New challenges for a second-generation low-molecular-weight heparin: focus on bemiparin

Pharmacological and clinical application of heparin progress: An essential drug for modern medicine

Heparin is the earliest and most widely used anticoagulant and antithrombotic drug that is still used in a variety of clinical indications. Since it was discovered in 1916, after more than a century of repeated exploration, heparin has not been replaced by other drugs, but a great progress has been made in its basic research and clinical application. Besides anticoagulant and antithrombotic effects, heparin also has antitumor, anti-inflammatory, antiviral, and other pharmacological activities. It is widely used clinically in cardiovascular and cerebrovascular diseases, lung diseases, kidney diseases, cancer, etc., as the first anticoagulant medicine in COVID-19 exerts anticoagulant, anti-inflammatory and antiviral effects. At the same time, however, it also leads to a lot of adverse reactions, such as bleeding, thrombocytopenia, elevated transaminase, allergic reactions, and others. This article comprehensively reviews the modern research progress of heparin compounds; discusses the structure, preparation, and adverse reactions of heparin; emphasizes the pharmacological activity and clinical application of heparin; reveals the possible mechanism of the therapeutic effect of heparin in related clinical applications; provides evidence support for the clinical application of heparin; and hints on the significance of exploring the wider application fields of heparin.

Bemiparin versus unfractionated heparin as bridging therapy in the perioperative management of patients on vitamin K antagonists: the BERTA study

BACKGROUND AND OBJECTIVE

The management of patients on vitamin K antagonist therapy who require an invasive procedure is problematic. A randomised, controlled, double-blind clinical trial was designed to compare the efficacy and safety of bemiparin, a low molecular weight heparin (LMWH), with unfractionated heparin (UFH) as bridging therapy: the BERTA (BEmiparin Randomised Trial on bridging Anticoagulants) study.

METHODS

Two hundred and six patients on long-term oral anticoagulation therapy (OAT) requiring an invasive procedure were randomized to receive bridging therapy with bemiparin + matching placebo or UFH. OAT was resumed on day 1. The study medication was continued for 5-6 days after the procedure. The primary efficacy endpoint was the combined incidence of arterial and venous thromboembolic events. The primary safety endpoint was the incidence of major bleeding within 10 days after the invasive procedure.

RESULTS

There were no thromboembolic events in the bemiparin group, but two events (2.2 %) occurred in the UFH group. No major bleeding occurred in either group, but minor bleeding occurred in four patients (4.3 %) and six patients (6.1 %) in the bemiparin and UHF groups, respectively. No deaths and no cases of severe thrombocytopenia occurred during the whole study period.

CONCLUSION

Despite its small size, the BERTA study is the first randomised, double-blind clinical trial comparing UFH with a fixed high-risk thromboprophylactic dose of an LMWH as bridging therapy. There were no thromboembolic events and fewer bleeding episodes in the bemiparin group than in the UFH group, hence we suggest that bemiparin is at least as safe as UFH as bridging therapy.

Homogeneous low-molecular-weight heparins with reversible anticoagulant activity

Low-molecular-weight heparins (LMWHs) are carbohydrate-based anticoagulants clinically used to treat thrombotic disorders, but impurities, structural heterogeneity or functional irreversibility can limit treatment options. We report a series of synthetic LMWHs prepared by cost-effective chemoenzymatic methods. The high activity of one defined synthetic LMWH against human factor Xa (FXa) was reversible in vitro and in vivo using protamine, demonstrating that synthetically accessible constructs can have a critical role in the next generation of LMWHs.

Differential effects of fondaparinux and bemiparin on angiogenic and vasculogenesis-like processes

INTRODUCTION

Conventional therapy for venous thromboembolism or acute coronary syndrome involves the administration of glycoanticoagulants (heparins) or oligosaccharides (fondaparinux). We evaluated the effects of such drugs on angiogenesis and vasculogenesis-like models.

MATERIALS AND METHODS

Human umbilical vein endothelial cells or human endothelial progenitor cells were treated with bemiparin, fondaparinux or unfractionated heparin, at concentrations reflecting the doses used in clinical practice. After 24h, cell viability, proliferation, tubule formation and angiogenic molecular mechanisms, such as activation of the serine/threonine kinase AKT, were assessed. In vivo angiogenesis was studied using a Matrigel sponge assay in mice.

RESULTS

Bemiparin gave a significant decrease of in vitro angiogenesis as shown by the reduction of endothelial cell tubule network, while both fondaparinux and unfractionated heparin did not show any significant effect. In assays of Matrigel sponge invasion in mice, unfractionated heparin was able to stimulate angiogenesis and, conversely, bemiparin inhibited angiogenesis. Furthermore, both bemiparin and fondaparinux caused a significant reduction in an in vitro vasculogenesis-like model, as demonstrated by the decrease of tubule network after co-seeding of endothelial progenitor cells and human umbilical vein endothelial cells. In addition, unfractionated heparin but not bemiparin was able to increase AKT phosphorylation.

CONCLUSIONS

In in vitro experiments, bemiparin was the only drug to show an anti-angiogenic and vasculogenic-like effect, unfractionated heparin showed only a trend to increase in angiogenesis assay and fondaparinux affected only the vasculogenesis-like model. Notably, the in vivo experiments corroborated these data. Such results are important for the choice of a patient-tailored therapy.

Chemoenzymatic synthesis of homogeneous ultralow molecular weight heparins

Ultralow molecular weight (ULMW) heparins are sulfated glycans that are clinically used to treat thrombotic disorders. ULMW heparins range from 1500 to 3000 daltons, corresponding from 5 to 10 saccharide units. The commercial drug Arixtra (fondaparinux sodium) is a structurally homogeneous ULMW heparin pentasaccharide that is synthesized through a lengthy chemical process. Here, we report 10- and 12-step chemoenzymatic syntheses of two structurally homogeneous ULMW heparins (MW = 1778.5 and 1816.5) in 45 and 37% overall yield, respectively, starting from a simple disaccharide. These ULMW heparins display excellent in vitro anticoagulant activity and comparable pharmacokinetic properties to Arixtra, as demonstrated in a rabbit model. The chemoenzymatic approach is scalable and shows promise for a more efficient route to synthesize this important class of medicinal agent.