Fondaparinux: a new antithrombotic agent

Glycomimetics for the inhibition and modulation of lectins

Carbohydrates are essential mediators of many processes in health and disease. They regulate self-/non-self- discrimination, are key elements of cellular communication, cancer, infection and inflammation, and determine protein folding, function and life-times. Moreover, they are integral to the cellular envelope for microorganisms and participate in biofilm formation. These diverse functions of carbohydrates are mediated by carbohydrate-binding proteins, lectins, and the more the knowledge about the biology of these proteins is advancing, the more interfering with carbohydrate recognition becomes a viable option for the development of novel therapeutics. In this respect, small molecules mimicking this recognition process become more and more available either as tools for fostering our basic understanding of glycobiology or as therapeutics. In this review, we outline the general design principles of glycomimetic inhibitors (Section 2). This section is then followed by highlighting three approaches to interfere with lectin function, i.e. with carbohydrate-derived glycomimetics (Section 3.1), novel glycomimetic scaffolds (Section 3.2) and allosteric modulators (Section 3.3). We summarize recent advances in design and application of glycomimetics for various classes of lectins of mammalian, viral and bacterial origin. Besides highlighting design principles in general, we showcase defined cases in which glycomimetics have been advanced to clinical trials or marketed. Additionally, emerging applications of glycomimetics for targeted protein degradation and targeted delivery purposes are reviewed in Section 4.

Tools for the Quality Control of Pharmaceutical Heparin

Heparin is a vital pharmaceutical anticoagulant drug and remains one of the few naturally sourced pharmaceutical agents used clinically. Heparin possesses a structural order with up to four levels of complexity. These levels are subject to change based on the animal or even tissue sources that they are extracted from, while higher levels are believed to be entirely dynamic and a product of their surrounding environments, including bound proteins and associated cations. In 2008, heparin sources were subject to a major contamination with a deadly compound-an over-sulphated chondroitin sulphate polysaccharide-that resulted in excess of 100 deaths within North America alone. In consideration of this, an arsenal of methods to screen for heparin contamination have been applied, based primarily on the detection of over-sulphated chondroitin sulphate. The targeted nature of these screening methods, for this specific contaminant, may leave contamination by other entities poorly protected against, but novel approaches, including library-based chemometric analysis in concert with a variety of spectroscopic methods, could be of great importance in combating future, potential threats.

Design, synthesis, and biomedical applications of synthetic sulphated polysaccharides

This review summarizes the synthetic methods to sulphated polysaccharides, describes their compositional and structural diversity in regards to activity, and showcases their biomedical applications.

The chemokine system, and its CCR5 and CXCR4 receptors, as potential targets for personalized therapy in cancer

Chemokines and their receptors regulate the trafficking of leukocytes in hematopoiesis and inflammation, and thus are fundamental to the immune integrity of the host. In parallel, members of the chemokine system exert a large variety of functions that dictate processes of cancer development and progression. Chemokines can act as pro-tumoral or anti-tumoral regulators of malignancy by affecting cells of the tumor microenvironment (leukocytes, endothelial cells, fibroblasts) and the tumor cells themselves (migration, invasion, proliferation, resistance to chemotherapy). Several of the chemokines are generally skewed towards the cancer-promoting direction, including primarily the CCR5-CCL5 (RANTES) and the CXCR4-CXCL12 (SDF-1) axes. This review provides a general view of chemokines and chemokine receptors as regulators of malignancy, describing their multi-faceted activities in cancer. The tumor-promoting activities of the CCR5-CCL5 and CXCR4-CXCL12 pathways are enlightened, emphasizing their potential use as targets for personalized therapy. Indeed, novel blockers of chemokines and their receptors are constantly emerging, and two chemokine receptor inhibitors were recently approved for clinical use: Maraviroc for CCR5 and Plerixafor for CXCR4. The review addresses ongoing pre-clinical and clinical trials using these modalities and others in cancer. Then, challenges and opportunities of personalized therapy directed against chemokines and their receptors in malignancy are discussed, demonstrating that such novel personalized cancer therapies hold many challenges, but also offer hope for cancer patients.

Anticoagulation Review

Anticoagulants, also known as antithrombotics, are among the most commonly prescribed medications in the United States. Understanding how these medications work, the propensity for interactions with other drugs, dietary factors, and disease states is important for clinicians assessing and providing care to patients in all environments. In this review, we seek to provide essential information for the home health care provider for evaluating patients receiving anticoagulants commonly prescribed in the home health care setting. The low-molecular-weight heparins and vitamin K antagonists are the most commonly used agents for outpatient anticoagulation. New agents, such as the direct factor Xa inhibitors and direct thrombin inhibitors have recently been approved with additional new agents in the approval process and development pipeline. We seek to review the most pertinent information for each of these classes of medications providing information on pharmacology, interactions with other drugs, diet, and diseases and important clinical information.

Case files of the Medical Toxicology Fellowship at Banner Good Samaritan Medical Center in Phoenix, AZ: a non-warfarin anticoagulant overdose

A 50-year-old man presented to the emergency department (ED) following an overdose of his "blood thinners." The patient had become increasingly depressed over financial concerns, prompting a suicide attempt. He declined to provide any details regarding his current medications or his past medical history. A review of the computerized medical record, however, revealed he had a Factor V Leiden mutation with multiple venothromboembolic events. He previously had an inferior vena cava filter placed, and had received tissue plasminogen activator (tPA) for a cerebrovascular accident. A toxicology consult was obtained in the ED.

Extracellular proteases as targets for drug development

Proteases constitute one of the primary targets in drug discovery. In the present review, we focus on extracellular proteases (ECPs) because of their differential expression in many pathophysiological processes, including cancer, cardiovascular conditions, and inflammatory, pulmonary, and periodontal diseases. Many new ECP inhibitors are currently under clinical investigation and a significant increase in new therapies based on protease inhibition can be expected in the coming years. In addition to directly blocking the activity of a targeted protease, one can take advantage of differential expression in disease states to selectively deliver therapeutic or imaging agents. Recent studies in targeted drug development for the metalloproteases (matrix metalloproteinases, adamalysins, pappalysins, neprilysin, angiotensin-converting enzyme, metallocarboxypeptidases, and glutamate carboxypeptidase II), serine proteases (elastase, coagulation factors, tissue/urokinase plasminogen activator system, kallikreins, tryptase, dipeptidyl peptidase IV) and cysteine proteases (cathepsin B) are discussed herein.

Severe bleeding secondary to misuse of fondaparinux: a case report

Venous thromboembolism (VTE) remains a great challenge because of its frequency and of its potential severity. However, VTE treatment can also lead to iatrogenic complications. We report a case of thigh haematoma by a 83-year-old woman under fondaparinux for a solear thrombosis. Then we discuss the indications of Unfractionated Heparin (UFH), Low-Molecular-Weight Heparins (LMWH) and Fondaparinux, which are the three classes of rapidly acting anticoagulant treatments nowadays available. As their efficacy is comparable, the choice between these classes relies on the risk of adverse effects, which depends on some patient's characteristics. LMWH and fondaparinux are contra-indicated by the patients with a renal clearance under 30 ml/min. Only UFH are authorized during the whole pregnancy even though LMWH are more and more used. Fondaparinux has proven its safety by patients over 100 kg. UFH requires a daily biological management whereas it is optional for LMWH and fondaparinux, as long as their contra-indications are taken into account. No Heparin-induced-thrombocytopenia Syndrome (HIT-Sd) has been proven yet under fondaparinux so that platelets management seems not necessary, contrary to UFH and LMWH which require a twice-weekly platelets count. The accuracy of the therapeutic indication should result in the best benefit/risk assessment.

Characterization of anticoagulant heparinoids by immunoprofiling

Heparinoids are used in the clinic as anticoagulants. A specific pentasaccharide in heparinoids activates antithrombin III, resulting in inactivation of factor Xa and–when additional saccharides are present–inactivation of factor IIa. Structural and functional analysis of the heterogeneous heparinoids generally requires advanced equipment, is time consuming, and needs (extensive) sample preparation. In this study, a novel and fast method for the characterization of heparinoids is introduced based on reactivity with nine unique anti-heparin antibodies. Eight heparinoids were biochemically analyzed by electrophoresis and their reactivity with domain-specific anti-heparin antibodies was established by ELISA. Each heparinoid displayed a distinct immunoprofile matching its structural characteristics. The immunoprofile could also be linked to biological characteristics, such as the anti-Xa/anti-IIa ratio, which was reflected by reactivity of the heparinoids with antibodies HS4C3 (indicative for 3-O-sulfates) and HS4E4 (indicative for domains allowing anti-factor IIa activity). In addition, the immunoprofile could be indicative for heparinoid-induced side-effects, such as heparin-induced thrombocytopenia, as illustrated by reactivity with antibody NS4F5, which defines a very high sulfated domain. In conclusion, immunoprofiling provides a novel, fast, and simple methodology for the characterization of heparinoids, and allows high-throughput screening of (new) heparinoids for defined structural and biological characteristics.

Review of fondaparinux sodium injection for the prevention of venous thromboembolism in patients undergoing surgery

The antithrombin binding sequence of heparin, a pentasaccharide, has been synthesized as fondaparinux, an indirect, selective, and reversible factor Xa inhibitor. It can be administered subcutaneously, is well absorbed, and has a half-life of c. 17 hours permitting once-daily injection. It has been evaluated in an extensive study program in major orthopedic surgery, including hip fracture, and in major abdominal surgery with a large proportion of surgery for cancer. The effect is at least as effective as for low-molecular-weight heparins and it has also been shown effective for extended prophylaxis in hip fracture patients. Several thousands of patients have been studied and the substance is safe, although a slightly higher frequency of bleedings is found than in patients on low-molecular-weight heparins. There is no specific antidote but if necessary, recombinant activated factor VII can be used. Other side-effects are rare. Fondaparinux is cost saving and sometimes cost neutral when compared with enoxaparin.

Updates in perioperative coagulation: physiology and management of thromboembolism and haemorrhage

Understanding of blood coagulation has evolved significantly in recent years. Both new coagulation proteins and inhibitors have been found and new interactions among previously known components of the coagulation system have been discovered. This increased knowledge has led to the development of various new diagnostic coagulation tests and promising antithrombotic and haemostatic drugs. Several such agents are currently being introduced into clinical medicine for both the treatment or prophylaxis of thromboembolic disease and for the treatment of bleeding. This review aims to elucidate these new concepts and to outline some consequences for clinical anaesthesia and perioperative medicine.

Delayed-type hypersensitivity skin reactions due to heparins and heparinoids. Tolerance of recombinant hirudins and of the new synthetic anticoagulant fondaparinux

Eczema-like, infiltrated plaques at subcutaneous heparin-injection sites are well-documented side effects of these anticoagulants. They are due to delayed-type hypersensitivity. In 4 patients, patch, intradermal and subcutaneous tests were performed with a panel of unfractionated heparins (UFHs), low-molecular-weight heparins (LMWHs), heparinoids, recombinant hirudins and a new synthetic pentasaccharide anticoagulant fondaparinux sodium, to find safe alternatives. 3 patients were sensitized to all the UFHs and LMWHs. The LMWH tinzaparin sodium and the heparinoid pentosan polysulfate were found to be a possible substitute in patient no. 1 and 2, respectively. The recombinant hirudins and fondaparinux sodium were tolerated without any side effects in all patients tested. Fondaparinux is a synthetic copy of a pentasaccharide sequence in the heparin molecule. It is the first in a new class of antithrombotic agents. Our study suggests that it is a new safe alternative in patients with eczema-like, infiltrated plaques at subcutaneous heparin-injection sites.