Regeneron cocktail reduces viral loads in hospitalized patients with COVID-19
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The antibody cocktail of casirivimab and imdevimab significantly reduced viral loads in hospitalized patients with COVID-19 who were receiving low-flow or no supplemental oxygen, data presented at IDWeek showed.
The combination therapy, known as REGEN-COV (Regeneron Pharmaceuticals), also reduced the risk for death within 28 days by around 36% (95% CI, 7.3%-55.7%) overall and around 56% (95% CI, 24.25-74%) among patients who were seronegative at baseline.
Eleftherios E. Mylonakis, MD, PhD, professor of infectious diseases and assistant dean of medicine at Brown University, and colleagues assessed REGEN-COV in a randomized, double-blind, placebo-controlled trial in hospitalized patients.
The therapy has been authorized for emergency use in the United States since last November. The authorization was expanded in July to allow for its use as post-exposure prophylaxis.
“You need to give monoclonal antibodies as early as possible,” Mylonakis told Healio. “The question is about people who are already in the hospital. Are they too advanced in their disease progression for the monoclonal antibodies to help them? And are the monoclonal antibodies causing harm?”
‘It’s personalized care’
For the study, Mylonakis and colleagues enrolled patients hospitalized with COVID-19 and randomly assigned them in a 1:1:1 ratio to receive either 2.4 g or 8 g of IV REGEN-COV (n = 360) or a placebo (n = 160).
Patients who were seronegative and were treated with REGEN-COV saw a significant reduction in viral load after 7 days (time-weighted average = –0.28 log10 copies/mL; 95% CI, –0.51 to –0.05).
“For the seropositive patients, we didn’t see any harm, but the benefit was not statistically significant,” Mylonakis said.
Among seronegative patients who received the cocktail, there was also a 47% relative risk reduction (RRR) in the proportion of patients who died or needed mechanical ventilation from days 1 to 29 (10.3% treated vs. 19.4% placebo). Additionally, there was a 55.6% (6.7% treated vs. 15% placebo) and 35.9% (7.3% treated vs. 11.5% placebo) RRR in mortality by day 29 in the treatment group.
“This is extremely important because it not only gives us an understanding that we don't do any harm, but it also helps us identify those patients who would benefit the most and also provides, for us clinicians, a way to stratify patients,” Mylonakis said. “We can now have ways to start thinking of what treatment is best for this person vs. another patient. It’s personalized care.”
Outpatient trial
Findings from an additional study published recently in The New England Journal of Medicine showed that, compared with placebo, REGEN-COV reduced the risk for COVID-19-related hospitalization and death from any cause among outpatients with COVID-19 who were at high risk for severe disease.
Among 1,355 patients who received 2,400 mg of REGEN-COV, 18 (1.3%) were hospitalized or died compared with 62 of 1,341 (4.6%) in the placebo arm (RRR = 71.3%; P < 0.001).
Among 736 patients who received a 1,200 mg dose of the cocktail, seven (1%) were hospitalized or died compared with 24 of 748 (3.2%) patients who received a placebo (RRR = 70.4%; P = 0.002).
The median time to resolution of symptoms was reduced by 4 days in those who received REGEN-COV compared with those who received the placebo (10 days vs. 14 days).
References:
Mylonakis E, et al. Abstract LB4. Presented at: IDWeek; Sept. 29-Oct. 3, 2021 (virtual meeting).
Weinreich DM, et al. N Engl J Med. 2021;doi:10.1056/NEJMoa2108163.
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Mylonakis E, et al. Abstract LB4. Presented at: IDWeek; Sept. 29-Oct. 3, 2021 (virtual meeting).
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