No Benefit of Rivaroxaban in COVID Outpatients: PREVENT-HD

November 10, 2022

A new US randomized trial has failed to show benefit of a 35-day course of oral anticoagulation with rivaroxaban for the prevention of thrombotic events in outpatients with symptomatic COVID-19.

The PREVENT-HD trial was presented at the American Heart Association (AHA) Scientific Sessions 2022 by Gregory Piazza, MD, Brigham and Women's Hospital, Boston, Massachusetts.

"With the caveat that the trial was underpowered to provide a definitive conclusion, these data do not support routine antithrombotic prophylaxis in nonhospitalized patients with symptomatic COVID-19," Piazza concluded.

PREVENT-HD is the largest randomized study to look at anticoagulation in nonhospitalized COVID-19 patients and joins a long list of smaller trials that have also shown no benefit with this approach.

However, anticoagulation is recommended in patients who are hospitalized with COVID-19.

Piazza noted that the issue of anticoagulation in COVID-19 has focused mainly on hospitalized patients, but most COVID-19 cases are treated as outpatients, who are also suspected to be at risk for venous and arterial thrombotic events, especially if they have additional risk factors. Histopathological evidence also suggests that at least part of the deterioration in lung function leading to hospitalization may be due to in situ pulmonary artery thrombosis.

The PREVENT-HD trial explored the question of whether early initiation of thromboprophylaxis dosing of rivaroxaban in higher risk outpatients with COVID-19 may lower the incidence of venous and arterial thrombotic events, reduce in situ pulmonary thrombosis and reduce the worsening of pulmonary function that may lead to hospitalization, and reduce all-cause mortality.

The trial included 1284 outpatients with a positive test for COVID-19 and who were within 14 days of symptom onset. They also had to have at least one of the following additional risk factors: age over 60 years; prior history of venous thromboembolism (VTE), thrombophilia, coronary artery disease, peripheral artery disease, cardiovascular disease or ischemic stroke, cancer, diabetes, heart failure, obesity (body mass index ≥ 35 kg/m2) or D-dimer > upper limit of normal. Around 35% of the study population had two or more of these risk factors.

Patients were randomized to rivaroxaban 10 mg daily for 35 days or placebo.

The primary efficacy endpoint was time to first occurrence of a composite of symptomatic VTE, myocardial infarction (MI), ischemic stroke, acute limb ischemia, noncentral nervous system (non-CNS) systemic embolization, all-cause hospitalization, and all-cause mortality up to day 35.

The primary safety endpoint was time to first occurrence of International Society on Thrombosis and Hemostasis (ISTH) critical site and fatal bleeding.

A modified intension-to-treat analysis (all participants taking at least one dose of study intervention) was also planned.

The trial was stopped early in April this year because of a lower than expected event incidence (3.2%) compared with the planned rate (8.5%), giving a very low likelihood of being able to achieve the required number of events.

Piazza said reasons contributing to the low event rate included a falling COVID-19 death and hospitalization rate nationwide, and increased use of effective vaccines.

Results of the main intention-to-treat analysis (in 1284 patients) showed no significant difference in the primary efficacy composite endpoint, which occurred in 3.4% of the rivaroxaban group versus 3.0% of the placebo group.

In the modified intention-to-treat analysis (which included 1197 patients who actually took at least one dose of the study medication) there was shift in the directionality of the point estimate (rivaroxaban 2.0% vs placebo 2.7%), which Piazza said was related to a higher number of patients hospitalized before receiving study drug in the rivaroxaban group. However, the difference was still nonsignificant. 

The first major secondary outcome of symptomatic VTE, arterial thrombotic events, and all-cause mortality occurred in 0.3% of rivaroxaban patients versus 1.1% of placebo patients, but this difference did not reach statistical significance.

However, a post-hoc exploratory analysis did show a significant reduction in the outcome of symptomatic VTE and arterial thrombotic events. 

In terms of safety, there were no fatal critical site bleeding events, and there was no difference in ISTH major bleeding, which occurred in one patient in the rivaroxaban group versus no patients in the placebo group.

There was, however, a significant increase in nonmajor clinically relevant bleeding with rivaroxaban, which occurred in nine patients (1.5%) versus one patient (0.2%) in the placebo group.

Trivial bleeding was also increased in the rivaroxaban group, occurring in 17 patients (2.8%) versus five patients (0.8%) in the placebo group.

Discussant for the study, Renato Lopes, MD, Duke University Medical Center, Durham, North Carolina, noted that the relationship between COVID-19 and thrombosis has been an important issue since the beginning of the pandemic, with many proposed mechanisms to explain the COVID-19–associated coagulopathy, which is a major cause of death and disability.

While observational data at the beginning of the pandemic suggested patients with COVID-19 might benefit from anticoagulation, looking at all the different randomized trials that have tested anticoagulation in COVID-19 outpatients, there is no treatment effect on the various different primary outcomes in those studies and also no effect on all-cause mortality, Lopes said. 

He pointed out that PREVENT-HD was stopped prematurely with only about one third of the planned number of patients enrolled, "just like every other outpatient COVID-19 trial."

He also drew attention to the low rates of vaccination in the trial population, which does not reflect the current vaccination rates in the United States, and said the different direction of the results between the main intention-to-treat and modified intention-to-treat analyses deserve further investigation.

However, Lopes concluded, "The results of this trial, in line with the body of evidence in this field, do not support the routine use of any antithrombotic therapy for outpatients with COVID-19."

The PREVENT-HD trial was sponsored by Janssen. Piazza has reported receiving research support from Bristol-Myers Squibb/Pfizer Alliance, Bayer, Janssen, Alexion, Amgen, and Boston Scientific, and consulting fees from Bristol-Myers Squibb/Pfizer Alliance, Boston Scientific, Janssen, NAMSA, Prairie Education and Research Cooperative, Boston Clinical Research Institute, and Amgen.

American Heart Association (AHA) 2022 Scientific Sessions: Presentation number 19481. Presented November 7, 2022.  

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