Mutations in isocitrate dehydrogenase 1 (IDH1) drive most low-grade gliomas and secondary glioblastomas and many chondrosarcomas and acute myeloid leukemia cases. Most tumor-relevant IDH1 mutations are deficient in the normal oxidization of isocitrate to α-ketoglutarate (αKG), but gain the neomorphic activity of reducing αKG to D-2-hydroxyglutarate (D2HG), which drives tumorigenesis. We found previously that IDH1 mutants exhibit one of two reactivities: deficient αKG and moderate D2HG production (including commonly observed R132H and R132C) or moderate αKG and high D2HG production (R132Q). Here, we identify a third type of reactivity, deficient αKG and high D2HG production (R132L). We show that R132Q IDH1 has unique structural features and distinct reactivities towards mutant IDH1 inhibitors. Biochemical and cell-based assays demonstrate that while most tumor-relevant mutations were effectively inhibited by mutant IDH1 inhibitors, R132Q IDH1 had up to a 16 300-fold increase in IC50 versus R132H IDH1. Only compounds that inhibited wild-type (WT) IDH1 were effective against R132Q. This suggests that patients with a R132Q mutation may have a poor response to mutant IDH1 therapies. Molecular dynamics simulations revealed that near the NADP+/NADPH-binding site in R132Q IDH1, a pair of α-helices switches between conformations that are more wild-type-like or more mutant-like, highlighting mechanisms for preserved WT activity. Dihedral angle changes in the dimer interface and buried surface area charges highlight possible mechanisms for loss of inhibitor affinity against R132Q. This work provides a platform for predicting a patient’s therapeutic response and identifies a potential resistance mutation that may arise upon treatment with mutant IDH inhibitors.
Zika virus (ZIKV), an emerging flavivirus that causes neurodevelopmental impairment to fetuses and has been linked to Guillain-Barré syndrome continues to threaten global health due to the absence of targeted prophylaxis or treatment. Nucleoside analogues are good examples of efficient anti-viral inhibitors, and prodrug strategies using phosphate masking groups (ProTides) have been employed to improve the bioavailability of ribonucleoside analogues. Here, we synthesized and tested a small library of 13 ProTides against ZIKV in human neural stem cells. Strong activity was observed for 2′-C-methyluridine and 2′-C-ethynyluridine ProTides with an aryloxyl phosphoramidate masking group. Substitution of a 2-(methylthio) ethyl phosphoramidate for the aryloxyl phosphoramidate ProTide group of 2′-C-methyluridine completely abolished antiviral activity of the compound. The aryloxyl phosphoramidate ProTide of 2′-C-methyluridine outperformed the hepatitis C virus (HCV) drug sofosbuvir in suppression of viral titers and protection from cytopathic effect, while the former compound’s triphosphate active metabolite was better incorporated by purified ZIKV NS5 polymerase over time. These findings suggest both a nucleobase and ProTide group bias for the anti-ZIKV activity of nucleoside analogue ProTides in a disease-relevant cell model.
Zika virus (ZIKV), an emerging flavivirus which causes neurodevelopmental impairment 22 to fetuses and has been linked to Guillain-Barré syndrome, continues to threaten global health due 23 to the absence of targeted prophylaxis or treatment. Nucleoside analogues are good examples of 24 efficient anti-viral inhibitors, and prodrug strategies using phosphate masking groups (ProTides) 25 have been employed to improve the bioavailability of ribonucleoside analogues. Here, we 26 synthesized and tested a library of 13 ProTides against ZIKV in human neural stem cells. Strong 27 activity was observed for 2'-C-methyluridine and 2'-C-ethynyluridine ProTides with an aryloxyl 28 phosphoramidate masking group. Conversion of the aryloxyl phosphoramidate ProTide group of 29 2'-C-methyluridine to a 2-(methylthio)ethyl phosphoramidate completely abolished antiviral 30 activity of the compound. The aryloxyl phosphoramidate ProTide of 2'-C-methyluridine 31 outperformed the hepatitis C virus (HCV) drug sofosbuvir in suppression of viral titers and 32 protection from cytopathic effect, while the former compound's triphosphate active metabolite was 33 better incorporated by purified ZIKV NS5 polymerase over time. Molecular superpositioning 34 revealed different orientations of residues opposite the 2'-fluoro group of sofosbuvir. These findings 35 suggest both a nucleobase and ProTide group bias for the anti-ZIKV activity of nucleoside analogue 36 ProTides in a disease-relevant cell model. 37 38 cells, RNA-dependent RNA polymerase 39 40 1. Introduction 41The explosive spread of Zika virus (ZIKV) during the 2015-2016 epidemics in Latin America 42 attracted worldwide attention to this previously neglected disease. The lack of effective vaccines or 43 small molecules to prevent or treat this infection remains a cause for concern and emphasizes the 44 urgent need for new therapeutic options [1]. ZIKV, an emerging flavivirus infection, causes several 48 manifestations of the disease, and in rare cases, ZIKV infection has been linked to the 49 neuroinflammatory Guillain-Barré syndrome [2]. 50 Viral polymerases remain attractive drug targets for the development of selective antiviral 51 therapies [3-5]. Generally, clinically-approved inhibitors that target these proteins fall into two broad 52 classes [6,7]. The first class consists of nucleoside analogues that mimic the natural substrate of the 53 enzyme. Upon analogue incorporation by the virally-encoded polymerase, DNA or RNA synthesis 54 is abrogated by preventing further nucleotide incorporation (chain termination), thereby arresting 55 viral replication. The second class is known as non-nucleoside inhibitors, which bind allosterically 56 and arrest viral nucleic acid synthesis by distorting the polymerase active site geometry to interfere 57 with nucleotide binding or nucleotide incorporation. 58 A common prodrug strategy used for antiviral ribonucleoside analogues involves the chemical 59 synthesis of nucleoside analogue monophosphates with metabolically-removable masking groups 60 [8...
Medical Research Society 9P(PHA, 81 050, Con A 97 920 and PWM 97 550 d.p.mJ0.2 x lo6 mononuclear cells). Only the PHA response in UC was significantly different from that observed in either hospital patient control group, being significantly lower (P < 0.05) and higher than that found in the malnourished group (PHA, 71 910). In Crohn's disease only the purified protein derivative (PPD) response (3809) was significantly lower than that of healthy adults (I7 870). Normally nourished hospital patient controls had significantly reduced PHA (57 980, P < 0.05). PWM (58660, P < 0.01) and PPD responses (3786, P < 0401) compared with those of healthy adults. In the malnourished hospital patient group the PPD (3096, P < 0.01) and PWM (63 350, P < 0.02) responses were significantly
Isocitrate dehydrogenase 1 and 2 (IDH1, IDH2) balance metabolite levels by catalyzing the reversible NADP+‐dependent oxidation of isocitrate to a‐ketoglutarate (αKG). Mutations in these enzymes drive many cancers such as gliomas, leukemias, and chondrosarcomas by ablating the normal reaction and, critically, by catalyzing a neomorphic reaction: the NADPH‐dependent reduction of αKG to D‐2‐hydroxyglutarate (D2HG), an oncometabolite. Most mutations affect residue R132, and the structural and chemical diversity of the mutants observed in patients, including R132H/C/G/L/S/Q, is striking. The most common mutants in IDH1 and IDH2 serve as bona fide therapeutic targets, with selective mutant IDH inhibitors currently in the clinic. Using steady‐state kinetics methods, we recently found that the catalytic efficiency of both the normal and neomorphic reactions vary widely depending on the mutation at residue 132. Importantly, we have identified one mutant, R132Q IDH1, that preserves some wild type activity, catalyzes very highly efficient D2HG production both in biochemical and cellular models, and is resistant to allosteric mutant IDH1 inhibitors. We also show intriguing evidence that the catalytic efficiency of D2HG production appears to play a role in dictating the intensity of cellular phenotypes, allowing us to relate catalytic profiles to cancer phenotype severity. Finally, using molecular dynamics simulations and structural methods, we identified an interesting pathway of water molecules that may help drive inhibitor selectivity in mutant IDH1. By establishing the molecular mechanisms of tumor‐driving IDH mutant catalysis and inhibition, we can generate tools for predicting patient prognosis and inhibitor response, and ultimately identify new targets and handles for drug design. Support or Funding Information This work was funded by a Research Scholar Grant, RSG‐19‐075‐01‐TBE, from the American Cancer Society (C.D.S.), National Institutes of Health R00 CA187594 (C.D.S.), U54CA132384 (SDSU) & U54CA132379 (UC San Diego), MARC 5T34GM008303 (SDSU), and IMSD 5R25GM058906 (SDSU), as well as the California Metabolic Research Foundation (SDSU).
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