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Small molecules targeting the PD-1/PD-L1 immune checkpoint are actively searched to offer anticancer oral treatment modalities. Different small molecules have been designed, such as BMS-202 and BMS-1166 which potently bind to PD-L1, sequestering the protein dimer and thus preventing cancer cells to escape antitumor immune responses. A (top → down) deconvolution of BMS compounds has characterized their central biphenyl unit as the minimal element required for PD-L1 protein binding. On this basis, we searched for approved drugs containing a similar biphenyl unit and endowed with immune modulatory activities. We identified the biphenyl anti-inflammatory drug flurbiprofen (FLB) as a potential candidate for PD-L1 interaction, and then proposed a (bottom → up) convolution to select similar molecules, used in Human, susceptible to engage stable interactions with PD-L1. The hypothesis was tested by molecular modeling using the crystal structure of BMS-202 bound to the PD-L1 dimer. The calculations suggest that both (R) and (S) isomers of FLB can form stable complexes with PD-L1, penetrating deep into the cylindric pocket at the interface of the protein dimer. However, the potential energy of interaction (ΔE) is reduced by ~40% for FLB compared to BMS compounds. Then, we identified three FLB analogues (diflunisal, CHF-5074 and HCT1026) forming stable complexes with PD-L1. The longer FLB derivative HCT1026 appears as a suitable binder of the PD-L1 dimer, sliding well along the BMS binding cavity. Our approach proposes a new strategy to discover PD-L1-binding small molecules and raises the intriguing possibility that FLB can bind transiently to PD-L1, thus possibly explaining some of its biological effects. Our study opens new perspectives for the use of FLB (and analogs) as an immune modulator in oncology and other therapeutic domains. Copyright © 2020 Elsevier Inc. All rights reserved.


Christian Bailly, Gérard Vergoten. Flurbiprofen as a biphenyl scaffold for the design of small molecules binding to PD-L1 protein dimer. Biochemical pharmacology. 2020 Aug;178:114042

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PMID: 32445869

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