Kronos Bio is a pre-commercial small-molecule drug discovery company that has effectively wound down operations. The company focused on discovering drugs that target transcription factors — proteins that control gene expression and are commonly dysregulated in cancer and autoimmune diseases. Rather than targeting these proteins directly, Kronos Bio used a computational approach to map transcription regulatory networks and identify adjacent, druggable proteins whose inhibition indirectly disrupts disease-driving transcription factors. Kronos Bio developed three programs entirely in-house, none of which reached commercialization. Its only clinical-stage program, istisociclib (KB-0742), an oral CDK9 inhibitor for ovarian cancer, was discontinued in November 2024 after serious neurological adverse events emerged. Two earlier-stage programs — KB-9558 and KB-7898, both p300 inhibitors targeting multiple myeloma and Sjogren's disease, respectively — were paused before entering the clinic. Kronos Bio's only external funding came from a 2023 collaboration with Genentech, under which Kronos Bio applied its platform to two oncology targets in exchange for an upfront payment and potential milestones; that collaboration was terminated in December 2024. Kronos Bio currently has no active revenue streams and is conducting a strategic review aimed at selling or partnering its remaining assets, merging with another company, or liquidating.