GLS and plasma cell myeloma: CB-839 (glutaminase inhibitor, inhibiting recombinant GLS with an IC50 ∼30 nM) exhibited an anti-proliferative IC50 <100 nM in vitro across 36 of the cell lines, whilst twice daily CB-839 dosing also resulted in a 71% decrease of RPMI-8226 (multiple myeloma) tumor volume.