Regeneron's COVID-19 antibody cocktail pads case for saving lives in hospitalized patients as FDA decision nears

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Regeneron has a request under FDA review to expand REGEN-COV’s emergency use authorization to cover hospitalized COVID-19 patients. (Tempura/Getty Images)

On a quest to expand REGEN-COV into hospitalized COVID-19 patients, Regeneron has rolled out more data showing the antibody cocktail could save lives.

REGEN-COV, a combination of casirivimab and imdevimab, reduced the risk of death by 36% over placebo at day 29 in hospitalized COVID-19 patients who didn’t require high-flow oxygen or mechanical ventilation when entering the trial, Regeneron unveiled at IDWeek 2021. All patients also received standard-of-care treatments.

Regeneron already has a request under FDA review to expand REGEN-COV’s emergency use authorization to cover hospital settings. The two-drug combo is currently authorized for treating certain outpatients and as a post-exposure prophylaxis method to prevent the development of symptomatic COVID-19 in high-risk individuals.

The 36% improvement didn’t meet the statistical significance bar. An early stop of the phase 2/3 trial thanks to slow enrollment was partly to blame. The efficacy data came from nearly 1,200 patients, just over a third of the trial size originally planned.

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The survival showing also appears to be mostly driven by patients who had no natural antibody response at baseline. In these seronegative patients, REGEN-COV’s death risk reduction was 56%. In seropositive patients, the decrease went down to 21%. Patients who have launched their own immune response against the novel coronavirus are generally less likely to die, so it could be difficult for a drug to improve upon that.

All told, 15 patients (7.6%) who took REGEN-COV died by day 29, while there were 72 deaths (15.4%) in the control group.

The trial also met its primary endpoint, showing REGEN-COV significantly reduced viral load within seven days of treatment.

The new data complement findings from a much larger U.K. trial dubbed RECOVERY. Among 9,785 patients, REGEN-COV reduced the risk of death by 20% among hospitalized patients who hadn’t mounted their own antibody response, Regeneron unveiled in June. The study found no additional survival benefit for the Regeneron therapy in seropositive patients.

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Still, as Regeneron Chief Scientific Officer George Yancopoulos, M.D., Ph.D., pointed out in a statement, the emergence of various coronavirus variants and widespread vaccination may be complicating how doctors make treatment decisions based solely on antibody status because “it might not be practical to assess whether patients' antibodies are for their current SARS-CoV-2 infection.”

REGEN-COV has shown it remains potent against several main variants of concern, including delta, gamma, beta and mu.

Regeneron has provided all data from the two trials to the FDA, and the company believes the agency would “allow for broad use in hospital settings,” a company spokesperson said in a statement to Fierce Pharma.

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After an initial lull with uptake, the recent increase in COVID-19 cases from coronavirus variants such as delta as well as expanded FDA authorizations have significantly driven up demand for antibody treatments. Just two weeks ago, the Biden administration moved to purchase 1.4 million additional doses of REGEN-COV for $2.94 billion, bringing the total to 3 million doses.

As a result, SVB Leerink analyst Geoffrey Porges has dialed up his projection of REGEN-COV’s U.S. sales to a total of $5.4 billion this year and $2.2 billion for 2022.

Through a collaboration signed last August, Roche is helping Regeneron manufacture the antibody cocktail and distribute it outside the U.S. REGEN-COV is known as Ronapreve in Europe.

Editors Note: This story has been updated with additional data and a statement from the company.