In Vitro: Senexin B inhibits CDK8/19 in low nanomolar range. Senexin B is a newly optimized derivative of Senexin A. It has the same high selectivity for CDK8/19 and is more potent than Senexin A. Senexin B strongly reduces the emergence of estrogen independent cells. Senexin B shows synergy with fulvestrant in MCF7, T47D-ER/Luc and BT474.
In Vivo: Pretreatment of tumor-free mice with Senexin B significantly inhibits the growth of triple-negative breast cancer (TNBC) cells inoculated into mice subsequently to Senexin B administration, indicating a general chemopreventive effect on the normal tissue “soil”. Senexin B potentiates the tumor-suppressive effect of doxorubicin on established TNBC xenografts; this effect is associated with the suppression of NFκB-mediated transcriptional induction of tumor-promoting cytokines. Senexin B inhibits invasive growth into the muscle layer in an orthotopic xenograft model of MDA-MB-468 TNBC cells. In a spleen-to-liver colon cancer metastasis model of syngeneic mouse CT26 tumors, Senexin B treatment of mice have the same effect as CDK8 knockdown in tumor cells: suppression of metastatic growth in the liver without a significant effect on primary tumor growth in the spleen. Senexin B suppresses tumor growth and augmentes the effects of fulvestrant in ER-positive breast cancer xenografts.