In a new study, stroke occurred more often in patients with thrombotic antiphospholipid syndrome (TAPS) who were treated with apixaban than with warfarin. Results of the study were published in the journal Blood Advances.

Warfarin has been the standard treatment for TAPS, for which indefinite anticoagulation is recommended due to an increased risk of recurrent thrombosis with the condition. Apixaban is a direct oral anticoagulant (DOAC) that has emerged as a possible alternative to warfarin, but efficacy and safety with apixaban in treatment of TAPS has been unclear, the study investigators explained in their report.

The study was a prospective, randomized, open-label trial ( Identifier: NCT02295475) that evaluated use of either apixaban or warfarin in patients with TAPS over a period of 12 months, with multiple follow-up encounters during this period to assess various outcomes. Some protocol modifications occurred during randomization, such as a dosage change in the apixaban arm, exclusion of patients with prior arterial thrombosis, and others.

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The study had a primary efficacy outcome of a combined rate of thrombosis and vascular death. Major and clinically relevant nonmajor bleeding (CRNMB) was the primary safety outcome. Primary efficacy and safety outcomes were assessed through blinded review.

A total of 23 patients were randomized to the apixaban arm, while 25 patients were randomized to the warfarin arm. Stroke was a thrombotic outcome that appeared to occur at different rates between treatment groups. In the apixaban arm, stroke occurred in 6 of the 23 patients. In the warfarin arm, stroke occurred in 0 of the 25 patients.

Thrombotic events did not occur in patients randomized to warfarin, but there was 1 major bleeding event in this treatment arm. There were no CRNMB events in the warfarin arm. In the apixaban arm, major bleeding or CRNMB reportedly did not occur in any patient.

When evaluating primary efficacy and safety outcomes overall, the researchers calculated rates of adverse outcomes per 1000 person-years totaling 318 with apixaban and 40 with warfarin. The study was discontinued early.

A secondary analysis of patient satisfaction based on the Anti-Clot Treatment Scale survey indicated that apixaban was associated with higher levels of patient satisfaction across time points than warfarin was.

“We observed an increased number of thrombotic strokes in patients receiving apixaban compared with those receiving warfarin, but our study was terminated early, and too few events occurred to make definitive conclusions,” the study investigators wrote in their report. “Nonetheless, our study is consistent with evidence for the role of DOACs among patients with TAPS and suggests that apixaban may not be an effective alternative to warfarin among patients with TAPS.”

Disclosures: Some authors have declared affiliations with or received grant support from the pharmaceutical industry. Please refer to the original study for a full list of disclosures.


Woller SC, Stevens SM, Kaplan D, et al. Apixaban compared with warfarin to prevent thrombosis in thrombotic antiphospholipid syndrome: a randomized trial. Blood Adv. 2022;6(6):1661-1670. doi:10.1182/bloodadvances.2021005808