X15695 is a selective and orally active estrogen receptor (ERα) degrader, acting as a ligand for the aryl hydrocarbon receptor (AHR). It facilitates the formation of a complex between AHR and ERα, promoting proteasomal degradation. X15695 inhibits the proliferation of breast cancer cells, induces cell cycle arrest, and triggers apoptosis, making it useful for breast cancer research.

X15695 inhibits the proliferation of MCF-7, MC7, and MC7 cells with IC50 values of 0.7 nM, 74.42 nM, and 0.38 nM, respectively, and in the presence of E2, the IC50 values are 10.28 nM, 48.01 nM, and 10.78 nM. Even when AHR activity is suppressed by CH223191, X15695 continues to inhibit the clonal growth of MCF-7 cells. Additionally, X15695 (1-10 μM, 7 days) suppresses the growth of organoids derived from patient-derived xenograft tumors (PDxO). At 1 μM for 48 hours, X15695 activates wild-type p53 and disrupts the oncogenic function of mutant p53, effectively arresting the cell cycle and inducing apoptosis in MCF-7, T47D, LNCaP, and LAPC-4 cells.

In mouse models, X15695 (administered at 15-30 mg/kg via gavage once daily for 16-42 days) effectively inhibited the growth of breast tumors, but showed limited efficacy against prostate tumor growth.