Rivaroxaban vs. Vitamin K Antagonists for Antiphospholipid Antibody Syndrome

Vitamin K antagonists (VKAs) such as warfarin have been the mainstay of therapy for patients with antiphospholipid antibody syndrome (APS). Recent trials have evaluated APS therapy with direct oral anticoagulants (DOACs), given their predictability and reliability. But concerns have been raised about the efficacy of DOACs in this setting.

Noting limitations in the prior trials, such as early study termination and the use of a laboratory surrogate as an outcome, investigators have conducted a 3-year randomized, open-label, noninferiority trial comparing the efficacy and safety of the DOAC rivaroxaban with that of VKAs in preventing recurrent thrombosis in 190 adults with thrombotic APS. The majority of patients were women with primary APS and prior venous thrombosis; one-third of patients had cardiovascular risk factors.

Key findings were as follows:

• Recurrent thrombosis (the primary endpoint) occurred in more rivaroxaban recipients than VKA recipients (11 vs. 6), demonstrating that rivaroxaban failed to meet noninferiority criteria; 9 of the thrombotic events in rivaroxaban recipients were arterial (stroke).
• The rate of major bleeding was similar between rivaroxaban recipients and VKA recipients (6.3% and 7.4%, respectively).
• A trend toward recurrent thrombosis was seen in rivaroxaban recipients who had a history of livedo racemosa and mitral valve disease.