Positive topline data were announced from a phase 3 trial evaluating Regeneron’s monoclonal antibody therapy, REGEN-COV™ (casirivimab with imdevimab), in high-risk COVID-19 outpatients (N=4567).

Results showed that treatment with REGEN-COV 1200mg and 2400mg, both administered intravenously, significantly reduced the risk of hospitalization or death by 70% (P =.0024) and 71% (P <.0001), respectively, when compared with placebo.  Additionally, COVID-19 symptom duration was shortened by an average of 4 days in both dose groups (median 10 days vs 14 days in the placebo arm).

In a companion dose-ranging phase 2 study (N=803), all tested doses (IV: 2400mg, 1200mg, 600mg, and 300mg; SC: 1200mg and 600mg) were found to significantly reduce viral load when compared with placebo. Similar efficacy was reported with even the lowest doses tested.

Continue Reading

“We will discuss the new data with regulatory authorities and request that the 1200mg dose be rapidly added to the US Emergency Use Authorization, in order for the anticipated REGEN-COV supply to be available to treat even more patients. These phase 3 data will also form the basis of a full Biologics License Application,” said George D. Yancopoulos, MD, PhD, President and Chief Scientific Officer at Regeneron.

REGEN-COV is currently authorized for emergency use by the Food and Drug Administration (FDA) in adults and pediatric patients 12 years of age and older weighing at least 40kg with positive results of direct SARS-CoV-2 viral testing who are at high risk for progressing to severe COVID-19. The product consists of 2 potent, virus-neutralizing antibodies that bind noncompetitively to the receptor binding domain of the SARS-CoV-2 spike protein, thereby blocking its interaction with the host cell. This is believed to decrease the ability of mutant viruses to escape treatment and protect against spike variants. The updated fact sheet for REGEN-COV states that it retains potency against the main variants of concern known to be circulating within the US.


Phase 3 trial shows REGEN-COV™ (casirivimab with imdevimab) antibody cocktail reduced hospitalization or death by 70% in non-hospitalized COVID-19 patients. [press release]. Tarrytown, NY: Regeneron Pharmaceuticals, Inc.; March 23, 2021.

This article originally appeared on MPR