Telaglenastat (CB 839) (IC50 of 24 nM), an effective, specific, and oral inhibitor, which is bioavailable glutaminase, for recombinant human GAC.

CB-839 exhibits time-dependent and slowly reversible kinetics. IC50 values for glutaminase inhibition by CB-839 following preincubation with rHu-GAC for-1 hour are < 50 nmol/L, at least 13-fold lower than with BPTES. CB-839 has antiproliferative activity in a triple-negative breast cancer (TNBC) cell line, HCC-1806, while no antiproliferative activity is observed in an estrogen receptor–positive cell line, T47D.[1]

In the mouse TNBC model, single agent CB-839 (200 mg/kg, p.o.) suppresses tumor growth by 61% relative to vehicle control. In the mouse JIMT-1 xenograft model, CB-839 alone (200 mg/kg, p.o.) results in 54% tumor growth inhibition (TGI) relative to vehicle control, combination of CB-839 (200 mg/kg, p.o.) with paclitaxel (10 mg/kg, p.o.) largely suppresses the regrowth of the tumors resulting in a TGI relative to vehicle control of 100%.[1]

Inhibition of CB-839 on rHu-GAC: The enzymatic activity is measured in assay buffer containing 50 mM Tris-Acetate pH 8.6, 150 mM K2HPO4 , 0.25 mM EDTA, 0.1 mg/mL bovine serum albumin, 1 mM DTT, 2 mM NADP+ and 0.01% Triton X-100. To measure inhibition, the inhibitor (prepared in DMSO) is first pre-mixed with glutamine and glutamate dehydrogenase (GDH) and reactions are initiated by the addition of rHu-GAC. Final reactions contains 2 nM rHu-GAC, 10 mM glutamine, 6 units/mL GDH and 2% DMSO. Generation of NADPH is monitored by fluorescence (Ex340/Em460 nm) every minute for 15 minutes on a SpectraMax M5e plate reader. Relative fluorescence units (RFU) are converted to units of NADPH concentration (μM) using a standard curve of NADPH. Each assay plate incorporates control reactions that monitores the conversion of glutamate (1 to 75 μM) plus NADP+ to α-ketoglutarate plus NADPH by GDH. Under these assay conditions, up to 75 μM glutamate is stoichiometrically converts to α-ketoglutarate/NADPH by GDH. Initial reaction velocities are calculated by fitting the first 5 minutes of each progress curve to a straight line. Inhibition curves are fitted to a four-parameter dose response equation of the form: % activity = Bottom + (Top-Bottom)/(1+10^((LogIC50-X)*HillSlope)).

For viability assays, all cell lines are treated with CB-839 at the indicated concentrations for 72 hours and analyzed for antiproliferative effects using Cell Titer Glo.(Only for Reference)