Idraparinux versus standard therapy for venous thromboembolic disease

New anticoagulants: how to deal with treatment failure and bleeding complications

Conventional anticoagulants have proven efficacy in the management of thromboembolism. Their adverse effects and a narrow therapeutic window, necessitating regular need for monitoring, however, have long been an incentive for the development of safer anticoagulants without compromising efficacy. Over the last decade or so several new parenteral and oral anticoagulants have been launched with efficacy comparable with conventional agents. From fondaparinux to its long acting derivative idraparinux, and the factor Xa inhibitor rivaroxaban to the direct thrombin inhibitor dabigatran, the advent of new anticoagulants is radically changing anticoagulation. For conventional anticoagulants, despite their shortcomings, effective methods of reversing their anticoagulant effects exist. Moreover, strategies to deal with the occurrence of fresh thrombotic events in the face of therapeutic anticoagulation with the conventional agents have also been addressed. Nevertheless, for the new anticoagulants, the optimal management of these complications remains unknown. This review explores these issues in the light of current evidence.

[New antithrombotic drugs for the treatment of venous thromboembolism]

Numerous newer anticoagulants are under advanced clinical development for the treatment of venous thromboembolism. These new drugs specifically inhibit activated factors II or X, with predictable effects and no need for dose modification and laboratory monitoring. The main direct activated factor X (FXa) inhibitors are rivaroxaban, apixaban and edoxaban. They are taken orally once or twice per day. Dabigatran is the main inhibitor of activated factor II (IIa) and is administered orally once daily. Dabigatran and rivaroxaban are already licensed for the prevention of thromboembolic events following major orthopedic surgery such as total hip and knee replacement. They will probably soon be authorized for the treatment of venous thromboembolism, if they both confirm their efficacy and safety, and can demonstrate their cost-effectiveness. However, only rivaroxaban has been tested as a stand-alone treatment, whereas dabigatran was compared to vitamin K antagonism after a standard treatment regimen based on heparin or its derivates.

Role of factor xa inhibitors in cancer-associated thrombosis: any new data?

The association between cancer and venous thromboembolism (VTE) has been well documented in the literature. Prevention and treatment of VTE in cancer patients is imperative. Typically, the mainstay regimen for VTE prevention and treatment has been anticoagulation therapy, unless contraindicated. This therapy consists of unfractionated heparin (UFH), low-molecular-weight heparin (LMWH), factor Xa inhibitor, or vitamin K antagonist (VKA). Current guidelines recommend LMWH over VKA for the treatment of VTE in cancer patients. Factor-specific anticoagulants have been proven safe and effective, and recently factor Xa inhibitors have emerged as a treatment alternative to heparins and VKA. Currently, three factor Xa inhibitors have been identified: fondaparinux (the only one approved so far by the US Food and Drug Administration), idraparinux (in clinical trials), and idrabiotaparinux (in clinical trials). This paper will examine the role of these agents, focusing on fondaparinux, for the prevention and treatment of VTE in cancer patients.

Inhibitors of propagation of coagulation: factors V and X

Cardiovascular diseases are still the most important cause of morbidity and mortality in western countries and antithrombotic treatment is nowadays widely used. Drugs able to reduce coagulation activation are the treatment of choice for a number of arterial and/or venous thromboembolic conditions. Some of the drugs currently used for this purpose, such as heparins (UFH or LMWH) and VKA, have limitations consisting of a narrow therapeutic window and an unpredictable response with the need of laboratory monitoring in order to assess their efficacy and safety. These drawbacks have stimulated an active research aimed to develop new drugs able to act on single factors involved in the coagulation network, with predictable response. Intense experimental and clinical work on new drugs has focused on synthetic agents, which could preferably be administered orally and at fixed doses. The most advanced clinical development with new anticoagulants has been achieved for those inhibiting FXa and some of them, like fondaparinux, are already currently used in clinical practice. Other agents, such as rivaroxaban, apixaban, otamixaban and edoxaban are under development and have already been studied or are currently under investigation in large scale phase III clinical trials for prevention and treatment of venous thromboembolism, atrial fibrillation and acute coronary syndromes. Some of them have proved to be more effective than conventional therapy. Data on some agents inhibiting FVa are still preliminary and some of these drugs have so far been considered only in patients with disseminated intravascular coagulation secondary to sepsis.

[New anticoagulants in the prevention and treatment of venous thromboembolism]

Clinical data on the risk factors, incidence, consequences and current treatment options of venous thromboembolism are reviewed. Current guidelines advise anticoagulant treatment for a few weeks or months in immobilized patients treated in hospital, and after major surgery. The initial treatment is based on heparin, followed by vitamin K antagonist treatment. Recently a number of new, partially orally administered medications have undergone clinical investigations and based on the results three of them were also registered for the prevention and treatment of venous thromboembolism. Direct thrombin inhibitors, direct and indirect Factor Xa inhibitors exhibited proven non-inferiority or superiority compared with traditional treatment options. The superior efficacy or non-inferiority was not accompanied with an increase in the bleeding risk. Results of the most important clinical trials are reviewed. Based on these results, prevention and treatment of venous thromboembolism will change substantially in the near future.

Emerging anticoagulants

INTRODUCTION

Thromboembolic disease encompasses a spectrum of conditions extending from deep vein thrombosis to stroke and myocardial infarction. The current anticoagulation therapy is cumbersome and characterized by several important drawbacks.

AREAS COVERED

Existing treatments and latest breakthroughs on emerging anticoagulants are presented. Oral and parenteral novel anticoagulants are being developed and tested for efficacy and safety and results are being published regularly. The introduction of novel anticoagulants marks a new era in the management of anticoagulated patients. It is important for the healthcare provider to understand the benefits and risks of the armamentarium of anticoagulants that will be available in the very near future. The critical conclusions drawn will help the reader look past what is the most highlighted feature of the new anticoagulantion era: the non-necessity for monitoring.

EXPERT OPINION

Currently, novel anticoagulants seem to lack the indefinable 'charm' of weakness. However, important questions remain unanswered and will require in-depth evaluations.

Outpatient versus inpatient treatment for patients with acute pulmonary embolism: an international, open-label, randomised, non-inferiority trial

BACKGROUND

Although practice guidelines recommend outpatient care for selected, haemodynamically stable patients with pulmonary embolism, most treatment is presently inpatient based. We aimed to assess non-inferiority of outpatient care compared with inpatient care.

METHODS

We undertook an open-label, randomised non-inferiority trial at 19 emergency departments in Switzerland, France, Belgium, and the USA. We randomly assigned patients with acute, symptomatic pulmonary embolism and a low risk of death (pulmonary embolism severity index risk classes I or II) with a computer-generated randomisation sequence (blocks of 2-4) in a 1:1 ratio to initial outpatient (ie, discharged from hospital ≤24 h after randomisation) or inpatient treatment with subcutaneous enoxaparin (≥5 days) followed by oral anticoagulation (≥90 days). The primary outcome was symptomatic, recurrent venous thromboembolism within 90 days; safety outcomes included major bleeding within 14 or 90 days and mortality within 90 days. We used a non-inferiority margin of 4% for a difference between inpatient and outpatient groups. We included all enrolled patients in the primary analysis, excluding those lost to follow-up. This trial is registered with ClinicalTrials.gov, number NCT00425542.

FINDINGS

Between February, 2007, and June, 2010, we enrolled 344 eligible patients. In the primary analysis, one (0·6%) of 171 outpatients developed recurrent venous thromboembolism within 90 days compared with none of 168 inpatients (95% upper confidence limit [UCL] 2·7%; p=0·011). Only one (0·6%) patient in each treatment group died within 90 days (95% UCL 2·1%; p=0·005), and two (1·2%) of 171 outpatients and no inpatients had major bleeding within 14 days (95% UCL 3·6%; p=0·031). By 90 days, three (1·8%) outpatients but no inpatients had developed major bleeding (95% UCL 4·5%; p=0·086). Mean length of stay was 0·5 days (SD 1·0) for outpatients and 3·9 days (SD 3·1) for inpatients.

INTERPRETATION

In selected low-risk patients with pulmonary embolism, outpatient care can safely and effectively be used in place of inpatient care.

FUNDING

Swiss National Science Foundation, Programme Hospitalier de Recherche Clinique, and the US National Heart, Lung, and Blood Institute. Sanofi-Aventis provided free drug supply in the participating European centres.

How to prevent, treat, and overcome current clinical challenges of VTE

Venous thromboembolism (VTE) is most commonly initially treated with low molecular weight heparin (LMWH), fondaparinux, or unfractionated heparin, in combination with vitamin-K antagonists (VKA) for long-term treatment. VKA have some drawbacks, however, which has led to the development of new anticoagulants. Most of these new drugs can be administered orally, and have been investigated in several phase III clinical trials. The benefits of these anticoagulants include their stable therapeutic effect, reduced interactions with other medication and food, and, therefore, the reduced need for regular monitoring. The duration of anticoagulant treatment for VTE is usually 3-12 months, but depends on the balance between the risks of recurrent thrombosis, major bleeding, and the patient's preference. Clinical decision rules to assess the risk of recurrence to tailor the duration of anticoagulant treatment are being investigated. The beneficial aspects of novel anticoagulants may prolong the duration of treatment. VTE treatment should be adjusted in special patient groups, such as in cases of malignancy, renal failure, pregnancy, or obesity. In this review, the current and future aspects of the treatment of VTE are explored.

Novos anticoagulantes para a profilaxia do tromboembolismo venoso em cirurgias ortopédicas de grande porte

Após cerca de 50 anos de experiência com a heparina e antagonistas da vitamina K (AVK), pesquisas e estudos com novos anticoagulantes vêm evoluindo de forma crescente nos últimos anos. Embora consagrados pelo uso, os anticoagulantes tradicionais têm limitações importantes em termos de controle laboratorial, complicações, efeitos colaterais, interações com medicamentos e dieta. A heparina não fracionada (HNF) tem interação com proteínas plasmáticas e parede vascular, pode desencadear trombocitopenia induzida pela heparina (TIH), só pode ser administrada por via parenteral, exige controle laboratorial pelo teste da tromboplastina parcial ativada (TTPa), pode provocar osteoporose e alopecia quando usada por períodos prolongados e sua produção tem origem biológica. A AVK tem a vantagem de poder ser ministrada por via oral, mas o controle (feito pela razão normatizada internacional) pode ser difícil em alguns casos, já que tem início de ação demorado, janela terapêutica estreita, interação com dieta e grande número de medicamentos, pode provocar necrose de pele em portadores de deficiência de antitrombina e de proteínas C e S, e pode induzir alterações fetais quando usada na gravidez. Na década de 1980, surgiram as heparinas de baixo peso molecular, que foram uma evolução da heparina não fracionada, pois apresentaram maior biodisponibilidade, dosagem por peso corporal, sem necessidade de controle laboratorial, administração por via subcutânea, menor risco de trombocitopenia induzida pela heparina, e eficácia e segurança similares à heparina não fracionada. Na última década surgiram, então, uma série de novos anticoagulantes no mercado, os quais têm apresentado resultados promissores em várias situações de profilaxia e tratamento do tromboembolismo venoso. Nesta revisão, são apresentados as novas heparinas de baixo peso molecular, as heparinas de ultrabaixo peso molecular, os pentassacarídeos, os novos inibidores diretos do fator Xa e inibidores do fator IIa.

Clinical pharmacology of direct and indirect factor Xa inhibitors

The limitations of conventional anticoagulants have stimulated the development of new anticoagulants. The central position of factor Xa (FXa) at the junction of the intrinsic and extrinsic pathways in the coagulation cascade means that direct and indirect FXa inhibitors have increasingly changed antithrombotic strategies. FXa inhibitors potently and selectively inhibit thrombin formation rather than thrombin activity. Direct FXa inhibitors may directly bind to FXa, whereas indirect inhibitors are dependent on antithrombin. Direct inhibitors may bind free FXa and, in contrast to indirect inhibitors, FXa within the prothrombinase complex or within clots as well. Fondaparinux is the prototype indirect FXa inhibitor and has been extensively studied in the prevention and treatment of thromboembolic diseases, including acute coronary syndromes. Due to a favourable efficacy and safety profile and convenient once-daily dosing without the need for monitoring, fondaparinux is preferentially recommended in recent guidelines dealing with antithrombotic treatment. A number of small-molecule direct FXa inhibitors are currently at different stages of clinical development. After an extensive clinical trial programme demonstrating superior efficacy without a significant increase in major bleeds compared with enoxaparin, rivaroxaban is now available for the prevention of thromboembolic events in patients undergoing orthopaedic surgery. Rivaroxaban also offers the convenience of oral once-daily dosing without the need for monitoring. Whereas most direct FXa inhibitors are orally active, otamixaban is administered intravenously, offering rapid on-off anticoagulant activity. Other compounds under development may offer additional options for tailored antithrombotic strategies according to differing indications, clinical situations and patient variables.

Randomized trial of the effect of the low molecular weight heparin nadroparin on survival in patients with cancer

PURPOSE

Earlier studies showed that low molecular weight heparin significantly prolongs the survival of a wide variety of patients with cancer without venous thromboembolism. This study was designed to confirm these findings in a more homogeneous group of patients with cancer.

PATIENTS AND METHODS

In this multicenter, randomized, open-label study, patients with non-small-cell lung cancer (stage IIIB), hormone-refractory prostate cancer, or locally advanced pancreatic cancer were randomly assigned to nadroparin or to no nadroparin in addition to their standard anticancer treatment. In the nadroparin arm, subcutaneous nadroparin was administered for 6 weeks (2 weeks at therapeutic dose, and 4 weeks at half therapeutic dose). The patients were eligible to receive additional cycles of nadroparin (2 weeks at therapeutic dose, and 4 weeks of washout period). Outcomes were overall survival, time to progression, and major bleeding. All study outcomes were adjudicated by an independent, blinded committee.

RESULTS

A total of 244 patients were allocated to nadroparin, and 259 were allocated to the control group. A median survival of 13.1 months was observed in the nadroparin recipients compared with 11.9 months in the no-treatment arm (hazard ratio, 0.94; 95% CI, 0.75 to 1.18, adjusted for cancer type). No difference in time to progression was observed. The number of major bleedings was comparable at 4.1% in the nadroparin set and 3.5% in the control set.

CONCLUSION

This study did not show a survival benefit of nadroparin in patients with advanced prostate, lung, or pancreatic cancer. Given the ongoing studies in this area and the previous data, the role of low molecular weight heparins in cancer survival remains undefined.

Comparison of tinzaparin and acenocoumarol for the secondary prevention of venous thromboembolism: a multicentre, randomized study

The objective of the present study was to evaluate the efficacy, safety and healthcare resource utilization of long-term treatment with tinzaparin in symptomatic patients with acute pulmonary embolism as compared to standard therapy. In this open-label trial, 102 patients with objectively confirmed pulmonary embolism were randomized to receive, after initial treatment with tinzaparin, either tinzaparin (175 IU/kg/day) or international normalized ratio-adjusted acenocoumarol for 6 months. Clinical endpoints were assessed during the 6 months of treatment. A pharmacoeconomic analysis was carried out to evaluate the cost of the long-term treatment with tinzaparin in comparison with the standard one. In an intention-to-treat analysis, one of 52 patients developed recurrent venous thromboembolism in the tinzaparin group compared with none of the 50 patients in the acenocoumarol group. One patient in each group had a major haemorrhagic complication. Six patients in the acenocoumarol group had minor bleeding compared with none in the tinzaparin group (P = 0.027). Median hospital length of stay was shorter in the tinzaparin group compared to the acenocoumarol group (7 versus 9 days; P = 0.014). When all the direct and indirect cost components were combined for the entire population, we found a slight, nonstatistically significant (mean difference €345; 95% CI 1382-2071; P = 0.69) reduction in total cost with tinzaparin. Symptomatic acute pulmonary embolism treatment with full therapeutic doses of tinzaparin for 6 months is a feasible alternative to conventional treatment with vitamin K antagonists.

New synthetic antithrombotic agents for venous thromboembolism: pentasaccharides, direct thrombin inhibitors, direct Xa inhibitors

Heparin and low molecular weight heparins have limitations in their efficacy and safety for the prevention and treatment of venous thromboembolism (VTE). New synthetic antithrombotic drugs, designed with the intention of improving the therapeutic window for prophylaxis and treatment, are in various stages of development. Synthetic pentasaccharides include fondaparinux and its long-acting analogue idraparinux. Dabigatran is a direct thrombin inhibitor that has undergone clinical trials for VTE prophylaxis and treatment. Direct factor Xa inhibitors include rivaroxiban, which has shown promising results for VTE prophylaxis and is being studied for VTE treatment, as well as apixaban and betrixaban, which are at earlier stages of clinical validation. These newer agents may represent viable options for prophylaxis and therapy as further clinical studies are performed.

Efficacy and safety of once weekly subcutaneous idrabiotaparinux in the treatment of patients with symptomatic deep venous thrombosis

BACKGROUND

Idraparinux, a long acting inhibitor of factor (F) Xa, is as effective as standard anticoagulant therapy for patients with symptomatic deep venous thrombosis. We investigated the potential use of the biotinylated molecule, idrabiotaparinux. Biotinylation enables reversal of the anticoagulant effect.

METHODS

We performed a randomized double-blind trial in 757 patients with symptomatic deep venous thrombosis, comparing equimolar doses of idrabiotaparinux (3 mg) with idraparinux (2.5 mg), both given subcutaneously, once weekly for 6 months. Inhibition of FXa activity was measured at days 15, 36, 57, 92 and 183. The efficacy outcome was recurrent venous thromboembolism. The safety outcomes were clinically relevant bleeding and death.

RESULTS

Inhibition of FXa was similar in the two treatment groups at each time point of measurement. Recurrent venous thromboembolism during the 6-month treatment period occurred in nine of 386 patients (2.3%) in the idrabiotaparinux group and in 12 of 371 patients (3.2%) in the idraparinux group, a difference of - 0.9% (95% confidence interval, -3.2-1.4%). The incidence of clinically relevant bleeding was 5.2% in the idrabiotaparinux group and 7.3% in the idraparinux group (P = 0.29), a difference of - 2.1% (95% confidence interval, -5.6-1.4%). Six patients (1.6%) who received idrabiotaparinux died, compared with 12 patients (3.2%) given idraparinux, a difference of - 1.7% (95% confidence interval, -3.9-0.5%).

CONCLUSIONS

Idrabiotaparinux has a similar time course of FXa inhibition, efficacy and safety to idraparinux for the treatment of deep venous thrombosis.

Oral rivaroxaban for symptomatic venous thromboembolism

BACKGROUND

Rivaroxaban, an oral factor Xa inhibitor, may provide a simple, fixed-dose regimen for treating acute deep-vein thrombosis (DVT) and for continued treatment, without the need for laboratory monitoring.

METHODS

We conducted an open-label, randomized, event-driven, noninferiority study that compared oral rivaroxaban alone (15 mg twice daily for 3 weeks, followed by 20 mg once daily) with subcutaneous enoxaparin followed by a vitamin K antagonist (either warfarin or acenocoumarol) for 3, 6, or 12 months in patients with acute, symptomatic DVT. In parallel, we carried out a double-blind, randomized, event-driven superiority study that compared rivaroxaban alone (20 mg once daily) with placebo for an additional 6 or 12 months in patients who had completed 6 to 12 months of treatment for venous thromboembolism. The primary efficacy outcome for both studies was recurrent venous thromboembolism. The principal safety outcome was major bleeding or clinically relevant nonmajor bleeding in the initial-treatment study and major bleeding in the continued-treatment study.

RESULTS

The study of rivaroxaban for acute DVT included 3449 patients: 1731 given rivaroxaban and 1718 given enoxaparin plus a vitamin K antagonist. Rivaroxaban had noninferior efficacy with respect to the primary outcome (36 events [2.1%], vs. 51 events with enoxaparin-vitamin K antagonist [3.0%]; hazard ratio, 0.68; 95% confidence interval [CI], 0.44 to 1.04; P<0.001). The principal safety outcome occurred in 8.1% of the patients in each group. In the continued-treatment study, which included 602 patients in the rivaroxaban group and 594 in the placebo group, rivaroxaban had superior efficacy (8 events [1.3%], vs. 42 with placebo [7.1%]; hazard ratio, 0.18; 95% CI, 0.09 to 0.39; P<0.001). Four patients in the rivaroxaban group had nonfatal major bleeding (0.7%), versus none in the placebo group (P=0.11).

CONCLUSIONS

Rivaroxaban offers a simple, single-drug approach to the short-term and continued treatment of venous thrombosis that may improve the benefit-to-risk profile of anticoagulation. (Funded by Bayer Schering Pharma and Ortho-McNeil; ClinicalTrials.gov numbers, NCT00440193 and NCT00439725.).

Characterization of the plasma and blood anticoagulant potential of structurally and mechanistically novel oligomers of 4-hydroxycinnamic acids

Recently, we designed sulfated dehydropolymers (DHPs) of 4-hydroxycinnamic acids that displayed interesting anticoagulant properties. Structurally and mechanistically, sulfated DHPs are radically different from all the anticoagulants studied to date. To assess whether their unique mechanism and structure is worth exploiting for further rational design of homogeneous DHP-based molecules, we investigated their anticoagulant potential in human plasma and blood using a range of clotting assays. Sulfated DHPs prolong plasma clotting times, prothrombin and activated partial thromboplastin times at concentrations comparable to the clinically used low-molecular-weight heparin, enoxaparin. Fibrin formation studies on human plasma show that there is a structural dependence of anticoagulant action. Human whole blood studies using thromboelastography and hemostasis analysis system indicate that they are 17-140-fold less potent than enoxaparin. These results demonstrate that sulfated DHPs possess good in-vitro and ex-vivo activity, which will likely be improved through a rational design.

Anticoagulation in the Elderly

Management of anticoagulation in elderly patients represents a particularly challenging issue. Indeed, this patient population is at high thromboembolic risk, but also at high hemorrhagic risk. Assessment of the benefit-risk balance of anticoagulation is the key point when decisions are made about introducing and/or continuing such treatments in the individual elderly patient. In order to maximise the safety of anticoagulation in the elderly, some specific considerations need to be taken into account, including renal insufficiency, modified pharmacodynamics of anticoagulants, especially vitamin K antagonists, and the presence of multiple comorbidities and concomitant medications. New anticoagulants could greatly simplify and possibly increase the safety of anticoagulation in the elderly in the near future.

New parenteral anticoagulants in development

The therapeutic armamentarium of parenteral anticoagulants available to clinicians is mainly composed by unfractionated heparin (UFH), low-molecular-weight heparin (LMWH), fondaparinux, recombinant hirudins (i.e. bivalirudin, desirudin, lepirudin) and argatroban. These drugs are effective and safe for prevention and/or treatment of thromboembolic diseases but they have some drawbacks. Among other inconveniences, UFH requires regular anticoagulant monitoring as a result of variability in the anticoagulant response and there is a risk of serious heparin-induced thrombocytopaenia (HIT). LMWH, fondaparinux and recombinant hirudins are mainly cleared through the kidneys and their use in patients with severe renal insufficiency may be problematic. LMWH is only partially neutralized by protamine while fondaparinux and recombinant hirudins have no specific antidote. Novel anticoagulants in development for parenteral administration include new indirect activated factor Xa (FXa) inhibitors (idrabiotaparinux, ultra-low-molecular-weight heparins [semuloparin, RO-14], new LMWH [M118]), direct FXa inhibitors (otamixaban), direct FIIa inhibitors (flovagatran sodium, pegmusirudin, NU172, HD1-22), direct FXIa inhibitors (BMS-262084, antisense oligonucleotides targeting FXIa, clavatadine), direct FIXa inhibitors (RB-006), FVIIIa inhibitors (TB-402), FVIIa/tissue factor inhibitors (tifacogin, NAPc2, PCI-27483, BMS-593214), FVa inhibitors (drotrecogin alpha activated, ART-123) and dual thrombin/FXa inhibitors (EP217609, tanogitran). These new compounds have the potential to complement established parenteral anticoagulants. In the present review, we discuss the pharmacology of new parenteral anticoagulants, the results of clinical studies, the newly planned or ongoing clinical trials with these compounds, and their potential advantages and drawbacks over existing therapies.

Novel anticoagulant therapy: principle and practice

Currently, there are several lines of evidence supporting the interplay between coagulation and inflammation in the propagation of various disease processes, including venous thromboembolism (VTE) and inflammatory diseases. Major advances in the development of oral anticoagulants have resulted in considerable progress toward the goal of safe and effective oral anticoagulants that do not require frequent monitoring or dose adjustment and have minimal food/drug interactions. Indirect inhibitors such as low-molecular-weight heparin (LMWH) and the pentasaccharide fondaparinux represent improvements over traditional drugs such as unfractionated heparin for acute treatment of VTE, constituting a more targeted anticoagulant approach with predictable pharmacokinetic profiles and no requirement for monitoring. Vitamin K antagonist, with its inherent limitations in terms of multiple food and drug interactions and frequent need for monitoring, remains the only oral anticoagulant approved for long-term secondary thromboprophylaxis in VTE. The oral-direct thrombin inhibitor ximelagatran was withdrawn from the world market due to safety concerns. Newer anticoagulant drugs such as parenteral pentasaccharides (idraparinux, SSR126517E), novel oral-direct thrombin inhibitors (dabigatran), oral-direct factor Xa inhibitors (rivaroxaban, apixaban, YM-150, DU-176b), and tissue factor/factor VIIa complex inhibitors have been "tailor-made" to target specific procoagulant complexes and have the potential to greatly expand oral antithrombotic targets for both acute and long-term treatment of VTE, acute coronary syndromes, and for the prevention of stroke in atrial fibrillation patients.

New aspects on treatment modalities for thromboembolic episodes

Venous thromboembolism (VTE) has been treated with a glycosaminoglycan, followed by a vitamin K antagonist during the past 60 years. During the past two decades the glycosaminoglycans have undergone refinement, allowing for simplification of care for these patients, but parenteral administration is still required. Therefore, the current completion of phase III trials with selective, predictable and orally available anticoagulants with rapid onset brings promise for a change in paradigm in the treatment of VTE in the next few years. Whereas these efforts will lead to further simplification of the therapy there are also trials conducted to advance the treatment by rapid resolution of the thromboembolism in order to improve long-term outcome. Catheter-directed thrombolysis, perhaps also with thrombus fragmentation and stent insertion, if demonstrated to be successful for the reduction of the postthrombotic syndrome, will only be an alternative for a minority of patients due to the complexity, risks and cost of therapy. This treatment increases the complexity at the same time as new drug regimens offer simplicity. This review focuses on the novel therapies for VTE although the new anticoagulants will also play a major role in the management of arterial disease, which will be briefly presented.

Alternatives to warfarin--the next generation of anticoagulants

Anticoagulation therapy plays an important role in the management of cardiovascular disease. Currently, oral anticoagulation therapy is reliant on vitamin K antagonists (VKA). In clinical practice, VKA present several limitations including a narrow therapeutic window and frequent drug and food interactions. Despite the clear clinical need for alternative anticoagulants it is only within the last decade that significant progress has been made. These new anticoagulants target specific factors in the hemostatic network and appear to overcome some of the difficulties seen with VKA. Many have now progressed to phase III clinical trials including patients with cardiovascular disease. This review aims to highlight the exciting progress that has been made in the development of these new anticoagulants. It will focus on the key agents that have demonstrated the most promise in clinical trials to date. This will include data on cardiovascular indications for anticoagulant therapy. Finally, the review aims to analyze the future prospects for these new agents. Several issues remain to be addressed for these agents to finally replace vitamin K antagonists as the mainstay of anticoagulant therapy.

[A new deal with new anticoagulants?]

The anticoagulant market has been very active recently with the development of new compounds including injectable anti-Xa such as fondaparinux, already available, and idraparinux, already replaced by its new biotynilateed form, and new oral drugs which can be divided into anti-IIa with dabigatran already available, and anti-Xa, such as the recently marketed rivaroxaban and apixaban still in the development stage. Others are coming forward. The competition is strong and the place for each drug remains to be determined. This review discusses these new anticoagulants in terms of efficacy and tolerance based on data in the literature. These recent reports mainly concern prophylaxis for orthopedic surgery but also consider treatment of deep venous thrombosis. The results of studies in heart patients have raised much curiosity since they will be determinant in the future use of innovating compounds, which could replace current oral anticoagulants. This will be upcoming but not yet for tomorrow.

Factors at admission associated with bleeding risk in medical patients: findings from the IMPROVE investigators

BACKGROUND

Acutely ill, hospitalized medical patients are at risk of VTE. Despite guidelines for VTE prevention, prophylaxis use in these patients is still poor, possibly because of fear of bleeding risk. We used data from the International Medical Prevention Registry on Venous Thromboembolism (IMPROVE) to assess in-hospital bleeding incidence and to identify risk factors at admission associated with in-hospital bleeding risk in acutely ill medical patients.

METHODS

IMPROVE is a multinational, observational study that enrolled 15,156 medical patients. The in-hospital bleeding incidence was estimated by Kaplan-Meier analysis. A multiple regression model analysis was performed to identify risk factors at admission associated with bleeding.

RESULTS

The cumulative incidence of major and nonmajor in-hospital bleeding within 14 days of admission was 3.2%. Active gastroduodenal ulcer (OR, 4.15; 95% CI, 2.21-7.77), prior bleeding (OR, 3.64; 95% CI, 2.21-5.99), and low platelet count (OR, 3.37; 95% CI, 1.84-6.18) were the strongest independent risk factors at admission for bleeding. Other bleeding risk factors were increased age, hepatic or renal failure, ICU stay, central venous catheter, rheumatic disease, cancer, and male sex. Using these bleeding risk factors, a risk score was developed to estimate bleeding risk.

CONCLUSIONS

We assessed the incidence of major and clinically relevant bleeding in a large population of hospitalized medical patients and identified risk factors at admission associated with in-hospital bleeding. This information may assist physicians in deciding whether to use mechanical or pharmacologic VTE prophylaxis.

Reversibility of the anti-FXa activity of idrabiotaparinux (biotinylated idraparinux) by intravenous avidin infusion

BACKGROUND

Idraparinux is an inhibitor of activated factor X (FXa) with a long half-life allowing once-weekly dosing. Idrabiotaparinux is a biotinylated version of idraparinux; its activity can be reversed with avidin.

OBJECTIVE

To investigate the tolerability, safety and pharmacodynamics of avidin in healthy subjects and patients with deep vein thrombosis (DVT) receiving idrabiotaparinux.

PATIENTS AND METHODS

In a placebo-controlled, randomized, double-blind Phase I study, 41 healthy males received subcutaneous idrabiotaparinux before being randomized to a 30-min intravenous avidin infusion or placebo. Idrabiotaparinux plus avidin were re-administered 10-14 months later in eight subjects. In addition, in a prospective substudy of the Phase III EQUINOX trial, 55 patients who received weekly idrabiotaparinux for 6 months were randomized to receive either 100 mg avidin (n = 33) or placebo (n = 22). The primary activity outcome was anti-FXa activity calculated immediately before and after avidin infusion. Adverse events were recorded to assess safety and tolerability.

RESULTS

Avidin rapidly reversed the anti-FXa activity of idrabiotaparinux, ranging from 66.1 to 90.3% in healthy subjects and from 67 to 97% (mean 78%) in DVT patients. Avidin was well tolerated, with a similar nature and frequency of adverse events to placebo. No venous thromboembolism recurrence occurred in the 3-month post-avidin infusion.

CONCLUSION

A 30-min intravenous infusion of avidin 100 mg is well tolerated, safe, and offers immediate and specific reversibility both after single and repeated doses of idrabiotaparinux in healthy subjects, and in DVT patients following a 6-month treatment period.

Comparison of the clinical history of symptomatic isolated distal deep-vein thrombosis vs. proximal deep vein thrombosis in 11 086 patients

BACKGROUND

The clinical significance of symptomatic isolated distal deep vein thrombosis (DVT) is uncertain. Consequently, this leads to important disparities in its management.

OBJECTIVE

To examine the clinical history of isolated distal DVT and to compare it with that of proximal DVT.

METHODS

Using data from the international, prospective, RIETE registry on patients with confirmed symptomatic venous thromboembolism (VTE), we compared the risk factors and 3-month outcome in patients with isolated distal DVT vs. proximal DVT.

RESULTS

Eleven thousand and eighty-six patients with symptomatic DVT, but without pulmonary embolism, were included between 2001 and 2008; 1921 (17.3%) exhibited isolated distal DVT. Anticoagulant treatment was received by 89.1% (1680/1885) of isolated distal DVT and 91.8% (7911/8613) of proximal DVT patients for the entire follow-up period. Isolated distal DVTs were more associated with transient risk factors (i.e. recent travel, hospitalization, recent surgery), whereas proximal DVTs were more associated with chronic states (i.e. > or =75 years or with active cancer). At 3 months, major bleeding rate was lower in patients with isolated distal DVT (1.0% vs. 2.2%, P < 0.01), whereas VTE recurrence rate was equivalent (2.0% vs. 2.7%, P = 0.07). The mortality rate was lower in patients with isolated distal DVT (2.7% vs. 7.5%; P < 0.001); this was mainly due to a lower rate of non-VTE-related deaths (2.2% vs. 6.3%; P < 0.001). Active cancer was the main predictive factor of death in patients with isolated distal DVT.

CONCLUSIONS

Proximal and isolated distal DVT patients differ in terms of risk factors and clinical outcomes, suggesting different populations. In the short term, the life expectancy of patients with isolated distal DVT depended chiefly on their cancer status.

Anticoagulation in the Treatment of Established Venous Thromboembolism in Patients With Cancer

Cancer-associated thrombosis is a frequent and costly complication in patients with cancer. Significant morbidity and mortality not only result from thrombotic events, but may also occur as a result of the therapeutic interventions. The established treatment for cancer-associated thrombosis is anticoagulant therapy. Of the few options available, low molecular weight heparin (LMWH) is the preferred agent because of its efficacy, safety, and convenience. Alternatives to LMWH have undesirable limitations and have demonstrated poorer efficacy and safety in the oncology population. Treatment of recurrent thrombosis, patients with concurrent bleeding issues, role of vena cava filter insertion, and duration of therapy are all areas in need of urgent research. Treatment of cancer-associated thrombosis remains a challenging task and is limited by the paucity of evidence-based data. Research is urgently needed to advance current practice and improve patient care.

A new era for anticoagulants

Selective inhibitors of specific coagulation factors represent a new class of antithrombotic agents, designed to overcome the limitations of traditional anticoagulants. Available clinical studies indicate that the most promising new anticoagulants are those selectively targeting factor Xa and thrombin. Typically, the standard steps for clinical evaluation of new anticoagulants are thromboprophylaxis in high risk orthopedic surgery, followed by treatment of established venous thromboembolism, nonvalvular atrial fibrillation and acute coronary syndromes. These agents - that have the potential to be more effective and easier to use than conventional drugs such as heparins and vitamin K antagonists - will greatly expand our armamentarium for the prevention and treatment of arterial and venous thromboembolism. The current knowledge on these antithrombotic agents is summarized in this review, particularly focusing on the early results of clinical trials.

Novel anticoagulants in clinical development: focus on factor Xa and direct thrombin inhibitors

Vitamin K antagonists are the mainstay in the prevention and treatment of thromboembolic diseases. Although effective under optimal conditions, several drawbacks are imminent to the long-term application of these drugs due to their narrow therapeutic window, interactions with other drugs as well as the need for regular monitoring and the risk of a recurrent event versus the risk of bleeding. To overcome these downsides, novel anticoagulants are being developed; in contrast to vitamin K antagonists, these novel agents specifically and selectively block central elements of the coagulation cascade. Several clinical trials have demonstrated the efficacy and safety of selective FXa inhibitors (such as fondaparinux, rivaroxaban, apixaban) and direct thrombin inhibitors (such as lepirudin, bivalirudin, dabigatran etexilate) in the treatment of typical indications for conventional vitamin K antagonists, in particular, the prevention and treatment of venous thromboembolism. This review summarizes the results and designs of recently published and ongoing clinical trials of novel anticoagulants.

Treatment of venous thromboembolism in patients with cancer: Guidelines of the Italian Society for Haemostasis and Thrombosis (SISET)

BACKGROUND

The treatment of venous thromboembolism (VTE) in cancer patients remains controversial.

PURPOSE

The Italian Society for Thrombosis and Haemostasis (SISET) commissioned a project to develop clinical practice guidelines for the therapy of VTE in patients with malignancies.

METHODS

Key questions about the treatment of VTE in patients with malignancies were formulated by a multidisciplinary working group consisting of experts in clinical medicine and research. After a systematic review and discussion of the literature, recommendations were formulated and graded according to the supporting evidence. For those questions for which the literature search did not yield any definitive answer (absence of evidence evidence of low quality, and contradictory evidence), a formal consensus method was used to issue clinical recommendations.

RESULTS

The results of the available literature on VTE treatment in cancer patients were reviewed and clinical recommendations were drafted.

CONCLUSION

We describe the results of a systematic literature review and an explicit approach to consensus techniques which resulted in recommendations for the key therapeutic issues in cancer patients with VTE.

How I treat the antiphospholipid syndrome

This article discusses how we approach medical decision making in the treatment of the various facets of the antiphospholipid syndrome (APS), including secondary prophylaxis in the setting of venous and arterial thrombosis, as well as treatment for the prevention of recurrent miscarriages and fetal death. The role of primary thromboprophylaxis is also discussed in depth. Great emphasis is given to incorporating the most up-to-date and relevant evidence base both from the APS literature, and from large, recent, randomized controlled trials (RCTs) of primary and secondary thrombotic prophylaxis in the general population setting (ie, the population that has not been specifically investigated for APS).