Clinical trials with direct oral anticoagulants for stroke prevention in atrial fibrillation: how representative are they for real life patients?

Impact of patient selection in clinical trials: application of ROCKET AF and ARISTOTLE criteria in GARFIELD-AF

BACKGROUND

The extent to which differences in results from Apixaban for Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation (ARISTOTLE) and Rivaroxaban Once Daily Oral Direct Factor Xa Inhibition Compared with Vitamin K Antagonism for Prevention of Stroke and Embolism Trial (ROCKET) atrial fibrillation (AF)-the landmark trials for the approval of apixaban and rivaroxaban, respectively, for non-valvular AF-were influenced by differences in their protocols is debated. The potential influence of selection criteria on trial results was assessed by emulating these trials in data from the Global Anticoagulant Registry in the Field (GARFIELD)-AF registry.

METHODS

Vitamin K antagonist (VKA) and non-vitamin K oral antagonist (NOAC) users from GARFIELD-AF were selected according to eligibility for the original ARISTOTLE or ROCKET AF trials. A propensity score overlap weighted Cox model was used to emulate trial randomisation between treatment groups. Adjusted HRs for stroke or systemic embolism (SE) within 2 years of enrolment were calculated for each NOAC versus VKA.

RESULTS

Among patients on apixaban, rivaroxaban and VKA, 2570, 3560 and 8005 were eligible for ARISTOTLE, respectively, and 1612, 2005 and 4368, respectively, for ROCKET AF. When selecting for ARISTOTLE criteria, apixaban users had significantly lower stroke/SE risk versus VKA (HR 0.57; 95% CI 0.34 to 0.94) while no reduction was observed with rivaroxaban (HR 0.98; 95% CI 0.68 to 1.40). When selecting for ROCKET AF criteria, safety and efficacy versus VKA were similar across the NOACs.

CONCLUSION

Apixaban and rivaroxaban showed similar results versus VKA in high-risk patients selected according to ROCKET AF criteria, whereas differences emerged when selecting for the more inclusive ARISTOTLE criteria. Our results highlight the importance of trial selection criteria in interpreting trial results and underline the problems faced in comparing treatments across rather than within clinical trials.

Comparison of Direct Oral Anticoagulant Use for the Treatment of Non-Valvular Atrial Fibrillation in Pivotal Clinical Trials vs. the Real-World Setting: A Population-Based Study from Southern Italy

Patients enrolled into pivotal randomized controlled trials (RCTs) may differ substantially from those treated in a real-world (RW) setting, which may result in a different benefit–risk profile. The aim of the study was to assess the external validity of pivotal RCT findings concerning direct oral anticoagulants (DOACs) for the treatment of nonvalvular atrial fibrillation (NVAF) by comparing patients recruited in RCTs to those treated with DOACs registered in a southern Italian local health unit (LHU) in the years 2013–2017. The Palermo LHU claims database was used to describe the baseline characteristics of incident DOAC users (washout > 1 year) with NVAF compared with those of enrolled patients in DOAC pivotal RCTs. In the RW, DOAC treatment discontinuation was calculated during the follow-up and compared with DOAC treatment discontinuation of enrolled patients in DOAC pivotal RCTs. Rates of effectiveness and safety outcomes during the follow-up were calculated in an unmatched and in a simulated RCT population, by matching individual incidental RW and RCT DOAC users (excluding edoxaban users) on age, sex, and CHADS₂ score. Overall, 42,336 and 7092 incident DOAC users with NVAF were identified from pivotal RCTs and from the RW setting, respectively. In RCTs, DOAC use was more common among males (62.6%) compared with an almost equal sex distribution in the RW. RCT patients were younger (mean age ± standard deviation: 70.7 ± 9.2 years) than RW patients (76.0 ± 8.6 years). Compared with RCTs, a higher proportion of RW dabigatran users (30.4% vs. 19.6%) and a lower proportion of RW apixaban (15.9% vs. 25.3%) and rivaroxaban (20.4% vs. 23.7%) users discontinued the treatment during the follow-up (p-value < 0.001). The rate of ischemic stroke was lower in RW high-dose dabigatran users (unmatched/-matched population: 0.40–0.11% per year) than in the Randomized Evaluation of Long-Term Anticoagulation Therapy (RE-LY) population (0.93% per year). Major bleeding rates were lower in RW users than in RCT users. In conclusion, except for dabigatran, a lower proportion of DOAC discontinuers was observed in the real-world than in pivotal RCT settings. This study provides reassurance to practicing physicians that DOAC use appears to be effective in stroke prevention and is likely safer in RW patients than in RCT enrolled patients. These results may be related to a lower burden of comorbidities despite more advanced age in the RW population compared to the pivotal RCT population.

The Number of Concomitant Drugs and the Safety of Direct Oral Anticoagulants in Routine Care Patients with Atrial Fibrillation

Background  The benefit of direct oral anticoagulants (DOACs) versus vitamin K antagonists (VKAs) on major bleeding was less prominent among atrial fibrillation (AF) patients with polypharmacy in post-hoc randomized controlled trials analyses. Whether this phenomenon also exists in routine care is unknown. The aim of the study is to investigate whether the number of concomitant drugs prescribed modifies safety and effectiveness of DOACs compared with VKAs in AF patients treated in general practice.

Study Design  Adult, nonvalvular AF patients with a first DOAC or VKA prescription between January 2010 and July 2018 were included, using data from the United Kingdom Clinical Practice Research Datalink. Primary outcome was major bleeding, secondary outcomes included types of major bleeding, nonmajor bleeding, ischemic stroke, and all-cause mortality. Effect modification was assessed using Cox proportional hazard regression, stratified for the number of concomitant drugs into three strata (0–5, 6–8, ≥9 drugs), and by including the continuous variable in an interaction term with the exposure (DOAC vs. VKA).

Results  A total of 63,600 patients with 146,059 person-years of follow-up were analyzed (39,840 person-years of DOAC follow-up). The median age was 76 years in both groups, the median number of concomitant drugs prescribed was 7. Overall, the hazard of major bleeding was similar between VKA-users and DOAC-users (hazard ratio [HR] 0.98; 95% confidence interval [CI] 0.87–1.11), though for apixaban a reduction in major bleeding was observed (HR 0.81; 95% CI 0.68–0.98). Risk of stroke was comparable, while risk of nonmajor bleeding was lower in DOAC users compared with VKA users (HR 0.92; 95% CI 0.88–0.97). We did not observe any evidence for an impact of polypharmacy on the relative risk of major bleeding between VKA and DOAC across our predefined three strata of concomitant drug use ( p -value for interaction = 0.65). For mortality, however, risk of mortality was highest among DOAC users, increasing with polypharmacy and independent of the type of DOAC prescribed ( p -value for interaction <0.01).

Conclusion  In this large observational, population-wide study of AF patients, risk of bleeding, and ischemic stroke were comparable between DOACs and VKAs, irrespective of the number of concomitant drugs prescribed. In AF patients with increasing polypharmacy, our data appeared to suggest an unexplained yet increased risk of mortality in DOAC-treated patients, compared with VKA recipients.

Appropriateness of direct oral anticoagulant dosing in patients with atrial fibrillation according to the drug labelling and the EHRA Practical Guide

BACKGROUND

This study aimed to evaluate the prevalence of potential drug-drug interactions (DDIs) and the appropriateness of direct oral anticoagulant (DOAC) dosing according to both the Summary of Product Characteristics (SmPC) and the European Heart Rhythm Association (EHRA) Practical Guide in a 'real-world' sample of non-valvular atrial fibrillation (NVAF) patients.

METHODS AND RESULTS

Data of a cross-sectional observational study in a primary care sample of 654 long-term DOAC users were used for this sub-analysis. A total of 262 potential DDIs were identified in 220 patients (33.6%). Pharmacodynamic DDIs were present in 163 patients (24.9%) and pharmacokinetic DDIs in 82 patients (12.5%). One-third of patients (33.8%) received reduced DOAC dose. According to the dosing recommendations in the SmPC, 81.7% of DOACs were dosed appropriately. According to the EHRA recommendations, 76.6% of DOACs were dosed appropriately. Dosing recommendations were consistent for 90.7% of patients, with both the SmPC and EHRA Practical Guide considering DOACs dosed appropriately in 74.5% of patients, overdosed in 7.8%, underdosed in 7.6% and contraindicated in 0.8%. However, for the remaining 9.3% dosing recommendations differed between SmPC and EHRA.

CONCLUSIONS

This 'real-world' analysis of DOAC dosing demonstrated that in about one-third of NVAF patients potential DDIs were present. In 18.3% and 23.4% of patients, DOACs were dosed inappropriately according to the SmPC and EHRA Practical Guide respectively. In almost 10% of the study population dosing advice was inconsistent between both references. More research is needed to ensure appropriate DOAC dosing in this 'grey zone' population.

Prescribers' compliance with summary of product characteristics of dabigatran, rivaroxaban and apixaban-A European comparative drug utilization study

Despite a tremendous increase of direct oral anticoagulants (DOACs) prescriptions in recent years, only few data is available analysing prescribers' adherence to Summary of Product Characteristics (SmPC). We aimed to assess adherence to registered indications, contraindications, special warnings/precautions, and potential drug-drug interactions for three DOAC compounds (dabigatran, rivaroxaban, and apixaban) in six databases of five European countries (The Netherlands, United Kingdom, Spain, Denmark, and Germany). We included adult patients (≥18 years) initiating DOACs between 2008 and 2015. For several SmPC items, broad definitions were used due to ambiguous SmPC terms or lacking data in some databases. Within the study period, a DOAC was initiated in 407 576 patients (rivaroxaban: 240 985 (59.1%), dabigatran: 95 303 (23.4%), and apixaban: 71 288 (17.5%)). In 2015, non-valvular atrial fibrillation was the most common indication (>60% in most databases). For the whole study period, a substantial variation between the databases was found regarding the proportion of patients with at least one contraindication (inter-database range [IDR]: 8.2%-55.7%), with at least one special warning/precaution (IDR: 35.8%-75.2%) and with at least one potential drug-drug interaction (IDR: 22.4%-54.1%). In 2015, the most frequent contraindication was "malignant neoplasm" (IDR: 0.7%-21.3%) whereas the most frequent special warning/precaution was "prescribing to the elderly" (≥75 years; IDR: 25.0%-66.4%). The most common single compound class interaction was "concomitant use of non-steroidal anti-inflammatory drugs" (IDR: 3.0%-25.3%). Contraindications, special warnings/precautions, and potential drug-drug interactions were present in a relevant number of new DOAC users. Due to broad definitions used for some SmPC terms, overall proportions for contraindications are prone to overestimation. However, for unambiguous SmPC terms documented in the databases sufficiently, the respective estimates can be considered valid. Differences between databases might be related to "true" differences in prescription behaviour, but could also be partially due to differences in database characteristics.

Appropriate Dosing Regimens of Non-Vitamin K Antagonist Oral Anticoagulants for Treatment of Patients With Non-Valvular Atrial Fibrillation: An Evidence-Based Consideration

Patients with non-valvular atrial fibrillation (NVAF) exhibit a high risk of stroke, which is associated with high mortality. Thus, stroke prevention is crucial for the overall management of NVAF. Two categories of drugs, vitamin K antagonist warfarin and non-vitamin K antagonist oral anticoagulants (NOACs), are clinically used to prevent NVAF-related stroke. In some circumstances, NOACs are superior to warfarin. However, NOACs selection for NVAF patients is affected by many factors, including individual patient characteristics, comorbidities, risk factors, or laboratory variables. This article summarizes the discrepancy in NOACs management with emphasis on the dosing regimens and influencing factors, such as stroke risk, age, body weight, renal function, gastrointestinal bleeding (GIB) risk, and combination of antiplatelet therapy, in order to identify individual groups with particular clinical characteristics who may obtain more benefit from a certain dosing regimen of NOACs. Determination of a particular subset of patient populations for the appropriate dose regimen of NOACs will help to achieve desired clinical outcomes. Furthermore, to compensate clinical evidence, we should place more emphasis on the findings of current clinical trials and supplement real-world data.

Real-world on-treatment and initial treatment absolute risk differences for dabigatran vs warfarin in older US adults

PURPOSE

Trials and past observational work compared dabigatran and warfarin in patients with atrial fibrillation, but few reported estimates of absolute harm and benefit under real-world adherence patterns, particularly in older adults that may have differing benefit-harm profiles. We aimed to estimate risk differences for ischemic stroke, death, and gastrointestinal bleeding after initiating dabigatran and warfarin in older adults (a) when patients adhere to treatment and (b) under real-world adherence patterns.

METHODS

In a 20% sample of nationwide Medicare claims from 2010 to 2015, we identified beneficiaries aged 66 years and older initiating warfarin and dabigatran. We followed individuals from initiation until death or October 2015 (initial treatment, IT) and separately censored individuals' follow-up after drug switches and gaps in supply (on-treatment, OT). We applied inverse probability of treatment and standardized morbidity ratio weights, as well as inverse probability of censoring weights, to estimate two-year risk differences (RDs) for dabigatran vs warfarin.

RESULTS

We identified 10,717 dabigatran and 74,891 warfarin initiators. Weighted OT RDs suggested decreased ischemic stroke risk for dabigatran vs warfarin; IT RDs indicated increased or no change in ischemic stroke risk. Regardless of follow-up approach and weighting strategy, risk of death appeared lower and risk of gastrointestinal bleeding appeared higher when comparing dabigatran vs warfarin.

CONCLUSIONS

Dabigatran use was associated with lower risks of mortality and ischemic stroke in routine care when older adults stayed on treatment. IT analyses suggested that these benefits may be diminished under real-world patterns of switching and discontinuation.

Incidence of direct oral anticoagulant use in patients with nonvalvular atrial fibrillation and characteristics of users in 6 European countries (2008-2015): A cross-national drug utilization study

Aims

To estimate the incidence of direct oral anticoagulant drug (DOAC) use in patients with nonvalvular atrial fibrillation and to describe user and treatment characteristics in 8 European healthcare databases representing 6 European countries.

Methods

Longitudinal drug utilization study from January 2008 to December 2015. A common protocol approach was applied. Annual period incidences and direct standardisation by age and sex were performed. Dose adjustment related to change in age and by renal function as well as concomitant use of potentially interacting drugs were assessed.

Results

A total of 186 405 new DOAC users (age ≥18 years) were identified. Standardized incidences varied from 1.93–2.60 and 0.11–8.71 users/10 000 (2011–2015) for dabigatran and rivaroxaban, respectively, and from 0.01–8.12 users/10 000 (2012–2015) for apixaban. In 2015, the DOAC incidence ranged from 9 to 28/10 000 inhabitants in SIDIAP (Spain) and DNR (Denmark) respectively. There were differences in population coverage among the databases. Only 1 database includes the total reference population (DNR) while others are considered a population representative sample (CPRD, BIFAP, SIDIAP, EGB, Mondriaan). They also varied in the type of drug data source (administrative, clinical). Dose adjustment ranged from 4.6% in BIFAP (Spain) to 15.6% in EGB (France). Concomitant use of interacting drugs varied between 16.4% (SIDIAP) and 70.5% (EGB). Cardiovascular comorbidities ranged from 25.4% in Mondriaan (The Netherlands) to 82.9% in AOK Nordwest (Germany).

Conclusion

Overall, apixaban and rivaroxaban increased its use during the study period while dabigatran decreased. There was variability in patient characteristics such as comorbidities, potentially interacting drugs and dose adjustment. (EMA/2015/27/PH).

Direct oral anticoagulant and antiplatelet combination therapy: Hemorrhagic events in coronary artery stent recipients

Direct oral anticoagulant (DOAC) use is growing as monotherapy and combined with platelet inhibitors. The safety of such combination therapy, especially in comparison to regimens including warfarin, in real world populations remains uncertain. We investigated hemorrhage associated with DOAC and antiplatelet combination therapy in a cohort of elderly coronary artery stent recipients. We employed Medicare data 2010-2013 for a 40% random sample of beneficiaries enrolled in inpatient, outpatient and prescription benefits. We used Cox proportional hazards models to examine the association of the combination anticoagulant (DOAC or warfarin) plus antiplatelets with major hemorrhage events (upper gastrointestinal or intracranial) in the 12 months following stent placement. We identified 70,900 stent recipients. 14.4% had atrial fibrillation (AF) diagnosis preoperatively. Among the 24.5 million observation days, exposure distribution was: 73.8% antiplatelets only, 4.7% antiplatelets plus warfarin, 0.6% antiplatelets plus DOAC, 2.2% warfarin only, 0.3% DOAC only and 18.4% no observed antiplatelets or anticoagulant. Overall, 8,029 patients (11.3%) experienced major hemorrhage. Among AF patients, compared to antiplatelets only, DOAC plus antiplatelets was associated with increased hemorrhage risk (HR, 1.94; 95%CI, 1.48-2.54); warfarin plus antiplatelets conferred comparable bleed risk (HR, 1.69; 95%CI, 1.47-1.94). In the non-AF group, compared to antiplatelets alone, combination DOAC plus antiplatelets (HR, 3.09; 95%CI, 2.15-4.46), and warfarin plus antiplatelets (HR, 2.21; 95%CI, 1.97-2.48) conferred greater bleed risk. Among elderly coronary artery stent recipients with AF, the two drug combinations, DOAC plus antiplatelets and warfarin plus antiplatelets, were associated with similarly increased risk of major hemorrhage compared to antiplatelets alone.

The representativeness of direct oral anticoagulant clinical trials to hospitalized patients with atrial fibrillation

PURPOSE

Trials of the direct oral anticoagulants (DOACs) dabigatran, rivaroxaban and apixaban provide the basis for prescribing for the prevention of stroke and systemic embolism in atrial fibrillation (AF). The objective of this study was to assess the representativeness of the three pivotal DOAC randomized controlled trials of dabigatran, rivaroxaban and apixaban for unselected hospitalized patients with AF.

METHODS

A cross-sectional study was undertaken. All patients discharged with AF between 2012 and 2015 from a large public hospital network in Melbourne, Australia, were identified. Inclusion and exclusion criteria from the DOAC trials were applied. The proportions of hospitalized patients with AF who would have been eligible for the dabigatran (RE-LY), rivaroxaban (ROCKET-AF) and apixaban (ARISTOTLE) trials were estimated, as was pooled eligibility for all three trials. Characteristics of eligible and ineligible patients were compared.

RESULTS

For the 4734 patients, application of the inclusion and exclusion criteria resulted in 60.5, 52.6 and 35.8% eligibility for the trials of apixaban, dabigatran and rivaroxaban, respectively. Pooled eligibility across all three trials demonstrated that 33.4% of the patients would have been eligible for all three trials but 36.7% ineligible for any trial. Ineligible patients who met exclusion criteria were older and experienced more comorbidities.

CONCLUSIONS

The apixaban and dabigatran trials may be the most representative of hospitalized patients with AF. The DOAC trial results can readily be extrapolated to, and guide prescribing for, at least two thirds of patients discharged from a large metropolitan health service in Australia.

From evidence-based medicine to personalized medicine, with particular emphasis on drug-safety monitoring

Nowadays, guidelines are derived from the findings of randomized controlled therapeutic trials. However, an overall significant P value does not exclude that some patients may be harmed by or will not respond to the therapeutic agent being studied. Trials in patients with a low risk of events and/or a limited chance of providing significant differences in therapeutic effects require a large patient population to demonstrate a beneficial effect. Composite efficacy endpoints are often employed to obviate the need for a large patient population when low rates of events or limited therapeutic efficacy are anticipated. Results of randomized controlled therapeutic trials are commonly expressed in terms of relative risk reduction, whereas absolute risk reduction allows the calculation of the "number needed to treat" to prevent an adverse outcome. The number needed to treat is a far more clinically relevant variable than relative risk reduction. The clinician's mission is to match treatment to patient with the goal of achieving optimal therapeutic response. Drug-safety monitoring is also of major importance to avoid exposing patients to irreversible adverse effects. Unfortunately, drug-safety monitoring is often overlooked in routine clinical practice. Finally, the lack of long-term therapeutic data (>5-10 years) is an unsolved dilemma, as most trials are limited to a duration of a few months or years.

DOACs - advances and limitations in real world

The group of new oral anticoagulants or NOACs, now termed direct oral anticoagulants or DOACs, with their favourable results from large scale phase III clinical trials, represent a major advancement and expanded armamentarium in antithrombotic therapy. Dabigatran, rivaroxaban, apixaban and edoxaban are now in clinical routine use for prevention and treatment of arterial and venous thrombotic diseases as addressed in their clinical trials. Usage of the DOACs is expected to increase as clinicians gain more experience and reassurance with data from the real world studies which are generally consistent with that from clinical trials. Development of specific antidotes in management of bleeding complications and development of coagulation assays for their plasma levels will further boost the confidence in the DOACs. Nonetheless, there are still limitations associated with the DOACs. Many patients in need of anticoagulant therapy for indications not studied in the clinical trials will not be eligible for treatment with a DOAC. Conditions where more data is required include DOACs use in the paediatric age group, patients with atrial fibrillation and valvular heart disease, thrombosis associated with the anti-phospholipid syndrome and cancer associated thrombosis. The affordability and access to these drugs may pose an issue for many patients under healthcare systems not providing for these medications. With four new anticoagulants coming onboard very quickly, the focus has shifted to the practical approach and management in real life as many clinicians are not yet familiar with the DOACs. Clinicians need to be educated on how to manage this new class for drugs, from choosing the appropriate drug to prevention and managing bleeding complications as a lack of knowledge and understanding in these drugs will lead to inappropriate use and compromise on patient safety.