Monoclonal Antibody Treatment Combination Reduces Hospitalization Among High-Risk COVID-19 Patients

In an observational study, researchers have reported that the combination of casirivimab and imdevimab - two monoclonal antibody treatments under Food and Drug Administration emergency use authorization – can keep high-risk patients out of the hospital when infected with mild to moderate COVID-19.

In the study that enrolled nearly 1,400 patients from Mayo Clinic (Rochester, Minn., USA), 696 received the drug combo between December 2020 and early April and an equal matched cohort did not receive it. Their status was evaluated at 14, 21 and 28 days after treatment. At each point, the numbers for hospitalization were significantly lower in the treated group.


At Day 14, 1.3% of the treated group was in the hospital, compared to 3.3% of those who had not been treated. At Day 21, only 1.3% treated was hospitalized, compared to 4.2% of those who had not been treated. At the end of 28 days, 1.6% of those treated was hospitalized versus 4.8% of those who had not been treated. This translated to 60-70% relative reduction in hospitalization among treated patients. Of those who were subsequently hospitalized, the rates of ICU admission and mortality were low.

A previous Mayo Clinic study involving 2,335 treated patients between November of 2020 and February had suggested that the use of bamlanivimab reduced hospitalizations in high-risk patients by 40-60%. Comparing their outcomes with 2,335 untreated patients, the ICU admission and mortality rates also were significantly lower with monoclonal antibody treatment. It should be noted that the FDA in April had revoked the EUA for bamlanivimab alone and now endorses the use of combination monoclonal antibodies.

"Once again, this real-world study suggests that when patients who are at high risk due to a range of comorbidities contract a mild or moderate case of COVID-19, this combination of monoclonal injections gives them a chance of a non-hospitalized recovery. In other words, they recover safely at home," said Raymund Razonable, M.D., a Mayo Clinic infectious diseases specialist and senior author of the study. "Our conclusion overall at this point is that monoclonal antibodies are an important option in treatment to reduce the impact of COVID-19 in high-risk patients."

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