In the context of mutant IDH gliomas, we have previously shown that HP [1-13C]αKG can be used to monitor both mutant IDH-driven 2HG production and normal αKG conversion to glutamate.22–24 We have also shown that in cells we can use 1H MRS to detect a drop in 2HG and an increase in glutamate following treatment with the clinically relevant IDH inhibitor AG-881. Here, IDH1 is linked to central nervous system cancer.