Abstract 951: CB-5083 is a novel first in class p97 inhibitor that disrupts cellular protein homeostasis and demonstrates anti-tumor activity in solid and hematological models
Authors: Moigne Ronan L. , Wong Steve , Soriano Ferdie , Valle Eduardo , Anderson Daniel J. , Djakovic Stevan , Menon Mary-Kamala , Yao Bing , Rice Julie , Wang Jinhai , Soly Szerenke Kiss Von , Kumar Brajesh , Chesi Marta , Bergsagel P. Leif , Zhou Han-Jie , Wustrow David , Rolfe Mark , Yakes F. Michael 
Published: May 2015

Background:

The AAA-ATPase p97/VCP facilitates the extraction and degradation of ubiquitinated proteins by converting chemical energy into mechanical force. p97 is closely involved in several facets of protein homeostasis, including ubiquitin-dependent protein degradation, endoplasmic reticulum-associated degradation (ERAD) and autophagy. p97 has been increasingly linked to cancer: it showed elevated protein expression in tumors, it can mediate the degradation of proteins in cancer-relevant pathways and is required for orchestrating the ubiquitin-governed DNA-damage response. In this context, p97 inhibitors may have an advantage versus other protein homeostasis inhibitors and may be active in solid tumors where 26S proteasome inhibitors, bortezomib and carfilzomib, have shown poor efficacy. We report here p97 inhibition as a novel approach to exploit cancer cell addiction to protein homeostatic mechanisms.

Results:

We have discovered novel small molecule inhibitors of p97 ATPase activity with nanomolar enzymatic and cellular potency. In cellular models, treatment of cancer cells with our lead compound CB-5083 causes disruptions in specific p97 functions, including ubiquitin-dependent protein degradation, ERAD, endocytosis and autophagy. In mouse models, CB-5083 is orally bio-available and causes rapid and sustained accumulation of poly-ubiquitin in tumor xenografts after a single administration. Concurrent with increases in polyubiquitin levels, activation of ER stress response pathways and induction of apoptosis markers are also observed. Sub-chronic oral administration of CB-5083 is generally well-tolerated with &lt;10% body weight loss and results in potent tumor growth inhibition in several solid tumor xenograft models. This result is in marked contrast to proteasome inhibitors that are inactive in the same solid tumor models. In the Vk*MYC transgenic mouse model of multiple myeloma, CB-5083 treatment resulted in &gt;50% reduction in M-spike. Additional efforts are focused on the development of translational assays to monitor p97 target engagement and antitumor efficacy in upcoming clinical trials of CB-5083.

Conclusion:

These data demonstrate that CB-5083 is a potent inhibitor of p97 that translates to tumor growth inhibition in multiple rodent models of human cancer. Furthermore, CB-5083 appears to exhibit greater potency over current proteasome inhibitors that further validate targeting p97 and protein homeostasis in the treatment of cancer.

Citation Format: Ronan Le Moigne, Steve Wong, Ferdie Soriano, Eduardo Valle, Daniel J. Anderson, Stevan Djakovic, Mary-Kamala Menon, Bing Yao, Julie Rice, Jinhai Wang, Szerenke Kiss Von Soly, Brajesh Kumar, Marta Chesi, P. Leif Bergsagel, Han-Jie Zhou, David Wustrow, Mark Rolfe, F. Michael Yakes. CB-5083 is a novel first in class p97 inhibitor that disrupts cellular protein homeostasis and demonstrates anti-tumor activity in solid and hematological models. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 951. doi:10.1158/1538-7445.AM2014-951