Idraparinux versus standard therapy for venous thromboembolic disease

[What's new on antithrombotics?]

Management of venous thromboembolism disease could be improved by new drugs with lower risk of bleeding and without the need of regular monitoring of anticoagulant effect. In this way, idraparinux, anti-Xa inhibitor, has been compared to conventional therapy (coumarins) for the treatment of deep vein thrombosis and pulmonary embolism. Is it worth to treat patients more than six months? This has been evaluated in an interesting study. Prophylaxis after hip replacement surgery is indicated to reduce the risk of venous thromboembolism, new drugs are under investigation. Dabigatran etexilate, a direct thrombin inhibitor, has been shown as effective as enoxaparin in reducing the risk of venous thromboembolism after total hip replacement surgery. In 2007, new european guidelines for non-STsegment elevation acute coronary syndromes have been published. Two new antithrombotic drugs, bivalirudin and fondaparinux, are now part of the different possible choices according to specific considerations. New factor Xa and factor IIa inhibitors are under investigation and are compared to heparin in PCI for NSTE-ACS. Fondaparinux and more recently otamixaban have given interesting results. These new recommendations have not yet taken into account new data published in 2007. What will be the positioning of prasugrel, a new thienopyridine, after the results of theTRITON trial? In patients with SCA treated by PCI, prasugrel reduced the ischemic events, while increasing major bleedings. In 2007, numerous publications and meta-analyses on drug-eluting stents (DES) have been published and tempered the fear about a possible increase in mortality with the use of DES.

Treatment of venous thromboembolism in cancer patients

Venous thromboembolism (VTE) is a major cause of morbidity and mortality in patients with cancer. Monotherapy with low-molecular-weight heparin is the recommended first-line approach in cancer patients with newly diagnosed VTE, and is usually continued for a minimum of 3-6 months. Other management issues that require further research include optimal duration of anticoagulant therapy, treatment of recurrent VTE, the role of vena cava filters, the effects of VTE and its treatment on quality of life, and the impact of anticoagulants on survival. Newer anticoagulants hold promise in providing more effective and convenient treatment of VTE for this high-risk population, but further studies are awaited.

Use of anticoagulants in elderly patients: practical recommendations

Elderly people represent a patient population at high thromboembolic risk, but also at high hemorrhagic risk. There is a general tendency among physicians to underuse anticoagulants in the elderly, probably both because of underestimation of thromboembolic risk and overestimation of bleeding risk. The main indications for anticoagulation are venous thromboembolism (VTE) prophylaxis in medical and surgical settings, VTE treatment, atrial fibrillation (AF) and valvular heart disease. Available anticoagulants for VTE prophylaxis and initial treatment of VTE are low molecular weight heparins (LMWH), unfractionated heparin (UFH) or synthetic anti-factor Xa pentasaccharide fondaparinux. For long-term anticoagulation vitamin K antagonists (VKA) are the first choice and only available oral anticoagulants nowadays. Assessing the benefit-risk ratio of anticoagulation is one of the most challenging issues in the individual elderly patient, patients at highest hemorrhagic risk often being those who would have the greatest benefit from anticoagulants. Some specific considerations are of utmost importance when using anticoagulants in the elderly to maximize safety of these treatments, including decreased renal function, co-morbidities and risk of falls, altered pharmacodynamics of anticoagulants especially VKAs, association with antiplatelet agents, patient education. Newer anticoagulants that are currently under study could simplify the management and increase the safety of anticoagulation in the future.

[Rivaroxaban: clinical pharmacology]

Rivaroxaban (Xarelto) is a new oral, direct and selective inhibitor of the factor Xa of the coagulation cascade. The main pharmacokinetic characteristics of rivaroxaban are a bioavailability of approximately 80-100%, a maximum concentration obtained in 2 to 4 hours, a terminal half-life of elimination of 7 to 11 hours, a renal elimination for 1/3 for the active hepatic metabolism from the cytochrome P450 (3A4) for the other 2/3. The main sources of variability are the renal and the liver function and potential interactions with some strong inhibitors or inducers of the CYP450 3A4. Phase II clinical studies have shown that this compound can be orally administrated, once or twice daily, without any biological monitoring and without any need for dose adjustment. There is a contra-indication in case of severe liver insufficiency and not recommended in case of severe renal impairment. Pharmacodynamically, Rivaroxaban is a direct and selective factor Xa inhibitor without any effect on the factor IIa and without any interaction on platelets. Four phases II with 2787 patients were carried out to for venous thromboembolic (VTE) prophylaxis after major orthopaedic surgery, showing that 10 mg once daily could be the optimal dose regimen to assess in phase III. Two phases II with 1446 patients were carried out for the treatment of VTE showing that 15 mg twice daily for 3 weeks and then 20 mg once daily could be the optimal dose regimen to evaluate in the following phases 3. No strong signal for a potential liver toxicity was shown during these 6 phases II.

The pharmacokinetics of idraparinux, a long-acting indirect factor Xa inhibitor: population pharmacokinetic analysis from Phase III clinical trials

BACKGROUND

Idraparinux, a long-acting synthetic pentasaccharide, is a specific antithrombin-dependent inhibitor of activated factor X that has been investigated in the treatment and prevention of thromboembolic events.

OBJECTIVES

To characterize the population pharmacokinetic profile of idraparinux in patients enrolled in van Gogh and Amadeus Phase III clinical trials.

PATIENTS AND METHODS

Idraparinux was administered once-weekly subcutaneously at a dose of 2.5 mg, or 2.5 mg (first dose) and then 1.5 mg for patients with severe renal insufficiency (creatinine clearance<30 mL min(-1)). A population pharmacokinetic model was developed using data from 704 patients with acute deep-vein thrombosis or pulmonary embolism, 1310 patients suffering from atrial fibrillation, and 40 healthy subjects. Potential covariates analyzed included demographics (age, sex, weight and ethnicity), and serum creatinine and creatinine clearance determinations.

RESULTS

A three-compartment model best described idraparinux pharmacokinetics, with interindividual variability on clearance, central volume of distribution, and absorption rate constant; residual variability was low. Typical clearance, central volume of distribution, absorption rate constant and volume of distribution at steady-state were 0.0255 L h(-1), 3.36 L, 1.37 h and 30.8 L, respectively. Peak concentration was reached at 2.5 h. The terminal half-life was 66.3 days and time to steady-state was 35 weeks. At steady-state, exposures were similar for patients without and with severe renal impairment receiving adjusted-dose. Creatinine clearance was the most important covariate affecting idraparinux clearance. The particular characteristics of idraparinux--rapid onset of action and long-acting anticoagulant effect--offer interesting clinical perspectives currently under investigation with idrabiotaparinux, the reversible biotinylated form of idraparinux.

Lessons learned from the contamination of heparin

Heparin is unique as one of the oldest drugs currently still in widespread clinical use as an anticoagulant, a natural product, one of the first biopolymeric drugs, and one of the few carbohydrate drugs. Recently, certain batches of heparin have been associated with anaphylactoid-type reactions, some leading to hypotension and death. These reactions were traced to contamination with a semi-synthetic oversulfated chondroitin sulfate (OSCS). This Highlight reviews the heparin contamination crisis, its resolution, and the lessons learned. Pharmaceutical scientists now must consider dozens of natural and synthetic heparinoids as potential heparin contaminants. Effective assays, which can detect both known and unknown contaminants, are required to monitor the quality of heparin. Safer and better-regulated processes are needed for heparin production.

[Care of acute pulmonary embolism]

Pulmonary embolism (PE) is common and potentially serious. Three stages are described: mild PE, moderate PE (associated with an ultrasound right ventricular dysfunction) and severe PE (associated with a shock). In the first category, the prognosis is highly favourable (mortality under 5%) and the initial phase of anticoagulant treatment is well documented and codified: the treatment is based on heparin therapy (non fractionated or derivatives) and oral anticoagulants. In the severe forms, fibrinolysis is indicated in addition to the heparin therapy, given the very high mortality (up to 50%). However, the optimum care of moderate PE (intermediate mortality between 10 and 15%) remains uncertain, due to the inability to demonstrate a benefits-risk ratio in favour of fibrinolysis. In addition, this entity is still poorly defined. Although cardiac ultrasound data is useful, other parameters, such as pro-BNP, provide a better identification of these forms of intermediate prognosis. Although the evaluation of the new oral and injectable anticoagulants is promising, it mainly concerns mild PE. In addition, trials are currently under way in patients with a gloomier prognosis. The purpose is to validate or invalidate the indication of classic treatments (fibrinolysis) or new treatments (optional caval filters).

Managing cancer-related venous thromboembolic disease: low-molecular-weight heparins and beyond

Venous thromboembolism is a major contributor to the morbidity and mortality of patients with cancer. For patients undergoing cancer surgery, several trials support the safety and efficacy of unfractionated heparin and of low-molecular-weight heparin for the prevention of venous thromboembolism, while data regarding the efficacy and safety of these agents in the setting of medical hospitalization is less definitive and must be extracted from trials including noncancer patients with different thrombotic risk factors. Randomized clinical studies confirm that patients with cancer who develop venous thromboembolism have superior outcomes when treated with long-term low-molecular-weight heparin as compared with warfarin. Novel anticoagulants that are orally bioavailable and function by directly inhibiting factor Xa or thrombin are entering the market. To date, data regarding the efficacy and safety of these novel anticoagulants as venous thromboembolism prophylaxis and treatment in cancer patients are not available and must be extracted from larger trials with heterogeneous patient populations.

Idrabiotaparinux, a Biotinylated Long-Acting Anticoagulant, in the Treatment of Deep Venous Thrombosis (EQUINOX Study): Safety, Efficacy, and Reversibility by Avidin

Idrabiotaparinux is a novel synthetic anticoagulant that links idraparinux, a specific, indirect factor Xa inhibitor, to biotin. The long half-life of idraparinux allows once-weekly (o.w.) subcutaneous (s.c.) injection. Avidin, a hen egg protein, specifically and tightly binds with biotin. When given by intravenous (i.v.) infusion, avidin (half life: 15-minutes) reverses the anti-factor Xa (a-Xa) activity of idrabiotaparinux by forming a complex that is rapidly cleared from the circulation. Idraparinux 2.5 mg s.c. o.w. was effective and safe in the van Gogh DVT trial of 2904 patients with deep vein thrombosis (DVT), when compared with standard anticoagulant therapy 1.

Methods: In EQUINOX, patients with symptomatic and confirmed DVT were randomised to receive weekly s.c. injection of equimolar amounts of idrabiotaparinux (3 mg) or idraparinux (2.5 mg) for 6 months. The aims of this multicentre, double-blind, study were to demonstrate, at the end of the 6 months of therapy, bioequipotency of idrabiotaparinux with idraparinux, to measure the effect of i.v. avidin on peak circulating a-Xa activity, and to document efficacy and safety. The main outcome events were clinically relevant bleeding (major or not), death, or symptomatic recurrent venous thromboembolism (VTE) within 6 months of randomisation, assessed by a blinded independent adjudication committee. Reversal of anticoagulant effect by 100 mg i.v. avidin infused over 30 minutes, and its safety, were assessed in a subset of patients re-randomised at 6 months and blindly allocated to receive avidin (idrabiotaparinux arm) or placebo (idrabiotaparinux and idraparinux arms, to preserve blinding). Avidin or placebo was infused 2–5 hours (around tmax) after the last injection of the 6 month treatment period; plasma a-Xa activity was measured just before avidin/placebo infusion, just after, and then for 5 days.

Results: Of 757 patients randomised, 385 received idrabiotaparinux and 370 idraparinux. Overall, 22.7% had previous venous thromboembolism (VTE), 5.2% had cancer within the past 6 months, 53.8% had apparently unprovoked thrombosis, and 36.2% were aged &gt;65. There was less clinically relevant bleeding (20 v. 27; 5.2% v. 7.3%) and less major bleeding (3 v. 14; 0.8% v. 3.8%) with idrabiotaparinux than with idraparinux. Rates of recurrent VTE and of fatal or non-fatal pulmonary embolism PE were similar with idrabiotaparinux and idraparinux (VTE: 9 v. 12; 2.3% v. 3.2%. PE: 6 v. 7; 1.6% v. 1.8%). Trough levels of a-Xa activity were identical in the treatment groups throughout 6 months. Of 52 idrabiotaparinux patients re-randomised at 6 months to receive i.v. avidin or placebo, 41 were analysable for reversal of a-Xa activity (23 avidin and 18 placebo). At the end of the 30 minute avidin infusion, mean anti-Xa activity was reduced by 77.8%, sustained for at least 5 days, compared with 2.4% after placebo (p = 3.45 × 10−15). No allergic reactions were observed to avidin.

Conclusion: A 6-month treatment period with idrabiotaparinux, compared to idraparinux in patients with DVT, showed a comparable efficacy with a trend to less bleeding. Trough a-Xa activity was identical in the two groups. Avidin infusion at around tmax after the last idrabiotaparinux injection led to rapid and substantial reversal of a-Xa activity, sustained for at least 5 days. Avidin infusion was well-tolerated.

New anticoagulants

PURPOSE OF REVIEW

Although current anticoagulants such as unfractionated and low-molecular-weight heparins and the vitamin K antagonists are effective for the prevention and treatment of thrombosis, they have several limitations. The vitamin K antagonists, the only approved oral anticoagulants, have a narrow therapeutic window, thereby requiring regular laboratory monitoring of the international normalized ratio and intermittent adjustments in dose. New anticoagulants have been developed that selectively inhibit thrombin or factor Xa, and have predictable dose-response relationships.

RECENT FINDINGS

Fondaparinux is a synthetic pentasaccharide, which binds to antithrombin, thereby indirectly inhibiting factor Xa. Fondaparinux demonstrated efficacy compared with low-molecular-weight heparin in randomized clinical trials and is approved for the prevention and treatment of venous thromboembolism. A number of oral direct factor Xa inhibitors and oral direct thrombin inhibitors are in advanced phases of clinical development for the prevention and treatment of thrombosis. The current status of these anticoagulants will be reviewed along with the challenges faced in designing pivotal clinical trials of these agents in comparison to existing anticoagulants.

SUMMARY

Selective inhibitors of specific coagulation factors have the potential to be more effective, safer, and easier to use than existing anticoagulants. Approval of one or more of these agents will lead to an improved drug armamentarium for the prevention and treatment of thrombosis.

Prophylactic and therapeutic anticoagulation for thrombosis: major issues in oncology

Venous thromboembolism (VTE) is a major cause of morbidity and mortality in patients with cancer. Primary prevention with pharmacologic agents (or mechanical methods, if anticoagulants are contraindicated) is recommended in all cancer patients hospitalized for surgical or medical reasons. The role of prophylaxis in outpatients is less certain because of the diversity of the patient populations and their cancer treatments with respect to the associated risks of VTE and bleeding. Treatment with low-molecular weight heparin is the recommended first-line approach in cancer patients with newly diagnosed VTE, and is usually continued for a minimum of 3-6 months. Other management issues that require further research include the optimum duration of anticoagulant therapy, the treatment of recurrent VTE, the role of vena cava filters, the effects of VTE and its treatment on quality of life, and the impact of anticoagulants on survival. Newer anticoagulants hold promise in providing more-effective and convenient treatment of VTE in this high-risk population, but further studies are awaited.

Reversible biotinylated oligosaccharides: a new approach for a better management of anticoagulant therapy

OBJECTIVE

In order to obtain a neutralizable antithrombotic, a chimeric molecule (SSR126517E) containing the sequence of a long-lasting antithrombin (AT)-dependent anti-factor Xa pentasaccharide, idraparinux, linked to a biotin molecule was synthesized and tested for anticoagulant and antithrombotic activity.

METHODS

SSR126517E was tested in several models in vitro and in vivo for its pharmacological properties as well as its ability to be neutralized by avidin.

RESULTS

SSR126517E displayed exactly the same properties as idraparinux. In vitro, SSR126517E had a very high affinity for AT (K(d) < 1 nm) and showed a potent anti-FXa effect and inhibition of thrombin generation with IC(50) values similar to those of idraparinux. Ex vivo, after intravenous administration to rats, SSR126517E produced a potent and long-lasting anti-FXa effect comparable to that obtained with idraparinux; as with idraparinux, the subcutaneous bioavailability was 100%. In vivo, SSR126517E was a potent antithrombotic in rat and mouse venous and arterial thrombosis models. Direct comparison in rats showed that SSR126517E was as active as idraparinux, when administered at the same molar dose. Furthermore, injection of avidin triggered the immediate elimination of SSR126517E from the bloodstream, resulting in complete neutralization of the antithrombotic activity of SSR126517E.

CONCLUSIONS

These results show for the first time that coupling an oligosaccharide with biotin has no effect on the former's pharmacokinetic and pharmacologic properties and renders neutralization easy by injection of avidin.

A dose-ranging study evaluating once-daily oral administration of the factor Xa inhibitor rivaroxaban in the treatment of patients with acute symptomatic deep vein thrombosis: the Einstein–DVT Dose-Ranging Study

We performed a randomized dose-ranging study, double-blind for rivaroxaban doses and open-label for the comparator (low-molecular-weight heparin followed by vitamin K antagonists) to assess the optimal dose of rivaroxaban for the treatment of deep vein thrombosis. A total of 543 patients with acute deep-venous thrombosis received rivaroxaban 20, 30, or 40 mg once daily or comparator. Treatment lasted for 84 days. The primary efficacy outcome was the 3-month incidence of the composite of symptomatic venous thromboembolic complications and asymptomatic deterioration in thrombotic burden as assessed by comparison of ultrasound and perfusion lung scanning at day 84 with baseline. The main safety outcome was the composite of major bleeding and clinically relevant nonmajor bleeding. A total of 449 (83%) of the 543 patients could be included in the per-protocol population. The primary efficacy outcome occurred in 6.1%, 5.4%, and 6.6% of the rivaroxaban 20-, 30-, and 40-mg treatment groups, respectively, and in 9.9% of those receiving standard therapy. The main safety outcome occurred in 5.9%, 6.0%, and 2.2% of the rivaroxaban 20-, 30-, and 40-mg treatment groups, respectively, and in 8.8% of those receiving standard therapy. These results with simple fixed-dose oral regimens justify phase 3 evaluations (www.ClinicalTrials.gov no.NCT00395772).

Characterization of total plasma glycosaminoglycan levels in healthy volunteers following oral administration of a novel antithrombotic odiparcil with aspirin or enoxaparin

Odiparcil is a novel, orally active beta-d-thioxyloside analog with antithrombotic activity associated with a reduced risk of adverse bleeding events. Its unique mechanism of action is postulated by means of an elevation in circulating endogenous chondroitin sulfate-related glycosaminoglycans (GAGs) levels. The purpose of these 2 separate clinical studies was to evaluate plasma GAG levels in healthy subjects administered odiparcil with either aspirin (ASA) or enoxaparin. Clinical plasma samples were processed and analyzed using validated HPLC bioassays that indirectly estimate GAG levels based on the simultaneous detection of the chondroitin disaccharide derivatives. The concomitant administration of odiparcil with or without ASA resulted in a significant elevation in GAG levels over baseline for both treatment groups. In the other clinical study, the concomitant administration of odiparcil with or without enoxaparin displayed significant increases in plasma DeltaDi-OS, DeltaDi-4S, and total disaccharide levels versus control group. Neither plasma GAG levels nor odiparcil plasma levels were correlated with a rise in hepatic transaminases, an adverse drug event observed in several subjects; and plasma odiparcil levels were indirectly correlated with plasma GAG levels. These clinical studies were proof of concept of preclinical rat studies indicating that chronic odiparcil treatment elevates endogenous GAG levels in human subjects.

New antithrombotic drugs: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This chapter focuses on new antithrombotic drugs that are in phase II or III clinical testing. Development of these new agents was prompted by limitations of existing antiplatelet, anticoagulant, or fibrinolytic drugs. Addressing these unmet needs, this chapter (1) outlines the rationale for development of new antithrombotic agents, (2) describes the new antiplatelet, anticoagulant, and fibrinolytic drugs, and (3) provides clinical perspectives on the opportunities and challenges faced by these novel agents.

Efficacy and safety of the oral direct factor Xa inhibitor apixaban for symptomatic deep vein thrombosis. The Botticelli DVT dose-ranging study

BACKGROUND

Apixaban, an oral potent reversible direct inhibitor of activated factor X, has shown promise in the prevention of venous thromboembolism following major orthopedic surgery. We conducted a dose-ranging study in patients with deep vein thrombosis.

METHODS

Consecutive patients with symptomatic deep vein thrombosis were included and randomized to receive 84-91 days of apixaban 5 mg twice-daily, 10 mg twice-daily, or 20 mg once-daily, or low molecular weight heparin (LMWH) followed by a vitamin K antagonist (VKA). The primary efficacy outcome was the composite of symptomatic recurrent venous thromboembolism and asymptomatic deterioration of bilateral compression ultrasound or perfusion lung scan. The principal safety outcome was the composite of major and clinically relevant, non-major bleeding.

RESULTS

The mean age of the 520 included patients was 59 years, and 62% were male. The primary outcome occurred in 17 of the 358 apixaban-treated patients [4.7%, 95% confidence interval (CI) 2.8-7.5%] and in five of the 118 LMWH/VKA-treated patients (4.2%, 95% CI 1.4-9.6%) who were evaluable. The incidence in all three apixaban groups was low and comparable without evidence of a dose response. The principal safety outcome occurred in 28 (7.3%) of the 385 apixaban-treated patients and in 10 (7.9%) of the 126 LMWH/VKA-treated patients. No dose response for apixaban was observed.

CONCLUSION

These observations warrant further evaluation of apixaban in phase III studies. The attractive fixed-dose regimen of this compound may meet the demand to simplify anticoagulant treatment in patients with established venous thromboembolism.

New anticoagulants for treatment of venous thromboembolism

Anticoagulant therapy is the cornerstone of treatment of venous thromboembolism (VTE). Such treatment is divided into 2 stages: Rapid initial anticoagulation is given to minimize the risk of thrombus extension and fatal pulmonary embolism, whereas extended anticoagulation is aimed at preventing recurrent VTE, thereby reducing the risk of postphlebitic syndrome. With currently available drugs, immediate anticoagulation can only be achieved with parenteral agents, such as heparin, low-molecular-weight heparin, or fondaparinux. Extended treatment usually involves the administration of vitamin K antagonists, such as warfarin. Emerging anticoagulants have the potential to streamline VTE treatment. These agents include idraparinux, a long-acting synthetic pentasaccharide that is given subcutaneously on a once-weekly basis, and new oral anticoagulants that target thrombin or factor Xa. This article (1) reviews the pharmacology of these agents, (2) outlines their potential strengths and weaknesses, (3) describes the results of clinical trials with these new drugs, and (4) identifies the evolving role of new anticoagulants in the management of VTE.

Extended prophylaxis of venous thromboembolism with idraparinux

BACKGROUND

The extended use of vitamin K antagonists for prophylaxis against venous thromboembolism is often constrained by risk-benefit limitations and inconvenience. We evaluated the efficacy and safety of a 6-month extension of prophylaxis against recurrent venous thromboembolism with idraparinux in patients who had initially received 6 months of prophylaxis with an anticoagulant.

METHODS

We randomly assigned patients who had completed 6 months of prophylaxis with idraparinux or a vitamin K antagonist and in whom extended anticoagulation was warranted to receive once-weekly injections of 2.5 mg of idraparinux or placebo for 6 months without monitoring. The primary efficacy and safety outcomes were recurrent venous thromboembolism and major bleeding.

RESULTS

Of 1215 patients, 6 of 594 (1.0%) in the idraparinux group and 23 of 621 (3.7%) in the placebo group had recurrent venous thromboembolism (P=0.002). Major bleeding occurred in 11 patients (1.9%) in the idraparinux group and in none in the placebo group (P<0.001). Of these 11 episodes, 3 were fatal intracranial hemorrhages. As compared with patients whose initial treatment was a vitamin K antagonist, patients whose initial treatment was idraparinux who were assigned to 6 months in the placebo group had a lower incidence of recurrent thromboembolism (0.7% vs. 5.9%); patients who received 6 additional months of idraparinux therapy had a higher incidence of major bleeding (3.1% vs. 0.9%).

CONCLUSIONS

During a 6-month extension of thromboprophylaxis, idraparinux was effective in preventing recurrent thromboembolism but was associated with an increased risk of a major hemorrhage. (ClinicalTrials.gov number, NCT00071279 [ClinicalTrials.gov].).