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Characterization of Clinically Evaluated Small-Molecule Inhibitors of PD-L1 for Immunotherapy
Alicja Slota1,2, Katarzyna Golebiowska-Mendroch1,2, Justyna Kocik-Krol1
1Jagiellonian University, Faculty of Chemistry, Department of Organic Chemistry, Gronostajowa 2, 30-387 Krakow, Poland.
Abstract:
Cancer immunotherapy aims to employ the immune system to target cancer cells. The PD-1/PD-L1 axis is a critical immune checkpoint that tumors exploit to evade immune surveillance. In this study, we characterized three small-molecule PD-L1 inhibitors, Evixapodlin, MAX-10181, and INCB086550, currently undergoing clinical trials for cancers such as non-small cell lung cancer, renal cell carcinoma, urothelial carcinoma, hepatocellular carcinoma, and melanoma. Using the homogeneous time resolved fluorescence assay, we confirmed that each compound potently disrupts human PD-1/PD-L1 binding with IC50 values in the nanomolar range. PD-L1 oligomerization upon inhibitor binding was demonstrated through NMR analysis and confirmed by X-ray crystallography, which finally elucidated the binding interactions that stabilize these inhibitors at the PD-L1 interface. Cellular assays revealed dose-dependent T-cell activation, demonstrating the immunomodulatory potential of each compound and its cytotoxicity profiles. These findings underscore the promise of small-molecule PD-L1 inhibitors as viable alternatives to antibody-based therapies in cancer immunotherapy.
Insights
Three small-molecule inhibitors targeting the PD-1/PD-L1 immune checkpoint show potent disruption of cancer cell immune evasion. These compounds activate T-cells, offering promising alternatives to antibody therapies for various cancers.
Area of Science:
- Oncology
- Immunology
- Pharmacology
Background:
- Tumors exploit the PD-1/PD-L1 immune checkpoint to evade immune surveillance.
- Cancer immunotherapy aims to reactivate the immune system against cancer cells.
Purpose of the Study:
- To characterize three small-molecule inhibitors of PD-L1: Evixapodlin, MAX-10181, and INCB086550.
- To evaluate their potential as cancer immunotherapies.
Main Methods:
- Homogeneous time-resolved fluorescence (HTRF) assay to measure PD-1/PD-L1 binding disruption.
- Nuclear Magnetic Resonance (NMR) and X-ray crystallography to elucidate binding interactions.
- Cellular assays to assess T-cell activation and cytotoxicity.
Main Results:
- All three compounds potently inhibited human PD-1/PD-L1 binding with nanomolar IC50 values.
- NMR and crystallography revealed inhibitor-induced PD-L1 oligomerization and stabilizing interactions.
- Cellular assays demonstrated dose-dependent T-cell activation and cytotoxicity.
Conclusions:
- Small-molecule PD-L1 inhibitors are effective in disrupting the PD-1/PD-L1 axis.
- These compounds exhibit immunomodulatory potential and cytotoxicity.
- Small-molecule inhibitors represent promising alternatives to antibody-based therapies in cancer treatment.
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