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bioRxiv · 10.1101/2023.05.05.539612

Probing the mechanism of Cbl-b inhibition by a small-molecule inhibitor

Kimani, S.·Perveen, S.·Szewczyk, M.·Zeng, H.·Dong, A.·Li, F.·Ghiabi, P.·Li, Y.·Chau, I.·Arrowsmith, C.·Barsyte-Lovejoy, D.·Santhakumar, V.·Vedadi, M.·Halabelian, L.
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Abstract

Cbl-b is a RING-type E3 ubiquitin ligase that is expressed in several immune cell lineages, where it negatively regulates the activity of immune cells. Cbl-b has specifically been identified as an attractive target for cancer immunotherapy due to its role in promoting an immunosuppressive tumor environment, and Nx-1607, is in phase I clinical trials for advanced solid tumor malignancies. Using a suite of biophysical and cellular assays, we confirmed potent binding of C7683 (an analogue of Nx-1607) to the full-length Cbl-b and its N-terminal fragment containing the TKBD-LHR-RING domains. To further elucidate its mechanism of inhibition, we determined the co-crystal structure of Cbl-b with C7683, revealing compound interaction with both the TKBD and LHR, but not the ring domain. Here, we provide structural insights into a novel mechanism of Cbl-b inhibition by a small-molecule inhibitor that locks the protein in an inactive conformation by acting as an intramolecular glue.

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Kimani, S., Perveen, S., Szewczyk, M., Zeng, H., Dong, A., Li, F., Ghiabi, P., Li, Y., Chau, I., Arrowsmith, C., Barsyte-Lovejoy, D., Santhakumar, V., Vedadi, M., Halabelian, L.. 2023-05-08. Probing the mechanism of Cbl-b inhibition by a small-molecule inhibitor. https://doi.org/10.1101/2023.05.05.539612

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