Abstract C176: TAS4464, a novel, highly potent, and selective inhibitor of NEDD8 activating enzyme demonstrates sustained target inhibition and antitumor activity in a preclinical model
Authors: Yoshimura Chihoko , Muraoka Hiromi , Ochiiwa Hiroaki , Tsuji Shingo , Hashimoto Akihiro , Takenaka Toru , Kazuno Hiromi , Ishida Keiji , Mizutani Takashi , Ohkubo Shuichi , Matsuo Kenichi , Utsugi Teruhiro , Iwasawa Yoshikazu 
Published: May 2016

BACKGROUND: NEDD8 activating enzyme (NAE) is an essential E1 enzyme in the NEDD8 conjugation (neddylation) pathway, which controls cancer cell growth and survival through activation of cullin-RING ligase complexes (CRLs). Therefore, NAE is considered to be a promising target for cancer therapy. Here we describe the profile of a novel, highly potent, and selective NAE inhibitor, TAS4464, which inactivates CRLs in tumors and has strong antitumor efficacy in a preclinical model.

MATERIALS AND METHODS: The selectivity of TAS4464 to E1 enzymes were assessed by various ubiquitin-like protein conjugation assays. The effects of TAS4464 on NEDD8 conjugation and the amounts of CRL substrates were evaluated by Western blot analysis. Cell viability was measured with a Cell Titer-Glo assay. The antitumor activity of TAS4464 was evaluated in an acute lymphoblastic leukemia (CCRF-CEM) xenograft model.

RESULTS: We demonstrated that TAS4464 was a mechanism-based NAE inhibitor. TAS4464 formed an NEDD8-TAS4464 adduct that could achieve nanomolar inhibition of NAE. TAS4464 selectively inhibited NAE enzyme activity relative to the other E1s, ubiquitin activating enzyme (UAE) and SUMO activating enzyme (SAE). TAS4464 treatment inhibited cullin neddylation and induced accumulation of key CRL substrate proteins such as CDT1, p27, and phosphorylated IκB in human cancer cell lines. Enzyme inhibitory and cellular NAE inhibitory activities of TAS4464 were higher than those of a known NAE inhibitor, MLN4924. Cytotoxicity profiling of TAS4464 revealed widespread antiproliferative activity against a panel of cancer cell lines. Almost all cell lines derived from hematological malignancies were highly sensitive to TAS4464. Whereas carbonic anhydrase inhibition by MLN4924 resulted in accumulation in red blood cells, the blood-to-plasma ratio of TAS4464 was close to equivalent because of higher selectivity. In addition, TAS4464 did not inhibit major cytochrome p450 enzymes and showed good metabolic stability in isolated hepatocytes in vitro. The pharmacodynamic action of TAS4464 in tumors assessed by measuring the amount of cullin-NEDD8 conjugation in CCRF-CEM xenografts revealed strong cullin neddylation inhibitory activity of TAS4464; the inhibitory activity was sustained longer than that of MLN4924. In the CCRF-CEM xenograft model, weekly administration of TAS4464 at a dose of 100 mg/kg was more efficacious than twice-weekly administration of MLN4924 at a dose of 120 mg/kg: TAS4464 led to complete tumor regression without marked weight loss.

CONCLUSION: TAS4464 is the most potent and selective NAE inhibitor reported to date, with good pharmaceutical properties and superior efficacy. Hematological cancer cell lines are highly sensitive to TAS4464. Based on its promising preclinical activity, a phase 1 clinical trial of TAS4464 is being planned.

Citation Format: Chihoko Yoshimura, Hiromi Muraoka, Hiroaki Ochiiwa, Shingo Tsuji, Akihiro Hashimoto, Toru Takenaka, Hiromi Kazuno, Keiji Ishida, Takashi Mizutani, Shuichi Ohkubo, Kenichi Matsuo, Teruhiro Utsugi, Yoshikazu Iwasawa. TAS4464, a novel, highly potent, and selective inhibitor of NEDD8 activating enzyme demonstrates sustained target inhibition and antitumor activity in a preclinical model. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C176.