Regeneron Pharmaceuticals, Inc. (NASDAQ: REGN) today announced that the New England Journal of Medicine (NEJM) has published initial clinical data from an ongoing seamless Phase 1/2/3 trial of the antibody cocktail casirivimab and imdevimab in non-hospitalized patients with COVID-19.

"The peer-reviewed NEJM publication of our first set of clinical data in recently infected COVID-19 patients showed that casirivimab and imdevimab effectively reduced viral load and the need for medically-attended visits, with the greatest benefit in patients who had not yet mounted their own effective immune response or had high viral load at baseline," said David Weinreich, M.D., Senior Vice President and Head of Global Clinical Development at Regeneron and lead author of the publication. "The investigational cocktail is now available to indicated high-risk U.S. patients under an Emergency Use Authorization, and we also continue a robust clinical development program."

"Building on these initial findings, we were gratified to recently report follow-on data from the next-stage analysis of this ongoing trial, which prospectively replicated these results in a rigorous and statistically significant manner. These follow-on data provided the first definitive prospective evidence demonstrating anti-viral activity for a treatment regimen now available for COVID-19, and also further documented the ability of this treatment to decrease the need for further medical attention," said George D. Yancopoulos, M.D., Ph.D., President and Chief Scientific Officer at Regeneron. "We are continuing to evaluate our antibody cocktail in this outpatient setting, as well as in late-stage trials in hospitalized patients and for prevention of infection, and will continue to share our findings as quickly as possible."

Regeneron previously announced the initial results featured in this NEJM publication from the Phase 1/2 portion of the trial that enrolled 275 patients randomized 1:1:1 to receive 8 grams casirivimab and imdevimab (high-dose, n=90), 2.4 grams casirivimab and imdevimab (low-dose, n=92) or placebo (n=93). Approximately 56% of patients were Latino/Hispanic, 13% were Black/African American and 64% had one or more underlying risk factors for severe COVID-19, including obesity (more than 40%).

Regeneron also subsequently announced additional prospective results in a total of 799 patients from the trial. In both the initial descriptive analyses of 275 patients, as well as in the following prospective analyses involving a total of 799 patients, a greater effect was observed in patients treated with the antibody cocktail who did not have SARS-CoV-2 antibodies at baseline ('sero-antibody-negative') or who had high viral load at baseline. As would be expected, a much higher proportion of sero-antibody-negative patients had high viral loads when they entered the trial. Additionally, a smaller proportion of antibody cocktail-treated patients required medically-attended visits due to COVID-19 (inclusive of hospitalizations, urgent care or emergency room visits, in-person physician or telemedicine visits) through day 29 compared to placebo; there was an even greater benefit on this endpoint among sero-antibody-negative patients.

In the initial 275 patients, rates of adverse events (AEs) were similar among groups. Serious AEs occurred in 2 placebo patients, 1 low-dose patient and 0 high-dose patients. AEs included infusion-related reactions (1 placebo patient, 0 low-dose patients, 2 high-dose patients) and hypersensitivity reactions (2 placebo patients, 0 low-dose patients, 1 high-dose patient).