A phase 1–3 clinical trial evaluated REGN-COV2, a neutralizing antibody cocktail, in nonhospitalized patients with Covid-19. The study aimed to assess its efficacy in reducing viral load and the risk of treatment-resistant mutations. Patients were randomly assigned to receive placebo, 2.4 g, or 8.0 g of REGN-COV2. The key end points included changes in viral load from day 1 to day 7 and the percentage of patients with medically attended visits through day 29. Among serum antibody-negative patients, REGN-COV2 significantly reduced viral load compared to placebo, with the greatest effect in those with high baseline viral loads. In the overall trial population, 6% of placebo recipients and 3% of REGN-COV2 recipients had medically attended visits, with a larger difference in serum antibody-negative patients. Safety outcomes were similar between the REGN-COV2 groups and the placebo group, with few and mostly low-grade adverse events. The study found that REGN-COV2 reduced viral load, particularly in patients whose immune response had not yet been initiated or who had high viral loads at baseline. The antibody cocktail was well-tolerated, with no significant differences in adverse events between the groups. The results support the hypothesis that reducing viral load can lead to clinical benefit in outpatients with Covid-19. The trial was conducted in accordance with ethical and regulatory standards, and data were analyzed using prespecified methods. The findings suggest that REGN-COV2 could be an effective treatment for reducing viral load and improving clinical outcomes in patients with Covid-19. Further studies are needed to confirm these results.A phase 1–3 clinical trial evaluated REGN-COV2, a neutralizing antibody cocktail, in nonhospitalized patients with Covid-19. The study aimed to assess its efficacy in reducing viral load and the risk of treatment-resistant mutations. Patients were randomly assigned to receive placebo, 2.4 g, or 8.0 g of REGN-COV2. The key end points included changes in viral load from day 1 to day 7 and the percentage of patients with medically attended visits through day 29. Among serum antibody-negative patients, REGN-COV2 significantly reduced viral load compared to placebo, with the greatest effect in those with high baseline viral loads. In the overall trial population, 6% of placebo recipients and 3% of REGN-COV2 recipients had medically attended visits, with a larger difference in serum antibody-negative patients. Safety outcomes were similar between the REGN-COV2 groups and the placebo group, with few and mostly low-grade adverse events. The study found that REGN-COV2 reduced viral load, particularly in patients whose immune response had not yet been initiated or who had high viral loads at baseline. The antibody cocktail was well-tolerated, with no significant differences in adverse events between the groups. The results support the hypothesis that reducing viral load can lead to clinical benefit in outpatients with Covid-19. The trial was conducted in accordance with ethical and regulatory standards, and data were analyzed using prespecified methods. The findings suggest that REGN-COV2 could be an effective treatment for reducing viral load and improving clinical outcomes in patients with Covid-19. Further studies are needed to confirm these results.