Regeneron (REGN) REGEN-COV Phase 3 RECOVERY Trial Meets Primary Outcome, Improving Survival in Hospitalized COVID-19 Patients Lacking an Immune Response to SARS-CoV-2

• UK RECOVERY investigators found REGEN-COV reduced risk of death by 20% in patients hospitalized with COVID-19 who had not mounted their own immune response (primary outcome for the primary analysis population)
• First trial to demonstrate that any antibody treatment improved survival in patients hospitalized with COVID-19
• Regeneron will share new data with regulatory authorities immediately and request that the U.S. EUA be expanded to include appropriate hospitalized patients

Regeneron Pharmaceuticals, Inc. (NASDAQ: REGN) today welcomed positive results from the largest trial assessing any monoclonal antibody treatment in patients hospitalized with severe COVID-19. The UK RECOVERY trial found that adding investigational REGEN-COV™ to usual care reduced the risk of death by 20% in patients who had not mounted a natural antibody response on their own against SARS-CoV-2, compared to usual care on its own.

"These results are very exciting. The hope was that by giving a combination of antibodies targeting the SARS-CoV-2 virus we would be able to reduce the worst manifestations of COVID-19," said Sir Peter Horby, Professor of Emerging Infectious Diseases in the Nuffield Department of Medicine, University of Oxford, and Joint Chief Investigator for the RECOVERY trial. "There was, however, great uncertainty about the value of antiviral therapies in late-stage COVID-19 disease. It is wonderful to learn that even in advanced COVID-19 disease, targeting the virus can reduce mortality in patients who have failed to mount an antibody response of their own."

RECOVERY is the first trial large enough to definitively determine whether REGEN-COV reduces mortality in patients hospitalized with severe COVID-19. Previous Phase 3 trials in non-hospitalized COVID-19 patients have shown that REGEN-COV reduced viral levels, shortened the time to resolution of symptoms and significantly reduced the risk of hospitalization or death. In a Phase 1/2 trial in hospitalized patients, REGEN-COV also rapidly reduced viral levels, with preliminary evidence suggesting that it lowered the risk of death or receiving mechanical ventilation, with the benefit driven by patients who entered the trial without having mounted a natural antibody response of their own (seronegative); and in the absence of REGEN-COV treatment, seronegative patients had higher mortality rates than patients who had already mounted their own immune response (seropositive).

Based on the above Phase 1/2 data, the independently-run RECOVERY trial prospectively focused on seronegative patients. Similar to the prior trial, patients in RECOVERY who received usual care alone had double the mortality rate at day 28 if they were seronegative (30%) compared to seropositive (15%); approximately one-third of hospitalized patients were seronegative (n=3,153), one-half were seropositive (n=5,272) and one-sixth had unknown serostatus (n=1,360). The mean age of patients for this comparison was 62 years, and more than 90% received corticosteroids across all groups.

The primary outcome of RECOVERY showed that adding REGEN-COV 8,000 mg to usual care reduced all-cause mortality by 20% in seronegative patients (primary analysis population), compared to usual care alone (24% of patients in the REGEN-COV group died versus 30% in the usual care group by day 28; rate ratio [RR]: 0.80; 95% confidence interval [CI]: 0.70-0.91; p=0.001). When combining the larger seropositive group (as well as those with unknown status) with the seronegative patients, there was no longer a significant effect on 28-day mortality (overall 20% of patients in the REGEN-COV group died, versus 21% in the usual care group; RR: 0.96; 95% CI: 0.86-1.03; p=0.17).

"Definitive Phase 3 trials have now demonstrated that REGEN-COV can alter the course of COVID-19 infection from prevention, to very early infection, all the way through to when patients are on a ventilator in the hospital," said George D. Yancopoulos, M.D., Ph.D., President and Chief Scientific Officer at Regeneron. "We are incredibly grateful to the RECOVERY team, participating investigators and patients for conducting this in-depth analysis, and hope that the results mean that even more patients may soon be able to benefit from this life-saving medicine. We intend to rapidly discuss these results with regulatory authorities, including in the U.S. where we will ask for our EUA to be expanded to include appropriate hospitalized patients."

Among seronegative patients in the RECOVERY trial, the median duration of hospital stay was 4 days shorter in the REGEN-COV group (13 days versus 17 days), and the proportion of patients discharged alive by day 28 was greater (64% versus 58%; RR: 1.19; 95% CI: 1.08-1.30). Among the seronegative patients not on invasive mechanical ventilation at baseline, the risk of progressing to the composite endpoint of invasive mechanical ventilation or death was lower among the REGEN-COV group than the usual care group (30% versus 37%; RR: 0.83; 95% CI: 0.75-0.92). No such benefits were seen in the overall trial population (combining patients with negative, positive, or unknown serostatus).

"The RECOVERY trial has shown that in patients who had not made their own antibodies against SARS-CoV-2, treating them with REGEN-COV antibodies dramatically reduced their risk of dying or being on a ventilator, and also shortened how many days they remained in the hospital," said David Weinreich, M.D., Executive Vice President, Global Clinical Development at Regeneron. "The trial was conducted at a time when most patients had not been fully vaccinated. These results provide hope to patients who have a poor immune response to either the vaccine or natural infection, as well as those who are exposed to variants for whom their existing antibodies might be sub-optimal."

Multiple analyses, including a recent publication in Cell, have shown that REGEN-COV retains potency against the main variants of concern circulating within the U.S.; consequently, REGEN-COV remains available for use in all 50 states. REGEN-COV retains potency against variants including P.1 (first identified in Brazil, now classified by the World Health Organization [WHO] as Gamma), B.1.351 (first identified in South Africa, now classified by the WHO as Beta) and B.1.162.2 (first identified in India, now classified by the WHO as Delta). The combined frequency of the P.1 and B.1.351 variants now exceeds 10% of new COVID-19 diagnoses across eight states (Arizona, California, Florida, Illinois, Indiana, Massachusetts, Oregon and Washington), and the prevalence of these and other variants continues to be closely monitored.

Today's data in hospitalized patients follow multiple positive Phase 3 results earlier this year from Regeneron-sponsored trials assessing the ability of REGEN-COV to treat outpatients already infected with SARS-COV-2 (including symptomatic outpatients and recently infected asymptomatic patients), and also to prevent infection in close contacts of infected individuals. REGEN-COV has not been approved by the U.S. Food and Drug Administration (FDA), but is currently authorized in the U.S. under an Emergency Use Authorization (EUA) to treat mild-to-moderate COVID-19 in adults and pediatric patients (12 years of age and older weighing ≥40 kg) with positive results of direct SARS-CoV-2 viral testing, and who are at high risk for progression to severe COVID-19, including hospitalization or death. This use is authorized only for the duration of the declaration that circumstances exist justifying the authorization of the emergency use under section 564(b)(1) of the Act, 21 U.S.C. § 360bbb-3(b)(1), unless the authorization is terminated or revoked sooner.

Regeneron is in discussions with the FDA to expand the current EUA to other populations, including the prevention and hospitalized patient settings. Later this summer, Regeneron expects to submit a full Biologics License Application (BLA) for REGEN-COV.

Regeneron is collaborating with Roche to increase global supply of REGEN-COV. Regeneron is responsible for development and distribution of the treatment in the U.S., and Roche is primarily responsible for development and distribution outside the U.S. The companies share a commitment to making the antibody cocktail available to COVID-19 patients around the globe and will support access in low- and lower-middle-income countries through drug donations to be made in partnership with public health organizations.

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.

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