KL201, a circadian clock modulator, is an isoform-selective cryptochrome 1 (CRY1) stabilizer that lengthens the period of circadian rhythms in cells and tissues [1].

KL201 induces a dose-dependent extension of the circadian cycle in both Bmal1-dLuc and Per2-dLuc reporter cells, with a more pronounced reduction in the luminosity of the Per2-dLuc reporter compared to Bmal1-dLuc, without compromising cell viability[1]. It interacts with CRY1, coinciding with the FBXL3 segment of the ubiquitin ligase complex, and its circadian-modulating effects are diminished by the silencing of FBXL3[1]. Moreover, KL201 extends the circadian rhythm and diminishes the brightness of the Per2::Luc reporter in mouse lung primary explants[1].