Casirivimab-Imdevimab treatment is associated with reduced rates of hospitalization among high-risk patients with mild to moderate coronavirus disease-19

Abstract

Background: Real-world clinical data to support the use of casirivimab-imdevimab for the treatment of outpatients with mild to moderate coronavirus disease-19 (COVID-19) is needed. This study aimed to assess the outcomes of casirivimab-imdevimab treatment of mild to moderate COVID-19.

Methods: A retrospective cohort of 696 patients who received casirivimab-imdevimab between December 4, 2020 and April 9, 2021 was compared to a propensity-matched control of 696 untreated patients with mild to moderate COVID-19 at Mayo Clinic sites in Arizona, Florida, Minnesota, and Wisconsin. Primary outcome was rate of hospitalization at days 14, 21 and 28 after infusion.

Findings: The median age of the antibody-treated cohort was 63 years (interquartile range, 52-71); 45·5% were ≥65 years old; 51.4% were female. High-risk characteristics were hypertension (52.4%), body mass index ≥35 (31.0%), diabetes mellitus (24.6%), chronic lung disease (22.1%), chronic renal disease (11.4%), congestive heart failure (6.6%), and compromised immune function (6.7%). Compared to the propensity-matched untreated control, patients who received casirivimab-imdevimab had significantly lower all-cause hospitalization rates at day 14 (1.3% vs 3.3%; Absolute Difference: 2.0%; 95% confidence interval (CI): 0.5-3.7%), day 21 (1.3% vs 4.2%; Absolute Difference: 2.9%; 95% CI: 1.2-4.7%), and day 28 (1.6% vs 4.8%; Absolute Difference: 3.2%; 95% CI: 1.4-5.1%). Rates of intensive care unit admission and mortality at days 14, 21 and 28 were similarly low for antibody-treated and untreated groups.

Interpretation: Among high-risk patients with mild to moderate COVID-19, casirivimab-imdevimab treatment was associated with a significantly lower rate of hospitalization.

Funding: Mayo Clinic.

Keywords: Casirivimab; Covid-19; Imdevimab; Monoclonal antibodies; Outcomes.

Fig. 1

Cohort selection criteria and patient counts. The diagram shows the inclusion criteria and propensity score matching procedure that was used to construct the Casirivimab–Imdevimab and control cohorts. In each box, the number of patients, starting with the full study population of 28,442 patients in the Mayo Clinic Electronic Health record database who had at least one positive SARS-CoV-2 PCR test between December 4, 2020 and April 9, 2021.

Fig. 2

Kaplan-Meier curves of hospitalization rates for casirivimab–imdevimab patients and propensity matched controls. For each patient in the casirivimab–imdevimab cohort (n = 696), the index date is set to be the date of infusion, and for each patient in the control cohort (n = 696), the index date is set using the date of infusion for the matched control. 95% confidence intervals are displayed for each curve, along with the median and interquartile range (IQR) of the follow-up time for the cohort. A table showing the number of events along with the number of patients at risk and censored over time is shown below. A log-rank test against the hypothesis of equal hazard rates gives p-value 3 × 10⁻⁴.

Fig. 3

Kaplan-Meier curves of Intensive Care Unit (ICU) admission rates for casirivimab–imdevimab patients and propensity matched controls. For each patient in the casirivimab–imdevimab cohort (n = 696), the index date is set to be the date of infusion, and for each patient in the control cohort (n = 696), the index date is set using the date of infusion for the matched control. 95% confidence intervals are displayed for each curve, along with the median and interquartile range (IQR) of the follow-up time for the cohort. A table showing the number of events along with the number of patients at risk and censored over time is shown below. A log-rank test against the hypothesis of equal hazard rates gives p-value 0.51.