# REGEN-COV as the First Line of Defense—A Single-Centre Experience

## TL;DR

This study shows that REGEN-COV reduced hospitalization and improved outcomes in high-risk COVID-19 patients before the Omicron variant emerged.

## Contribution

The study provides real-world evidence of REGEN-COV's effectiveness against dominant SARS-CoV-2 variants in a single-center setting.

## Key findings

- REGEN-COV was associated with significantly lower hospitalization rates compared to non-REGEN-COV patients.
- Mortality was notably lower in the REGEN-COV group, though the difference was not significant in matched analysis.
- Survival analysis showed a significant difference favoring the REGEN-COV group.

## Abstract

Background: Casirivimab–imdevimab (REGEN-COV) is a neutralizing antibody cocktail that has been shown to prevent the progression of COVID-19 and serious adverse outcomes in patients with COVID-19 disease. During the period preceding the emergence of the Omicron variant, REGEN-COV demonstrated clinical activity against several circulating SARS-CoV-2 variants. The delta variant was dominant worldwide during much of the study period. Aim: This retrospective observational study aimed to show the single centre’s results in treating patients with REGEN-COV. Methods: This study included adult patients who received REGEN-COV at our COVID-19 centre from 01 June 2021 to 31 January 2022 (REGEN-COV group) and a comparison group that included patients who did not meet the eligibility criteria for REGEN-COV (non-REGEN-COV group). The primary end-point was the need for hospitalization. The secondary end-point was all-cause mortality. Intensive care unit admission was also evaluated. Results: This study included 206 patients, of whom 69 received REGEN-COV, and 137 comprised the non-REGEN-COV group. During follow-up, 128 patients (62%) required hospitalization, including 11 (15.9%) in the REGEN-COV group and 117 (85.4%) in the non-REGEN-COV group (p < 0.001). Mortality occurred in 2 patients (2.9%) treated with REGEN-COV compared with 30 patients (21.9%) in the non-REGEN-COV group. In the propensity score-matched analysis, the average marginal absolute risk difference for mortality between the groups was −4.0% (95% CI −9.8 to 1.8), p = 0.178; however, Kaplan–Meier survival analysis demonstrated a significant difference in survival between groups (log-rank p < 0.001). Conclusions: Our study showed that in high-risk patients, with specific variants of SARS-CoV-2, the use of REGEN-COV was associated with a lower risk of hospitalization, and it was associated with better disease outcomes. One of the limitations of this study was the variant-specific effectiveness of REGEN-COV, which may limit generalizability.