Efficacy of Monoclonal Antibodies for COVID-19 Not Associated With Early vs Late Administration

antibodies and immunoglobulin, COVID19
Antibody and Immunoglobulin concept as antibodies attacking contagious virus cells and pathogens as a 3D illustration.
In this retrospective cohort study, researchers assessed the rate of treatment failure among patients with COVID-19 infection who received bamlanivimab vs those who received casirivimab/imdevimab.

In patients with COVID-19 infection who received treatment with monoclonal antibodies (mAb), the rate of treatment failure was increased among those who received bamlanivimab compared with those who received casirivimab/imdevimab, according to findings from Open Forum Infectious Diseases.

A retrospective, observational cohort study was conducted at a large community medical center among patients with mild to moderate COVID-19 infection at increased risk for progression to severe disease. Patients included were those who received either mAB infusions with either bamlanivimab or casirivimab/imdevimab between November 2020 and May 2021. The primary outcome was the rate of hospitalization due to treatment failure within a 30-day follow-up period. Multivariable logistic regression was used to adjust for confounders related to hospitalization.

Among a total of 453 patients included, 183 received bamlanivimab and 270 received casirivimab/imdevimab. The mean patient age was approximately 67 years, and the mean BMI was 30.6 kg/m2. Prior to treatment initiation, 113 (61.7%) and 190 (70.4%) patients who received bamlanivimab and casirivimab/imdevimab, respectively, had been symptomatic for 3 or more days, and patient characteristics between those with early vs late symptom onset were similar between both treatment groups.

The researchers found a statistically significant decrease in 30-day treatment failure rates among patients who received casirivimab/imdevimab vs those who received bamlanivimab (odds ratio [OR], 0.36; 95% CI, 0.17-0.75). Of 8 patients who reported adverse drug reactions, 5 were hospitalized, all of whom received bamlanivimab. Among patients who received bamlanvimab, the rate of treatment failure was not statistically significantly different between those with early (≥ 3 days) vs late (≤ 3 days) symptom onset (15% vs 11.4%; OR, 1.47; 95% CI, 0.57-3.81). Similar results in regard to the rate of treatment failure between early vs late symptom onset were observed among patients who received casirivimab/imdevimab (P =.561).

This study was limited by its observational design, potential reporting bias, the lack of data on the efficacy of mAb treatment against the Omicron variant, and the inability to control for prescribing patterns that may have affected external validity.

For future studies, the researchers noted that, “close monitoring of viral evolution is essential with [mAb treatment] because viral variant evolution and dissemination can occur quickly.”

Disclosure: Some authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.


San Filippo S, Crovetto B, Bucek J, Nahass RG, Milano M, Brunetti L. Comparative efficacy of early COVID-19 monoclonal antibody therapies: a retrospective analysis. Open Forum Infect Dis. Published online February 14, 2022. doi:10/1093/ofid/ofac080