N Engl J Med

COBRRA trial delivers a clear winner in VTE anticoagulation safety

March 17, 2026

The large, international COBRRA trial randomized 2,760 patients with acute symptomatic pulmonary embolism (PE) or proximal deep vein thrombosis (DVT) to receive either apixaban or rivaroxaban for 3 months using standard FDA-approved dosing. Apixaban was given as 10 mg twice daily for 7 days, then 5 mg twice daily; rivaroxaban was given as 15 mg twice daily for 21 days, then 20 mg once daily. Clinically relevant bleeding—a composite of major bleeding or clinically relevant nonmajor bleeding—occurred in 3.3% of patients receiving apixaban vs. 7.1% receiving rivaroxaban (relative risk, 0.46; 95% confidence interval, 0.33-0.65; P <0.001). Major bleeding was lower with apixaban (0.4% vs. 2.4%), while no difference in recurrent venous thromboembolism (VTE) was observed between groups. The most common bleeding types were vaginal and gastrointestinal. No bleeding-related deaths occurred in either group during the 3-month period. The difference in bleeding risk may be partly explained by rivaroxaban's extended 21-day high-dose lead-in phase (compared with apixaban’s 7-day lead-in) and its once-daily dosing, which produces greater peak-trough variation in plasma concentrations than apixaban's twice-daily regimen.

Notably, the trial excluded patients with active cancer, body weight >120 kg, and severe renal impairment—populations that commonly require VTE treatment. Additionally, the 3-month treatment duration limits conclusions about longer-term anticoagulation, which many patients with unprovoked or recurrent VTE require. The study population was approximately 90% White, limiting generalizability to more diverse patient populations.

In an accompanying editorial in the New England Journal of Medicine, Dr. Lisa K. Moores of Uniformed Services University of the Health Sciences describes the COBRRA trial as a "landmark trial" that provides the first randomized, head-to-head comparison evidence to guide clinicians in choosing between these two direct oral anticoagulants (DOACs) for VTE treatment. The editorial characterizes the trial as "ending the venous thromboembolism safety toss-up" that has persisted for over a decade since DOACs became available.

Clinical takeaway: For most patients with acute DVT or PE, apixaban should be favored over rivaroxaban as first-line oral anticoagulation to meaningfully reduce bleeding risk without compromising protection against recurrent VTE.

Sources:

Castellucci, LA et al. (2026, March 11). N Engl J Med. Bleeding Risk with Apixaban vs. Rivaroxaban in Acute Venous Thromboembolism. https://www.nejm.org/doi/full/10.1056/NEJMoa2510703

Moores, Lisa K. (2026, March 11). N Engl J Med. The COBRRA Trial — Ending the Venous Thromboembolism Safety Toss-up. https://www.nejm.org/doi/full/10.1056/NEJMe2600525