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First Author:  Tingting Li 

Journal/preprint name: bioRxiv 

Paper DOI10.1101/2020.06.09.143438 

Tags: Nanobody; Sybodiesin vivo, neutralization, binding kinetics, therapy 


  • In this study Tingting Li et al demonstrate for first time that nanobodies can protect mice from live SARS-CoV-2. The most potent construct developed suggested an antagonistic mechanism to block the ACE2-RBD interaction. Not only they test their efficacy but they analyze the mechanism of binding by crystallography. In summary, they develop an efficient in vitro platform to generate neutralizing sybodies with a high affinity, neutralization activity and in vivo stability making them good candidates to treat COVID-19.  

Research Highlights  

  1.  SR4, MR17 and MR3 neutralize SARS-CoV-2 by competitivity blocking the ACE2-RBD binding 

  1.  LR1, LR5 and MR3 bind to RBD.  

  1. The biparatopic LR5-MR3 sybodies were more potent than either sybodies alone despite the length of GS-linker. 

  1. The MR3-MR3 showed optimal neutralization activity with the longest GS-linker and similar activity to inhibit pseudotypes harboring the original SARS-CoV-2 S or the D614G mutant. Turning to be the most potent divalent sybody. 

  1. The addition of ABD to the MR3-MR3 gave the sybody the capacity to bind human albumin while retaining its ability to bind RBD and extend its in vivo stability, displaying neutralization activity up to 24hrs p.i  

Impact for COVID-19 research:  

  • This study does not alter out view of the disease but it demonstrates the efficacy and stability in vivo of a sybodies. What they propose here is a new alternative to antibodies to treat Covid-19. As it is demonstrated, the MR3-MR3-ABD sybodie should be considered as a candidate and therefore should be considered in clinical trial 


  • Study Typein vitro and in vivo. 

  • Important cell lines/viral models used: Escherichia coli MC1061 was used to expressed all the sybodies except the MR3-MR3-ABD which was expressed in Pichia Pastoris GS115 and SMD1168H. 

  • Key Techniques: SARS-CoV-2 S-RBD binders were selected by perming one round of ribosome display using three high-diversity libraries and three rounds of phage display using the RBD as the bait under increasingly stringent conditions. This was followed by an ELISA and screened by fluorescence-detector size exclusion chromatography (FSEC) assay. Other techniques are bio-layer interferometry assay for binding kinetics; Crystallization and subsequent data collection at beamline BL19U1 structure determination for which they used 2Fo-Fc maps in Coot and refined using Phenix. 


  • In the in vivo study only one single doses of 25mg/kg is administered. Might be worth to use different doses of the sybodies.