Abstract 2921: SNV5686 a differentiated inhibitor of Werner helicase with potent activity against both WT WRN and WRN-C727S mutant proteins for treatment of MSI-H tumors

Abstract Tumors with defects in mismatch repair genes can present with microsatellite instability (MSI) characterized by expansions of short, repeated DNA sequences. Functional genomic screens revealed that MSI-high (MSI-H) cell lines were uniquely vulnerable to depletion of Werner (WRN) which encodes an ATP-dependent helicase. Importantly inhibitors of WRN phenocopy genetic depletion leading to selective inhibition of MSI-H tumor growth. SNV5686 is a novel, reversible inhibitor of WRN with potent inhibitory activity in biochemical and cellular assays. SNV5686 shows exquisite selectivity against related RECQ helicases. The viability of MSI-H cells is selectively inhibited by SNV5686 through a mechanism involving activation of the DNA Damage response, loss of WRN protein and time- and dose-dependent increases in DNA breaks. In vivo, oral administration of low daily doses of SNV5686 potently depletes WRN and induces p21 in tumors and leads to deep tumor regression in an MSI-H colorectal xenograft model. Irreversible WRN inhibitors and the non-covalent inhibitor HRO761 leverage binding to CYS727 in the active site to attain potency and selectivity, and published data show that mutation of CYS727 severely abrogates their activity. SNV5686 in contrast retains potent inhibition of WRN-C727S in both biochemical and cellular assays thereby exhibiting a differentiated profile. Acquired resistance to covalent inhibitors against other cancer targets such as EGFR and BTK though mutation of the covalent-bonded CYS (EGFR-C797, BTK-C481) is a well-documented clinical phenomenon. By maintaining potency SNV5686 has the potential to be a best-in-class inhibitor of WRN through its activity against both WT and mutant WRN as well as favorable physical-chemical properties and excellent preclinical PK profile. Furthermore, toxicology studies with SNV5686 have not revealed adverse findings in hematology or clinical chemistry supporting the potential to combine with standard of care agents including chemotherapy. These data support the clinical investigation of SNV5686 for tumors characterized by MSI-H. Citation Format: Phillip C.C. Liu, Jeffrey Yang, Daniele Ferrante, Lin You, Mingming Gao, Yu Bai, Qipeng Fang, Yu Li, Zhentian Li, Chunhong He, Liyang Wang, Fei Zhou, Robert Landman, Hewen Zheng, Ken Mukai, Sabiha Chowdhury, Colin Zhang, Chao Qi, Liangxing Wu, Wenqing Yao. SNV5686 a differentiated inhibitor of Werner helicase with potent activity against both WT WRN and WRN-C727S mutant proteins for treatment of MSI-H tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2921.