Simultaneous inhibition of Vps34 kinase would enhance PI3Kδ inhibitor cytotoxicity in the B-cell malignancies.

// Xiaochuan Liu 1, 2, * , Aoli Wang 2, 3, * , Xiaofei Liang 2, 4, * , Juanjuan Liu 2, 3, * , Fengming Zou 2, 4, * , Cheng Chen 2, 4, * , Zheng Zhao 2, 4 , Yuanxin Deng 2, 3 , Hong Wu 2, 3 , Ziping Qi 2, 4 , Beilei Wang 2, 4 , Li Wang 2, 4 , Feiyang Liu 2, 3 , Yunhe Xu 1 , Wenchao Wang 2, 4 , Stacey M. Fernandes 5 , Richard M. Stone 5 , Ilene A. Galinsky 5 , Jennifer R. Brown 5 , Teckpeng Loh 1 , James. D. Griffin 5 , Shanchun Zhang 4, 6 , Ellen L. Weisberg 5 , Xin Zhang 2 , Jing Liu 2, 4 , Qingsong Liu 2, 3, 7 1 Department of Chemistry, University of Science and Technology of China, Anhui, Hefei, 230036, P. R. China 2 High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, 230031, Anhui, P. R. China 3 University of Science and Technology of China, Anhui, Hefei, 230036, P. R. China 4 CHMFL-HCMTC Target Therapy Joint Laboratory, Hefei, 230031, Anhui, P. R. China 5 Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA 6 Hefei Cosource Medicine Technology Co. LTD. Hefei, 230031, Anhui, P.R.China 7 Hefei Science Center, Chinese Academy of Sciences, Hefei, 230031, Anhui, P. R. China * These authors have contributed equally to this work Correspondence to: Ellen L. Weisberg, email: Ellen_weisberg@dfci.harvard.edu Xin Zhang, email: xinzhang@hmfl.ac.cn Jing Liu, email: jingliu@hmfl.ac.cn Qingsong Liu, email: qsliu97@hmfl.ac.cn Keywords: PI3Kδ, Vps34, combination, chronic lymphatic leukemia, acute myeloid leukemia Received: April 19, 2016      Accepted: June 03, 2016      Published: July 18, 2016 ABSTRACT PI3Kδ has been found to be over-expressed in B-Cell-related malignancies. Despite the clinical success of the first selective PI3Kδ inhibitor, CAL-101, inhibition of PI3Kδ itself did not show too much cytotoxic efficacy against cancer cells. One possible reason is that PI3Kδ inhibition induced autophagy that protects the cells from death. Since class III PI3K isoform PIK3C3/Vps34 participates in autophagy initiation and progression, we predicted that a PI3Kδ and Vps34 dual inhibitor might improve the anti-proliferative activity observed for PI3Kδ-targeted inhibitors. We discovered a highly potent ATP-competitive PI3Kδ/Vps34 dual inhibitor, PI3KD/V-IN-01, which displayed 10-1500 fold selectivity over other PI3K isoforms and did not inhibit any other kinases in the kinome. In cells, PI3KD/V-IN-01 showed 30-300 fold selectivity between PI3Kδ and other class I PI3K isoforms. PI3KD/V-IN-01 exhibited better anti-proliferative activity against AML, CLL and Burkitt lymphoma cell lines than known selective PI3Kδ and Vps34 inhibitors. Interestingly, we observed FLT3-ITD AML cells are more sensitive to PI3KD/V-IN-01 than the FLT3 wt expressing cells. In AML cell inoculated xenograft mouse model, PI3KD/V-IN-01 exhibited dose-dependent anti-tumor growth efficacies. These results suggest that dual inhibition of PI3Kδ and Vps34 might be a useful approach to improve the PI3Kδ inhibitor’s anti-tumor efficacy.