KS15 is a chemical compound that acts as an inhibitor on the interactions between cryptochromes, specifically CRY1 and CRY2, and the CLOCK: BMAL1 heterodimer. This compound, with an EC50 value of 4.9 μM, hinders the feedback actions of CRYs on E-box-dependent transcription. The CLOCK: BMAL1 heterodimer is a vital transcriptional regulator for the mammalian circadian clock. In addition, KS15 exhibits significant anti-proliferative activity.

Applications of KS15 at different concentrations from 1 μM to 10 μM restored the E-box-driven luciferase activities in a dose-dependent manner, indicating that KS15 evidently impairs the suppressive actions of CRYs on CLOCK:BMAL1-induced transcription. KS15 inhibits the interactions between CRYs and BMAL1, resulting in the enhanced transcriptional activity in the core loop of the molecular circadian clock[1]. KS15 directly binds to the C-terminal region of cryptochromes (CRYs: CRY1 and CRY2) and enhances E-box-mediated transcription[2]. KS15 decreases the speed of cell growth and increased the chemosensitivity of MCF-7 cells to Doxorubicin and Tamoxifen. KS15 exerts an anti-proliferative effect and increases sensitivity to anti-tumor drugs in a specific type of breast cancer[2].