USP1-IN-15 is an orally effective and selective inhibitor of USP1 with an IC50 of 12.3 nM. It demonstrates high specificity towards USP1, with negligible inhibition of off-target deubiquitinating enzymes. USP1-IN-15 blocks cell colony formation, induces S phase arrest, and stabilizes ubiquitinated PCNA. Additionally, USP1-IN-15 exhibits synergistic antiproliferative activity and significantly inhibits tumor growth in vivo. This compound can be utilized for research on BRCA-mutated breast cancer.

USP1:12.3 nM

USP1-IN-15 (compound 43) effectively balances potent antiproliferative properties with strong metabolic stability, exhibiting an IC₅₀ of 0.07 μM in MDA-MB-436 cells and a metabolic stability half-life (t₁/₂) exceeding 120 minutes. At 1 μM, USP1-IN-15 demonstrates high specificity towards USP1 with negligible inhibition of other deubiquitinating enzymes including USP5, USP7, USP8, USP9X, USP14, USP15, USP25, USP28, BAP1, and OTUD1. In concentrations of 0-1000 nM over 0-168 hours, USP1-IN-15 effectively and durably inhibits the deubiquitination of proliferating cell nuclear antigen (PCNA) and induces p-H2AX protein in MDA-MB-436 breast cancer cells in a dose- and time-dependent manner. This compound also induces S phase arrest at concentrations of 100-1000 nM for 48 hours or 2-3 weeks in MDA-MB-436 cells. Combined use of USP1-IN-15 (0.1-10 μM) with Olaparib over 7 days or 2-3 weeks enhances growth inhibition more effectively than monotherapy in a dose-dependent manner in MDA-MB-436 cells. At 1 μM for 48 hours, USP1-IN-15 exhibits significant synergistic activity with Olaparib, amplifying DNA damage induction and cell cycle arrest in MDA-MB-436 cells.

USP1-IN-15 (compound 43) administered orally at 40 mg/kg once daily for 45 days demonstrates significant antitumor activity as a monotherapy in a xenograft mouse model and synergistically enhances the effect of Olaparib, with minimal systemic toxicity.