AZD7442 (Tixagevimab/Cilgavimab) for Post-exposure Prophylaxis of Symptomatic COVID-19

Abstract Background We report primary results of a phase 3 trial of AZD7442 (tixagevimab/cilgavimab) for post-exposure prophylaxis to prevent symptomatic coronavirus disease 2019 (COVID-19) Methods Adults without prior SARS-CoV-2 infection or COVID-19 vaccination were enrolled within 8 days of exposure to a SARS-CoV-2–infected individual and randomized 2:1 to a single 300-mg AZD7442 dose (one 1.5-mL intramuscular injection each of tixagevimab and cilgavimab consecutively) or placebo. Primary endpoints were safety and first post-dose SARS-CoV-2 reverse-transcription–polymerase-chain-reaction (RT-PCR)–positive symptomatic COVID-19 event before day 183. Results 1121 participants were randomized and dosed (mean age 46 years; 49% females; AZD7442, n=749; placebo, n=372). Median (range) follow-up was 49 (5–115) and 48 (20–113) days for AZD7442 and placebo, respectively. Adverse events occurred in 162/749 (21.6%) and 111/372 (29.8%) participants with AZD7442 and placebo, respectively, mostly mild/moderate. RT-PCR–positive symptomatic COVID-19 occurred in 23/749 (3.1%) and 17/372 (4.6%) AZD7442- and placebo-treated participants, respectively (relative risk reduction 33.3%; 95% confidence interval [CI] –25.9 to 64.7; P=.21). In predefined subgroup analyses of 1073 (96%) participants who were SARS-CoV-2 RT-PCR–negative (n=974 [87%]) or missing an RT-PCR result (n=99 [9%]) at baseline, AZD7442 reduced RT-PCR–positive symptomatic COVID-19 by 73.2% (95% CI 27.1 to 90.1) versus placebo. Conclusions This study did not meet the primary efficacy endpoint of post-exposure prevention of symptomatic COVID-19 with AZD7442 versus placebo. However, predefined analysis of participants who were SARS-CoV-2 RT-PCR–negative or missing an RT-PCR result at baseline support a role for AZD7442 in preventing symptomatic COVID-19.