Human and mouse PD-L1: similar molecular structure, but different druggability profiles

Abstract

In the development of PD-L1-blocking therapeutics, it is essential to transfer initial in vitro findings into proper in vivo animal models. Classical immunocompetent mice are attractive due to high accessibility and low experimental costs. However, it is unknown whether inter-species differences in PD-L1 sequence and structure would allow for human-mouse cross applications. Here, we disclose the first structure of the mouse (m) PD-L1 and analyze its similarity to the human (h) PD-L1. We show that mPD-L1 interacts with hPD-1 and provides a negative signal toward activated Jurkat T cells. We also show major differences in druggability between the hPD-L1 and mPD-L1 using therapeutic antibodies, a macrocyclic peptide, and small molecules. Our study indicates that while the amino acid sequence is well conserved between the hPD-L1 and mPD-L1 and overall structures are almost identical, crucial differences determine the interaction with anti-PD-L1 agents, that cannot be easily predicted in silico.

PD-L1 Inhibitors: Different Classes, Activities, and Mechanisms of Action

“…Durvalumab blocks the human PD-L1 but not the mouse PD-L1 protein, as we have shown in our recent manuscript [36]. In our hands, none of the small molecules and macrocyclic peptides tested in our laboratory were able to bind to mouse PD-L1, as we have verified either with the NMR study or the hybrid, mPD-L1/hPD-1 ICB assay [36]. Importantly, similar observations have been reported by others.…”

“…Out of the tested therapeutic antibodies, atezolizumab blocks both human and mouse PD-L1 (mPD-L1). Durvalumab blocks the human PD-L1 but not the mouse PD-L1 protein, as we have shown in our recent manuscript [36]. In our hands, none of the small molecules and macrocyclic peptides tested in our laboratory were able to bind to mouse PD-L1, as we have verified either with the NMR study or the hybrid, mPD-L1/hPD-1 ICB assay [36].…”

“…When defining the right model for the in vivo evaluation of the bioactivity of a drug candidate, it is crucial to determine interspecies specificity towards the molecular target. We have shown recently that despite the remarkable similarity in the structure and sequence, the mouse and human PD-L1 analogs differ greatly in their druggability profiles [36]. In the case of molecules blocking PD-L1 protein, it is thus crucial, but rare, in the manuscripts to verify the interaction with mouse PD-L1 before proceeding to the immunocompetent syngeneic mouse models.…”

Terphenyl-Based Small-Molecule Inhibitors of Programmed Cell Death-1/Programmed Death-Ligand 1 Protein–Protein Interaction

“…The results are, therefore, consistent with our previous studies, in which we showed that the biphenyl moiety from anti-PD-L1 inhibitors binds to human PD-L1 and not to the murine analogue. 31 …”

Sanguisorbae Radix Suppresses Colorectal Tumor Growth Through PD-1/PD-L1 Blockade and Synergistic Effect With Pembrolizumab in a Humanized PD-L1-Expressing Colorectal Cancer Mouse Model

“…The humanized immune checkpoint mice are carefully designed as immuno-oncology mouse models for reliable in vivo evaluation and validation of checkpoint blockers drugs and their combination with other antitumor drugs ( 29 ). According to previous studies, although there are structural similarities between human and mouse PD-L1 proteins, there are significant differences in the druggability of these two proteins ( 30 ). In line with reported results, our study showed that small molecules, peptides, and some human anti-PD-L1 antibodies bound to human PD-L1, but not to mouse PD-L1.…”