FDW028, a novel FUT8 inhibitor, impels lysosomal proteolysis of B7-H3 via chaperone-mediated autophagy pathway and exhibits potent efficacy against metastatic colorectal cancer

Metastatic colorectal cancer (mCRC) is a major cause of cancer-related mortality due to the absence of effective therapeutics. Thus, it is urgent to discover new drugs for mCRC. Fucosyltransferase 8 (FUT8) is a potential therapeutic target with high level in most malignant cancers including CRC. FUT8 mediates the core fucosylation of CD276 (B7-H3), a key immune checkpoint molecule (ICM), in CRC. FUT8-silence-induced defucosylation at N104 on B7-H3 attracts heat shock protein family A member 8 (HSPA8, also known as HSC70) to bind with 106-110 SLRLQ motif and consequently propels lysosomal proteolysis of B7-H3 through the chaperone-mediated autophagy (CMA) pathway. Then we report the development and characterization of a potent and highly selective small-molecule inhibitor of FUT8, named FDW028, which evidently prolongs the survival of mice with CRC pulmonary metastases (CRPM). FDW028 exhibits potent anti-tumor activity by defucosylation and impelling lysosomal degradation of B7-H3 through the CMA pathway. Taken together, FUT8 inhibition destabilizes B7-H3 through CMA-mediated lysosomal proteolysis, and FDW028 acts as a potent therapeutic candidate against mCRC by targeting FUT8. [Figure: see text]