Regeneron, a pharmaceutical company, is currently developing an antibody cocktail known currently as REGN-COV2 for the SARS-CoV-2 virus. This cocktail is a combination of two non-competing neutralizing antibodies that bind to the receptor-binding domain (RBD) of the virus' spike protein. Results from animal and laboratory studies have been published for the REGN-COV2 antibody cocktail, and preliminary data from a combined (seamless) phase 1/2/3 trial has recently been announced by Regeneron in a September press release. Regeneron stated they hoped this data could support and emergency use authorization (EUA). Additional phase 3 studies are also planned and ongoing. [1]
Preliminary data from the phase 1/2/3 trial of REGN-COV2 reported data on the first 275 patients included. The trial included non-hospitalized (outpatient) adults with COVID-19. Symptoms must have been onset less than 7 days from randomization. Participants were then randomized to a lower dose (2.4 g) antibody cocktail, higher dose (8 g) antibody cocktail, or placebo. The clinical endpoints were time to symptom alleviation and the proportion of patients with medically-attended visits through 29 days; the virologic endpoint was the change from baseline viral load from day 1 to day 7. [1]
Participants were stratified based on their antibody status at baseline. Patients showed a 0.51 log10 copies/mL greater reduction in nasopharyngeal viral load with the higher dose (P=0.0049) from baseline and 0.23 log10 copies/mL greater reduction with the lower dose (P=0.20) compared to placebo by day 7. The viral load reduction was greater in patients who were seronegative at baseline. Additionally, patients with higher baseline levels correlated with greater viral load reductions by day 7. [1]
The time to symptom alleviation was 6 days in the low dose group, 8 days in the high dose group, and 9 days with placebo. In patients who were seronegative at baseline, the time to symptom alleviation was 6 days in the low dose group (P=0.09), 8 days in the high dose group (P=0.22), compared to 13 days with placebo. [1]
There were only 12 medically attended visits (defined as hospitalizations, emergency room, urgent care, or telemedicine visits for COVID-19) reported: three in each of the treatment groups and six in the placebo group. This is likely because most non-hospitalized patients recover well at home. Overall, both doses of REGN-COV2 were well tolerated, with only two infusion reactions reported in the treatment groups. There were no deaths reported in this trial. [1]
Non-human data of REGN-COV2 has been published that show promise in non-human primates, hamsters, and mice. A laboratory study shows that the antibodies in REGN-COV2 work against the SARS-CoV-2 variants seen in humans. When assessed for resistance to the antibodies, none appeared to develop when the antibody cocktail was used; however, novel spike mutants rapidly appeared in the presence of individual antibodies after in vitro. [2], [3], [4]