Results of a double-blind, randomized, controlled trial, in which apixaban use was assessed in patients with venous thromboembolism (VTE) who had already completed 6–12 months of anticoagulation therapy, have been published in the New England Journal of Medicine. Uncertainty about whether anticoagulation therapy should be continued or ceased existed for all 2,486 patients enrolled in the AMPLIFY-EXT trial. The investigators found that a 12-month, twice-daily regimen of either 2.5 mg or 5.0 mg of apixaban was “effective, safe, and simple to use” in this patient population.

During the 1-year active study period, 11.6% of the placebo group reached the primary efficacy end point—symptomatic recurrent VTE (fatal or nonfatal pulmonary embolism or deep-vein thrombosis) or death from any cause—compared with 3.8% in the 2.5 mg apixaban group (relative risk [RR] 0.33, 95% CI 0.22–0.48) and 4.2% in the 5.0 mg apixaban group (RR 0.36, 95% CI 0.25–0.53). Over the same period, 8.8% of the placebo group experienced symptomatic recurrent VTE or death related to VTE, compared with 1.7% in both the 2.5 mg apixaban (RR 0.19, 95% CI 0.11–0.33) and 5.0 mg apixaban (RR 0.20, 95% CI 0.11–0.34) groups.

The primary safety end point, major bleeding, was not significantly different between the three treatment groups (0.5%, 0.2%, and 0.1% for placebo, 2.5 mg apixaban, and 5.0 mg apixaban, respectively). The rates of other adverse events were also similar between the three treatment groups.

The AMPLIFY-EXT investigators concluded, therefore, that “for patients with VTE for whom there is uncertainty about the benefits and risks of continued therapy, the results of this study provide a rationale for continuing anticoagulation therapy for an additional 12 months”. They warn clinicians, however, that more data are needed for patients aged >75 years, for those with body weight <60 kg, and for individuals with moderate-to-severe renal impairment, because few such patients were included in the AMPLIFY-EXT trial. The investigators also highlight the need for additional studies to assess the extension of apixaban treatment beyond 18–24 months.