Safety of Factor XI Inhibition With Abelacimab in Atrial Fibrillation by Kidney Function

Importance Chronic kidney disease is common in patients with atrial fibrillation (AF) and is associated with higher rates of bleeding with anticoagulation. In the AZALEA-TIMI 71 randomized clinical trial, abelacimab, a novel factor XI inhibitor, reduced rates of major or clinically relevant nonmajor (CRNM) bleeding compared with rivaroxaban in patients with AF. Objective To examine the safety of abelacimab vs rivaroxaban across a range of kidney function. Design, Setting, and Participants The AZALEA-TIMI 71 study randomized patients with AF to 1 of 2 abelacimab doses (150 mg or 90 mg monthly) or to rivaroxaban, with stratification by creatinine clearance (CrCl). Patients with CrCl less than 15 mL/min or receiving dialysis were excluded. This secondary analysis of AZALEA-TIMI 71 examines outcomes by randomized treatment and CrCl at randomization. Intervention Patients randomized to rivaroxaban with a CrCl greater than 50 mL/min received rivaroxaban, 20 mg, daily, and those with a CrCl of 50 mL/min or less received rivaroxaban, 15 mg, daily. Patients randomized to abelacimab received the assigned dose irrespective of CrCl. Main Outcomes and Measure The primary outcome was major bleeding or CRNM bleeding. Results Among 1284 patients, median (IQR) age was 74 (69-78) years and 572 patients (44.5%) were female. Median (IQR) CrCl was 71 (54-90) mL/min, with 264 patients (20.6%) having a CrCl of 50 mL/min or less. In the rivaroxaban group, patients with CrCl of 50 mL/min or less experienced higher rates of major or CRNM bleeding compared with those with CrCl greater than 50 mL/min despite dose reduction (incidence rates, 13.6 vs 7.0 per 100 person-years). Abelacimab reduced major or CRNM bleeding vs rivaroxaban irrespective of CrCl (CrCl ≤50 mL/min: hazard ratio [HR], 0.26; 95% CI, 0.12-0.54; >50 mL/min: HR, 0.40; 95% CI, 0.26-0.62; P value for interaction = .33), with absolute risk reductions of 10.1 vs 4.2 per 100 person-years in those with CrCl of 50 mL/min or less vs greater than 50 mL/min, respectively ( P value for interaction = .09). This risk reduction was consistent for major bleeding alone and for a broader composite inclusive of major, CRNM, and minor bleeding. Results were similar when comparing the individual abelacimab doses to rivaroxaban. Conclusions and Relevance In this secondary analysis of the AZALEA-TIMI 71 randomized clinical trial, abelacimab consistently reduced the risk of bleeding relative to rivaroxaban irrespective of kidney function. These findings suggest that abelacimab may offer a particularly favorable safety profile among those with chronic kidney disease; however, larger studies are necessary to characterize the efficacy of abelacimab for stroke prevention in AF.