Apixaban: a novel oral inhibitor of factor Xa

A mini review on the regulation of coagulation homeostasis through interfering with vitamin K-dependent coagulation/anticoagulation factors

Coagulation disorders, such as excessive bleeding or thrombosis, present significant health challenges. Vitamin K-dependent proteins (VKDPs), including coagulation and anticoagulation factors, are essential for maintaining the coagulation homeostasis due to their key roles in the coagulation cascade. Therefore, VKDPs have become significant targets for regulating coagulation homeostasis, and various strategies have been developed, primarily including small molecule drugs and nanomaterials. This review presents the summary of these strategies, focusing on the mechanisms, effectiveness and limitations. It first discusses the pivotal role of VKDPs in the coagulation cascade, followed by an in-depth analysis of how small molecule drugs and nanomaterials to regulate hemostasis through interfering with VKDPs. Furthermore, this review addresses the challenges faced in the current approaches and potential future research directions. We hope this review will contribute to advancing the development of novel methods for modulating coagulation homeostasis through VKDP interference.

Assessment of Anti-Xa activity in patients receiving concomitant apixaban with strong p-glycoprotein inhibitors and statins

WHAT IS KNOWN AND OBJECTIVES

Although the apixaban Food and Drug Administration (FDA) package insert recommends dose reduction in patients administered dual strong inhibitors of p-glycoprotein (P-gp) and cytochrome P-450 (CYP) 3A4, there are limited published data regarding potential drug-drug interactions between apixaban (Eliquis) and common p-glycoprotein (P-gp) and CYP3A4 inhibitors co-administered with statins. The aim of this study was to investigate the degree of elevation relative to apixaban serum peak and trough concentration after the co-administration of amiodarone, diltiazem and statins (atorvastatin, rosuvastatin and simvastatin).

METHODS

Patients prescribed apixaban 5mg twice daily for at least one week were identified from the anticoagulation clinic database and contacted for potential enrolment. A total of 117 volunteers were enrolled with eight excluded due to discontinued use, resulting in 109 volunteers (44 females and 65 males delineated into age groups 40-64 and ≥65 years old) completing the observational study. Fifty-five volunteers were administered apixaban without the P-gp inhibitors amiodarone or diltiazem, with or without statins (atorvastatin, rosuvastatin and simvastatin). Fifty-four volunteers were administered apixaban with either amiodarone or diltiazem, with or without statins (atorvastatin, rosuvastatin or simvastatin). Peak and trough concentrations were assessed for each patient utilizing an apixaban anti-Xa assay.

RESULTS

Of the combinations studied, the mean apixaban trough concentration upon co-administration of amiodarone without a statin was elevated compared to apixaban alone (experimental 156.83 +/- 79.59 ng/ml vs. control 104.09 +/- 44.56 ng/ml; p = 0.04). The co-administration of diltiazem and rosuvastatin, and the administration of amiodarone without a statin led to greater than 1.5-fold increase in apixaban concentrations (peak experimental 315.19 +/- 157.53 ng/ml vs control 207.6 +/- 83.38 ng/ml; p = 0.08 and trough experimental 182.03 +/- 95.93 ng/ml vs control 112.32 +/- 37.78 ng/ml; p = 0.17) suggesting the need to assess dose adjustment for patients per the FDA package insert. In addition, the aggregated mean peak (p = 0.0056) and trough (p = 0.0089) elevation of CYP3A4 experimental groups (atorvastatin and simvastatin) co-administered apixaban and diltiazem were statistically significant compared with the aggregated non-CYP3A4 control groups (no statin and rosuvastatin).

WHAT IS NEW AND CONCLUSION

Herein, we report novel data regarding peak and trough apixaban concentrations after concomitant administration of P-gp and CYP3A4 inhibitors (amiodarone or diltiazem) co-administered with statins (atorvastatin, rosuvastatin or simvastatin). Providers should consider utilizing the apixaban anti-Xa assay or comparative heparin anti-Xa assay to determine if patients require dose reduction to decrease adverse events in high-risk patients prescribed apixaban and concomitant p-glycoprotein and CYP3A4 inhibitors amiodarone or diltiazem with and without a CYP3A4 or non-3A4 statin.

Safety and Effectiveness of Apixaban in Japanese Patients With Venous Thromboembolism in Clinical Practice - A Post-Marketing Surveillance

BACKGROUND

A post-marketing surveillance study (STANDARD-VTE) evaluated the real-world safety and effectiveness of apixaban in Japanese patients prescribed for either the treatment of venous thromboembolism (VTE) or prevention of recurrent VTE.

METHODS AND RESULTS

Patients newly initiated on apixaban were followed up for 52 weeks or 28 days post-discontinuation. Subgroup analysis was performed on patients with and without active cancer, and on patients with provoked VTE and with unprovoked VTE. A total of 1,119 patients were enrolled. Of these, 43.1% were aged ≥75 years, 46.4% had body weight ≤60 kg, and 21.3% had active cancer; mean serum creatinine was 0.76 mg/dL. The incidence of adverse drug reactions (ADRs) was 8.85%, and that of severe ADRs was 3.22%. Incidence of any bleeding, major bleeding, and recurrent VTE was 6.70%, 3.40%, and 0.80%, respectively. In patients starting apixaban 10 mg twice daily, THE incidence of any bleeding and major bleeding was 7.72% and 3.86%, respectively. In patients with active cancer, THE incidence of any bleeding and major bleeding was 16.81% and 9.24%, respectively.

CONCLUSIONS

No new safety signals of apixaban were identified in Japanese patients with VTE. In this study, the safety and effectiveness of apixaban in real-world practice was consistent with the results of the apixaban phase III trial.

Clinically Important Drug-Drug Interactions Between Antiarrhythmic Drugs and Anticoagulants

Until the last decade, vitamin K antagonists (VKAs) were the only agents available for oral anticoagulation. Although effective and accessible, their use was complicated by a narrow therapeutic window, the need for regular monitoring of the international normalized ratio, and an associated susceptibility to interactions with both food and numerous medications. Furthermore, the onset of action was delayed, often requiring bridging with intravenous agents. In more recent years, we have enjoyed the development of nonvitamin-K-dependent, direct oral anticoagulants (DOACs), which either directly inhibit the activity of factor IIa (eg, dabigatran) or factor Xa (eg, rivaroxaban, apixaban, edoxaban). These medications boast a more rapid onset of action, predictable pharmacokinetics, wider therapeutic window, and equal or superior safety profiles. Although these medications appear to have fewer drug–drug interactions than VKAs, their interactions remain of clinical importance, particularly in one of the largest populations requiring anticoagulation: patients with atrial fibrillation. These patients are rarely on single medications, with the majority of them requiring some form of rate or rhythm control due to their arrhythmia. Unfortunately, data on interactions between DOACs and antiarrhythmic medications, despite their common coadministration, remain limited. Here, we summarize the interactions between antiarrhythmics and VKAs and review existing knowledge regarding their interactions with DOACs.

New antiplatelet drugs and new oral anticoagulants

In our daily anaesthetic practice, we are confronted with an increasing number of patients treated with either antiplatelet or anticoagulant agents. During the last decade, changes have occurred that make the handling of antithrombotic medication a challenging part of anaesthetic perioperative management. In this review, the authors discuss the most important antiplatelet and anticoagulant drugs, the perioperative management, the handling of bleeding complications, and the interpretation of some laboratory analyses related to these agents.

Prothrombin Complex Concentrate for Warfarin-Associated Intracranial Bleeding in Neurosurgical Patients: A Single-Center Experience

Objective: The number of patients presenting with warfarin-associated intracranial bleeding and needing neurosurgical intervention is growing. Prothrombin complex concentrate (PCC) is commonly used for anti-coagulation reversal before emergent surgery. We present our experience with PCC use in patients presenting with coagulopathy and needing urgent craniotomy. Methods: We retrospectively identified all patients presenting with intracranial bleeding and coagulopathy due to warfarin use, requiring urgent neurosurgical procedures, from January, 2014 (implementation of 4-PCC therapy) until December, 2016. For coagulation reversal, all patients received 4-PCC (Octaplex) and vitamin K. Results: Thirty-five consecutive patients (17 men; median age 72 years) were administered 4-PCC before emergent neurosurgical procedures. The majority of patients presented with traumatic subdural hematoma (62%) and spontaneous intracerebral hemorrhage (32%). All patients were taking warfarin. Median international normalized ratio (INR) on admission was 2.94 (range: 1.20 to 8.60). Median 4-PCC dose was 2000 I.U. (range: 500 I.U. to 3000 I.U.). There was a statically significant decrease in INR (p < 0.01), PT (p < 0.01), and PTT (p = 0.02) after 4-PCC administration. Postoperative INR values were ≤3.00 in all patients, and seven (20%) patients had normal INR values. There were no 4-PCC related complications. Four (11%) patients developed subdural/epidural hematoma and 20 (57%) patients died. Mortality was associated with lower Glasgow coma scale (GCS) score. Conclusions: The 4-PCC facilitates INR reversal and surgery in patients presenting with warfarin-associated coagulopathy and intracranial bleeding requiring urgent neurosurgical intervention.

Non-Vitamin K Antagonist Oral Anticoagulants: The Clinician's New Challenge

Millions of US patients are prescribed oral anticoagulants. Traditionally, oral anticoagulation was achieved with vitamin K antagonists (VKAs). In recent years, non-VKA oral anticoagulants (NOACs) have emerged that provide an effective and convenient alternative to VKAs. These agents possess very different pharmacologic properties from what the medical community has grown accustom to with the VKAs. Thus, a new knowledge base is required for NOACs. One particular challenge with the NOACs is the lack of specific reversal agent, resulting in difficulties correcting the coagulopathy induced by these drugs when needed. A review of the current literature is presented to assist clinicians in gaining knowledge of the NOACs to care for patients.

An Overview of Severe Acute Respiratory Syndrome-Coronavirus (SARS-CoV) 3CL Protease Inhibitors: Peptidomimetics and Small Molecule Chemotherapy

Severe acute respiratory syndrome (SARS) is caused by a newly emerged coronavirus that infected more than 8000 individuals and resulted in more than 800 (10-15%) fatalities in 2003. The causative agent of SARS has been identified as a novel human coronavirus (SARS-CoV), and its viral protease, SARS-CoV 3CL(pro), has been shown to be essential for replication and has hence been recognized as a potent drug target for SARS infection. Currently, there is no effective treatment for this epidemic despite the intensive research that has been undertaken since 2003 (over 3500 publications). This perspective focuses on the status of various efficacious anti-SARS-CoV 3CL(pro) chemotherapies discovered during the last 12 years (2003-2015) from all sources, including laboratory synthetic methods, natural products, and virtual screening. We describe here mainly peptidomimetic and small molecule inhibitors of SARS-CoV 3CL(pro). Attempts have been made to provide a complete description of the structural features and binding modes of these inhibitors under many conditions.

Management of Venous Thromboembolism: Recent Advances in Oral Anticoagulation Therapy

OBJECTIVE

To review clinical data on direct oral anticoagulants (DOACs) used in the acute treatment of venous thromboembolism (VTE) as well as practical considerations when using these products.

DATA SOURCES

Searches of PubMed and Google Scholar for VTE, deep vein thrombosis, pulmonary embolism, and relevant drug international nonproprietary names were conducted. Additional online searches were conducted for prescribing information.

STUDY SELECTION AND DATA EXTRACTION

Relevant articles on dabigatran, rivaroxaban, apixaban, and edoxaban for the management of VTE compared with oral vitamin K antagonists (VKAs; published between 1966 and December 2015) were reviewed and summarized, together with information on dosing, pharmacokinetics/pharmacodynamics, and drug-drug interactions.

DATA SYNTHESIS

The DOACs have the potential to circumvent many of the disadvantages of VKAs. At a minimum, they greatly increase the available therapeutic options, thus providing a greater opportunity for clinicians to select a management option that best fits the needs of individual patients. Despite the significant advance that DOACs represent, they are not without risk and require careful consideration of a number of clinical issues to optimize safety and efficacy.

CONCLUSIONS

The emergence of DOACs for the management of thromboembolic disorders represents a paradigm shift from oral VKAs. The DOACs provide similar efficacy and improved safety in selected patients as compared with VKAs. Clinicians treating VTE need to be familiar with the intricacies involved in using these agents, including the appropriate dose selection for the relevant indication, avoidance of drug-drug and drug-disease interactions, and consideration of dose adjustments in specific clinical situations, such as organ dysfunction.

Plasma Exchange for Urgent Apixaban Reversal in a Case of Hemorrhagic Tamponade after Pacemaker Implantation

We report the case of an 82-year-old man in whom hemorrhagic pericardial effusion occurred one week after pacemaker implantation, while he was taking apixaban. Few therapies exist for reversing the anti-Xa effect of apixaban. To reverse anticoagulation, our patient underwent plasma exchange, which facilitated pericardiocentesis and prevented possible surgical intervention. To our knowledge, this is the first report of the use of plasmapheresis to reverse the anticoagulant effect of apixaban.

Determination of Apixaban Levels in Human Plasma by a High-Throughput Liquid Chromatographic Tandem Mass Spectrometry Assay / Determinarea rapidă a apixabanului în plasma umană prin cromatografie de lichide de înaltă performanță cuplată cu spectrometrie de masă în tandem

A high-throughput liquid chromatography method with detection by tandem mass spectrometry (LC-MS/MS) was developed and validated for the quantification of apixaban in human plasma. The separation was performed on a Gemini-NX column under isocratic conditions using a 33:67 (v/v) mixture of acetonitrile and 1 mM ammonium formate in water at 40 ºC with a flow rate of 0.5 mL/min. The detection of apixaban was performed in multiple reaction monitoring mode (m/z 417.2 from m/z 460.2) with electrospray positive ionization. A single-step protein precipitation with methanol was used for plasma sample preparation. The method was validated with respect to selectivity, linearity (r > 0.994), intra-day and inter-day precision (CV < 14.4 %) and accuracy (bias < 9.5 %) over the range of 9.70 - 970.00 ng/mL plasma. The lower limit of quantification (LLOQ) was 9.70 ng/mL and the recovery was between 97.4 - 104.5 %. The method is fast, efficient, requires the processing of a small volume of plasma (50 μL), a short run-time (1 min) for chromatographic analysis, and a simple and rapid preparation of samples. It is very well suited for clinical therapeutic drug monitoring and pharmacokinetic studies.

Race against the clock: overcoming challenges in the management of anticoagulant-associated intracerebral hemorrhage

Patients receiving anticoagulation therapy who present with any type of intracranial hemorrhage--including subdural hematoma, epidural hematoma, subarachnoid hemorrhage, and intracerebral hemorrhage (ICH)--require urgent correction of their coagulopathy to prevent hemorrhage expansion, limit tissue damage, and facilitate surgical intervention as necessary. The focus of this review is acute ICH, but the principles of management for anticoagulation-associated ICH (AAICH) apply to patients with all types of intracranial hemorrhage, whether acute or chronic. A number of therapies--including fresh frozen plasma (FFP), intravenous vitamin K, activated and inactivated prothrombin complex concentrates (PCCs), and recombinant activated factor VII (rFVIIa)--have been used alone or in combination to treat AAICH to reverse anticoagulation, help achieve hemodynamic stability, limit hematoma expansion, and prepare the patient for possible surgical intervention. However, there is a paucity of high-quality data to direct such therapy. The use of 3-factor PCC (activated and inactivated) and rFVIIa to treat AAICH constitutes off-label use of these therapies in the United States. However, in April 2013, the US Food and Drug Administration (FDA) approved Kcentra (a 4-factor PCC) for the urgent reversal of vitamin K antagonist (VKA) anticoagulation in adults with acute major bleeding. Plasma is the only other product approved for this use in the United States. (1) Inconsistent recommendations, significant barriers (e.g., clinician-, therapy-, or logistics-based barriers), and a lack of approved treatment pathways in some institutions can be potential impediments to timely and evidence-based management of AAICH with available therapies. Patient assessment, therapy selection, whether to use a reversal or factor repletion agent alone or in combination with other agents, determination of site-of-care management, eligibility for neurosurgery, and potential hematoma evacuation are the responsibilities of the neurosurgeon, but ultimate success requires a multidisciplinary approach with consultation from the emergency department (ED) physician, pharmacist, hematologist, intensivist, neurologist, and, in some cases, the trauma surgeon.

The role of prothrombin complex concentrates in reversal of target specific anticoagulants

Over the past several years a new era for patients requiring anticoagulation has arrived. The approval of new target specific oral anticoagulants offers practitioners several advantages over traditionally used vitamin K antagonist agents including predictable pharmacokinetics, rapid onset of action, comparable efficacy and safety, all without the need for routine monitoring. Despite these benefits, hemorrhagic complicates are inevitable with any anticoagulation treatment. One of the major disadvantages of the new oral anticoagulants is lack of specific antidotes or reversal agents for patients with serious bleeding or need for urgent surgery. As use of the new target specific oral anticoagulants continues to increase, practitioners will need to understand both the pharmacodynamics and pharmacokinetic properties of the agents, as well as, the available literature with use of non-specific therapies to reverse anticoagulation. Four factor prothrombin complex concentrates have been available for several years in Europe, and recently became available in the United States with approval of Kcentra. These products have shown efficacy in reversing anticoagulation from vitamin K antagonists, however their usefulness with the new target specific oral anticoagulants is poorly understood. This article will review the properties of dabigatran, rivaroxaban and apixaban, as well as the limited literature available on the effectiveness of prothrombin complex concentrates in reversal of their anticoagulant effects. Additional studies are needed to more accurately define the role of prothrombin complex concentrates in patients with life threatening bleeding or who require emergent surgery, as current data is both limited and conflicting.

Latest developments in anticoagulant drug discovery

Thromboembolic diseases have increased in number over the past years. Oral anticoagulants impair the formation and progression of thrombotic processes and are therefore of great importance in the treatment of these diseases. Until recently, vitamin K antagonists were used to block the coagulation system. But these agents display a lot of interactions besides their narrow therapeutic range and have potential risk of hemorrhage complications. Therefore, other factors of the coagulation cascade are currently being explored as therapeutic targets for the development of novel anticoagulants. This review will provide an overview of new drugs promising more effectiveness in the treatment of arterial and venous embolism. Furthermore, pharmacodynamics and drug interactions regarding new anticoagulants will be reported.

Novel oral anticoagulants for stroke prevention in the geriatric population

Prior to the availability of several newer anticoagulant medications, there had been no new advances in anticoagulation management for stroke prevention since the advent of warfarin in the 1950s. The availability of the novel oral anticoagulants (NOACs) dabigatran, rivaroxaban,and apixaban represent improvements over warfarin in many respects, including the elimination of the need for therapeutic drug monitoring, fewer drug and food interactions,and favorable efficacy; however, these agents are not without risk. Specifically, the use of the NOACs in the geriatric population, who are more likely to have an increased risk of stroke due to atrial fibrillation and other medical comorbidities, is not without risk. The objective of this review is to update the clinician on the use of the NOACs in the geriatric population and introduce the controversies and risks surrounding these newer therapies.

The use of novel oral anticoagulants for thromboprophylaxis after elective major orthopedic surgery

Venous thromboembolism is a common cause of morbidity and mortality among patients undergoing elective orthopedic surgery. Due to the high incidence of venous thromboembolism in this setting, perioperative anticoagulation is the recommended approach for thromboprophylaxis. Low molecular weight heparin (LMWH), fondaparinux and warfarin are the agents commonly used for thromboprophylaxis. The well-recognized limitations of warfarin and the inconvenience and discomfort associated with the subcutaneous administration of low molecular weight heparin and fondaparinux inspired intense investigation to develop novel oral anticoagulants (NOACs) with more predictable pharmacokinetics, fewer drug interactions and no need for regular laboratory monitoring. Three NOACs have been demonstrated to be effective for thromboprophylaxis after total hip arthroplasty (THA) and total knee arthroplasty (TKA) in large randomized controlled trials. Here we review the pharmacology of rivaroxaban, dabigatran, and apixaban, summarize the major clinical trials of these agents in thromboprophylaxis after THA and TKA, and discuss the clinical factors to be considered by providers when selecting a NOAC for their patients.

Novel oral anticoagulants for the prevention and treatment of thromboembolism

Over the last 5 years, new oral anticoagulant options, including dabigatran, rivaroxaban and apixaban, have become available. Prior to this, vitamin K antagonists were the sole oral anticoagulants, which have been in use for more than 60 years. These novel agents have been studied in a variety of patient populations, including atrial fibrillation, acute coronary syndrome, treatment of venous thromboembolism and thromboprophylaxis. Compared with standard care, these agents have largely been found to be noninferior or superior for efficacy end points, with similar or improved rates of bleeding. As a result, these agents have become attractive alternatives to vitamin K antagonists for the prevention and treatment of thromboembolic disease. This article provides a summary of clinical trial data to help clinicians determine which agent is most appropriate for a given patient.

Importance of pharmacokinetic profile and variability as determinants of dose and response to dabigatran, rivaroxaban, and apixaban

Warfarin has been the mainstay oral anticoagulant (OAC) medication prescribed for stroke prevention in atrial fibrillation (AF) patients. However, warfarin therapy is challenging because of marked interindividual variability in dose and response, requiring frequent monitoring and dose titration. These limitations have prompted the clinical development of new OACs (NOACs) that directly target the coagulation cascade with rapid onset/offset of action, lower risk for drug-drug interactions, and more predictable response. Recently, NOACs dabigatran (direct thrombin inhibitor), and rivaroxaban and apixaban (factor Xa [FXa] inhibitors) have gained regulatory approval as alternative therapies to warfarin. Though the anticoagulation efficacy of these NOACs has been characterized, differences in their pharmacokinetic and pharmacodynamic profiles have become a significant consideration in terms of drug selection and dosing. In this review, we outline key pharmacokinetic and pharmacodynamic features of each compound and provide guidance on selection and dosing of the 3 NOACs relative to warfarin when considering OAC therapy for AF patients. Importantly, we show that by better understanding the effect of clinical variables such as age, renal function, dosing interval, and drug metabolism (CYP3A4) and transport (P-glycoprotein), we might be able to better predict the risk for sub- and supratherapeutic anticoagulation response and individualize OAC selection and dosing.

Apixaban: a new factor Xa inhibitor for stroke prevention in patients with nonvalvular atrial fibrillation

Atrial fibrillation (AF) is an independent risk factor for ischemic stroke occurrence, severity, recurrence, and mortality. Anticoagulation therapy for the prevention of thromboembolism is critical in patients with AF who are at risk of stroke. Warfarin has been an efficacious anticoagulant for this purpose, but its use has been limited by frequent laboratory monitoring, drug interactions, unpredictable individual response, delayed onset of action, and bleeding. Apixaban is the second oral direct selective factor Xa inhibitor approved for the prevention of stroke/systemic embolism in patients with nonvalvular AF. It was significantly better than aspirin in reducing stroke (ischemic or hemorrhagic) or systemic embolism without increasing the risk of major bleeding in patients with AF who were at increased risk of stroke and for whom warfarin was unsuitable. In a randomized, double-blind trial that was originally designed to test for noninferiority, apixaban was superior to warfarin (target international normalized ratio 2-3) in preventing stroke or systemic embolism, caused less bleeding, and resulted in lower mortality in patients with AF. Apixaban has a half-life of about 12 hours, and the normal dosage is 5 mg orally twice daily. However, it may be reduced to 2.5 mg twice daily based on individual factors of the patient (age, renal function, and body weight) and the concomitant use of potent dual inhibitors of cytochrome P450 3A4 and P-glycoprotein. Similar to other novel oral anticoagulants (dabigatran and rivaroxaban), apixaban has no reversal agent for its anticoagulant effect. Overall, apixaban is a safe and efficacious alternative for stroke prophylaxis in high-risk patients who have AF and who are unable to achieve therapeutic goals with warfarin therapy.