Structure-Guided Discovery of Potent, Selective, and Orally Bioavailable Werner Syndrome RecQ Helicase Inhibitors for the Treatment of Microsatellite Instability-High Tumors.

Despite recent advances in immunotherapy for microsatellite instability-high (MSI-H) tumors, challenges of resistance persist, necessitating alternative therapeutic approaches. The synthetic lethal interaction between WRN helicase inhibition and MSI status presents a promising therapeutic strategy. Guided by the key structural features of the WRN-HRO761 complex, we rationally designed two classes of WRN inhibitors─spirocyclic compounds and benzo-fused heterocyclic analogs─by targeting the solvent-exposed region. Among these, Q15 exhibited potent in vitro activity and excellent cellular selectivity. Compared with HRO761 in vivo, Q15 demonstrated more favorable oral pharmacokinetic properties and superior antitumor efficacy at 10 mg/kg, comparable efficacy at 20 mg/kg, and achieved complete tumor regression at 40 mg/kg. Preliminary safety evaluation further indicated that Q15 possesses a favorable safety profile. These findings support Q15 as a promising WRN inhibitor candidate for the treatment of MSI-H tumors.