Abstract: REGEN-COV antibody cocktail (casirivimab/imdevimab) for the treatment of inpatients with early hospital-acquired COVID-19: a single center experience Antonio Faraone (  antfaraone@gmail.com ) Ospedale San Giovanni di Dio https://orcid.org/0000-0001-6095-8403 Francesca Fabbrizzi Department of Internal Medicine, San Giovanni di Dio Hospital, Florence Tommaso Picchioni Department of Internal Medicine, San Giovanni di Dio Hospital, Florence Elena Lovicu Department of Internal Medicine, San Giovanni di Dio Hospital, Florence Lorenzo Tofani Department of Statistics, Computer Science, Applications, University of Florence, Florence Giulia Scocchera Department of Internal Medicine, San Giovanni di Dio Hospital, Florence Aldo Lo Forte Department of Internal Medicine, San Giovanni di Dio Hospital, Florence Andrea Crociani Department of Internal Medicine, San Giovanni di Dio Hospital, Florence Paolo Carrai Department of Internal Medicine, San Giovanni di Dio Hospital, Florence Serena Sbaragli Department of Internal Medicine, San Giovanni di Dio Hospital, Florence Michael Bettucchi Department of Internal Medicine, San Giovanni di Dio Hospital, Florence Alberto Fortini Department of Internal Medicine, San Giovanni di Dio Hospital, Florence Research Article Keywords: casirivimab/imdevimab, COVID-19, hospital-acquired, inpatient, monoclonal antibody, REGENCOV. Page 1/17 Posted Date: May 5th, 2022 DOI: https://doi.org/10.21203/rs.3.rs-1170976/v1 License:   This work is licensed under a Creative Commons Attribution 4.0 International License. Read Full License Page 2/17 Abstract Inpatients with hospital-acquired (HA) COVID-19 have mortality rates above 30%. Subjects with early diagnosis of COVID-19 and risk factors for disease progression are suitable for treatment with anti-SARSCoV-2 neutralizing monoclonal antibodies (mAbs). We retrospectively assessed the outcome of a cohort of hospitalized patients with laboratory confirmed SARS-CoV-2 nosocomial infection who were admitted to the COVID-19 general ward of an acute-care Italian hospital between October 25, 2020 and April 30, 2021. Patients receiving the REGEN-COV mAb cocktail (casirivimab/imdevimab) were compared with those receiving standard care. Of 34 patients, 11 (mean age, 73.1; 9 males) underwent treatment with REGEN-COV and 23 received standard care. The 2 study groups were well balanced regarding age, sex, comorbidities, acute illness severity at diagnosis of SARS-CoV-2 infection, and all participants had at least 2 risk factors for disease progression. Five of 11 patients in the REGEN-COV group and 16 of 23 in the standard care group were asymptomatic at diagnosis; the remaining had symptoms of mild COVID-19. All patients received REGENCOV within 3 days of infection confirmation. Treatment with REGEN-COV was inversely associated with oxygen requirement for COVID-19 during hospital stay (OR 0.02, CI 0–0.52, p=0.0174). No 28-day deaths were registered in the REGEN-COV group, compared to 8 (34.8%) in the standard care group (p=0.0339). Kaplan-Meier analysis confirmed the survival advantage of REGEN-COV group (log-rank p=0.00324). No serious adverse events related to REGEN-COV administration were recorded. Based on these findings, REGEN-COV appears safe and might prevent disease progression in high-risk inpatients with early diagnosis of HA-COVID-19.