id author title date pages extension mime words sentences flesch summary cache txt cord-355728-wivk0bm0 Schoof, Michael An ultra-potent synthetic nanobody neutralizes SARS-CoV-2 by locking Spike into an inactive conformation 2020-08-17 .txt text/plain 3613 377 68 Here, we develop single-domain antibodies (nanobodies) that potently disrupt the interaction between the SARS-CoV-2 Spike and ACE2. Cryogenic electron microscopy (cryo-EM) revealed that one exceptionally stable nanobody, Nb6, binds Spike in a fully inactive conformation with its receptor binding domains (RBDs) locked into their inaccessible down-state, incapable of binding ACE2. Class I nanobodies emerged with highly 144 variable activity in this assay with Nb6 and Nb11 as two of the most potent clones with IC50 145 values of 370 and 540 nM, respectively (Table 1) To define the binding sites of Nb6 and Nb11, we determined their cryogenic electron 156 microscopy (cryo-EM) structures bound to Spike* ( Fig. 2A state RBDs only contacts a single RBD (Fig. 2D) . 277 278 mNb6-tri displays further gains in potency in both pseudovirus and live SARS-CoV-2 infection 279 assays with IC50 values of 120 pM (5.0 ng/mL) and 54 pM (2.3 ng/mL), respectively (Fig. 4H-I, 280 Table 1). ./cache/cord-355728-wivk0bm0.txt ./txt/cord-355728-wivk0bm0.txt