Discovery of USP7 small-molecule allosteric inhibitors

Ubiquitin specific protease-7 (USP7) is considered an attractive target for cancer therapy by promoting degradation of the tumor suppressor p53 and negatively affecting the immune response to tumors. However, the development of selective non-covalent USP7 inhibitors has proven challenging. In this work we report the NMR characterization of a weak binder from SPR screening of an in-house fragment library which reveals that it binds to the allosteric palm site of the catalytic domain. Molecular modeling combined with ¹HNMR saturation transfer difference and NOESY experiments enabled structure-based design of additional compounds showing IC₅₀ values in the low-micromolar range with good selectivity over the closest homolog USP47. The most potent analogue represents a promising starting point for the development of novel, selective USP7 inhibitors.