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Oncotarget. 2017 Oct 6;8(52):90215-90224. doi: 10.18632/oncotarget.21652. eCollection 2017 Oct 27.

Structural basis of the therapeutic anti-PD-L1 antibody atezolizumab.

Author information

1
Hongqiao International Institute of Medicine, Shanghai Tongren Hospital/Faculty of Basic Medicine, Key Laboratory of Cell Differentiation and Apoptosis of The Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
2
Faculty of Basic Medicine, Nanjing Medical University, Nanjing, China.
3
The Therapeutic Antibody Research Center of SEU-Alphamab, Southeast University, Nanjing, China.
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Contributed equally

Abstract

Monoclonal antibodies targeting PD-1/PD-L1 signaling pathway have achieved unprecedented success in cancer treatment over the last few years. Atezolizumab is the first PD-L1 monoclonal antibody approved by US FDA for cancer therapy; however the molecular basis of atezolizumab in blocking PD-1/PD-L1 interaction is not fully understood. Here we have solved the crystal structure of PD-L1/atezolizumab complex at 2.9 angstrom resolution. The structure shows that atezolizumab binds the front beta-sheet of PD-L1 through three CDR loops from the heavy chain and one CDR loop from the light chain. The binding involves extensive hydrogen-bonding and hydrophobic interactions. Notably there are multiple aromatic residues from the CDR loops forming Pi-Pi stacking or cation-Pi interactions within the center of the binding interface and the buried surface area is more than 2000 Å2, which is the largest amongst all the known PD-L1/antibody structures. Mutagenesis study revealed that two hot-spot residues (E58, R113) of PD-L1 contribute significantly to the binding of atezolizumab. The structure also shows that atezolizumab binds PD-L1 with a distinct heavy and light chain orientation and it blocks PD-1/PD-L1 interaction through competing with PD-1 for the same PD-L1 surface area. Taken together, the complex structure of PD-L1/atezolizumab solved here revealed the molecular mechanism of atezolizumab in immunotherapy and provides basis for future monoclonal antibody optimization and rational design of small chemical compounds targeting PD-L1 surface.

KEYWORDS:

PD-L1; atezolizumab; crystal structure; hot-spot residue; immunotherapy

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