IDH1 and glioma: Indeed, in a breakthrough study the R132H IDH1 variant was shown to enhance the production of the endogenous metabolite 2-hydroxyglutarate (2HG), which was observed to accumulate to concentrations in the range 3–35 μM/g of tumour in patient R132H IDH1 glioma tissues, whilst wild-type IDH1 tumours manifested over 100-fold less 2HG [4].