Design, Synthesis, and Structure−Activity Relationship Studies of Triazolo-pyrimidine Derivatives as WRN Inhibitors for the Treatment of MSI Tumors

Werner syndrome RecQ helicase (WRN), a member of the RecQ helicase family, has recently been identified as a synthetic lethal target in microsatellite instability (MSI) tumors. The triazolo-pyrimidine compound HRO761 is the first WRN inhibitor to enter clinical trials, but research on this scaffold remains limited. Here, we designed a series of derivatives to systematically study the structure-activity relationship (SAR) of triazolo-pyrimidine scaffolds, leading to the discovery of compound S35. S35 exhibited excellent WRN helicase inhibitory activity (ADP-Glo kinase assay IC₅₀ = 16.1 nM, fluorometric helicase assay IC₅₀ = 23.5 nM). Additionally, S35 exhibited excellent cellular selectivity, with antiproliferative activity against multiple MSI cell lines (GI₅₀ = 36.4−306 nM), while the GI₅₀ values for multiple microsatellite stability (MSS) cell lines were greater than 20000 nM. Furthermore, we observed that compound S35 induced DNA damage and caused G2/M cell cycle arrest in MSI cells, which did not occur in MSS cells. S35 demonstrated favorable oral pharmacokinetic properties, with oral administration resulting in dose-dependent tumor growth inhibition in the SW48 xenograft model. These findings provide a promising outlook for the development of WRN inhibitors for the treatment of MSI tumors.