevention of venous thromboembolism after hip or knee arthroplasty: a pooled analysis of three trials.

BACKGROUND: Three randomized, double-blind trials compared dabigatran, an oral direct thrombin inhibitor, with enoxaparin for the primary prevention of venous thromboembolism (VTE) in patients undergoing elective total hip and knee arthroplasty. OBJECTIVES AND METHODS: We conducted a pre-specified pooled analysis of these trials. 8,210 patients were randomized, of whom 8,135 were treated (evaluable for safety) with dabigatran 220 mg or 150 mg once-daily, or subcutaneous enoxaparin (40 mg once-daily or 30 mg twice-daily). Efficacy analyses were based on the modified intention-to-treat population of 6,200 patients with an evaluable outcome. The common risk difference (RD) of treatment effect between each dabigatran dose and enoxaparin was estimated using fixed-effects models, and statistical heterogeneity was estimated using the I2 statistic. RESULTS: The composite outcome of major VTE (proximal deep vein thrombosis and/or pulmonary embolism) and VTE-related mortality occurred in 3.3% of the enoxaparin group versus 3.0% of the dabigatran 220 mg group (RD vs. enoxaparin -0.2%, 95% CI -1.3% to 0.9%, I2=37%) and 3.8% of the 150 mg group (RD vs. enoxaparin 0.5%, -0.6% to 1.6%, I2=0%). Major bleeding occurred in 1.4% of the enoxaparin group versus 1.4% of the dabigatran 220 mg group (RD vs. enoxaparin -0.2%, -0.8% to 0.5%, I2=40%) and 1.1% of the 150 mg group (RD vs. enoxaparin -0.4%, -1.0% to 0.2%, I2=0%). CONCLUSIONS: Oral dabigatran was as effective as subcutaneous enoxaparin in reducing the risk of major VTE and VTE-related mortality after hip or knee arthroplasty and has a similar bleeding profile.

Angiotensin II, adhesion, and cardiac fibrosis.

Angiotensin II (AII) plays a critical role in cardiac remodeling. This peptide promotes cardiac myocyte hypertrophy and cardiac fibroblast interstitial fibrotic changes associated with left ventricular hypertrophy, post myocardial infarction remodeling and congestive heart failure. AII mediates cardiac myocyte hypertrophy directly via induction of immediate early genes through a MAP kinase dependent pathway. In addition, it mediates cardiac hypertrophy indirectly by stimulating release of norepinephrine from cardiac nerve endings and endothelin from endothelial cells. AII also has multiple effects on cardiac fibroblasts: it induces cardiac fibroblast proliferation, synthesis and secretion of adhesion molecules and extracellular matrix proteins, and expression of integrin adhesion receptors. In addition it stimulates cardiac fibroblasts to adhere more vigorously to defined matrixes. This review will discuss the molecular pathways that have been implicated in these AII induced effects in the cardiac fibroblast.

High-level expression of antibody-plasminogen activator fusion proteins in hybridoma cells.

We show that the mouse gamma 2b heavy chain or human beta-globin 3' untranslated region can greatly enhance protein expression in myeloma cells transfected by genes coding for antibody-plasminogen activator fusion proteins. Expression plasmids were constructed containing a cloned genomic heavy chain variable region from fibrin-specific monoclonal antibody 59D8, a cloned genomic constant region of the mouse gamma 2b heavy chain, and DNA sequence coding for either tissue-type plasminogen activator (tPA) or a segment of urokinase (UK) and their respective 3' untranslated sequences. Cell lines transfected with these constructs, pSVtPA (tPA) and pSVUKG(UK), produced extremely low levels of mRNA and protein (0.008-0.06 micrograms/ml) in comparison with the parental 59D8 myeloma cell line (7.6-10 micrograms/ml). In vitro nuclear run-off analysis indicated that the low steady-state levels of mRNA encoded by pSVUKG(UK) did not result from a lower rate of transcription of the transfected gene (relative to the rate of transcription of the endogenous heavy chain gene in the 59D8 parent cells). In an attempt to increase protein secretion, we assembled the expression plasmids pSVtPA(Ig), pSVUKG(Ig), and pSVUKG(beta), in which the 3' untranslated region of the mouse gamma 2b heavy chain or human beta-globin gene was substituted for the 3' untranslated region of the plasminogen activator gene. Analysis of supernatant media from cell lines transfected with these constructs showed an increase in recombinant protein secretion of 68 to 100 fold in comparison with that from cell lines transfected with pSVtPA(tPA) or pSVUKG(UK).

Construction and expression of a recombinant antibody-targeted plasminogen activator.

Covalent linkage of tissue-type plasminogen activator (t-PA) to a monoclonal antibody specific for the fibrin beta chain (anti-fibrin 59D8) results in a thrombolytic agent that is more specific and more potent than t-PA alone. To provide a ready source of this hybrid molecule and to allow tailoring of the active moieties for optimal activity, we have engineered a recombinant version of the 59D8-t-PA conjugate. The rearranged 59D8 heavy chain gene was cloned and combined in the expression vector pSV2gpt with sequence coding for a portion of the gamma 2b constant region and the catalytic beta chain of t-PA. This construct was transfected into heavy chain loss variant cells derived from the 59D8 hybridoma. Recombinant protein was purified by affinity chromatography and analyzed with electrophoretic transfer blots. These revealed a 65-kDa heavy chain-t-PA fusion protein that is secreted in association with the 59D8 light chain in the form of a 170-kDa disulfide-linked dimer. Chromogenic substrate assays showed the fusion protein to have 70% of the peptidolytic activity of native t-PA and to activate plasminogen as efficiently as t-PA. In a competitive binding assay, reconstituted antibody was shown to have a binding profile similar to that of native 59D8. Thus, by recombinant techniques, we have produced a hybrid protein capable of high-affinity fibrin binding and plasminogen activation.