Calithera Biosciences announced yesterday that the FDA has granted fast track designation to CB-839 for use in combination with everolimus for the treatment of patients with metastatic renal cell carcinoma (RCC) who received at least two prior courses of treatment. Fast track designation by the FDA expedites the review process to facilitate development of drugs which treat a serious or life-threatening condition and fill an unmet medical need.

CB-839 is a first-in-class, oral, selective, potent glutaminase inhibitor. Genetic changes in the metabolic pathways of tumours often cause a dramatic rise in the uptake of the nutrients glucose and glutamine. Removal of glutamine leads to a substantial reduction in cell growth or induces cell death in certain types of cancer cells, indicating that these cells are dependent on, or “addicted” to, glutamine. Normal cells do not show this pronounced dependence on glutamine. The enzyme glutaminase, which converts glutamine to glutamate, has been identified as critical in the use of glutamine by cancer cells. CB-839 blocks glutaminase and prevents cancer cells from being able to use glutamine, potentially leading to reduced tumour cell growth and/or cell death.

There is an ongoing phase 1/phase 2 study, which is looking at CB-839 in combination with everolimus in patients with solid tumours, including renal cell carcinoma, triple-negative breast cancer, non-small cell lung cancer and melanoma.

“We are pleased that CB-839 has been granted fast track designation, demonstrating the FDA’s commitment to facilitate the development and expedite the review of our glutaminase inhibitor as an important new therapy for patients with relapsed renal cell carcinoma,” Susan Molineaux, PhD, president and CEO of Calithera, said in a company-issued press release.

The company plans to initiate a global, randomised trial of the combination this year.

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