Fig. 6: BLI binding and competition analysis for mono- and bispecific constructs with various variant spike/RBD proteins.

A AHC sensors were loaded with anti-SARS-CoV-2 mono- and bispecific Abs and then dipped into wells containing different Spike variants. Amplitude of the binding signal for each variant was normalized to that Ab format’s binding of the Wuhan spike. Though the parental Abs, IgG fusions, and Ab 12/Ab 2-7 tandem BsAbs exhibit marginal affinity to the variants tested, Ab 2-7/Ab 12 constantly binds at a greater level than either of the parental Abs, indicating a synergistic binding pattern. B Competition with ACE2 for binding to Wuhan, B.1.351, B.1.617.2, and B.1.1.529 RBDs was performed with biotinylated RBD proteins and soluble ACE2. Though our BsAbs weakly bind mutant spikes at low concentration, at high concentrations they are able to effectively block ACE2 binding to the RBD. Two chimeric antibodies from Acro Biosystems were used as experimental controls, as both are cross-reactive but only AM122 has been demonstrated to compete with ACE2 binding. The percent binding experiment was performed in triplicate and mean values are shown. Competition was performed as a single experiment. Source data are provided as a Source Data file.