Conference Coverage

FREEDOM COVID: Full-dose anticoagulation cut mortality but missed primary endpoint

Study conducted in noncritically ill


AT ACC 2023

– In the international FREEDOM COVID trial that randomized non–critically ill hospitalized patients, a therapeutic dose of anticoagulation relative to a prophylactic dose significantly reduced death from COVID-19 at 30 days, even as a larger composite primary endpoint was missed.

The mortality reduction suggests therapeutic-dose anticoagulation “may improve outcomes in non–critically ill patients hospitalized with COVID-19 who are at increased risk for adverse events but do not yet require ICU-level of care,” reported Valentin Fuster, MD, PhD, at the joint scientific sessions of the American College of Cardiology and the World Heart Federation.

Dr. Valentin Fuster, Physician-in-Chief, Mount Sinai Hospital, New York Ted Bosworth/MDedge News

Dr. Valentin Fuster

These data provide a suggestion rather than a demonstration of benefit because the primary composite endpoint of all-cause mortality, intubation requiring mechanical ventilation, systemic thromboembolism or ischemic stroke at 30 days was not met. Although this 30-day outcome was lower on the therapeutic dose (11.3% vs. 13.2%), the difference was only a trend (hazard ratio, 0.85; P = .11), said Dr. Fuster, physician-in-chief, Mount Sinai Hospital, New York.

Missed primary endpoint blamed on low events

The declining severity of more recent COVID-19 variants (the trial was conducted from August 2022 to September 2022) might be one explanation that the primary endpoint was not met, but the more likely explanation is the relatively good health status – and therefore a low risk of events – among patients randomized in India, 1 of 10 participating countries.

India accounted for roughly 40% of the total number of 3,398 patients in the intention-to-treat population. In India, the rates of events were 0.7 and 1.3 in the prophylactic and therapeutic anticoagulation arms, respectively. In contrast, they were 17.5 and 9.5, respectively in the United States. In combined data from the other eight countries, the rates were 22.78 and 20.4, respectively.

“These results emphasize that varying country-specific thresholds for hospitalization may affect patient prognosis and the potential utility of advanced therapies” Dr. Fuster said.

In fact, the therapeutic anticoagulation was linked to a nonsignificant twofold increase in the risk of the primary outcome in India (HR, 2.01; 95% confidence interval, 0.57-7.13) when outcomes were stratified by country. In the United States, where there was a much higher incidence of events, therapeutic anticoagulation was associated with a nearly 50% reduction (HR, 0.53; 95% CI, 0.31-0.91).

In the remaining countries, which included those in Latin America and Europe as well as the city of Hong Kong, the primary outcome was reduced numerically but not statistically by therapeutic relative to prophylactic anticoagulation (HR, 0.89; 95% CI, 0.71-1.11).

Enoxaparin and apixaban are studied

In FREEDOM COVID, patients were randomized to a therapeutic dose of the low-molecular-weight heparin (LMWH) enoxaparin (1 mg/kg every 12 hours), a prophylactic dose of enoxaparin (40 mg once daily), or a therapeutic dose of the direct factor Xa inhibitor apixaban (5 mg every 12 hours). Lower doses of enoxaparin and apixaban were used for those with renal impairment, and lower doses of apixaban were employed for elderly patients (≥ 80 years) and those with low body weight (≤ 60 kg).

The major inclusion criteria were confirmed COVID-19 infection with symptomatic systemic involvement. The major exclusion criteria were need for ICU level of care or active bleeding.

The therapeutic anticoagulation arms performed similarly and were combined for comparison to the prophylactic arm. Despite the failure to show a difference in the primary outcome, the rate of 30-day mortality was substantially lower in the therapeutic arm (4.9% vs. 7.0%), translating into a 30% risk reduction (HR, 0.70; P = .01).

Therapeutic anticoagulation was also associated with a lower rate of intubation/mechanical ventilation (6.4% vs. 8.4%) that reached statistical significance (HR, 0.75; P = .03). The risk reduction was also significant for a combination of these endpoints (HR, 0.77; P = .03).

The lower proportion of patients who eventually required ICU-level of care (9.9% vs. 11.7%) showed a trend in favor of therapeutic anticoagulation (HR, 0.84; P = .11).

Bleeding rates did not differ between arms

Bleeding Academic Research Consortium major bleeding types 3 and 5 were slightly numerically higher in the group randomized to therapeutic enoxaparin (0.5%) than prophylactic enoxaparin (0.1%) and therapeutic apixaban (0.3%), but the differences between any groups were not significant.

Numerous anticoagulation trials in patients with COVID-19 have been published previously. One 2021 trial published in the New England Journal of Medicine also suggested benefit from a therapeutic relative to prophylactic anticoagulation. In that trial, which compared heparin to usual-care thromboprophylaxis, benefits were derived from a Bayesian analysis. Significant differences were not shown for death or other major outcome assessed individually.

Even though this more recent trial missed its primary endpoint, Gregg Stone, MD, a coauthor of this study and a colleague of Dr. Fuster at the Mount Sinai School of Medicine, New York, reiterated that these results support routine anticoagulation in hospitalized COVID-19 patients.

“These are robust reductions in mortality and intubation rates, which are the most serious outcomes,” said Dr. Stone, who is first author of the paper, which was published in the Journal of the American College of Cardiology immediately after Dr. Fuster’s presentation.

COVID-19 has proven to be a very thrombogenic virus, but the literature has not been wholly consistent on which anticoagulation treatment provides the best balance of benefits and risks, according to Julia Grapsa, MD, PhD, attending cardiologist, Guys and St. Thomas Hospital, London. She said that this randomized trial, despite its failure to meet the primary endpoint, is useful.

“This demonstrates that a therapeutic dose of enoxaparin is likely to improve outcomes over a prophylactic dose with a low risk of bleeding,” Dr. Grapsa said. On the basis of the randomized study, “I feel more confident with this approach.”

Dr. Fuster reported no potential conflicts of interest. Dr. Stone has financial relationships with more than 30 companies that make pharmaceuticals and medical devices. Dr. Grapsa reported no potential conflicts of interest.

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