Bispecific VH/Fab antibodies targeting neutralizing and non-neutralizing Spike epitopes demonstrate enhanced potency against SARS-CoV-2
Shion A. Lim,
Josef A. Gramespacher,
Katarina Pance,
Nicholas J. Rettko,
Paige Solomon,
Jing Jin,
Irene Lui,
Susanna K. Elledge,
Jia Liu,
Colton J. Bracken,
Graham Simmons,
Xin X. Zhou,
Kevin K. Leung,
James A. Wells
Affiliations
Shion A. Lim
Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, USA
Josef A. Gramespacher
Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, USA
Katarina Pance
Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, USA
Nicholas J. Rettko
Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, USA
Paige Solomon
Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, USA
Jing Jin
Vitalant Research Institute and Department of Laboratory Medicine, University of California San Francisco, University of California San Francisco, California, USA
Irene Lui
Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, USA
Susanna K. Elledge
Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, USA
Jia Liu
Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, USA
Colton J. Bracken
Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, USA
Graham Simmons
Vitalant Research Institute and Department of Laboratory Medicine, University of California San Francisco, University of California San Francisco, California, USA
Xin X. Zhou
Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, USA
Kevin K. Leung
Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, USA
James A. Wells
Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, USA
Numerous neutralizing antibodies that target SARS-CoV-2 have been reported, and most directly block binding of the viral Spike receptor-binding domain (RBD) to angiotensin-converting enzyme II (ACE2). Here, we deliberately exploit non-neutralizing RBD antibodies, showing they can dramatically assist in neutralization when linked to neutralizing binders. We identified antigen-binding fragments (Fabs) by phage display that bind RBD, but do not block ACE2 or neutralize virus as IgGs. When these non-neutralizing Fabs were assembled into bispecific VH/Fab IgGs with a neutralizing VH domain, we observed a ~ 25-fold potency improvement in neutralizing SARS-CoV-2 compared to the mono-specific bi-valent VH-Fc alone or the cocktail of the VH-Fc and IgG. This effect was epitope-dependent, reflecting the unique geometry of the bispecific antibody toward Spike. Our results show that a bispecific antibody that combines both neutralizing and non-neutralizing epitopes on Spike-RBD is a promising and rapid engineering strategy to improve the potency of SARS-CoV-2 antibodies.
