"Pseudotyped virus neutralization assays indicated that only 5SB12 and 1 - 2SA8 can neutralize a diverse panel of pseudotyped virus - expressing S protein variants with an IC 50 below the nanomolar to picomolar ranges ( Supplementary Fig. 3d ). Their bindings to the S protei ns of various variants in a cell - based assay were also confirmed, which possess the EC 50 values below nanomolar levels against various S proteins of the indicated (sub)variants ( Supplementary Fig. 3e ). Biolayer interferometry analysis further demonstrated that all three mAbs bind to WT S protein with K D at the (sub)nano molar to pico molar concentration level ( Supplementary Fig. 3f ). Together, these data indicate that 5SB12 , 1 - 2SA8 and 3 - 2SF9 mAbs can all bind with WT S protein at (sub)nano molar to pico molar levels and possess ADCC activity against S - 293T cells . We next examined the prophylactic activity of 5SB12 and 1 - 2SA8 mAbs in hamsters or K18 - hACE2 transgenic mice 26 challenged with the WT SARS - CoV -"