Recommendations for the use of andexanet alfa in the management of bleeding in patients on oral factor Xa inhibitors in Switzerland: Guideline from the Working Party Hemostasis of the Swiss Society of Hematology

Anticoagulants are essential in preventing and treating thrombosis. Unfortunately, their use is accompanied by an enhanced risk of bleeding. Since the introduction of direct oral anticoagulants (DOACs), the risk of major bleeding has been reduced but not eliminated. Major bleeding events related to the use of factor Xa inhibitors can be challenging to manage. In recent years, four-factor prothrombin complex concentrates have been used in patients with severe bleeding taking oral direct factor Xa inhibitors (apixaban, edoxaban and rivaroxaban). Andexanet alfa (OndexxyaTM, AstraZeneca AG) is a specially designed recombinant version of human factor Xa that acts as a decoy receptor to reverse the effects of factor Xa inhibitors. Since 2 December 2020, andexanet alfa has been used in Switzerland for adult patients receiving apixaban or rivaroxaban when reversal of anticoagulation is required because of life-threatening or uncontrolled bleeding. However, the use of andexanet alfa remains a challenge owing to its cost, the reported thrombotic complications and the fact that its efficacy mainly relates to intracranial haemorrhage. Moreover, the use of nonspecific reversal agents together with andexanet alfa is controversial. The present recommendations on the use of andexanet alfa in the management of bleeding in patients on factor Xa inhibitors in Switzerland were developed by a group of Swiss experts from the Working Party Hemostasis of the Swiss Society of Hematology. These recommendations aim to provide support to clinicians in their decision-making in the management of patients with major bleeding receiving factor Xa inhibitors.

Assessment of DOAC in GEriatrics (Adage Study): Rivaroxaban/Apixaban Concentrations and Thrombin Generation Profiles in NVAF Very Elderly Patients

BACKGROUND

 Although a growing number of very elderly patients with atrial fibrillation (AF), multiple conditions, and polypharmacy receive direct oral anticoagulants (DOACs), few studies specifically investigated both apixaban/rivaroxaban pharmacokinetics and pharmacodynamics in such patients.

AIMS

 To investigate: (1) DOAC concentration-time profiles; (2) thrombin generation (TG); and (3) clinical outcomes 6 months after inclusion in very elderly AF in-patients receiving rivaroxaban or apixaban.

METHODS

 Adage-NCT02464488 was an academic prospective exploratory multicenter study, enrolling AF in-patients aged ≥80 years, receiving DOAC for at least 4 days. Each patient had one to five blood samples at different time points over 20 days. DOAC concentrations were determined using chromogenic assays. TG was investigated using ST-Genesia (STG-ThromboScreen, STG-DrugScreen).

RESULTS

 We included 215 patients (women 71.1%, mean age: 87 ± 4 years), 104 rivaroxaban and 111 apixaban, and 79.5% receiving reduced-dose regimen. We observed important inter-individual variabilities (coefficient of variation) whatever the regimen, at C _max [49-46%] and C _min [75-61%] in 15 mg rivaroxaban and 2.5 mg apixaban patients, respectively. The dose regimen was associated with C _max and C _min plasma concentrations in apixaban (p = 0.0058 and p = 0.0222, respectively), but not in rivaroxaban samples (multivariate analysis). Moreover, substantial variability of thrombin peak height (STG-ThromboScreen) was noticed at a given plasma concentration for both xabans, suggesting an impact of the underlying coagulation status on TG in elderly in-patients. After 6-month follow-up, major bleeding/thromboembolic event/death rates were 6.7%/1.0%/17.3% in rivaroxaban and 5.4%/3.6%/18.9% in apixaban patients, respectively.

CONCLUSION

 Our study provides original data in very elderly patients receiving DOAC in a real-life setting, showing great inter-individual variability in plasma concentrations and TG parameters. Further research is needed to understand the potential clinical impact of these findings.

Thrombin generation assays to personalize treatment in bleeding and thrombotic diseases

Treatment of bleeding and thrombotic disorders is highly standardized and based on evidence-based medicine guidelines. These evidence-based treatment schemes are well accepted but may lead to either insufficient treatment or over-dosing, because the individuals' hemostatic properties are not taken into account. This can potentially introduce bleeding or thrombotic complications in individual patients. With the incorporation of pharmacokinetic (PK) and pharmacodynamic (PK-PD) parameters, based on global assays such as thrombin generation assays (TGAs), a more personalized approach can be applied to treat either bleeding or thrombotic disorders. In this review, we will discuss the recent literature about the technical aspects of TGAs and the relation to diagnosis and management of bleeding and thrombotic disorders. In patients with bleeding disorders, such as hemophilia A or factor VII deficiency, TGAs can be used to identify patients with a more severe bleeding phenotype and also in the management with non-replacement therapy and/or bypassing therapy. These assays have also a role in patients with venous thrombo-embolism, but the usage of TGAs in patients with arterial thrombosis is less clear. However, there is a potential role for TGAs in the monitoring of (long-term) antithrombotic therapy, for example with the use of direct oral anticoagulants. Finally this review will discuss controversies, limitations and knowledge gaps in relation to the introduction of TGAs to personalize medicine in daily medical practice.

Automated Thrombin Generation Assay for Rivaroxaban, Apixaban, and Edoxaban Measurements

Background: The thrombin generation assay (TG) is a promising approach to measure the degree of anticoagulation in patients treated with direct oral anticoagulants (DOAC). A strong association with plasma drug concentrations would be a meaningful argument for the potential use to monitor DOAC. Objectives: We aimed to study the correlation of TG with rivaroxaban, apixaban, and edoxaban drug concentrations in a large, prospective multicenter cross-sectional study. Methods: Five-hundred and fifty-nine patients were included in nine tertiary hospitals. The Technothrombin® TG was conducted in addition to an anti-Xa assay; LC-MS/MS was performed as the reference standard. Results: Correlation (r_s) between thrombin generation measurements and drug concentrations was -0.72 for peak thrombin generation (95% confidence interval, CI, -0.77, -0.66), -0.55 for area under the curve (AUC; 95% CI -0.61, -0.48), and 0.80 for lag time (95% CI 0.75, 0.84). In contrast, r_s was 0.96 with results of the anti-Xa activity (95% CI 0.95-0.97). Sensitivity with regard to the clinically relevant cut-off value of 50 μgL^-1 was 49% in case of peak thrombin generation (95% CI, 44, 55), 29% in case of AUC (95% CI, 24, 34), and 64% in case of lag time (95% CI, 58, 69). Sensitivity of the anti-Xa assay was 95% (95% CI, 92, 97). Conclusions: The correlation of thrombin generation measurements with DOAC drug concentrations was weak, and clinically relevant drug levels were not predicted correctly. Our results do not support an application of TG in the monitoring of DOAC.

Use of direct-acting oral anticoagulants in solid organ transplantation: A systematic review

The use of direct-acting oral anticoagulants (DOACs) has increased secondary to the mounting evidence for comparable efficacy and potentially superior safety to vitamin K antagonists (VKAs) in the general population. However, insufficient data regarding DOAC use in solid organ transplant (SOT) recipients and numerous pharmacokinetic and pharmacodynamic considerations limit their use in this highly selected patient population. A systematic review of recent clinical evidence on the safety and efficacy of DOACs compared to VKAs in SOT recipients was conducted. Additional considerations including transplant-specific strategies for DOAC reversal and common pharmacokinetic/pharmacodynamic concerns were also reviewed. Although current evidence is limited to single-center retrospective analyses, DOACs, especially apixaban, appear to be a safe and effective alternative to VKAs for SOT recipients with stable graft function and without drug-drug interactions. Reliable data on DOAC reversal at the time of transplant surgery are lacking, and clinicians should consider idarucizumab, andexanet alfa, and other non-specific reversal agents on an individual patient basis. There is no evidence supporting deviations from the Food and Drug Administration labeling recommendations for DOAC dosing in the setting of drug-drug interactions, obesity, and renal function, especially in patients on hemodialysis.

Inhibition of thrombin generation 12 hours after intake of direct oral anticoagulants

BACKGROUND

The residual antithrombotic activity 12 hours after intake of direct oral anticoagulants (DOACs) is of clinical relevance in the setting of bleeding or urgent surgery.

OBJECTIVE

To evaluate the effects of DOACs on thrombin generation 12 hours after DOAC intake in comparison to baseline and a healthy control group.

METHODS

Eighty patients were recruited, 20 patients for each approved DOAC: apixaban, edoxaban, rivaroxaban, and dabigatran. The patients were either to be put on anticoagulation for the first time or had stopped taking oral anticoagulation for at least 48 hours. Blood plasma was sampled before (baseline) and 12 hours after starting DOAC for quantification of drug levels and thrombin generation assayed using an automated system (ST Genesia). Sixty-one blood donors served as control group.

RESULTS

The factor Xa inhibitors significantly increased lag time (137%-219%) and reduced thrombin peak (47%-76%) and velocity index (17%-44%) after 12 hours compared to baseline. Dabigatran showed prolongation of lag time to 133% and time to peak to 119%. All patients had residual antithrombotic activity, with reduced thrombin generation parameters 12 hours after DOAC intake compared to baseline and to the healthy control group. This effect remained significant in patients with low residual DOAC plasma levels <50 ng/mL.

CONCLUSION

Thrombin generation remains reduced 12 hours after DOAC intake. While thrombin peak is particularly modified by factor Xa inhibitors, all DOACs prolong the lag time and time to thrombin peak. In the setting of bleeding or urgent surgery, the automated thrombin generation assay may assist in decision making and antidote administration.

Thrombin generation in a woman with heterozygous factor V Leiden and combined oral contraceptives: A case report

Combined oral contraceptives and factor V Leiden mutation are multiplicative risk factors for venous thromboembolism. However, it remains unknown whether this multiplicative effect is reflected in thrombin generation assays. We report here the evolution of the thrombin generation profile while taking combined oral contraceptives and after their discontinuation in a woman with heterozygous factor V Leiden mutation. The proband exhibited a distinctly prothrombotic thrombin generation profile including markedly decreased thrombomodulin (TM) sensitivity, compared to the control population. This profile possibly reflected a high thrombotic risk. After discontinuation of combined oral contraceptives, thrombin generation and TM sensitivity improved greatly, leaving only a slightly prothrombotic profile. Therefore, the multiplied thrombotic risk occurring with simultaneous combined oral contraceptives and factor V Leiden mutation is reflected by a thrombin generation assay performed without and with TM. This could be a promising tool to identify women taking combined oral contraceptives at high risk for venous thromboembolism. Further studies are needed to verify this hypothesis.

Use of Direct Oral Anticoagulants in Morbidly Obese Patients

In 2016, the International Society on Thrombosis and Haemostasis (ISTH) published guidelines advising caution when using direct oral anticoagulants (DOACs) in patients with morbid obesity due to limited clinical efficacy and safety data supporting their use in this patient population. In this review, we analyzed published articles in the MEDLINE database (from inception through May 29, 2019), and the Cochrane Library, Google Scholar, and EMBASE databases (from inception through April 26, 2019) that evaluated morbidly obese patients with atrial fibrillation (AF) or venous thromboembolism (VTE) who received DOACs. A total of 19 studies, which included pharmacokinetic studies, original phase III trials for the DOACs, post hoc analyses of phase III trials, and retrospective cohort studies, were evaluated. Although currently available data do not indicate that using DOACs in the morbidly obese is problematic, DOAC-specific pharmacokinetic variations have been observed. Additionally, less data evaluating DOAC efficacy and safety exist for VTE treatment compared with the data for stroke prevention in patients with AF. The overall quality of the studies included in this review was low due to limited prospective randomized trial data, limiting the ability to form definitive judgments on efficacy and safety DOACs in the morbidly obese. Continued caution is recommended when considering DOAC use in the morbidly obese, particularly for those requiring anticoagulation for VTE treatment, until additional higher-quality data become available.

Rivaroxaban pharmacodynamics in healthy volunteers evaluated with thrombin generation and the active protein C system: Modeling and assessing interindividual variability

BACKGROUND

Rivaroxaban is a direct factor Xa inhibitor with substantial inter-individual pharmacokinetic (PK) variability. Pharmacodynamic (PD) variability, especially assessed with thrombin generation (TG), has been less documented.

OBJECTIVES

(i) To assess TG parameter time profiles in healthy volunteers, with TG being studied under different conditions and (ii) to model the relationship between rivaroxaban concentrations and TG parameters and subsequently estimate interindividual variability.

METHODS

Sixty healthy male volunteers (DRIVING-NCT01627665) received a single 40-mg rivaroxaban dose. Blood sampling was performed at baseline and 10 predefined time points over 24 h. The TG was investigated with the fully automated ST-Genesia system (Stago), using two tissue-factor (TF) concentrations, in the absence (-), or presence (+) of thrombomodulin (TM) for the lowest one. The PD models were built to characterize the relationships between plasma rivaroxaban concentrations and endogenous thrombin potential (ETP) or peak height induced by the lowest TF concentration.

RESULTS

Thrombin generation parameter time profiles with the lowest TF concentration showed a good sensitivity to rivaroxaban, especially +TM (active protein C negative feedback). The relationship between rivaroxaban concentrations and TG parameters was modeled with a sigmoidal relation. Mean rivaroxaban concentrations halving the baseline value of ETP and peak height (-TM) (C50 ) were of 284 and 33.2 ng/mL, respectively: +TM, C50 declined to 19.4 and 13.8 ng/mL, reflecting a powerful inhibitory effect. The estimated C50 population coefficients of variation were of 12.2% (-TM) and 31.3% (+TM) with the peak height models, 34.8% (+TM) with the ETP model.

CONCLUSIONS

This low-rivaroxaban to moderate-rivaroxaban PD variability in healthy volunteers contrasts with the substantial PK variability and deserves to be studied in different patient settings.