An NSD3-targeting PROTAC (Proteolysis Targeting Chimeric) suppresses the NSD3 and cMyc oncogenic nodes in cancer cells

Nuclear receptor binding SET domain protein 3 (NSD3), a gene located within the 8p11-p12 amplicon frequently detected in human cancers, encodes a chromatin modulator and an attractive onco-target. However, agent that can effectively suppress the NSD3-mediated oncogenic actions is currently lacking. Here, we report an NSD3-targeting proteolysis targeting chimera (PROTAC), termed MS9715, which achieves effective and specific depletion of NSD3 and interacting partners (including cMyc) in tumor cells. We show that MS9715-induced NSD3 degradation relies on BI-9321, an antagonist module binding the PWWP1 domain of NSD3, and VHL, which is chemically conjugated to BI-9321 via a linker and a VHL ligand. Importantly, compared to BI-9321, a recently disclosed NSD3 antagonist, MS9715 is more potent in suppressing growth of the NSD3-dependent hematological cancer including models of MLL-rearranged acute myeloid leukemia (AML) and B-cell acute lymphoblastic leukemia (B-ALL) and multiple myeloma (MM), and uniquely mediates simultaneous depletion of cellular NSD3 and cMyc. Transcriptome profiling further demonstrates effective actions of MS9715 but not BI-9321 in suppressing both the NSD3- and cMyc-mediated gene-expression programs, a phenomenon reminiscent of the CRISPR/cas9-mediated knockout (KO) of NSD3. Together, this study reports a first-in-class NSD3 degrader suitable for co-suppressing NSD3- and cMyc-related oncogenic nodes in cancer, suggesting a novel therapeutic strategy, Overall design: Examination of transcriptome profiles in the EOL-1 cells post-treatment with 2.5 µM of either DMSO, BI-9321 (an NSD3 PWWP1 binding inhibitor), MS9715 (a BI-9321- and VHL-dependent PROTAC degrader of NSD3) or MS9715N (an MS9715-related analog compound incapable of binding to VHL E3 ligase).