Stroke Prophylaxis With Apixaban in Chronic Kidney Disease Stage 5 Patients With Atrial Fibrillation

Background and rationale: Atrial fibrillation (AF) is common (15-30%) in patients with chronic kidney disease (CKD) and AF prevalence increases with severity of CKD. In late stages of CKD, randomized control trials (RCT) of both efficacy and safety of any anticoagulation therapy, both warfarin and direct oral anticoagulation (DOAC) drugs, for stroke prophylaxis in AF are lacking. The efficacy of warfarin and DOACs have been evaluated in observational trials in patients with stage 5 CKD, but the results have been conflicting, and these studies were all subjected to selection bias in one way or the other. Instead, observational studies have demonstrated several adverse side-effects. Among them an increased number of bleedings including hemorrhagic stroke in patients treated with warfarin, and calciphylaxis, a very serious complications unknown in the normal population linked to the withdrawal of vitamin-K-dependent protection of vascular calcification in CKD. With apixaban treatment several benefits were reported. Firstly, a potential protective effect against ischemic stroke. Secondly, a lower incidence of bleeding complications as observed in the major trials, and thirdly, no disturbance in vitamin K turnover as compared to warfarin treatment. In addition, apixaban treatment does not require routine monitoring and have fewer drug/food interactions. For patients with CKD stage 5, treatment with apixaban appears to have a lower bleeding risk than warfarin treatment.

Rationale to study design: There are no previous randomized controlled clinical trials in this study population. The SACK study is conducted in approximately 50 sites in Sweden, Finland, Norway, Iceland and Poland, and additional European countries, if necessary. In Sweden, the study will be register-randomized (via the national Swedish Renal Register [SNR]) whereas the other countries in the study will include patients in a traditional way for clinical trials.

The study design will be an individually randomized two-armed parallel-group design. Apixaban will be prescribed and renewed by the local investigator via regular prescription or distributed by the investigating site at regular intervals in all participating countries. Due to open-label prescription and safety reasons, the study will be conducted as an open-label trial with end-point evaluation. Patients who are randomized to apixaban and those who are randomized to standard of care with no anti-coagulation will receive all other guideline-recommended standard of care treatments. Patients already on prior warfarin or apixaban therapy, or on regular low molecular weight heparin (LMWH) can also be randomized to either treatment arm (their current anticoagulation is discontinued at the inclusion visit) after an individualized risk assessment. At inclusion, patients will provide routine blood samples including hemoglobin, eGFR, and coagulation parameters.

The end of the clinical study for each individual patient is defined as the End of Study (EoS) visit. The EoS for a patient is after 72 months or when 247 primary events have been reached, whichever comes first. An interim analysis will take place after 1000 patient-years with the purpose to evaluate event rate and to be able to closer determine the exact number of patients and duration of the trial. The end of the clinical trial is defined as the last visit of the last subject in the study (LVLS).

A Data and Safety Monitoring Board (DSMB) will supervise this study, and primary safety and efficacy endpoints and major bleedings will additionally be evaluated by independent external reviewers according to a predefined Central Event Adjudication charter.

Exploratory outcomes: Time to first thromboembolic event defined as a composite of deep vein thrombosis, pulmonary embolism, transient ischemic attack Time to dialysis access thrombosis Time to kidney replacement therapy Delayed graft function in patients undergoing kidney transplantation Thrombosis of renal artery or vein in patients undergoing kidney transplantation

Among the secondary safety outcomes are time to major bleeding according to ISTH criteria. We are especially interested in the safety outcomes of the subgroup undergoing a kidney transplantation from the waiting list and therefore we have an extended protocol for those participants.