ATLANTA – An extra year of apixaban reduced the risk of recurrent events in patients with venous thromboembolism by 80%, while keeping major bleeding rates in line with placebo in the randomized AMPLIFY-EXT trial.
The number needed to treat with apixaban (Eliquis) to prevent one fatal or nonfatal recurrent VTE was only 14, while the number needed to treat to cause one episode of major or clinically relevant nonmajor bleeding was 200, Dr. Giancarlo Agnelli reported in a late-breaking abstract at the annual meeting of the American Society of Hematology.
"We really believe this study, for its design and results, is a remarkable achievement, and [may lead to a] change in clinical practice," he said during a press briefing at the meeting.
Apixaban was approved by the Food and Drug Administration in late December for the prevention of stroke and systemic embolism in patients with non-valvular atrial fibrillation, based largely on data demonstrating superiority to warfarin in patients with AF in the ARISTOTLE trial.*
In the meantime, the results of AMPLIFY-EXT (Apixaban After the Initial Management of Pulmonary Embolism and Deep Vein Thrombosis with First-Line Therapy–Extended Treatment) provide some guidance for physicians uncertain about whether to extend or stop standard anticoagulation therapy in patients with VTE in the absence of recurrent events. Stopping warfarin therapy increases the risk of recurrent VTE by up to 10% in patients without reversible risk factors, but also requires frequent laboratory monitoring and increases the risk of bleeding.
Apixaban, an oral factor Xa inhibitor, is given in fixed doses without the need for laboratory monitoring, said Dr. Agnelli, director of the internal and cardiovascular medicine/stroke unit at the University of Perugia, Italy.
Given the efficacy demonstrated in AMPLIFY-EXT, apixaban may also be an attractive option for those VTE patients with renal impairment, because it is the least dependent on renal clearance compared with two other fixed-dose anticoagulants, rivaroxaban (Xarelto) and dabigatran (Pradaxa), said press briefing moderator Dr. Agnes Lee, medical director of the thrombosis program and associate professor of medicine at the University of British Columbia, Vancouver, and Vancouver Coastal Health.
Notably, a recent prespecified substudy of ARISTOLE demonstrated that apixaban produced 35%-52% fewer major bleeding events in patients with renal dysfunction and atrial fibrillation.
Patrice Wendling/IMNG Medical Media
Dr. Giancarlo Agnelli
The double-blind AMPLIFY-EXT trial randomized 842 patients to apixaban 2.5 mg, 815 to apixaban 5 mg, and 829 to placebo, all twice daily for 12 months. Three-fourths had an initial diagnosis of deep vein thrombosis and one-fourth pulmonary embolism. All had received 6-12 months of anticoagulation therapy and reached clinical equipoise about the continuation or cessation of anticoagulation therapy.
VTE was associated with a transient or reversible risk factor in less than 10% of patients. Two patients from each apixaban group were excluded from the intention-to-treat efficacy analysis. Their average age was roughly 56.
The composite primary efficacy endpoint of symptomatic VTE recurrence or all-cause death occurred in 3.8% of patients on apixaban 2.5 mg and in 4.2% of patients on apixaban 5 mg, compared with 11.6% of patients given placebo, Dr. Agnelli said.
Symptomatic recurrent VTE or death from VTE occurred in 1.7% of patients in both apixaban groups vs. 8.8% of placebo-treated patients.
Major bleeding was reported in 0.2% of the 2.5-mg apixaban group, 0.1% of the 5-mg group, and 0.5% of the placebo group. Clinically relevant nonmajor bleeding rates were slightly higher at 3.0% and 4.2% in the apixaban groups vs. 2.3% in the placebo group, he said.
Further study will be needed to determine if the results can be directly applied to cancer patients who face an increased risk of VTE because of the disease, as only about 2% of the study population had active cancer, Dr. Agnelli said in an interview.
The study was simultaneously published in the New England Journal of Medicine (2012 Dec. 8 [doi: 10.1056/NEJMoa1207541]).
AMPLIFY-EXT was funded by Bristol-Myers Squibb and Pfizer. Dr. Agnelli reported commercial relationships with Bristol-Myers Squibb, Daiichi Sankyo, and other companies. His coauthors reported relationships with the study sponsors. Dr. Lee disclosed consulting for Bristol-Myers Squibb.
*This article was updated January 2, 2013.