REGEN-COV Antibody Combination in Outpatients With COVID-19 – Phase 1/2 Results

Background Continued SARS-CoV-2 infections and COVID-19-related hospitalizations highlight the need for effective anti-viral treatments in the outpatient setting. In a descriptive interim analysis of the phase 1/2 portion of a double-blind phase 1/2/3 trial in COVID-19 outpatients conducted between June 16, 2020 and September 4, 2020, REGEN-COV® (casirivimab plus imdevimab) antibody combination reduced SARS-CoV-2 viral load versus placebo. Methods This final phase 1/2 analysis comprises 799 outpatients, including 275 from the previous descriptive analysis (group-1) and 524 from phase 2 (group-2). Patients were randomized (1:1:1) to placebo, REGEN-COV 2400mg, or REGEN-COV 8000mg. Prespecified hierarchical analyses of virologic endpoints were performed in group-2. The proportion of patients with ≥1 COVID-19–related medically attended visit (MAV) through day 29 was assessed in group-1+2. Efficacy was assessed in patients confirmed SARS-CoV-2–positive by baseline nasopharyngeal RT-qPCR. Safety was assessed in all treated patients. Results Data from 799 outpatients enrolled from June 16, 2020 to September 23, 2020 are reported. Time-weighted average daily reduction in viral load through day 7 was significantly greater in the REGEN-COV combined 2400mg+8000mg group versus placebo in patients with baseline viral load >107 copies/mL (prespecified primary endpoint): -0.68 log10 copies/ml (95% CI, -0.94 to -0.41; P <.0001). This reduction was - 0.73 ( P <.0001) and -0.36 ( P =.0003) log10 copies/mL in serum antibody–negative patients and in the overall population, respectively. REGEN-COV reduced the proportion of patients with ≥1 COVID-19–related MAV versus placebo (2.8% [12/434] REGEN-COV combined dose group versus 6.5% [15/231] placebo; P =.024; relative risk reduction [RRR]=57%); in patients with ≥1 risk factor for hospitalization, the treatment effect was more pronounced (RRR=71%). Adverse events were similar across groups. Conclusions In COVID-19 outpatients enrolled prior to the widespread circulation of delta and omicron variants, treatment with REGEN-COV significantly reduced viral load and COVID-19–related MAVs. ### Competing Interest Statement ICMJE disclosure forms provided by the authors are available with the full text of this article. ### Clinical Trial NCT04425629 ### Funding Statement Supported by Regeneron Pharmaceuticals, Inc. Certain aspects of this project have been funded in whole or in part with federal funds from the Department of Health and Human Services; Office of the Assistant Secretary for Preparedness and Response; Biomedical Advanced Research and Development Authority, under OT number: HHSO100201700020C. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethics approval was obtained from the following ethics review boards: WCG IRB, Puyallup, WA (IRB00000533); Providence St Joseph's Health, Renton, WA (STUDY2020000465); Research Compliance Office, Palo Alto, CA (IRB 5 Registration4593/Eprotocol: 57728). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Qualified researchers may request access to study documents (including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan) that support the methods and findings reported in this manuscript. Individual anonymized participant data will be considered for sharing once the indication has been approved by a regulatory body, if there is legal authority to share the data and there is not a reasonable likelihood of participant re-identification. Submit requests to https://vivli.org/.