REVIEW: New Antithrombotics for Atrial Fibrillation

Safety and Tolerability of Tecarfarin (ATI-5923) in Healthy Chinese Volunteers: Multiple Oral Dose-Escalation Phase I Trial

BACKGROUND

Tecarfarin (ATI-5923), a structural analog of warfarin, was designed to provide more uniform and stable anticoagulation.

OBJECTIVE

We aimed to evaluate the safety, tolerability, pharmacokinetic and pharmacodynamic profile of tecarfarin when administered in multiple ascending doses (MADs) to healthy Chinese volunteers.

METHODS

Forty healthy Chinese volunteers were enrolled into four sequential cohorts (10, 20, 30, and 40 mg), with 10 subjects in each cohort. Participants in the MAD study for each sequential cohort were dose-titrated to achieve the target international normalized ratio (INR 1.7-2.0) for 14 days. Safety and tolerability were assessed throughout the study.

RESULTS

The pharmacokinetic and pharmacodynamic profile of tecarfarin was investigated in a healthy Chinese population. Dose titration of tecarfarin was necessary to keep the INR in the target range in all subjects in the 20, 30 and 40 mg cohorts and a few subjects (n = 3) in the 10 mg cohort. Tecarfarin was well tolerated without serious adverse events. Only one treatment-related adverse event (hematochezia) resulted in early withdrawal from the MAD 40 mg cohort.

CONCLUSION

Tecarfarin was well-tolerated by Chinese volunteers. Dose titration was needed for tecarfarin doses larger than 20 mg to keep the INR in the target range.

REGISTRATION

ClinicalTrials.gov identifier: NCT04627116.

Rivaroxaban differentially influences ex vivo global coagulation assays based on the administration time

It was the objective of this study to quantify the effects of rivaroxaban administration on global coagulation parameters associated with routine clinical procedures, we collected plasma samples from patients undergoing major orthopaedic surgery receiving rivaroxaban at various time points after drug administration. Forty-seven patients received rivaroxaban (10 mg daily) for venous thromboembolism prophylaxis. Blood samples were collected at four different time points: A) before surgery; B) before drug administration at day 4–5 after surgery (steady state of rivaroxaban); C) 2 hours (h) after drug administration and D) 12 h after drug administration. The prothrombin time (PT), activated partial thromboplastin time (aPTT), thrombin time (TT), antithrombin (AT) level, fibrinogen level by Clauss method (FibC), and derived fibrinogen (dFIB) level were assessed with various reagents. At 2 h after rivaroxaban administration, the PT and aPTT clotting times were significantly prolonged to different extents up to 1.4 fold, whereas 12 h after drug administration, no significant effect was observed. Rivaroxaban administration had no influence on the TT or the FibC concentration. The dFIB assay was differentially affected by rivaroxaban when different reagents were tested. The AT assay dependent on thrombin activity was not influenced by rivaroxaban, whereas the AT levels dependent on factor Xa activity were significantly increased by rivaroxaban. Clinicians should be aware of the time-dependent influence of rivaroxaban on factor Xa-dependent routine coagulation assays. Therefore, routine coagulation parameters should be assessed directly before drug administration to keep the interaction of rivaroxaban low.

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.

An evidence-based review of apixaban and its potential in the prevention of stroke in patients with atrial fibrillation

Atrial fibrillation (AF) is a common cardiac arrhythmia, especially in the elderly population. It is associated with cardioembolic complications, particularly strokes, resulting in severe functional deficit or death. AF patients are first stratified into low, intermediate, and high risk for thromboembolic events using the CHADS(2) and CHA(2)DS(2)-VASc score systems. Depending on their risks, patients are treated with either therapeutic anticoagulation with warfarin or acetylsalicylic acid for stroke prevention. Although warfarin is the recommended therapy, it is underutilized clinically due to concern for narrow therapeutic window, drug-to-drug and drug-to-food interactions, and hemorrhagic complications. Newer anticoagulant agents such as dabigatran (a direct thrombin inhibitor) and rivaroxaban (a direct factor Xa inhibitor) have already been approved by US Food and Drug Administration for stroke prevention in patients with nonvalvular atrial fibrillation. Apixaban is the newest oral direct factor Xa inhibitor and it has been extensively studied in the AVERROES and ARISTOTLE trials. Apixaban demonstrated reduced incidence of primary outcome of stroke and bleeding events when compared with warfarin. Apixaban is currently being reviewed by the Food and Drug Administration as a stroke prophylactic agent. In addition, there are several other indirect factor Xa inhibitors and vitamin K antagonists under study presently. Results from these studies will provide us with information about possible alternatives to warfarin.

Role of emerging antithrombotic therapy in the prevention of cardioembolic complications in patients with atrial fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and is an independent risk factor of potentially catastrophic cardioembolic strokes. AF patients are categorized into high-, intermediate-, and low-risk for thromboembolic complications using the CHADS(2) or CHA(2)DS(2)-VASc scoring system. Oral anticoagulation using warfarin has been the standard therapy for stroke prevention in intermediate- to high-risk AF patients. However, warfarin use has been limited by several factors such as narrow therapeutic windows, drug-drug and drug-food interactions, and hemorrhagic complications. Rigorous research evaluated dual antiplatelet therapy of clopidogrel and aspirin (acetylsalicylic acid) as a potential alternative to warfarin in the ACTIVE W trial. Dual antiplatelet therapy of clopidogrel and aspirin was found to be inferior to warfarin in preventing stroke and systemic embolism with increased bleeding risk. Other extensive research has led to the development of new antithrombotic agents. Recently, dabigatran etexilate 150 mg twice daily, a direct thrombin inhibitor, was approved by the US FDA for stroke prevention in patients with non-valvular AF after it was found to be superior to warfarin in preventing thromboembolic events and associated with less bleeding in the RE-LY trial. It was also cost effective when compared with warfarin. Dabigatran can be considered in high-risk AF patients who are unable or unwilling to comply with the frequent laboratory and clinic visits that are required when receiving treatment with warfarin. Factor Xa inhibitors are another class of new anticoagulants that have been developed. Oral rivaroxaban was non-inferior to warfarin in thromboprophylaxis and with similar bleeding in the ROCKET-AF trial (HR 0.88; p = 0.117). Apixaban, another factor Xa inhibitor, was superior to aspirin in reducing stroke and systemic embolism in patients with AF in the AVERROES trial (HR 0.45; p < 0.001). The results of the ARISTOTLE trial, which is evaluating apixaban against warfarin in ∼18 000 patients with AF, are expected to be available later this year. Edoxaban, another oral factor Xa inhibitor, is currently being evaluated against warfarin in the ENGAGE AF-TIMI 48 trial in ∼20 000 patients with AF. With these new developments, there is a necessity for the clinical practitioner to become familiar with these new and upcoming therapies and guidelines. This review provides an overview of the available data regarding the clinical usefulness of these agents.