a, Footprints of neutralizing monoclonal antibodies on the RBD. Left, top view of SARS-COV-2 spike with one RBD in the ‘up’ conformation (PDB: 6zgg). The RBD and NTD are coloured green and peach, respectively. The positions of the inner and outer sides are indicated on the up RBD with the ACE2-binding site coloured yellow. Right, the antibody footprints on the RBD. b, Neutralization of B.1.1.7, B.1.351 and wild-type (WA1) viruses by select RBD monoclonal antibodies. The horizontal dotted lines on each graph indicate 50% and 0% neutralization. The dashed outlines in b indicate the grouping of the monoclonal antibodies according to their epitopes shown in a. Data are mean ± s.e.m. of technical triplicates and represent one of two independent experiments. Neutralization by negative control monoclonal antibodies is shown in Extended Data Fig. 2a.