Existing data27,28 show that current chemoradiation therapies are also effective in reducing 2HG levels. expression6C10. Gliomas are rarely curable tumors with a low survival rate (34%) at 5 years (SEER, CBTRUS 2012). Even though mutant glioma are more amenable to gross-total resection11 and seem to respond better to standard chemoradiation12C14 especially ?when associated 1p/19q co-deletion, the mutations represent a clear opportunity for more targeted treatment either by BF-168 small-molecule inhibitors of the mutant enzyme15, immunotherapy16, or by synthetic lethality strategies17,18. Recently, mutant targeted therapeutic strategies have joined Phase I clinical trials, and neuroimaging can accelerate the clinical translation of these treatments19C21. Preliminary data from your clinical trials in acute myeloid leukemia (AML) suggest that there is benefit of mutant inhibition?and lowering of 2HG concentration22, however no data are yet available from clinical trials in mutant glioma patients. Our study sheds light around the metabolic effects in response to mutant inhibition in glioma patients. The unique biology of 2HG makes this metabolite a very specific biomarker that can be used for the diagnostic, prognostic, prediction, and pharmacodynamics assessment?by probing the tumor burden, malignancy pathways, and treatment mechanisms in the mutant gliomas. 2HG can be detected noninvasively by in vivo magnetic resonance spectroscopy (MRS), and several methods23C26 have been demonstrated to handle the spectral BF-168 overlap between 2HG and other normally occurring brain metabolites. In particular, for monitoring the treatment in mutant glioma patients the non-invasive MRS detection of 2HG is usually more feasible27,28 and has clear advantages, compared to biopsies: (1) you will find no associated risks, (2) the technique can be repeated multiple occasions, (3) the technique can probe multiple tumor regions, and (4) MRS can investigate normal appearing brain as internal control. Alternative methods29C33, such as measuring 2HG in blood, urine, and CSF samples have shown mixed results for mutant glioma, with some studies reporting elevated 2HG only in CSF33, while others found elevated 2HG only in urine32. The lack of standard results may be related to lack of a standard protocol with differences in analytical methods, sample collection, and preservation that add to the biological variability. In addition, 2HG levels in periphery are diluted, the spatial localization is usually lost, tumor heterogeneity cannot be probed, and collecting CSF is not without complication, especially for longitudinal monitoring. Besides tumor production, 2HG levels in serum and urine are also influenced by other factors, such as the bloodCbrain barrier (BBB), which is usually less compromised in mutant glioma, and the shedding of tumor material may thus be reduced. The combination of all these factors BF-168 make the detection of 2HG in CSF, serum, and urine less straightforward in mutant IDH glioma patients, compared to AML patients. On the other hand, MRS methods are quick, easy to perform, and inexpensive, relative to genomics or other in vivo molecular imaging, such as PET or SPECT. 2HG imaging provides better specificity for detection of mutations than alternate MRI methods34C39, and could help distinguish true/pseudo-response in treatment assessment40. In addition, in the case of mutant inhibitors, 2HG as a direct pharmacodynamic biomarker is usually expected to probe earliest the target modulation, compared to either standard anatomical magnetic resonance imaging, such as contrast enhanced T1-weigted and fluid attenuated inversion recovery (FLAIR) MRI that are a part of RANO criteria41,42 or the more advanced diffusion/perfusion MRI43. In this study we used a recently exhibited 3D MRS imaging (MRSI) method for 2HG detection27 to assess the pharmacodynamic effects of the new investigational drug IDH305 (Novartis Pharmaceuticals) in mutant glioma patients enrolled in an open label first-in-human?Phase I clinical trial (ClinicalTrials.gov identifier: “type”:”clinical-trial”,”attrs”:”text”:”NCT02381886″,”term_id”:”NCT02381886″NCT02381886). IDH305 is an orally available, brain penetrant, mutant-selective allosteric high affinity inhibitor that functions on both canonical (R132H) and non-canonical (R132C) NFKBIA mutated enzymes, but BF-168 has much lower affinity for wild-type or mutant enzymes. IDH305 potently reduces the 2HG production in preclinical models, in which a single dose of 100?mg/kg is sufficient to reduce the tumor 2HG levels by 95% in nude mice with mutant flank tumors, and has shown in vitro antiproliferative.
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