Profile of betrixaban and its potential in the prevention and treatment of venous thromboembolism

Investigating Betrixaban Maleate drug degradation profiles, isolation and characterization of unknown degradation products by mass-triggered preparative HPLC, HRMS, and NMR

Betrixaban Maleate, a novel oral, once-daily factor Xa inhibitor drug substance, was subjected to stress testing under a wide range of degradation conditions, including acidic hydrolysis, alkaline hydrolysis, oxidative, thermal, and photolytic, to determine its inherent stability. The drug was biodegradable in acidic and alkaline environments, and three new degradation products were identified. Two degraded products are formed in an acidic environment, while the third is in alkaline conditions. The three degradants were identified using UPLC-ESI/MS and isolated using mass-triggered preparative HPLC, and their structures were unambiguously elucidated using HRMS and 2D NMR techniques. Based on spectral and chromatographic data, it was firmly proven that these distinct degradation products were the betrixaban chemical's hydrolysis components. The formation of the degradants has been hypothesized through several possible mechanisms.

Current and emerging drug strategies for the prevention of venous thromboembolism in acutely ill medical inpatients

INTRODUCTION

Venous thromboembolism (VTE) is a common complication in patients hospitalized for acute medical illnesses. Therefore, medical inpatients require a careful VTE and bleeding risk assessment to drive optimal strategies for VTE prevention. Low molecular weight heparin and fondaparinux have long been used for inhospital prophylaxis for patients at increased risk of VTE. The selection of patients who require post-discharge prophylaxis, and the role of direct oral anticoagulants remain debated. New molecules currently under development may contribute to improve the risk benefit of VTE prevention in this setting.

AREAS COVERED

This text summarizes the evidence on approved treatments and on other drugs for the prevention of VTE in acutely ill medical patients. The main focus is on their pharmacological proprieties, clinical efficacy and safety, and the current license approved by the FDA (Food and Drug Administration) and EMA (European Medicines Agency), giving the readers a way to compare available drugs to date. The trials presented consider both inhospital and extended prophylaxis.

EXPERT OPINION

Thanks to the potentially favorable safety profile, factor XI inhibitors may play a role in the prevention of VTE in this setting. The expert opinion section discusses pharmacological properties, prophylaxis trials, and potential clinical applications of this novel class of drugs.

Switching from warfarin to direct-acting oral anticoagulants: it is time to move forward!

Oral vitamin K antagonists (VKAs), warfarin, have been in routine clinical use for almost 70 years for various cardiovascular conditions. Direct-Acting Oral Anticoagulants (DOACs) have emerged as competitive alternatives for VKAs to prevent stroke in patients with non-valvular atrial fibrillation (AF) and have become the preferred choice in several clinical indications for anticoagulation. Recent guidelines have limited the use of DOACs to patients with non-valvular AF to reduce the risk of cardioembolic complications and to treat venous thromboembolism (VTE). Although emerging evidence is suggestive of its high efficacy, there was a lack of data to support DOACs safety profile in patients with mechanical valve prosthesis, intracardiac thrombi, or other conditions such as cardiac device implantation or catheter ablation. Therefore, several clinical trials have been conducted to assess the beneficial effects of using DOACs, instead of VKAs, for various non-guideline-approved indications. This review aimed to discuss the current guideline-approved indications for DOACs, advantages, and limitations of DOACs use in various clinical indications highlighting the potential emerging indications and remaining challenges for DOACs use. Several considerations are in favour of switching from warfarin to DOACs including superior efficacy, better adverse effect profile, fewer drug-drug interactions, and they do not require frequent international normalized ratio (INR) monitoring. Large randomized controlled trials are required to determine the safety and efficacy of their use in various clinical indications.

The Clinical Significance of Drug-Food Interactions of Direct Oral Anticoagulants

Cardiovascular diseases are the most common cause of death in the world. For almost 60 years, vitamin K antagonists (VKAs) were the mainstay of anticoagulation therapy, but in recent years direct oral anticoagulants (DOACs) have become the anticoagulant treatment of choice. DOACs were initially considered drugs with no significant food interactions; however, clinical observations from daily practice have proved otherwise as interactions with food ingredients have been reported. Food, dietary supplements or herbs may contain substances that, when administered concomitantly with DOACs, can potentially affect the plasma concentration of the drugs. The aim of this paper was to evaluate the clinical significance of drug-food interactions of DOACs, such as dabigatran, rivaroxaban, apixaban, edoxaban and betrixaban. Patients treated with anticoagulants should avoid products containing St. John's wort and take special care with other food ingredients. As the interest in dietary supplements is on the rise, healthcare providers can contribute to the development of well-designed clinical trials on interactions between DOACs and food, and distribute sufficient knowledge about the proper use of these supplements among patients.

Laboratory Monitoring of Direct Oral Anticoagulants (DOACs)

The introduction of direct oral anticoagulants (DOACs), such as dabigatran, rivaroxaban, apixaban, edoxaban, and betrixaban, provides safe and effective alternative to previous anticoagulant therapies. DOACs directly, selectively, and reversibly inhibit factors IIa or Xa. The coagulation effect follows the plasma concentration-time profile of the respective anticoagulant. The short half-life of a DOAC constrains the daily oral intake. Because DOACs have predictable pharmacokinetic and pharmacodynamic responses at a fixed dose, they do not require monitoring. However in specific clinical situations and for particular patient populations, testing may be helpful for patient management. The effect of DOACs on the screening coagulation assays such as prothrombin time (PT), activated partial thromboplastin time (APTT), and thrombin time (TT) is directly linked to reagent composition, and clotting time can be different from reagent to reagent, depending on the DOAC's reagent sensitivity. Liquid chromatography-mass spectrometry (LC-MS/MS) is considered the gold standard method for DOAC measurement, but it is time consuming and requires expensive equipment. The general consensus for the assessment of a DOAC is clotting or chromogenic assays using specific standard calibrators and controls. This review provides a short summary of DOAC properties and an update on laboratory methods for measuring DOACs.

Relationship between the degree of renal dysfunction and the safety and efficacy outcomes in patients with atrial fibrillation receiving direct oral anticoagulants

BACKGROUND

The clinical evaluation of a direct oral anticoagulant (DOAC) treatment for atrial fibrillation (AF) patients with renal dysfunction has not been sufficiently studied. This study aimed to evaluate the safety and efficacy of DOACs for patients with a severely impaired renal function.

METHODS

This was a retrospective and observational study in a single center. We enrolled 894 consecutive AF patients who were prescribed DOACs, and divided them into three groups based on their creatinine clearance (CrCl) value: CrCl ≥ 50 mL/min group (n = 634), CrCl 30-49 mL/min group (n = 207), and CrCl 15-29 mL/min group (n = 53). We evaluated the occurrence of major bleeding (MB) as the safety outcome and thromboembolic events (TEs) as the efficacy outcome during the follow-up.

RESULTS

The incidence of MB in the CrCl 15-29 mL/min group was significantly higher than in the other groups (CrCl ≥ 50 mL/min group, 0.8/100 person-years; CrCl 30-49 mL/min group, 1.2/100 person-years; CrCl 15-29 mL/min group, 9.0/100 person-years, log rank test, P < .001). On the other hand, there was no significant difference in the incidence of TEs among the three groups. A multivariate analysis using a Cox proportional hazard model adjusted for the age revealed that the CrCl 15-29 mL/min group was significantly associated with increased MB compared to the CrCl ≥ 50 mL/min group (hazard ratio: 9.76, 95% confidence interval: 2.69-35.5, P < .001). Similar results were observed when adjusting for other multiple clinical factors.

CONCLUSION

This study demonstrated that the degree of renal dysfunction was a significant prognostic factor for MB in AF patients receiving DOACs.

Efficacy and Safety of Direct Oral Anticoagulants in Elderly Patients With Atrial Fibrillation: A Network Meta-Analysis

Background: Direct oral anticoagulants (DOACs) have been widely used in patients with atrial fibrillation (AF) for antithrombotic prophylaxis, which were shown to have a favorable risk–benefit profile. However, there are no guidelines for the use of DOACs in elderly patients (aged ≥75 years) with AF, which creates uncertainty about the optimal antithrombotic treatment in these patients.

Methods: After comprehensively searching Embase, PubMed, and Cochrane databases, five phase III randomized controlled trials involving 28,137 elderly participants were included in this study. The efficacy outcome was stroke or systemic embolism, and the safety outcome was major bleeding. We conducted a network meta-analysis by using a Bayesian random-effect model for the first time to evaluate the efficacy and safety of main DOACs (apixaban, edoxaban, rivaroxaban, and dabigatran) and warfarin in elderly patients with AF. Hazard ratios (HRs) and their corresponding 95% confidence intervals (CIs) were used to assess the effect of drugs on efficacy and safety. The rank probabilities were used to reflect the hierarchy of drugs, and a larger rank probability value symbolized a better rank of drugs.

Results: In the prophylaxis of stroke or systemic embolism, apixaban was found to be the best among DOACs compared to warfarin (HR, 0.71; 95% CI: 0.33–1.50), though this finding was not statistically significant. Apixaban ranked the best (rank probabilities, 41.2%) in efficacy of drugs, followed by rivaroxaban, edoxaban, dabigatran, and warfarin (rank probabilities, 31.8, 15.9, 10.9, and 0.2%, respectively). In reducing the risk of major bleeding, apixaban was found to be the best among DOACs too, compared to warfarin (HR, 0.64; 95% CI: 0.33–1.30), though this finding was not statistically significant. In safety, apixaban ranked the best (rank probabilities, 71.4%), followed by edoxaban, dabigatran, warfarin, and rivaroxaban (rank probabilities, 21.0, 5.8, 0.9, and 0.8%, respectively).

Conclusions: DOACs showed a lower incidence of stroke/systemic embolism and major bleeding compared with warfarin in antithrombotic therapy in elderly patients (aged ≥75 years), with apixaban being the best of those interventions. Therefore, apixaban should be given priority as an anticoagulant in stroke prevention for elderly patients with AF.

Drug-Drug Interactions with Direct Oral Anticoagulants

A large body of evidence suggests that not only direct anticoagulant effects but also major bleeding events and stroke prevention depend on plasma concentrations of direct oral anticoagulants (DOACs). Concomitant drugs that cause drug–drug interactions (DDIs) alter DOAC exposure by increasing or decreasing DOAC bioavailability and/or clearance; hence, they might affect the efficacy and safety of DOAC therapy. Patients with renal impairment already receive smaller DOAC maintenance doses because avoidance of elevated DOAC exposure might prevent serious bleeding events. For other causes of increased exposure such as DDIs, management is often less well-defined. Considering that DOAC patients are often older and have multiple co-morbidities, polypharmacy is highly prevalent. However, the effect of multiple drugs on DOAC exposure, and especially the impact of DDIs when concurring with drug–disease interactions as observed in renal impairment, has not been thoroughly elucidated. In order to provide effective and safe anticoagulation with DOACs, understanding the mechanisms and magnitude of DDIs appears relevant. Instead of avoiding drug combinations with DOACs, more DDI trials should be conducted and new strategies such as dose adjustments based on therapeutic drug monitoring should be investigated. However, dose adjustments based on concentration measurements cannot currently be recommended because evidence-based data are missing.

Direct-Acting Oral Anticoagulants and Their Reversal Agents-An Update

Background: Over the last ten years, a new class of drugs, known as the direct-acting oral anticoagulants (DOACs), have emerged at the forefront of anticoagulation therapy. Like the older generation anticoagulants, DOACs require specific reversal agents in cases of life-threatening bleeding or the need for high-risk surgery. Methods: Published literature was searched, and information extracted to provide an update on DOACS and their reversal agents. Results: The DOACs include the direct thrombin inhibitor—dabigatran, and the factor Xa inhibitors—rivaroxaban, apixaban, edoxaban, and betrixaban. These DOACs all have a rapid onset of action and each has a predictable therapeutic response requiring no monitoring, unlike the older anticoagulants, such as warfarin. Two reversal agents have been approved within the last five years: idarucizumab for the reversal of dabigatran, and andexanet alfa for the reversal of rivaroxaban and apixaban. Additionally, ciraparantag, a potential “universal” reversal agent, is currently under clinical development. Conclusions: A new generation of anticoagulants, the DOACs, and their reversal agents, are gaining prominence in clinical practice, having demonstrated superior efficacy and safety profiles. They are poised to replace traditional anticoagulants including warfarin.

Simultaneous analysis of betrixaban and hexazinone using liquid chromatography/tandem mass spectrometry in aqueous solutions

A new analytical method has been developed, optimised, and validated for simultaneous detection and identification of betrixaban, an oral anticoagulant drug approved recently by food and drug administration (FDA), and hexazinone, a broad-spectrum triazine herbicide, in aqueous media by liquid chromatography/tandem mass spectrometry (LC–MS/MS) using multiple reaction monitoring (MRM). The method was validated by the limit of detection (LOD), the limit of quantification (LOQ), linearity, matrix effect, recovery, precision, and accuracy. The recovery experiments were carried out on raw wastewater samples, spiked with these two compounds, using solid phase extraction (SPE). It is the first time that betrixaban has been analysed for environmental samples. The developed analytical method can be applied for more in-depth studies on the fate and occurrence of these compounds in the engineered and natural aquatic environment. The key benefits of the method described here are:

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It is highly suitable for betrixaban and hexazinone detection and quantification in aqueous samples.

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It can be successfully applied for understanding the fate of betrixaban and hexazinone in real-world water samples.

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Method validation revealed that the method is repeatable, robust, and accurate and can be expanded to include detection of other pharmaceuticals and pesticides in aqueous media.

Anticoagulation in Venous Thromboembolism Prophylaxis in Medically Ill Patients: Potential Impact of NOACs

While substantial evidence supports the use of standard-duration injectable anticoagulants for venous thromboembolism (VTE) prophylaxis, consensus is mixed about which agents may be preferred in acutely ill patients with ongoing need of VTE prophylaxis past the first 10-day duration of hospital stay and post-discharge. Non-vitamin K antagonist oral anticoagulants (NOACs) provide Factor Xa inhibition to prevent the thrombin generation essential in thromboembolism development, but evidence for the efficacy and safety of most NOACs is conflicting regarding extended-duration prophylaxis. Enoxaparin, a preferred injectable anticoagulant in standard-duration VTE prophylaxis, has shown an increased risk of major bleeding events when used in extended-duration prophylaxis, which outweighs its benefit. Rivaroxaban has demonstrated efficacy in extended-duration prophylaxis, but both rivaroxaban and apixaban have shown increased risks of major bleeding. Betrixaban remains the only NOAC approved in the USA for extended-duration VTE prophylaxis, and it demonstrates efficacy, with fewer adverse effects than other NOACs. This review evaluates the appropriateness of different NOAC agents compared with current therapies for the extended-duration VTE prophylaxis setting in medically ill populations.

Cost-Effectiveness of Betrixaban Compared with Enoxaparin for Venous Thromboembolism Prophylaxis in Nonsurgical Patients with Acute Medical Illness in the United States

BACKGROUND

Studies show that the risk of venous thromboembolism (VTE) continues post-discharge in nonsurgical patients with acute medical illness. Betrixaban is the first anticoagulant approved in the United States (US) for VTE prophylaxis extending beyond hospitalization.

OBJECTIVE

The aim was to establish whether betrixaban for VTE prophylaxis in nonsurgical patients with acute medical illness at risk of VTE in the US is cost-effective compared with enoxaparin.

METHODS

A cost-effectiveness analysis was conducted, estimating the cost per quality-adjusted life-year (QALY) gained with betrixaban (35-42 days) compared with enoxaparin (6-14 days) from a US payer perspective over a lifetime horizon. A decision tree (DT) estimated primary VTE events, thrombotic events, and treatment complications in the first 3 months based on data from the phase III Acute Medically Ill VTE Prevention with Extended Duration Betrixaban study. A Markov model estimated recurrent events and long-term complication risks from published literature. EuroQoL-5 Dimensions utility data and costs inflated to 2017 US dollars (US$) were from published literature. Results were discounted at 3.0% per annum. Deterministic and probabilistic sensitivity analyses explored uncertainty.

RESULTS

Betrixaban dominated enoxaparin, with savings of US$784 and increased QALYs of 0.017 per patient. In addition, betrixaban dominated enoxaparin across all sensitivity analyses, but was most sensitive to utilities and DT probabilities. Furthermore, probabilistic sensitivity analysis found that betrixaban was more cost-effective than enoxaparin at all willingness-to-pay thresholds.

CONCLUSION

Betrixaban can be considered cost-effective for nonsurgical patients with acute medical illness at risk of VTE, requiring longer VTE prophylaxis from hospitalization through post-discharge.

Novel reversal agents and laboratory evaluation for direct-acting oral anticoagulants (DOAC): An update

Novel oral anticoagulants (NOACs) are no longer "novel" but their reversal agents definitely are. Although NOACs enjoy high clinical efficacy, monitoring and reversal of their effect is a challenge which this review attempts to surmount. Ideally, for NOAC activity measurement, specific anti-Factor IIa levels and anti -Factor Xa levels should be monitored (chromogenic assays), but such tests are not readily available. Modifications of the existing coagulation tests catering to this unmet need for quantification of DOAC activity have been reviewed. The available United States Food and Drug Administration (FDA) approved reversal agents, idarucizumab for dabigatrin and andexanet alfa for anti-Xa direct acting oral anticoagulants have given promising results but are prohibitively priced. Medline, Embase, and Scopus databases were thoroughly searched for clinical trials on laboratory investigations and specific as well as non-specific reversal-agents for DOACs.

Extended-duration betrixaban versus shorter-duration enoxaparin for venous thromboembolism prophylaxis in critically ill medical patients: an APEX trial substudy

PURPOSE

To assess the efficacy and safety of betrixaban for venous thromboembolism (VTE) prophylaxis among critically ill patients.

METHODS

The APEX trial randomized 7513 acutely ill hospitalized patients to betrixaban for 35-42 days or enoxaparin for 10 ± 4 days. Among those, 703 critically ill patients admitted to the intensive care unit were included in the analysis, and 547 patients who had no severe renal insufficiency or P-glycoprotein inhibitor use were included in the full-dose stratum. The risk of VTE, bleeding, net clinical benefit (composite of VTE and major bleeding), and mortality was compared at 35-42 days and at 77 days.

RESULTS

At 35-42 days, extended betrixaban reduced the risk of VTE (4.27% vs 7.95%, P = 0.042) without causing excess major bleeding (1.14% vs 3.13%, P = 0.07). Both VTE (3.32% vs 8.33%, P = 0.013) and major bleeding (0.00% vs 3.26%, P = 0.003) were decreased in the full-dose stratum. Patients who received betrixaban had more non-major bleeding than enoxaparin (overall population: 2.56% vs 0.28%, P = 0.011; full-dose stratum: 3.32% vs 0.36%, P = 0.010). Mortality was similar at the end of study (overall population: 13.39% vs 16.19%, P = 0.30; full-dose stratum: 13.65% vs 16.30%, P = 0.39).

CONCLUSIONS

Compared with shorter-duration enoxaparin, critically ill medical patients who received extended-duration betrixaban had fewer VTE without more major bleeding events. The benefit of betrixaban was driven by preventing asymptomatic thrombosis and offset by an elevated risk of non-major bleeding. The APEX trial did not stratify by intensive care unit admission and the present study included a highly selected population of critically ill patients. These hypothesis-generating findings need to be validated in future studies.

CLINICAL TRIAL REGISTRATION

http://www.clinicaltrials.gov . Unique identifier: NCT01583218.

Betrixaban for Extended Venous Thromboembolism Prophylaxis in High-Risk Hospitalized Patients: Putting the APEX Results into Practice

Acutely ill hospitalized medical patients remain at high thromboembolic risk for several weeks after discharge. Previous trials with extended-duration thromboprophylaxis using enoxaparin, apixaban, and rivaroxaban failed to achieve acceptable net clinical benefit, largely due to excess of major bleeding. Betrixaban is a novel factor Xa inhibitor with unique pharmacokinetic properties, including low renal clearance, long half-life, and low peak-to-trough ratio. The phase III APEX trial (N = 7513) compared a betrixaban 160 mg loading dose followed by 80 mg once daily for 35-42 days, with enoxaparin 40 mg once daily for 6-14 days; the betrixaban dose was reduced for renal impairment or a concomitant strong P-glycoprotein (P-gp) inhibitor. The primary efficacy endpoint of composite thrombotic events was not different between treatment arms in cohort 1 (D-dimer ≥ 2 × upper limit of normal). Subsequent exploratory analyses showed a statistically significant difference favoring betrixaban for symptomatic venous thromboembolism and net clinical benefit in the overall population. For the primary safety outcome, betrixaban did not significantly increase major bleeding compared with enoxaparin. Based on available data from the APEX trial and subanalyses, the use of betrixaban in patients similar to those enrolled in the APEX trial can reduce the risk of thromboembolic events without increasing the risk of major bleeding. Patients who may benefit more from betrixaban therapy include those with elevated D-dimer, history of venous thromboembolism, hospitalized for ischemic stroke, hospitalized for heart failure with N-terminal pro-B-type natriuretic peptide ≥ 1975 ng/L, or two or more VTE risk factors. Reduced-dose betrixaban does not appear to provide the same clinical utility as full-dose betrixaban.

Has time come for the use of direct oral anticoagulants in the extended prophylaxis of venous thromboembolism in acutely ill medical patients? No

Acutely ill hospitalized medical patients are at high risk of venous thromboembolism (VTE). Although thromboprophylaxis in these patients is recommended since 2004 by the American College of Chest Physicians, it is widely underused. The doubt as to whether or not to treat patients at high VTE risk after hospital discharge came from the knowledge that this risk may persist after the hospital admission period. Two meta-analyses comparing extended- versus short-duration prophylaxis are published. The results demonstrate an unfavorable balance between VTE prevention and incidence of major bleeding in patients assigned to extended-duration thromboprophylaxis. Only in the APEX study, betrixaban, a direct inhibitor of factor Xa, shows similar efficacy and safety compared to enoxaparin. However, while it is very promising, oral anticoagulant phase III studies and post-marketing registers are lacking. Moreover, betrixaban has a long half-life, an excretion in the gut by means of P-glycoprotein, and the lack of an antidote. These characteristics and the meta-analysis results prompt us to answer no to the extended thromboprophylaxis in hospitalized medical patients, at least now.

Pharmacological properties of betrixaban

Venous thromboembolism (VTE) in acute medically ill patients is a leading cause of in-hospital morbidity and mortality. A majority of these VTE events occur post-discharge, and patients remain at increased VTE risk for up to 3 months post-discharge. Recent clinical trials of extended-duration thromboprophylaxis with enoxaparin, rivaroxaban, and apixaban in acute medically ill patients did not demonstrate a net clinical benefit compared with in-hospital thromboprophylaxis, and were shown to be associated with higher risks of major bleeding. Betrixaban is a new direct oral anticoagulant (DOAC) with a different pharmacokinetic profile than other DOACs. Betrixaban has the longest half-life among the DOAC class, with a terminal half-life of 35-45 h and an effective half-life of 19-27 h. Betrixaban has a low peak-to-trough ratio compared with other anticoagulants and a predictable duration of drug exposure, leading to overall consistent anticoagulant effect over 24 h. Betrixaban is mainly cleared via the hepatobiliary system and therefore not contraindicated in patients with severe renal insufficiency. Betrixaban was recently approved for the indication of extended thromboprophylaxis in the United States based on the APEX trial of betrixaban 80 mg once daily for 35-42 days compared with low molecular weight heparin enoxaparin for 10 ± 4 days in hospitalized acute medically ill patients. This study demonstrated that extended-duration betrixaban reduced VTE compared with standard-duration enoxaparin in acute medically ill patients, without increased risk of major bleeding. This patient population at risk of VTE may benefit from extended prophylaxis, ensuring continuum of care from in-hospital to post-discharge.

Betrixaban (Bevyxxa): A Direct-Acting Oral Anticoagulant Factor Xa Inhibitor

Betrixaban (Bevyxxa): a direct-acting oral anti-coagulant factor Xa inhibitor.

Betrixaban: A New Oral Factor Xa Inhibitor for Extended Venous Thromboembolism Prophylaxis in High-Risk Hospitalized Patients

OBJECTIVE

To review the pharmacology, pharmacokinetics, efficacy, and safety of the factor Xa (FXa) inhibitor betrixaban for extended-duration prophylaxis of acute medically ill patients with venous thromboembolism (VTE) risk factors.

DATA SOURCES

A MEDLINE/PubMed (January 1990 to October 2017) search was conducted using the following keywords: betrixaban, PRT054021, FXa inhibitor, novel oral anticoagulant, NOAC, direct oral anticoagulant, DOAC, and target specific oral anticoagulant, TSOAC. References of identified articles were searched by hand for additional relevant citations.

STUDY SELECTION AND DATA EXTRACTION

We included English-language articles evaluating betrixaban pharmacology, pharmacokinetics, efficacy, or safety in human subjects for VTE prophylaxis.

DATA SYNTHESIS

Betrixaban is a FXa inhibitor that decreases prothrombinase activity and thrombin generation. Betrixaban efficacy and safety has been compared with that of enoxaparin for prophylaxis of VTE in acutely ill medical patients. In the APEX trial and substudies, extended-duration betrixaban was superior in efficacy to standard-duration enoxaparin in patients at high risk for VTE, including those with elevated D-dimer levels (≥2× upper limit of normal) and of older age (≥75 years). Betrixaban is noninferior to enoxaparin in rates of major bleeding, but the former is associated with more clinically relevant nonmajor bleeding events.

CONCLUSION

Betrixaban is the first oral agent approved for extended-duration VTE prophylaxis in acutely ill hospitalized patients. Extended-duration thromboprophylaxis with betrixaban reduces the risk of VTE compared with standard-duration thromboprophylaxis with enoxaparin but is associated with increased risk of bleeding.

Formulary Drug Review: Betrixaban

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Management of Elective Surgery and Emergent Bleeding with Direct Oral Anticoagulants

PURPOSE OF REVIEW

The purpose of this review was to offer practical management strategies for when patients receiving direct oral anticoagulants require elective surgery or present with bleeding complications.

RECENT FINDINGS

Clinical practice guidelines are now available on the timing of periprocedural interruption of treatment with the newer direct oral anticoagulants based on their pharmacodynamics and pharmacokinetics and based on findings from cohort studies and clinical trials. An antibody that reverses the effects of dabigatran is now available, and a factor Xa decoy is being developed as an antidote to apixaban, betrixaban, edoxaban, and rivaroxaban. The timing of interruption of direct oral anticoagulants for elective surgery is based on multiple factors, including pharmacologic properties and interactions, the patient's renal function, and the type of planned surgery. There is little role for low-molecular-weight heparin bridging. Idarucizumab is the treatment of choice for dabigatran-related life-threatening bleeding, while andexanet alfa is being developed to reverse factor Xa inhibitors.

The use of direct oral anticoagulants in inherited thrombophilia

To review the use of the direct oral anticoagulant (DOAC) agents in inherited thrombophilia based on the literature. MEDLINE, International Pharmaceutical Abstracts, and Google Scholar searches (1970-May 2016) were conducted for case reports, case series, retrospective cohorts, or clinical trials using the key words: protein C deficiency, protein S deficiency, antithrombin deficiency, activated protein C resistance, Factor V Leiden, hypercoagulable, NOACs, dabigatran, apixaban, rivaroxaban, betrixaban, edoxaban, Xa inhibitor, direct thrombin inhibitor. Results were limited to English-only articles. Clinical studies evaluating the use of DOACs for hypercoagulable states related to inherited thrombophilia were selected and evaluated. Thrombophilia, a predisposition to thrombosis, manifests predominantly as venous thromboembolism. Causes of inherited thrombophilia include antithrombin deficiency, deficiencies of proteins C and S, and Factor V Leiden mutation. Many patients with thrombophilia receive anticoagulant therapy for primary or secondary prevention of VTE, historically either warfarin or a heparin product. DOAC's have been considered as potential alternatives to traditional agents based on their pharmacologic activity. Case reports and a post-hoc analysis of a clinical trial have indicated positive results in patients with inherited thrombophilia and VTE. Positive results have been reported for the use of DOACs in inherited thrombophilia. Further robust studies are needed for definitive decision making by clinicians.

Role of Novel Oral Anticoagulants in the Treatment of Antiphospholipid Syndrome

Background: Antiphospholipid syndrome (APS) is an autoimmune disease characterized by thrombosis or pregnancy loss with persistent positive antibodies. Standard treatment for APS with history of thromboembolism is heparin or low-molecular-weight heparin followed by a vitamin K antagonist (VKA). Novel oral anticoagulants (NOACs) could be effective in patients with APS, but none carry indications for treatment related to APS. Clinical Evidence: Five case reports or series with rivaroxaban and dabigatran suggest thrombotic events occur most often in the higher risk population (arterial thrombosis and/or triple positive antibodies) or in patients who had recurrent VTEs on warfarin therapy. An observational cohort in 26 APS patients using dabigatran or rivaroxaban described a recurrent thrombotic event in only 1 patient after 8 months of treatment. The event-free survival rate was 87.9% at 12 months. Three controlled clinical trials are underway to evaluate the thrombotic risk of NOACs (RAPS, TRAPS, and ASTRO-APS). Discussion: There are no completed studies that evaluate the use of NOACs in APS compared to VKAs. One major disadvantage of the NOACs is the limited availability of reversal agents for patients with a major bleeding episode. An increased risk of thrombotic events is associated with arterial occlusions and triple antibody positivity APS with both warfarin and NOACs; this is currently being researched in the TRAPS study. Conclusion: Based on current available evidence, VKAs remain the standard of care in the treatment of APS. Results of ongoing trials may offer more guidance on how to appropriately use NOACs for patients with APS.

New Direct Oral Anticoagulants (DOAC) and Their Use Today

The ideal anticoagulant is oral, has a wide therapeutic range, predictable pharmacokinetics and pharmacodynamics, a rapid onset of action, an available antidote, minimal side effects and minimal interactions with other drugs or food. With the development of the novel direct oral anticoagulants (DOAC), we now have an alternative to the traditional vitamin K antagonists (VKA) for the prevention and treatment of thrombosis. DOACs have limited monitoring requirements and very predictable pharmacokinetic profiles. They were shown to be non-inferior or superior to VKA in the prophylaxis or treatment of thromboembolic events. Particularly in terms of safety they were associated with less major bleeding, including intracranial bleeding, thus providing a superior benefit for the prevention of stroke in patients with atrial fibrillation. Despite these advantages, there are remaining limitations with DOACs: their dependence on renal and hepatic function for clearance and the lack of an approved reversal agent, whereas such antidotes are successively being made available. DOACs do not need regular monitoring to assess the treatment effect but, on the other hand, they interact with other drugs and interfere with functional coagulation assays. From a practical point of view, the properties of oral administration, simple dosing without monitoring, a short half-life allowing for the possibility of uncomplicated switching or bridging, and proven safety overwhelm the disadvantages, making them an attractive option for short- or long-term anticoagulation.

Reversing anticoagulant effects of novel oral anticoagulants: role of ciraparantag, andexanet alfa, and idarucizumab

Novel oral anticoagulants (NOACs) are increasingly used in clinical practice, but lack of commercially available reversal agents is a major barrier for mainstream use of these therapies. Specific antidotes to NOACs are under development. Idarucizumab (aDabi-Fab, BI 655075) is a novel humanized mouse monoclonal antibody that binds dabigatran and reverses its anticoagulant effect. In a recent Phase III study (Reversal Effects of Idarucizumab on Active Dabigatran), a 5 g intravenous infusion of idarucizumab resulted in the normalization of dilute thrombin time in 98% and 93% of the two groups studied, with normalization of ecarin-clotting time in 89% and 88% patients. Two other antidotes, andexanet alfa (PRT064445) and ciraparantag (PER977) are also under development for reversal of NOACs. In this review, we discuss commonly encountered management issues with NOACs such as periprocedural management, laboratory monitoring of anticoagulation, and management of bleeding. We review currently available data regarding specific antidotes to NOACs with respect to pharmacology and clinical trials.

Management of Antithrombotic Agents in Oral Surgery Maria Martinez and Dimitrios A. Tsakiris

Systemic anticoagulation with intravenous or oral anticoagulants and antiplatelet agents is an efficient treatment against thromboembolic or cardiovascular disease. Invasive dental procedures or oral surgery might be associated with bleeding complications if carried out under anticoagulants. Patients on vitamin K antagonists, new direct anticoagulants or antiplatelet agents having dental interventions with low-risk for bleeding do not need interruption of anticoagulation. In case of bleeding complications local hemostatic measures, such as local surgical sutures, fibrin glue, local antifibrinolytic treatment with tranexamic acid, or e-aminocaproic acid suffice to stop bleeding. In patients with high risk of bleeding an individual assessment of the benefit/risk ratio of interrupting anticoagulation should be carried out. Bridging the long-term anticoagulation with short-term anticoagulants should be planned according to national or international guidelines. The introduction of the newer direct oral anticoagulants having more flexible pharmacokinetic properties has facilitated bridging, allowing short-term interruption without increasing the risk of relapsing thrombotic or cardiovascular events.