Related Experiment Video
Updated: Nov 25, 2025
Dynamic Monitoring of Seroconversion using a Multianalyte Immunobead Assay for Covid-19
Published on: February 16, 2022
REGN-COV2, a Neutralizing Antibody Cocktail, in Outpatients with Covid-19
David M Weinreich1, Sumathi Sivapalasingam1, Thomas Norton1
1From Regeneron Pharmaceuticals, Tarrytown, NY (D.M.W., S.S., T.N., S.A., H.G., R.B., B.J.M., Y. Soo, D.R., J.I., C. Perry, C. Pan, R.H., A.M., J.D.D., K.C.T., A.T.H., J.D.H., A.B., C.A.K., Y.K., A.C., W.K., B.K., T.D., N.S., L.L., N.B., G.H., G.D.Y.); Arizona Liver Health, Tucson (A.K.), and Arizona Liver Health, Chandler (Y. Sachdeva); and AGA Clinical Trials, Hialeah, FL (X.G.).
Background:
Recent data suggest that complications and death from coronavirus disease 2019 (Covid-19) may be related to high viral loads.
Methods:
In this ongoing, double-blind, phase 1-3 trial involving nonhospitalized patients with Covid-19, we investigated two fully human, neutralizing monoclonal antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein, used in a combined cocktail (REGN-COV2) to reduce the risk of the emergence of treatment-resistant mutant virus. Patients were randomly assigned (1:1:1) to receive placebo, 2.4 g of REGN-COV2, or 8.0 g of REGN-COV2 and were prospectively characterized at baseline for endogenous immune response against SARS-CoV-2 (serum antibody-positive or serum antibody-negative). Key end points included the time-weighted average change in viral load from baseline (day 1) through day 7 and the percentage of patients with at least one Covid-19-related medically attended visit through day 29. Safety was assessed in all patients.
Results:
Data from 275 patients are reported. The least-squares mean difference (combined REGN-COV2 dose groups vs. placebo group) in the time-weighted average change in viral load from day 1 through day 7 was -0.56 log10 copies per milliliter (95% confidence interval [CI], -1.02 to -0.11) among patients who were serum antibody-negative at baseline and -0.41 log10 copies per milliliter (95% CI, -0.71 to -0.10) in the overall trial population. In the overall trial population, 6% of the patients in the placebo group and 3% of the patients in the combined REGN-COV2 dose groups reported at least one medically attended visit; among patients who were serum antibody-negative at baseline, the corresponding percentages were 15% and 6% (difference, -9 percentage points; 95% CI, -29 to 11). The percentages of patients with hypersensitivity reactions, infusion-related reactions, and other adverse events were similar in the combined REGN-COV2 dose groups and the placebo group.
Conclusions:
In this interim analysis, the REGN-COV2 antibody cocktail reduced viral load, with a greater effect in patients whose immune response had not yet been initiated or who had a high viral load at baseline. Safety outcomes were similar in the combined REGN-COV2 dose groups and the placebo group. (Funded by Regeneron Pharmaceuticals and the Biomedical and Advanced Research and Development Authority of the Department of Health and Human Services; ClinicalTrials.gov number, NCT04425629.).
Insights
This study shows that the REGN-COV2 antibody cocktail effectively reduced viral load in COVID-19 patients. The treatment was well-tolerated, with similar safety outcomes compared to placebo.
Area of Science:
- Virology
- Immunology
- Clinical Medicine
Background:
- High viral loads in COVID-19 correlate with increased complications and mortality.
- Understanding the role of viral load is crucial for developing effective treatments.
Purpose of the Study:
- To evaluate the efficacy and safety of REGN-COV2, a monoclonal antibody cocktail, in nonhospitalized patients with COVID-19.
- To assess the impact of REGN-COV2 on viral load reduction and medically attended visits.
- To investigate the potential of REGN-COV2 in preventing treatment-resistant mutant virus emergence.
Main Methods:
- Phase 1-3, double-blind, randomized trial involving 275 nonhospitalized COVID-19 patients.
- Patients received placebo, 2.4g, or 8.0g of REGN-COV2.
- Key endpoints included viral load change and medically attended visits, with baseline immune response stratification.
Main Results:
- REGN-COV2 significantly reduced viral load compared to placebo, particularly in antibody-negative patients.
- A trend towards fewer medically attended visits was observed in the REGN-COV2 groups.
- Adverse events, including hypersensitivity and infusion reactions, were similar across all treatment groups.
Conclusions:
- The REGN-COV2 antibody cocktail demonstrates efficacy in reducing SARS-CoV-2 viral load.
- The treatment shows a greater effect in patients with no prior immune response or high baseline viral load.
- REGN-COV2 exhibits a favorable safety profile comparable to placebo.
