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Calithera Biosciences Presents Preclinical Data for CB-839 at the 55th American Society ofHematology Annual Meeting

12/10/13

For Immediate Release

CB-839 Demonstrates In Vitro and In Vivo Activity Against HematologicMalignancies

South San Francisco, CA; December 10, 2013 – Calithera Biosciences, a biotechnology company focused on the development of novel cancer therapeutics, today announced the presentation of preclinical data for its lead anti-cancer therapeutic candidate, CB-839, at the 55th American Society of Hematology (ASH) Annual Meeting. CB-839 is a potent, selective, orally available glutaminase inhibitor that interferes with tumor metabolism and blocks cancer cell growth and survival.

“Glutaminase is an enzyme responsible for converting glutamine into a form that can be used by cells for energy production and the synthesis of macromolecules. Many tumor types rely on glutamine for growth and survival, so with CB-839, we hope to block glutaminase activity and thereby starve the tumor of its energy source,” said Susan Molineaux, PhD, President and Chief Executive Officer of Calithera Biosciences. “The data being presented at ASH demonstrate that CB-839 is a potent inhibitor of glutaminase and provide strong evidence for its potential therapeutic benefit in treating patients with hematologic malignancies. We look forward to advancing CB-839 into Phase 1 studies in hematological patient populations early next year.”

Calithera researchers evaluated the anti-tumor activity of CB-839 in diverse cell lines of B-cell malignancies including multiple myeloma, acute lymphocytic leukemia, and non-Hodgkin’s lymphoma. Treatment with CB-839 had anti-proliferative effects on the majority of tumor cell lines evaluated (36out of 44)and induced cell death in a significant fraction of those cell lines. In a xenograft model of multiple myeloma, oral twice-daily dosing of CB-839 resulted ina 70 percent inhibition of tumor growth. Anti-tumor activity was dose dependent and was correlated with tumor glutamine accumulation, tumor glutamate decrease, and glutaminase inhibition. Efficacious doses of CB-839 were well tolerated with no effects on hematologic cell counts or body weight. The strong correlation between glutamine dependence and sensitivity to CB-839 in B cell tumor lines suggests that glutamine supports cell growth and survival in these tumors through metabolism of glutamine by glutaminase. Calithera plans to advance CB-839into Phase 1 clinical trials in patients with advanced solid and hematological tumors in early 2014.

Calithera’s in vitro and in vivo data on CB-839 were presented in a poster entitled, “Antitumor Activity of the Glutaminase Inhibitor CB-839 in Hematological Malignancies,” (Abstract #4226), during the Chemical Biology and Experimental Therapeutics on December 9, 2013.

About Calithera Biosciences
Calithera is discovering and developing novel small molecule oncology therapeutics that inhibit pathways critical to tumor growth and survival. The Calithera team has the experience and the ability needed to discover novel therapeutics and advance these discoveries through clinical development. The company is applying this expertise to build a pipeline of anti-cancer compounds that are distinct from other oncology therapeutics. Calithera’s lead clinical candidate, CB-839, blocks glutaminase, an enzyme critical to tumor metabolism, and is poised to enter Phase 1 clinical testing. Calithera Biosciences is a privately held company located in South San Francisco, CA. For more information, please visit www.calithera.com.

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Contacts:
Susan M. Molineaux, PhD
President and CEO
Calithera Biosciences
info@calithera.com

BCC Partners
Karen L. Bergman or
Michelle Corral
650.575.1509
415.794.8662