Calithera Biosciences, Inc., a clinical stage biotechnology company, announced that data from its lead, first-in-class programme CB-839 will be presented at the 20th Congress of the European Hematology Association (EHA) June 11-15, 2015, in Vienna, Austria. These preliminary data demonstrate the clinical activity, tolerability and unique mechanism of action of CB-839 in patients with acute leukaemia.

"We are very encouraged by these early clinical data," said Susan Molineaux, PhD, President and chief executive officer of Calithera. "While the primary objectives of this study are to determine the safety and tolerability of CB-839, we were also able to demonstrate promising clinical activity including a complete response in the bone marrow, with incomplete recovery of peripheral counts (CRi) in one patient."

As of March 1, 2015, fifteen patients with acute myeloid leukemia (AML) had been treated in Calithera's phase I clinical trial of CB-839 in patients with relapsed or refractory acute leukaemias.  Oral CB-839 was administered continuously in 21-day treatment cycles from 100 to 1000 mg three times daily. There were no dose limiting toxicities identified.  Treatment-related adverse events of any grade that occurred in >10% of patients were limited to increases in transaminases (4 patients) and bilirubin (2 patients).  There were no Grade =3 adverse events that were considered treatment-related in >10% of patients. Stable disease for 4-10 cycles was observed in 5 (33%) of 15 efficacy-evaluable AML patients across all dose levels, with patients remaining on study for an average of 134 days (>6 cycles). One of these patients achieved a complete response in the bone marrow with incomplete recovery of peripheral counts (CRi) after 6 cycles of dosing.  All of the patients with stable disease or better were over 65 years of age, and not eligible for high dose therapy.

Updated data will be presented at the meeting in a poster titled, "Phase I Study: Safety and Tolerability of Increasing Doses of CB-839, an Orally Administered Small Molecule Inhibitor of Glutaminase, in Acute Leukaemia," by lead author Marina Y. Konopleva from the MD Anderson Cancer Center from 9:30 a.m. CEST Friday, June 12, 2015, to 6:45 p.m. CEST Saturday, June 13, 2015 (Abstract #E947).  

Calithera Biosciences is a clinical-stage company focused on discovering and developing novel small molecule drugs directed against tumour metabolism and tumour immunology.