Phase 3 Data Presented at ATS 2021 Show REGEN-COV™ (casirivimab with imdevimab) Reduced Risk of Hospitalization or Death by 70% in Non-hospitalized COVID-19 Patients

• Patients treated with REGEN-COV had 4-day shorter duration of symptoms and significantly reduced viral load compared to placebo

• Similar efficacy observed with both doses (1,200 mg and 2,400 mg); U.S. FDA is currently reviewing request to add lower 1,200 mg dose to EUA

Regeneron Pharmaceuticals, Inc. (NASDAQ: REGN) today announced the presentation of detailed results from the Phase 3 pivotal trial showing REGEN–COV™ (casirivimab with imdevimab) significantly reduced the risk of hospitalization or death, shortened symptom duration and reduced viral load in non-hospitalized patients (outpatients) with COVID-19. These data were presented at the 2021 American Thoracic Society International Conference (ATS 2021) in the Breaking News: Clinical Trial Results in Pulmonary Medicine Scientific Symposium, which features late-breaking information on leading clinical trials in pulmonary and critical care medicine.

"Despite increasing vaccination rates, many continue to be diagnosed with COVID-19 who could benefit from REGEN-COV due to underlying conditions like asthma or COPD that put them at higher risk for severe disease," said Julie Philley, M.D., Chair of Internal Medicine at the University of Texas Health Science Center and trial investigator. "The Phase 3 trial showed REGEN-COV helped patients avoid hospitalization or even death while speeding up recovery time. These results add to the growing body of clinical evidence, real-world experience and strong recommendations by the National Institutes of Health COVID-19 treatment guidelines that collectively underscore the urgent need to ensure all appropriate patients are treated."

The Phase 3, randomized, double-blind, placebo-controlled trial evaluated REGEN–COV in 4,567 high-risk outpatients with COVID-19. Two REGEN-COV doses were studied in the trial – the currently authorized 2,400 mg dose and a 1,200 mg dose under evaluation with the U.S. Food and Drug Administration (FDA). All patients evaluated for efficacy had at least one risk factor for severe COVID-19, such as chronic lung disease (including asthma), obesity, cardiovascular disease or being at least 50 years of age.

Positive topline results from the trial were announced in March 2021, showing REGEN–COV met its primary and all secondary endpoints, with similar efficacy observed for both doses. These data demonstrated patients treated with 1,200 mg or 2,400 mg REGEN–COV experienced:

• 70% (p=0.0024) and 71% (p<0.0001) reduced risk of hospitalization or death through day 29, compared to placebo.

• 4-day shorter time to symptom resolution, with a median of 10 days with both REGEN-COV groups compared to a median of 14 days with placebo.

• Reduced viral load by 0.71 log10 copies/mL and 0.86 log10 copies/mL in seven days, compared to placebo (p<0.0001 for both).

A safety assessment in 5,531 patients was conducted up to day 169, and the safety profile was consistent with previously reported data. Serious adverse events (SAEs) were largely related to COVID-19 and occurred in 1.1% of patients in the 1,200 mg group, 1.3% in the 2,400 mg group and 4.0% in the placebo group. There was 1 death in the 1,200 mg group (n=827), 1 death in the 2,400 mg group (n=1,849) and 5 deaths in the placebo groups (n=1,843).

REGEN–COV is an investigational antibody cocktail authorized for emergency use in the U.S. for patients with mild-to-moderate COVID-19 who are at high-risk of severe disease or hospitalization, and is strongly recommended by the National Institutes of Health COVID-19 Treatment Guidelines for these patients. In addition, research has shown that REGEN–COV retains potency in vitro against the main variants of concern known to be circulating within the U.S. (see fact sheet for further information). REGEN–COV is administered intravenously (IV), with infusion times as short as 20 minutes.

REGEN–COV continues to be assessed in the outpatient (symptomatic and asymptomatic infections), prevention and certain hospitalized COVID-19 patient settings. In April 2021, Regeneron announced positive initial results from a Phase 3 trial evaluating the ability of REGEN-COV to prevent COVID-19 infection among household contacts of SARS-CoV-2 infected individuals.

The development and manufacturing of REGEN–COV have been funded in part with federal funds from the Biomedical Advanced Research and Development Authority (BARDA), part of the U.S. Department of Health and Human Services, Office of the Assistant Secretary for Preparedness and Response, under OT number: HHSO100201700020C.