SOUTH SAN FRANCISCO, Calif., Nov. 11, 2016 (GLOBE NEWSWIRE) -- Calithera Biosciences, Inc. (Nasdaq:CALA), a clinical stage biotechnology company focused on discovering and developing novel small molecule drugs directed against tumor metabolism and tumor immunology targets for the treatment of cancer, today announced that data for its drug candidates CB-839, the company's novel glutaminase inhibitor, and CB-1158, the company's novel arginase inhibitor, will be presented at the Society for Immunotherapy of Cancer (SITC) 2016 Annual Meeting, which is being held from November 9-13, 2016 in National Harbor, Maryland. "Both CB-839 and CB-1158 have the distinction of targeting metabolic and immune checkpoints which we believe, through rational combinations, have the potential to be transformational in the treatment of cancer. CB-839 and CB-1158 are each in clinical trials with cohorts planned in combination with approved immunotherapy agents," said Susan Molineaux, Ph.D., President and Chief Executive Officer of Calithera. "We are pleased that CB-1158 shows significant pharmacodynamic effects in patients at the first dose level tested." Preclinical CB-839 data will be presented in a poster titled, "Targeting tumor glutamine metabolism with CB-839 enhances the efficacy of immune checkpoint inhibitors," by Andy MacKinnon, Ph.D., Calithera Biosciences (Poster #230). Included in the presentation are data that provide further insights into the mechanism by which inhibition of glutaminase by CB-839 enhances T-cell activation and increases the anti-tumor activity of anti-PD-L1 and anti-PD-1 antibodies. Glutamine deprivation during T-cell activation was shown to block Myc expression and Myc-driven metabolic re-programming, and to promote expression of T-cell suppressive markers such as BTLA, CTLA-4, PD-1, and CD73. In two syngeneic animal models, CT26 (colon cancer) and B16 (melanoma) the combination of CB-839 and anti-PD-L1 or anti-PD-1 showed significantly enhanced anti-tumor activity over checkpoint inhibition alone resulting in increased tumor regressions in the CT26 model. Depletion of CD8+ T-cells from these tumor-bearing animals reversed the anti-tumor effects of the combination, confirming an immune-mediated mechanism of action.