Monoclonal Antibody Therapy

Monoclonal antibody therapy – Monoclonal antibodies that target severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continue to be evaluated in outpatients with mild to moderate disease, and trial results suggest a benefit from these agents. In the United States, the following monoclonal antibody therapies are available through emergency use authorization (EUA) for select outpatients at risk for severe disease:

• Regen-COV - Casirivimab-imdevimab


Bamlanivimab-etesevimab Authorization of this combination had previously been suspended because of variants with likely resistance; however, it has since been reinstated with decline in prevalence of those variants.

The FDA EUAs are for non-hospitalized COVID-19 patients with mild to moderate illness (eg, not requiring supplemental oxygen or, if on chronic supplemental oxygen, without an increased oxygen requirement) who have certain risk factors for severe disease. These risk factors for adults (≥18 years) include any of the following:

In addition, other conditions may place an individual at high risk for progression to severe COVID-19, and the use of monoclonal antibody therapy is not strictly limited to those with the risk factors listed above.

The choice among monoclonal antibody options depends on local availability. If all are available options, some (providers) favor casirivimab-imdevimab because it appears more likely to retain neutralizing activity against certain SARS-CoV-2 variants (Alpha, Beta, Gamma, Delta) that have mutations in the spike protein (the binding target) than bamlanivimab-etesevimab, and complete peer-reviewed trial results for sotrovimab are not available.

According to the EUA, monoclonal antibody treatment should be given as soon as possible after diagnosis and within 10 days of symptom onset; we favor administering it within seven days. Although direct data on timing of monoclonal antibody therapy are limited, indirect evidence from studies of convalescent plasma suggest that benefit is maximized with early administration.

SARS-CoV-2 variants, particularly those with mutations affecting the spike protein, are likely to impact the clinical efficacy of available monoclonal antibody therapies. Information on the in vitro neutralization of various recognized SARS-CoV-2 variants’ spike proteins by each monoclonal antibody therapy is available for review on the US Food and Drug Administration (FDA) EUAs for casirivimab-imdevimab, sotrovimab, and bamlanivimab-etesevimab; clinicians should be aware of the prevalence of variants in their local area [99,100] and the potential resistance of variants to these agents.

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