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The Novel Protein HSF1 Stress Pathway Inhibitor Bisamide CCT361814 Demonstrates Pre-Clinical Anti-Tumor Activity in Myeloma

2017; Elsevier BV; Volume: 130; Linguagem: Inglês

10.1182/blood.v130.suppl_1.3072.3072

1528-0020

Karen Menezes, Grace Aram, Fabio Mirabella, David C. Johnson, Amy L. Sherborne, Richard S. Houlston, Matthew D. Cheeseman, Elisa Pasqua, Paul A. Clarke, Paul Workman, Keith Jones, Martin Kaiser,

Computational Drug Discovery Methods

Abstract Introduction Multiple myeloma (MM) is a plasma cell malignancy, characterized by the constant production of immunoglobulins (Ig), making the tumor cells reliant on protein homeostasis for their survival. MM cells are therefore highly susceptible to therapies that target protein homeostasis, such as proteasome inhibitors. Several protein homeostasis mechanisms, when disturbed, converge on the heat shock pathway, a critical survival pathway for tumor cells comprising among other components molecular chaperones, the heat shock proteins (HSPs), and heat shock factor 1 (HSF1) - a master transcription factor and regulator of the heat shock response (HSR). Targeting HSP90 with small-molecule inhibitors has anti-myeloma activity (Stuhmer et al, 2009; Ishii et al, 2011), but leads to compensatory activation of the HSR, which makes inhibition of the HSR itself an attractive target. Recently, we discovered a chemical probe bisamide (CCT251236) that disrupts the HSF1 pathway (Cheeseman MD et al, 2017). This led to the identification of CCT361814 with bioavailability features compatible with clinical use. Here we present first data demonstrating marked antitumor activity by CCT361814 in MM. Methods and Results We evaluated CCT361814 activity in 16 human myeloma cell line (HMCL) models including KMS11, KMS12BM, H929, L363 and RPMI-8226 using MTS cell proliferation assay and found that most HMCL cell lines displayed a GI50 in the nanomolar range (20-300nM, median GI50 147nM) whilst bone marrow stromal HS5 cells had a GI50 of around 700nM suggesting a therapeutic window. Cell lines with the t(11;14) translocation affecting CCND1 such as MOLP8, U266 and KMS12BM appeared to be particularly sensitive to the drug with median GI50 values of 88nM. Western blot analysis showed that CCT361814 caused a concentration-dependent loss of HSP27 and HSP72, as markers of HSF-1 pathway inhibition, and a reduced HSF1 phosphorylation at serine 326. Annexin V/DAPI staining was performed in 8 cell lines and demonstrated consistent induction of apoptosis in all lines, with MM1.S as an example showing a 9-fold increase in apoptosis compared to vehicle control (student's t-test, P= Conclusions Our data shows that CCT361814 affects the heat shock pathway as evidenced by a concentration-dependent loss of HSP27 and HSP72 proteins and also has highly potent anti-myeloma activity in all HMCL models studied. Further functional validation of the gene expression data and assessing the effect of CCT361814 treatment in combination with clinically used drugs is underway. Our discovery of CCT361814 and its potent inhibition of the HSR in protein homeostasis-addicted MM cells makes it an attractive drug to be further evaluated in early phase clinical trials. Disclosures Workman: Institute of Cancer Research: Employment. Jones: Institute of Cancer Research: Employment. Kaiser: Celgene: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Other: Travel expenses; Amgen: Consultancy, Honoraria; Takeda: Consultancy; Janssen: Honoraria; Chugai: Consultancy.