Ximelagatran/Melagatran

Clinical Studies with Anticoagulants that Have Changed Clinical Practice

Anticoagulant therapy is the cornerstone of treatment and prevention of arterial and venous thromboembolism. Taking a historical perspective, starting in the 1960s, and progressing through to 2022, we discuss key clinical trials of anticoagulants that have changed clinical practice, and examine obstacles encountered in bringing these anticoagulants to the clinic. The design of some of the early studies that shaped clinical practice was poor by current standards, but their results were influential because nothing better was available. Both heparin and vitamin K antagonists had been in clinical use for several decades before well-designed trials in the 1980s optimized their dosing and enhanced their safety and efficacy. Low-molecular-weight heparin then replaced unfractionated heparin because it had a more predictable dose-response and a longer half-life, thereby allowing it to be used conveniently in out-of-hospital settings. More recently, direct oral anticoagulants became the oral anticoagulants of choice for most indications because they were shown to be at least as safe and effective as vitamin K antagonists when used in fixed doses without the need for laboratory monitoring. The design of the trials that led to the approval of the direct oral anticoagulants was excellent, but further studies are required to optimize their dosing in selected patients who were underrepresented in these trials.

Synthesis of Chiral Tetrasubstituted Azetidines from Donor-Acceptor Azetines via Asymmetric Copper(I)-Catalyzed Imido-Ylide [3+1]-Cycloaddition with Metallo-Enolcarbenes

The all-cis stereoisomers of tetrasubstituted azetidine-2-carboxylic acids and derivatives that possess three chiral centers have been prepared in high yield and stereocontrol from silyl-protected Z-γ-substituted enoldiazoacetates and imido-sulfur ylides by asymmetric [3+1]-cycloaddition using chiral sabox copper(I) catalysis followed by Pd/C catalytic hydrogenation. Hydrogenation of the chiral p-methoxybenzyl azetine-2-carboxylates occurs with both hydrogen addition to the C=C bond and hydrogenolysis of the ester.

New Anticoagulants for the Prevention and Treatment of Venous Thromboembolism

Anticoagulant drugs, like vitamin K antagonists and heparin, have been the mainstay for the treatment and prevention of venous thromboembolic disease for many years. Although effective if appropriately used, traditional anticoagulants have several limitations such as unpredictable pharmacologic and pharmacokinetic responses and various adverse effects including serious bleeding complications. New oral anticoagulants have recently emerged as an alternative because of their rapid onset/offset of action, predictable linear dose-response relationships and fewer drug interactions. However, they are still associated with problems such as bleeding, lack of reversal agents and standard laboratory monitoring. In an attempt to overcome these drawbacks, key steps of the hemostatic pathway are investigated as targets for anticoagulation. Here we reviewed the traditional and new anticoagulants with respect to their targets in the coagulation cascade, along with their therapeutic advantages and disadvantages. In addition, investigational anticoagulant drugs currently in the development stages were introduced.

Thrombin inhibitors: surgical considerations and pharmacology

The new thrombin inhibitors have provided an exciting opportunity for effective thromboprophylaxis without some of the disadvantages of the current anticoagulants. These drugs are orally administered, have predictable pharmacokinetics and dose-response, do not require monitoring and have an acceptable safety profile when used appropriately. However, inappropriate prescribing of these drugs may lead to catastrophic consequences. Clinicians need to be aware of some of the drawbacks associated with the use of dabigatran and, in particular, its reduced clearance in the setting of renal failure and the lack of an effective reversing agent when bleeding does occur. In this review, the evidence for efficacy and safety of dabigatran is discussed. We also aim to provide practical clinical advice on the pre- and post-operative management of the elective and emergency surgical patient on dabigatran and provide guidelines for the management of acute haemorrhage in the context of dabigatran therapy.

Looking at the proteases from a simple perspective

Proteases have received enormous interest from the research and medical communities because of their significant roles in several human diseases. Some examples include the involvement of thrombin in thrombosis, HIV-1 protease in Acquired Immune Deficiency Syndrome, cruzain in Trypanosoma cruzi infection, and membrane-type 1 matrix metalloproteinase in tumor invasion and metastasis. Many efforts has been undertaken to design effective inhibitors featuring potent inhibitory activity, specificity, and metabolic stability to those proteases involved in such pathologies. Protease inhibitors usually target the active site, but some of them act by other inhibitory mechanisms. The understanding of the structure-function relationships of proteases and inhibitors has an impact on new inhibitor drugs designing. In this paper, the structures of four proteases (thrombin, HIV-protease, cruzain, and a matrix metalloproteinase) are briefly reviewed, and used as examples of the importance of proteases for the development of new treatment strategies, leading to a longer and healthier life.

Review article: thromboprophylaxis after total hip replacement

The risk of secondary haematologic complications such as deep vein thrombosis or pulmonary embolism increases significantly when a transient period of hypercoagulability is induced after total hip replacement (THR). A number of drug-based anticoagulant approaches are available to modulate this risk, but the optimal length of therapy for such approaches remains unclear. The literature was reviewed for evidence-based support of the routine use of an extended course (>14 days) of thromboprophylaxis after THR. Electronic databases and real-time online literature searches were performed, using the PubMed (Medline), EMBASE, CINAHL and GoogleScholar, and the Cochrane and British Medical Journal Clinical Evidence libraries. Author-defined key word searches were performed. Only articles in the English language, for which full text could be retrieved, were reviewed. There is robust evidence to support an extended course (>14 days) of thromboprophylaxis after THR. Such recommendations have been translated into the guidelines of key professional bodies, including those of the American College of Chest Physicians. Meta-review suggests a clear benefit of such regimens and supports wider adoption, even when weighed against a small increase in adverse events.

Complications in Peripheral Vascular Interventions: Emerging Role of Direct Thrombin Inhibitors

Unfractionated heparin is associated with a high rate of bleeding and thrombotic complications during peripheral vascular interventions (PVIs). Newer anticoagulants such as direct thrombin inhibitors might offer significant advantages over heparin. Early data with bivalirudin in the peripheral circulation are promising. Bivalirudin appears safe and effective when used during PVIs. Data with the use of other direct thrombin inhibitors (hirudin, r-hirudin, argatroban, and melagatran) in peripheral interventions are still lacking. Among these, argatroban and melagatran have pharmacologic properties that might offer some advantages in PVI, but further studies are needed to demonstrate their safety and effectiveness.

Assessment of the Risk and the Prophylaxis of Venous Thromboembolism in Surgical Patients

This review article first deals with risk factors for developing postoperative venous thromboembolism. The various pharmacological prophylactic methods available today are summarized with focus on dominating method low molecular weight heparin and the two new ones, the Xa inhibitor fondaparinux and the IIa inhibitor ximelagatran, both approved in orthopaedic surgery. The optimal timing to start prophylaxis is between 2 hours before and 10 hours after surgery. Evidence is accumulating that some in risk groups prolonged prophylaxis is indicated, ie. elective hip surgery, probably hip fracture surgery and probably also patients operated on for abdominal/pelvic cancer.

Transitioning from Traditional to Novel Anticoagulants: The Impact of Oral Direct Thrombin Inhibitors on Anticoagulation Management

Limitations of traditional anticoagulants have led to the need for structured services to provide anticoagulation monitoring. Anticoagulation management services have historically filled this role. Novel antithrombotic agents currently in development have the potential to improve on the limitations of vitamin K antagonists and injectable forms of heparin and to change the field of anticoagulation management. Of the emerging agents, oral direct thrombin inhibitors present the most promise and have a more practical clinical profile. The introduction of the oral direct thrombin inhibitors may present both an opportunity and a threat to anticoagulation management services and anticoagulation service providers. Traditional anticoagulation monitoring services will have to retool for the future if they are to remain relevant in the new era of novel antithrombotic.agents.

New approaches to anticoagulation in atrial fibrillation

Oral direct thrombin inhibitors (DTIs) are a potential alternative to vitamin K antagonists, such as warfarin, for anticoagulant therapy. The oral DTI at the most advanced stage of clinical development is ximelagatran, which is rapidly absorbed and bioconverted to the active form melagatran. Oral ximelagatran has been evaluated in randomized, controlled trials for several indications, including stroke prevention in atrial fibrillation (AF). Recently, two pivotal phase III trials demonstrated that fixed-dose oral ximelagatran, 36 mg twice daily without coagulation monitoring, prevents stroke and systemic embolic events in patients with nonvalvular AF as effectively as well-controlled, adjusted-dose warfarin. Oral ximelagatran was generally well tolerated and caused less total (major plus minor) bleeding than warfarin. In a minority of ximelagatran-treated patients, elevated serum alanine aminotransferase levels were reported, but were typically not associated with specific symptoms, and returned toward the pretreatment baseline whether treatment was continued or discontinued. In AF, oral ximelagatran promises a better benefit to risk ratio than warfarin.