Biological Activity
Senexin B is a potent, highly water-soluble and bioavailable CDK8/19 inhibitor, with Kds of 140 nM for CDK8 and 80 nM for CDK19.
In Vitro
Senexin B inhibits CDK8/19 in low nanomolar range[1]. 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[2].
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[1]. Senexin B suppresses tumor growth and augmentes the effects of fulvestrant in ER-positive breast cancer xenografts[2].
Target
CDK19:80 nM (Kd)
CDK8:140 nM (Kd)
Animal Administration
Mice: Once tumors reach 100-200 mm3 volume, 4 groups of mice are treated with vehicle, Senexin B dimaleate (100 mg/kg; twice daily, oral gavage in 6.25% 2-Hydroxypropyl-β-cyclodextrin, 1% Dextrose buffer) alone or in combination with fulvestrant (5 mg/mouse; s.c; once/week). Tumor volumes are measured twice weekly with calipers and volumes are calculated. After 40 days mice are euthanized, tumors are excised and weighed[2].
References & source
[1]. Porter D, et al. Abstract PR08: Targeting tumor microenvironment with selective small-molecule inhibitors of CDK8/19. Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr PR08. doi:10.1158/1538-7445.CHTME14-PR08
[2]. McDermott MS, et al. Inhibition of CDK8 mediator kinase suppresses estrogen dependent transcription and the growth of estrogen receptor positive breast cancer. Oncotarget. 2017 Feb 21;8(8):12558-12575.
[3]. CDK8-CDK19 selective inhibitors and their use in anti-metastatic and chemopreventative methods for cancer. US 9321737 B2
Published experimental findings depend on the model and assay conditions. They do not guarantee equivalent performance in every application. For laboratory research use only.