SOUTH SAN FRANCISCO, Calif., Nov. 29, 2016 (GLOBE NEWSWIRE) -- Calithera Biosciences, Inc. (Nasdaq:CALA), a clinical stage biotechnology company focused on the development of novel cancer therapeutics, announced that clinical data from its lead product candidate CB-839, a first-in-class glutaminase inhibitor, will be presented in a plenary session at the 28th EORTC-NCI-AACR Symposium on Molecular Targets and Cancer Therapeutics in Munich, Germany. The data demonstrate the clinical activity, tolerability and unique mechanism of action of CB-839 in patients with renal cell carcinoma. "CB-839 is the first tumor metabolism drug to target a pathway that starves cancer cells by directly depriving them of a key nutrient. We are pleased to present combination data of CB-839 with everolimus that demonstrates high rates of disease control with a well-tolerated combination therapy," said Susan Molineaux, PhD, President and Chief Executive Officer of Calithera. Dr. Funda Meric-Bernstam from MD Anderson Cancer Center will present in a plenary session, "Phase I study of CB-839, a small molecule inhibitor of glutaminase, in combination with everolimus in patients with clear cell and papillary renal cell carcinoma." As of October 25, 2016, 15 renal cell carcinoma patients were treated and evaluable for response, including 12 clear cell patients, and three papillary patients. Ninety-three percent (93%) have disease control; one patient has a partial response, one patient has progressive disease, and 13 patients have stable disease. The median progression free survival is 8.5 months and for the majority of patients, their time on therapy is longer than their time on treatment in their prior therapy. In the clear cell patient population the disease control rate is 100% and eight patients remain on study. For comparison, in a separate trial of everolimus vs. cabozantinib, the progression free survival of patients in the everolimus group from the Meteor Phase 3 study in second and third line patients was 3.9 months. 1 Patients enrolled in the trial had advanced or metastatic disease and had received a median of two prior treatments, which included tyrosine kinase inhibitors, mTOR inhibitors, and checkpoint inhibitors. Patients were administered CB-839 in oral doses that ranged from 400-800 mg twice a day in combination with a fixed oral dose of everolimus at 10 mg once a day. The addition of CB-839 to full dose everolimus has been well tolerated, with a similar safety profile to the known profile of everolimus alone. Grade 3 events include two events of hyperglycemia and one event each of diarrhea, anemia and fatigue. On the basis of this efficacy and safety data, the company plans to continue development in combination therapy for clear cell renal cell carcinoma. Clear cell is the most common form of kidney cancer comprising 75%-85% of cases.