On November 08, 2015 Calithera Biosciences, Inc. (Nasdaq:CALA), a clinical stage biotechnology company focused on the development of novel cancer therapeutics, reported that it will announce new clinical data from the solid tumor expansion cohorts of its lead anti-cancer therapeutic candidate, CB-839, at the 2015 AACR (Free AACR Whitepaper)-NCI-EORTC International Conference on Molecular Targets in Boston, Massachusetts (Press release, Calithera Biosciences, NOV 8, 2015, View Source;p=RssLanding&cat=news&id=2110182 [SID:1234508340]). CB-839 is a potent, selective, orally bioavailable glutaminase inhibitor in phase I clinical trials. The data support earlier findings of the clinical activity, tolerability and unique mechanism of action of CB-839 in patients with solid tumors, as well as show one partial response according to RECIST criteria.

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The new data to be presented by Funda Meric-Bernstam, MD, from MD Anderson Cancer Center (Abstract #C49), demonstrate stable disease across a variety of tumor types, as well as a single agent partial response (PR, on study >5 months) in a renal cell carcinoma (RCC) patient. This patient showed a 32% reduction in target lesions by RECIST with generalized shrinkage of lymph node metastases. Among the fifteen evaluable patients with RCC, nine (60%) had stable disease lasting at least three cycles (63 days) or a partial response, with four patients remaining on study. Among efficacy-evaluable patients across a range of tumor types treated on the current dosing schedule of twice-daily with food, 22 of 50 patients (44%) experienced stable disease or better. Five stable disease patients currently on study have been treated with CB-839 for over 8 months without progression (2 triple negative breast cancer, 1 RCC, 1 mesothelioma and 1 IDH1 mutant chondrosarcoma).

"We are very encouraged by these findings in that they reinforce the published safety and efficacy profile of CB-839. We believe that this first partial response in solid tumors points to the potential of our novel agent’s efficacy in renal cell carcinoma, and we look forward to sharing data as our single agent and combination studies mature," said Susan Molineaux, PhD, President and Chief Executive Officer of Calithera. "We are currently expanding enrollment of CB-839 as a monotherapy in renal cell carcinoma patients, as well as dosing CB-839 in combination with everolimus."

The Phase 1 multi-center open label dose escalation study was designed to evaluate the safety and tolerability of CB-839 in locally advanced, metastatic and/or refractory solid tumors. Oral CB-839 was administered in doses of 100 mg to 1000 mg, in 21 day cycles using one of two regimens: TID or BID with food. As of October 1, 2015, 98 patients were enrolled in the solid tumor study (32 TID, 66 BID with food) and evaluable for safety; 77 were evaluable for efficacy. All future patients enrolled to the study will be dosed on the BID with food regimen.

Safety Data

Among 98 patients evaluable for safety, a maximum tolerated dose has not been established. CB-839 was generally well tolerated with the majority of treatment-emergent adverse events being mild to moderate, Grade 1/2 and reversible. Among patients in the BID with food regimen, 4.5% (3/66) experienced a Grade 3/4 adverse event suspected to be related to CB-839 and 3% discontinued due to drug-related adverse events (2/66). The rate of Grade 3 alanine aminotransferase (ALT) elevations of 1.5% (1/66) in the BID with food cohort was substantially reduced relative to that observed in the TID cohort 16% (5/32).

In addition, a preclinical poster was presented by Calithera’s collaborators. Details for the presentation are as follows:

Targeting glutamine metabolism in colorectal cancers with PIK3CA mutations

Abstract #C115
Zhenghe John Wang, Ph.D., Case Western Reserve University
Poster Session C