Minimally modified human blood coagulation factor X to bypass direct factor Xa inhibitors.

BACKGROUND: Direct oral factor (F)Xa inhibitors are widely used as alternatives to conventional vitamin K antagonists in managing venous thromboembolism and nonvalvular atrial fibrillation. Unfortunately, bleeding-related adverse events remain a major concern in clinical practice. In case of bleeding or emergency surgery, rapid-onset reversal agents may be required to counteract the anticoagulant activity. OBJECTIVES: The ability of FXa variants to bypass the direct oral FXa inhibitors was assessed. METHODS: Human FXa variants were generated through substitution of phenylalanine 174 (F174) for either alanine, isoleucine, or serine. FXa variants were stably expressed in HEK293 cells and purified to homogeneity using ion-exchange chromatography. RESULTS: F174-substituted human FX variants demonstrated efficacy in restoring thrombin generation in plasma containing direct FXa inhibitors (apixaban, rivaroxaban, edoxaban). Their ability to bypass the anticoagulant effects stems from a significantly reduced sensitivity for the direct FXa inhibitors due to a decrease in binding affinity determined using molecular dynamics simulations and free energy computation. Furthermore, F174 modification resulted in a partial loss of inhibition by tissue factor pathway inhibitor, enhancing the procoagulant effect of F174-substituted FX. Consequently, the F174A- and F174S-substituted FX variants effectively counteracted the effects of 2 widely used anticoagulants, apixaban and rivaroxaban, in plasma of atrial fibrillation and venous thromboembolism patients. CONCLUSION: These human FX variants have the potential to serve as a rescue reversal strategy to overcome the effect of direct FXa inhibitors in case of life-threatening bleeding events or emergency surgical interventions.

Latest advances in the reversal strategies for direct oral anticoagulants.

BACKGROUND: Since the late 2000s, Europe has granted approval for various thrombotic risk-related uses of direct oral anticoagulants (DOACs). Unlike traditional anticoagulants, DOACs do not necessitate routine coagulation monitoring. Nevertheless, clinical practice often encounters bleeding events associated with these medications, making the need for effective reversal strategies evident. OBJECTIVES: The study aims to take stock of current reversal strategies for DOACs, with a particular emphasis on the latest compounds that have been developed or are currently under development. METHODS: For obtaining information regarding the ongoing reversal strategies and the compounds under development, we referred to ClinicalTrials website, PubMed, and Google Scholar. RESULTS: In 2024, two specific antidotes to DOACs have already received approval when reversal of anticoagulation is needed owing to life-threatening or uncontrolled bleeding: idarucizumab that reverses the effects of dabigatran, and andexanet alfa, designed to counteract activated factor X inhibitors such as apixaban and rivaroxaban. Furthermore, ciraparantag, a potential universal reversal agent, is currently in advanced stages of clinical development. Concerns remain regarding the safety of specific reversal agents, especially concerning the risk of thrombosis. Additionally, the cost of these antidotes remains high. Consequently, nonspecific strategies to counteract anticoagulant medications, including activated charcoal, hemodialysis, and concentrates of coagulation factors, still have utility. CONCLUSION: With the validation of specific and nonspecific antidotes, DOACs could supplant traditional oral anticoagulants. This progress represents a significant advancement in anticoagulation therapy. However, ongoing research is crucial to address remaining safety concerns of the specific reversion agents of DOACs in clinical practice.

Cancer-associated thrombosis: How many patients seen in clinical practice would be eligible for a direct oral anticoagulant randomized controlled trial?

Based on the results of randomized clinical trials (RCT) assessing direct oral anticoagulants (DOACs) for the treatment of patients with cancer-associated thrombosis (CAT), DOACs have been proposed as alternative to low molecular weight heparin by several international guidelines. However, the proportion of CAT patients who would have not been eligible for such trials is currently unknown. Our primary aim was to assess the proportion of patients seen in clinical practice for acute CAT who would not have been eligible for CARAVAGGIO or HOKUSAI-VTE RCT. Secondary aim was to describe patients outcomes according to eligibility. In a multicenter, observational study, all patients consecutively admitted from January 2017 to December 2019 for an acute CAT event were retrospectively analyzed. Patients were classified according to the presence or absence of non-inclusion criteria for CARAVAGGIO or HOKUSAI-VTE RCT. Event free survival during a 6-month follow-up were analyzed as secondary endpoints. Among the 302 patients (women: 53 %, mean age: 67.9 ± 13.2) analyzed, 138 (46 %) for HOKUSAI-VTE cancer and 161 (53 %) for CARAVAGGIO met one or more non-inclusion criteria. Main criteria were upper limb and unsual site thrombosis (n = 63, 18.5 %), anemia/thrombopenia (n = 43, 14.2 %), brain tumors (n = 33, 10.9 %), ECOG PS >2 (n = 28, 9.3 %), severe renal failure (n = 16, 5.3 %). At 6 months, the event-free survival rate was not statistically different between the two groups. Almost half of CAT patients would have not been able to participate to a modern DOAC RCT. Evaluation of DOACs safety and efficacy in this subset of patients deserves further research.