Comparative effectiveness and safety of apixaban versus warfarin in patients with venous thromboembolism

Purpose. Compared with conventional therapy (enoxaparin followed by warfarin), the direct-acting oral anticoagulant apixaban is thought to offer similar protection against recurrent venous thromboembolism (VTE) with lower bleeding risk. However, evidence regarding the heterogeneity of treatment effect from real-world data is lacking. The study described here aimed to compare the effectiveness and safety of use of apixaban versus warfarin in patients with VTE. Methods. We conducted a retrospective cohort analysis of commercial and Medicare supplemental databases (data coverage period, 2014-2017) among patients with a diagnosis of VTE who were new users of apixaban or warfarin. We controlled for confounding using propensity score [PS] 1:4 matching. Cox proportional hazard models were used to obtain hazard ratios (HRs) and 95% confidence intervals (CIs). Heterogeneity of treatment effect was assessed among patients with provoked VTE versus unprovoked VTE. Results. After PS matching, a total of 36,907 patients were included in the cohort (n = 8,094 apixaban users and n = 28,813 warfarin users). In Cox regression models, the use of apixaban versus warfarin was associated with lower risks of recurrent VTE (HR, 0.54; 95% CI, 0.45-0.65) and major bleeding events (HR, 0.67; 95% CI, 0.54-0.84); these results remained consistent in patients with provoked VTE and those with unprovoked VTE. Conclusion. This population-based analysis of patients with VTE extends results of randomized clinical trials indicating lower risks of development of recurrent VTE and major bleeding events with use of apixaban versus warfarin in real-world settings. The observed benefits of apixaban extended to selected subgroups of the VTE population, including patients with provoked VTE.