Repeat Subcutaneous Administration of REGEN-COV® in Adults is Well-Tolerated and Prevents the Occurrence of COVID-19

Background Data show that a single dose of casirivimab and imdevimab (REGEN-COV ® ) is effective in treating hospitalized individuals and outpatients with COVID-19 and in post-exposure prophylaxis. We present results from a phase 1, double-blind, placebo-controlled trial evaluating the safety, tolerability, and efficacy of repeat monthly doses of subcutaneous (SC) REGEN-COV in uninfected adult volunteers who were healthy or had chronic stable medical conditions. Methods Subjects were randomized (3:1) to SC REGEN-COV 1200 mg or placebo dosed every 4 weeks for up to 6 doses. The primary and secondary endpoints evaluated the safety, pharmacokinetics, and immunogenicity of multiple-dose administration of REGEN-COV. Efficacy was evaluated by the incidence of COVID-19 or SARS-CoV-2 seroconversion. Results In total, 969 subjects were treated. Repeat monthly dosing of SC REGEN-COV led to a 92.4% relative risk reduction in clinically-defined COVID-19 compared to placebo (3/729 [0.4%] vs 13/240 [5.4%]; odds ratio: 0.07 [95% CI, 0.01–0.27]), and a 100% reduction in laboratory-confirmed COVID-19 (0/729 vs 10/240 [4.2%]; odds ratio 0.00). Development of anti-drug antibodies was low (<5% subjects). No grade ≥3 injection-site reactions (ISRs) or hypersensitivity reactions were reported. A slightly higher percentage of subjects reported TEAEs with REGEN-COV (54.9%) than placebo (48.3%), due to ISRs (all grade 1-2). Serious adverse events were rare and occurred at similar percentages in the REGEN-COV and placebo groups. No deaths were reported in the 6-month treatment period. Conclusions Repeated monthly administration of 1200 mg SC REGEN-COV was well-tolerated with low immunogenicity, and showed a substantial risk reduction in COVID-19 occurrence. ( ClinicalTrials.gov identifier, NCT04519437 )