Body weights and survival in mice treated with F61 or F61+H121 monoclonal antibodies in a prophylactic analysis of challenge with the wild strain (WIV04) or beta variant (B.1.351). A–D Body weights and survival curves of K18-hACE2 mice treated with 20 mg/kg F61 or F61+H121 via intranasal route before infection with 200 TCID50 (A, B) or 1000 TCID50 (C, D) of the wild strain of SARS-CoV-2 (WIV04). E–H, Body weights and survival curves of K18-hACE2 mice treated with 20 mg/kg F61 or F61+H121 via intranasal route before infection with 200 TCID50 (E, F) or 1000 TCID50 (G, H) of the beta variant. As a negative control, PBS was administered via intranasal route 2 h before infection (A–H). Body weight curve values represent means ± standard errors of the mean (n = 3 mice/group). Significant differences between the antibody treatment group and negative control are shown. ns, P > 0.05; ∗, P < 0.05; ∗∗, P < 0.0001, as determined by Student's t-test.