KS15 is a cryptochrome (CRY) inhibitor that promotes G1 cell cycle arrest, enhances drug sensitivity in MCF-7 cells, and exhibits antitumour activity against human breast cancer cells.

KS15 (1-10 μM) significantly restored E-box-driven luciferase activity in a dose-dependent manner, indicating that KS15 effectively attenuates the inhibitory effect of CRY proteins on CLOCK: BMAL1 complex-induced transcription. By suppressing the interaction between CRYs and BMAL1, KS15 enhances the transcriptional activity of the core molecular clock feedback loop [1].
KS15 directly binds to the C-terminal broussonetia papyrifera domain of cryptochromes (CRYs, including CRY1 and CRY2), thereby promoting E-box-mediated transcriptional processes [2].
KS15 not only reduces cell proliferation rates but also enhances the chemosensitivity of MCF-7 breast cancer cells to doxorubicin and tamoxifen. KS15 exhibits anti-proliferative activity in specific breast cancer subtypes and improves the efficacy of anti-tumor drugs [2].