Inhibition Of Isocitrate Dehydrogenase Research Articles

Multiparametric Magnetic Resonance Imaging Correlates of Isocitrate Dehydrogenase Mutation in WHO high-Grade Astrocytomas.

Isocitrate dehydrogenase (IDH) mutation and O-6 methyl guanine methyl transferase (MGMT) methylation are surrogate biomarkers of improved survival in gliomas. This study aims at studying the ability of semantic magnetic resonance imaging (MRI) features to predict the IDH mutation status confirmed by the gold standard molecular tests. The MRI of 148 patients were reviewed for various imaging parameters based on the Visually AcceSAble Rembrandt Images (VASARI) study. Their IDH status was determined using immunohistochemistry (IHC). Fisher's exact or chi-square tests for univariate and logistic regression for multivariate analysis were used. Parameters such as mild and patchy enhancement, minimal edema, necrosis < 25%, presence of cysts, and less rCBV (relative cerebral blood volume) correlated with IDH mutation. The median age of IDH-mutant and IDH-wild patients were 34 years (IQR: 29-43) and 52 years (IQR: 45-59), respectively. Mild to moderate enhancement was observed in 15/19 IDH-mutant patients (79%), while 99/129 IDH-wildtype (77%) had severe enhancement (p-value <0.001). The volume of edema with respect to tumor volume distinguished IDH-mutants from wild phenotypes (peritumoral edema volume < tumor volume was associated with higher IDH-mutant phenotypes; p-value < 0.025). IDH-mutant patients had a median rCBV value of 1.8 (IQR: 1.4-2.0), while for IDH-wild phenotypes, it was 2.6 (IQR: 1.9-3.5) {p-value = 0.001}. On multivariate analysis, a cut-off of 25% necrosis was able to differentiate IDH-mutant from IDH-wildtype (p-value < 0.001), and a cut-off rCBV of 2.0 could differentiate IDH-mutant from IDH-wild phenotypes (p-value < 0.007). Semantic imaging features could reliably predict the IDH mutation status in high-grade gliomas. Presurgical prediction of IDH mutation status could help the treating oncologist to tailor the adjuvant therapy or use novel IDH inhibitors.

Efficacy and Safety of IDH Inhibitors in AML: A Systematic Review of Clinical Trials

Background: Isocitrate dehydrogenase (IDH) gene mutation leads to the accumulation of oncometabolite. IDH 1 and 2 gene mutations are associated with multiple malignancies including gliomas, leukemias, etc. Despite improving treatment for hematological malignancies, advanced acute myeloid leukemia is associated with a poor prognosis. In this systematic review, we assessed the efficacy and safety of IDH 1 and 2 inhibitors used alone or in combination with other drugs in IDH 1 and 2 mutated AML. Methods: We followed PRISMA guidelines to conduct this systematic review. A literature search was performed on PubMed, Web of Science, and Embase (Ovid) with mesh terms, "Acute Myeloid Leukemia" and "Isocitrate dehydrogenase" from the inception of data till 6/15/2022. We screened 3,263 articles and included 3 randomized clinical trials (RCTs, N=398) and 4 non-randomized clinical trials (nRCTs, N=609) measuring the efficacy and safety of IDH inhibitors in AML. Results: In 7 clinical trials, 1,007 adult patients with IDH mutated AML were included. 472 patients had IDH-2 mutation (mIDH-2) while 535 patients had IDH-1 mutation (mIDH-1). 582 patients had relapsed/refractory (R/R) disease while 425 patients had newly diagnosed (ND) disease. In a clinical trial on R/R mIDH-2 AML patients treated with enasidenib (N=280), overall response rate (ORR), complete response (CR), morphologic free state (MLFS), and median overall survival (mOS) were 39.6%, 18.9%, 5.7%, and 8.8 months, respectively. In two clinical trials (N=192) on ND mIDH-2 AML patients, ORR was 74%-89%, CR was 54%-55%, and MLFS was 4%-11% with enasidenib + chemotherapy/azacytidine as compared to ORR of 36%, CR of 12%, and MLFS of 0% with azacytidine alone. However, the mOS was not significantly different among the two groups. Table 1. In two clinical trials (N=206) on ND mIDH-1 AML patients, ORR was 63%-87%, CR was 47%-68%, and MLFS was 7%-8% with ivosedanib + chemotherapy/azacytidine as compared to ORR of 19%, CR of 15%, and MLFS of 0% with azacytidine alone. The hazard ratio (HR) of OS was significantly in favor of ivosedanib + azacytidine as compared to azacytidine alone. In a clinical trial on R/R mIDH-1 AML patients treated with ivosedanib (N=179), ORR, CR, MLFS, and mOS were 39.1%, 21.8%, 5.6%, and 9.3 months, respectively. In two clinical trials, ORR with BAY1436032 (N=27) and olutasidenib (N=123) were 15% and 46% respectively. Table 1. ≥Grade 3 hyperbilirubinemia, thrombocytopenia, IDH differentiation syndrome, anemia, thrombocytopenia, neutropenia, diarrhea, and long QT syndrome were the common side effects reported in AML patients treated with IDH inhibitors. Table 1. Conclusion: IDH inhibitors were well tolerated by most of the patients with AML. Enasidenib significantly improved the response rates in patients with mIDH-2 AML. However, the OS was not improved with the addition of enasidenib in ND mIDH-2 AML patients in phase 2 RCT. Ivosedanib significantly improved the response rates and survival rates in patients with mIDH-1 AML. Olutasidenib was also effective in patients with R/R mIDH-1 AML. More randomized double-blind multicenter clinical trials are needed to confirm these results. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Fructose Treatment Targets Myeloid Leukemogenesis in IDH2 Mutants By Exhausting Alpha-Ketoglutarate Pools

Acute Myeloid Leukemia (AML) is a heterogeneous group of hematological malignancies and represents the most frequent cause of leukemia-related deaths. The uncontrolled growth of myeloblasts in the Bone Marrow (BM) leads to accelerated metabolic processes and high consumption of nutrients, especially glucose. Isocitrate dehydrogenase (IDH) 1 and 2 are frequently mutated in human cancer, affecting up to 15% of AML patients. The neo-morphic activity conferred by IDH 1 or 2 mutations (mIDH1/2) converts α-ketoglutarate (α-KG) to the R-enantiomer of 2-hydroxyglutarate (2-HG), which competitively inhibits α-KG-dependent dioxygenases (Figueroa et al., 2010, Su et al.,2018, Li et al.,2017) and contributes to a block in myeloid differentiation and leukemic transformation. mIDH1/2 are clinically validated therapeutic targets as specific inhibitors have been approved by the FDA for the treatment of AML(DiNardo et al., 2018; Rohle et al., 2013; Stein et al., 2019; Wang et al., 2013) However, only 40% or less of mIDH AML patients respond to IDH inhibitor therapy (DiNardo et al., 2018; Stein et al., 2017) and little is known of how IDH mutations can be exploited for new metabolic vulnerabilities. We recently reported a novel metabolic dependency in AML cells that express low levels of the fructose transporter GLUT5. In fructose conditions these AMLs rewired their metabolism away from glycolysis and toward the serine synthesis pathway (SSP), (Jeong and Savino, Cell Metabolism 2021). Inhibiting the SSP by blocking PHGDH under these metabolic conditions resulted in reduced tumor burden. Additionally, patients with FLT-ITD alterations were sensitive to SSP blockade (Bjelosevic et. al. 2021). Although we previously found that myeloid leukemia cells grow normally in fructose, AML cell lines engineered to express IDH2 R140Q (TF1 knock in, and transduced MOLM13, U937 and OCIAML2) had a 50% reduction in cellular growth and 1.6-fold increase in differentiation (CD15 marker). Remarkably, a similar effect was observed in mIDH1 or 2 chondrosarcoma cell lines, suggesting that this metabolic program is more generally applicable. Excitingly, this new fructose induced therapeutic vulnerability could be recapitulated in vivo. We found that the fructose treated mice could delay myeloid leukemogenesis by 9-10 days (MOLM13 IDH2 R140Q) or in a primary patient sample successfully engrafted with IDH2 R140Q (n=6 mice/group p=0.0012; 3 weeks, I.P. 4 g/kg). To understand the basic mechanism for this new metabolic vulnerability, we first focused on the flux though the SSP. We found an increase in the end product of the SSP, glycine, as measured by LC-MS in the fructose condition compared to glucose. This SSP addiction under fructose was further demonstrated by reduced growth upon PHGDH inhibition (mIDH2: 75% reduction vs 50% WT IDH2 p=.0004; NCT503 5uM). Utilization of the SSP results in the generation of cytosolic α-KG, the substrate of IDH mutant enzymes. Thus, we hypothesized that mIDH AML cells might display enhanced dependency due to the requirement of α-KG for SSP, mIDH2 activity and to sustain the otherwise defective TCA cycle. Consistent with α-KG's central role in fructose driven metabolic addiction, we rescued the cell growth reduction by treating with cell permeable a-KG. Furthermore, in fructose conditions, we observed significant accumulation of the TCA cycle intermediate malate as well as aspartate, suggesting an engagement of the malate-aspartate shuttle in maintaining the redox balance. Previously, we found that AML cell lines (i.e THP1 cells) with moderate to high abundance of surface GLUT5, were not dependent on SSP in fructose. Surprisingly, by introducing IDH2 R140Q or by treating the cells with exogenous D-2HG, we found a 2-fold reduction of surface GLUT5 protein. This reduction of GLUT5 rewired the metabolism toward the SSP-addiction and resulted in a 50% reduction in cell growth in fructose. Interestingly, GLUT5 was controlled through transcriptional regulation of the locus as early as 8hrs post D-2HG treatment. Importantly, this relationship was found to be associated in patients, where PHGDH expression was significantly increased in mIDH2 AML patients with low vs high GLUT5 (n=15, n=16 p<.038) compared to other mutational subtypes (n=155, n=155 ns). In summary, we find a surprising new metabolic dependency based on sugar conditions in mIDH2 AML that could pave the way for a new therapeutic strategy.

Targeting Cell Adhesion Molecules in IDH Mutant Myeloid Malignances

Neomorphic mutations in the genes encoding isocitrate dehydrogenase (IDH) are common in human cancers including myeloid malignancies. The oncometabolite (R)-2-hydroxyglutarate (R-2-HG) produced by mutant IDH promotes leukemia development by competitively inhibiting α-ketoglutarate (α-KG)-dependent dioxygenases, causing epigenetic dysregulation of histone and DNA methylation in myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). FDA-approved allosteric inhibitors (ivosidenib and enasidenib targeting mutant IDH1 and IDH2 respectively) are used for treating newly diagnosed and/or relapsed/refractory AML patients with IDH mutations. However, the low response rate and primary resistance to IDHmut inhibitors are major clinical challenges. Moreover, acquired resistance to IDH inhibition can occur through multiple mechanisms, including R-2-HG-restoring second-site IDH mutations and the selection of sub-clonal mutations in RUNX1/CEBPA or RAS-RTK pathway. These findings underscore the importance of developing new and more effective approaches for the treatment of IDH-mutant MDS and AML patients. To identify mutant IDH-mediated alterations and actionable dependencies, we generated isogenic TF-1 myeloid leukemia cell lines containing endogenous, hotspot IDH mutations (IDH1R132H, IDH2R140Q, IDH2R140W, and IDH2R172K) by CRISPR/Cas9-mediated base-editing. By comparative transcriptomic (RNA-seq) and epigenomic (ATAC-seq and ChIP-seq) profiling of base-edited versus parental isogenic leukemia cells, we identified cell adhesion molecules, especially CD44, as the top upregulated genes in IDH-mutant leukemia cells. CD44 expression is significantly upregulated in IDH-mutant AML patient samples relative to normal CD34+ hematopoietic stem/progenitor cells (HSPCs) or other AML samples without IDH mutations. Increased CD44 expression is also associated with overall poorer survival and therapy resistance in independent AML cohorts. Importantly, we found that ectopic CD44 expression promotes cytokine-independent cell growth of TF-1 myeloid leukemia cells, resembling the effect observed upon expression of mutant IDH. Moreover, CD44 depletion led to decreased R-2-HG levels in base-edited IDH-mutant TF-1 leukemia cells, and impaired the propagation of IDH-mutant leukemia cells in vitro and in xenotransplanted recipient mice. These studies establish direct evidence that IDH mutations cause aberrant activation of cell adhesion molecules such as CD44, and CD44 is required for the propagation of IDH-mutant myeloid leukemia cells. Mechanistically, we found that the aberrantly activated CD44 is first cleaved by matrix metalloproteinases MMP2 and MMP9 for proteolytic release of its ectodomain from membrane, followed by γ-secretase-mediated intramembranous cleavage to produce the CD44 intracellular domain (CD44ICD). CD44ICD subsequently activates the pentose phosphate pathway (PPP) for the production of NADPH, a critical cofactor for mutant IDH enzymes to convert α-KG to R-2-HG. Hence, mutant IDH-mediated activation of CD44 functions to rewire intracellular metabolism to facilitate IDHmut-catalyzed R-2-HG production, supporting a model for mutant IDH-induced feed-forward oncogenic programs. CD44 also activates AKT/ERK signaling pathway to promote the proliferation and cytokine-independent growth of IDH-mutant leukemia cells. More importantly, primary and resistant IDH-mutant leukemia cells are sensitive to combination regimens consisting of IDHmut inhibitors and humanized monoclonal antibody specific for CD44 (RG7536) or MMP2/9 inhibitors (SB-3CT) invitro and invivo. Taken together, our findings uncover the cell adhesion molecule-mediated metabolic signaling as a new targetable dependency of IDH-mutant leukemia cells, with therapeutic implications for more effective treatment of primary and resistant IDH-mutant myeloid malignancies.

Targeting STAT5 Signaling Overcomes Resistance to IDH Inhibitors in Acute Myeloid Leukemia through Suppression of Stemness.

A CRISPR knockout screen identifies a mechanism of resistance to IDH inhibitors in AML involving activated STAT5 signaling, suggesting a potential strategy to improve the clinical efficacy of IDH inhibitors.

Metabolic reprogramming in the OPA1-deficient cells.

OPA1, a dynamin-related GTPase mutated in autosomal dominant optic atrophy, is essential for the fusion of the inner mitochondrial membrane. Although OPA1 deficiency leads to impaired mitochondrial morphology, the role of OPA1 in central carbon metabolism remains unclear. Here, we aim to explore the functional role and metabolic mechanism of OPA1 in cell fitness beyond the control of mitochondrial fusion. We applied [U-13C]glucose and [U-13C]glutamine isotope tracing techniques to OPA1-knockout (OPA1-KO) mouse embryonic fibroblasts (MEFs) compared to OPA1 wild-type (OPA1-WT) controls. Furthermore, the resulting tracing data were integrated by metabolic flux analysis to understand the underlying metabolic mechanism through which OPA1 deficiency reprograms cellular metabolism. OPA1-deficient MEFs were depleted of intracellular citrate, which was consistent with the decreased oxygen consumption rate in these cells with mitochondrial fission that is not balanced by mitochondrial fusion. Whereas oxidative glucose metabolism was impaired, OPA1-deficient cells activated glutamine-dependent reductive carboxylation and subsequently relied on this reductive metabolism to produce cytosolic citrate as a predominant acetyl-CoA source for de novo fatty acid synthesis. Prevention of cytosolic glutamine reductive carboxylation by GSK321, an inhibitor of isocitrate dehydrogenase 1 (IDH1), largely repressed lipid synthesis and blocked cell proliferation in OPA1-deficient MEFs. Our data support that, when glucose oxidation failed to support lipogenesis and proliferation in cells with unbalanced mitochondrial fission, OPA1 deficiency stimulated metabolic anaplerosis into glutamine-dependent reductive carboxylation in an IDH1-mediated manner.

Abstract IA21: Molecular Pathogenesis and Cells of Origin of Intrahepatic Cholangiocarcinoma

Abstract Intrahepatic cholangiocarcinoma (iCCA) originates in the intrahepatic biliary tree above the second order bile ducts. There are two primary histological subtypes of iCCA: small bile duct iCCAs which arise at the level of the smaller intrahepatic bile ducts, and large bile duct iCCAs which arise in the large intrahepatic bile ducts. Hepatic stem or progenitor cells and cuboidal cholangiocytes are the cells of origin of small bile duct iCCA, whereas large bile duct iCCAs arise from columnar mucous cholangiocytes or peribiliary glands. The molecular pathogenesis of iCCA is distinct from the other anatomic subtypes of CCA. Potentially actionable genomic aberrations that occur in iCCA include fibroblast growth factor receptor 2 (FGFR2) gene fusions, isocitrate dehydrogenase (IDH) 1 and 2 mutations, BRAF mutations, and neutrotrophic tyrosine receptor kinase (NTRK) gene fusions. Epigenetic aberrations that occur in iCCA include inactivating mutations of chromatin remodeling genes such as BAP1 and ARIDIA. Additionally, IDH 1/2 mutations lead to the production of oncometabolites with consequent widespread epigenetic changes. IDH inhibitors and FGFR inhibitors have now received FDA approval for IDH mutated and FGFR altered CCA, respectively. Immune checkpoint inhibition has received tissue agnostic FDA approval for mismatch repair deficient/MSI high CCAs. Other targeted therapies such as PARP inhibitors and CDK4/6 inhibitors are under active investigation. Citation Format: Sumera I Ilyas. Molecular Pathogenesis and Cells of Origin of Intrahepatic Cholangiocarcinoma [abstract]. In: Proceedings of the AACR Special Conference: Advances in the Pathogenesis and Molecular Therapies of Liver Cancer; 2022 May 5-8; Boston, MA. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(17_Suppl):Abstract nr IA21.

De novo pyrimidine synthesis is a targetable vulnerability in IDH mutant glioma.

SUMMARYMutations affecting isocitrate dehydrogenase (IDH) enzymes are prevalent in glioma, leukemia, and other cancers. Although mutant IDH inhibitors are effective against leukemia, they seem to be less active in aggressive glioma, underscoring the need for alternative treatment strategies. Through a chemical synthetic lethality screen, we discovered that IDH1-mutant glioma cells are hypersensitive to drugs targeting enzymes in the de novo pyrimidine nucleotide synthesis pathway, including dihydroorotate dehydrogenase (DHODH). We developed a genetically engineered mouse model of mutant IDH1-driven astrocytoma and used it and multiple patient-derived models to show that the brain-penetrant DHODH inhibitor BAY 2402234 displays monotherapy efficacy against IDH-mutant gliomas. Mechanistically, this reflects an obligate dependence of glioma cells on the de novo pyrimidine synthesis pathway and mutant IDH’s ability to sensitize to DNA damage upon nucleotide pool imbalance. Our work outlines a tumor-selective, biomarker-guided therapeutic strategy that is poised for clinical translation.

Resistance to the isocitrate dehydrogenase 1 mutant inhibitor ivosidenib can be overcome by alternative dimer-interface binding inhibitors

Ivosidenib, an inhibitor of isocitrate dehydrogenase 1 (IDH1) R132C and R132H variants, is approved for the treatment of acute myeloid leukaemia (AML). Resistance to ivosidenib due to a second site mutation of IDH1 R132C, leading to IDH1 R132C/S280F, has emerged. We describe biochemical, crystallographic, and cellular studies on the IDH1 R132C/S280F and R132H/S280F variants that inform on the mechanism of second-site resistance, which involves both modulation of inhibitor binding at the IDH1 dimer-interface and alteration of kinetic properties, which enable more efficient 2-HG production relative to IDH1 R132C and IDH1 R132H. Importantly, the biochemical and cellular results demonstrate that it should be possible to overcome S280F mediated resistance in AML patients by using alternative inhibitors, including some presently in phase 2 clinical trials.

P430: MOLECULAR CHARACTERIZATION OF CLINICAL RESPONSE IN NEWLY-DIAGNOSED ACUTE MYELOID LEUKEMIA PATIENTS TREATED WITH IVOSIDENIB + AZACITIDINE COMPARED TO PLACEBO + AZACITIDINE

Background: Acute myeloid leukemia (AML) is a disease with a dynamic mutational landscape; 6–10% of patients (pts) have somatic mutations in isocitrate dehydrogenase 1 (IDH1), which can drive oncogenesis. Ivosidenib (IVO) is a potent oral targeted inhibitor of mutant IDH1 (mIDH1). IVO 500 mg QD + azacitidine (AZA) 75 mg/m2 SC or IV for 7 days in 28-day cycles was shown to significantly improve event-free survival (HR=0.33 [95% CI 0.16, 0.69], p=0.0011), median overall survival (24.0 vs 7.9 months), and complete remission + partial hematologic recovery rates (CR/CRh; 52.8% vs 17.6%) vs placebo + AZA in the double-blind phase 3 AGILE study (NCT03173248) in pts with newly diagnosed IDH1-mutated AML (ND-AML). Aims: To assess the impact of IVO+AZA on IDH1-mutation clearance (IDH1-MC) and baseline co-mutation analysis from AGILE. Methods: Genomic DNA from bone marrow mononuclear cells (BMMCs) or peripheral blood mononuclear cells (PBMCs), and/or bone marrow aspirate (BMA) were used for molecular studies. IDH1-MC analysis on BMMCs was performed by BEAMing digital PCR (limit of detection 0.02%-0.04%). BMA, BMMCs and PBMCs were utilized for co-mutational analysis by next-generation sequencing, ACE Extended Cancer Panel (detection limit 2%). All patients gave written informed consent. Results: 146 pts were randomized: 72 to IVO+AZA; 74 to placebo+AZA. Median (range) baseline mIDH1 variant allele frequency in BMMCs was 36.7% (3.1–50.5%) in the IVO+AZA arm and 35.5% (3.0–48.6%) in the placebo+AZA arm. Updated IDH1-MC data (October 2021) from 47 IVO+AZA and 32 placebo+AZA treated pts with at least 1 on-treatment sample demonstrated IDH1-MC in 21/35 (60%) IVO+AZA pts achieving CR/CRh vs 4/11 (36%) placebo+AZA pts. In CR/CRh pts with time points available after IDH1-MC, suppression of the mIDH1 was durable and IDH1-MC maintained in all subsequent samples in 17/17 (100%) IVO+AZA treated pts and 1/3 (33%) placebo+AZA pts. Further analysis of baseline co-mutations on 120 pts (IVO+AZA: n=58; placebo+AZA: n=62) showed that DNMT3A, SRSF2, and RUNX1 were the most frequent in both treatment arms. Importantly, comparison of CR/CRh and non CR/CRh responses by cohort did not identify any single gene or pathway associated with an inferior outcome in IVO+AZA pts compared to placebo+AZA pts (p<0.05, Fisher’s Exact test). Several genes (DNMT3A, RUNX1, SRSF2, STAG2) and pathways (Differentiation, Epigenetics, Splicing) were associated with improved outcomes with IVO+AZA, including the RTK pathway, which was previously reported to be associated with primary resistance to IVO monotherapy. Further analysis of patient subgroups, including R132 variants (i.e., R132C vs R132S), will be presented. Summary/Conclusion: These data suggest that improved clinical outcomes with IVO+AZA are associated with sustained clearance of the mIDH1 clone including pts with disease that harbor mutations implicated in resistance to IVO monotherapy (e.g., with RTK pathway mutations).

Enasidenib vs conventional care in older patients with late-stage mutant-IDH2 relapsed/refractory AML: a randomized phase 3 trial

AbstractThis open-label, randomized, phase 3 trial (NCT02577406) compared enasidenib, an oral IDH2 (isocitrate dehydrogenase 2) inhibitor, with conventional care regimens (CCRs) in patients aged ≥60 years with late-stage, mutant-IDH2 acute myeloid leukemia (AML) relapsed/refractory (R/R) to 2 or 3 prior AML-directed therapies. Patients were first preselected to a CCR (azacitidine, intermediate-dose cytarabine, low-dose cytarabine, or supportive care) and then randomized (1:1) to enasidenib 100 mg per day or CCR. The primary endpoint was overall survival (OS). Secondary endpoints included event-free survival (EFS), time to treatment failure (TTF), overall response rate (ORR), hematologic improvement (HI), and transfusion independence (TI). Overall, 319 patients were randomized to enasidenib (n = 158) or CCR (n = 161). The median age was 71 years, median (range) enasidenib exposure was 142 days (3 to 1270), and CCR was 36 days (1 to 1166). One enasidenib (0.6%) and 20 CCR (12%) patients received no randomized treatment, and 30% and 43%, respectively, received subsequent AML-directed therapies during follow-up. The median OS with enasidenib vs CCR was 6.5 vs 6.2 months (HR [hazard ratio], 0.86; P = .23); 1-year survival was 37.5% vs 26.1%. Enasidenib meaningfully improved EFS (median, 4.9 vs 2.6 months with CCR; HR, 0.68; P = .008), TTF (median, 4.9 vs 1.9 months; HR, 0.53; P < .001), ORR (40.5% vs 9.9%; P <.001), HI (42.4% vs 11.2%), and red blood cell (RBC)-TI (31.7% vs 9.3%). Enasidenib safety was consistent with prior reports. The primary study endpoint was not met, but OS was confounded by early dropout and subsequent AML-directed therapies. Enasidenib provided meaningful benefits in EFS, TTF, ORR, HI, and RBC-TI in this heavily pretreated older mutant-IDH2 R/R AML population.

The first-in-human phase I study of a brain penetrant mutant IDH1 inhibitor DS-1001 in patients with recurrent or progressive IDH1-mutant gliomas.

Approximately 70% of lower-grade gliomas harbor isocitrate dehydrogenase 1 (IDH1) mutations, resulting in accumulation of oncometabolite D-2-hydroxyglutarate (D-2-HG); this leads to epigenetic dysregulation, oncogenesis, and subsequent clonal expansion. DS-1001 is an oral brain-penetrant mutant IDH1 selective inhibitor. This first-in-human study investigated the safety, pharmacokinetics, pharmacodynamics, and efficacy of DS-1001. This was a multicenter, open-label, dose-escalation, phase I study of DS-1001 for recurrent/progressive IDH1-mutant (R132) glioma (N = 47) (NCT03030066). DS-1001 was administered orally at 125-1400mg twice daily. Dose escalation used a modified continual reassessment method. The maximum tolerated dose was not reached. Eight patients were continuing treatment at the data cut-off. Most adverse events (AEs) were grade 1-2. Twenty patients (42.6%) experienced at least one grade 3 AE. No grade 4 or 5 AEs or serious drug-related AEs were reported. Common AEs (>20%) were skin hyperpigmentation, diarrhea, pruritus, alopecia, arthralgia, nausea, headache, rash, and dry skin. The objective response rates were 17.1% for enhancing tumors and 33.3% for non-enhancing tumors. Median progression-free survival was 10.4 months (95% confidence interval [CI], 6.1 to 17.7 months) and not reached (95% CI, 24.1 to not reached) for the enhancing and non-enhancing glioma cohorts, respectively. Seven on-treatment brain tumor samples showed a significantly lower amount of D-2-HG compared with pre-study archived samples. DS-1001 was well-tolerated with a favorable brain distribution. Recurrent/progressive IDH1-mutant glioma patients responded to treatment. A study of DS-1001 in patients with chemotherapy- and radiotherapy-naïve IDH1-mutated WHO grade 2 glioma is ongoing (NCT04458272).

2-Hydroxyglutarate in Acute Myeloid Leukemia: A Journey from Pathogenesis to Therapies.

The oncometabolite 2-hydroxyglutarate (2-HG) plays a key role in differentiation blockade and metabolic reprogramming of cancer cells. Approximatively 20–30% of acute myeloid leukemia (AML) cases carry mutations in the isocitrate dehydrogenase (IDH) enzymes, leading to a reduction in the Krebs cycle intermediate α-ketoglutarate (α-KG) to 2-HG. Relapse and chemoresistance of AML blasts following initial good response to standard therapy account for the very poor outcome of this pathology, which represents a great challenge for hematologists. The decrease of 2-HG levels through pharmacological inhibition of mutated IDH enzymes induces the differentiation of AML blasts and sensitizes leukemic cells to several anticancer drugs. In this review, we provide an overview of the main genetic mutations in AML, with a focus on IDH mutants and the role of 2-HG in AML pathogenesis. Moreover, we discuss the impact of high levels of 2-HG on the response of AML cells to antileukemic therapies and recent evidence for highly efficient combinations of mutant IDH inhibitors with other drugs for the management of relapsed/refractory (R/R) AML.

Ivosidenib in patients with IDH1-mutant relapsed/refractory myelodysplastic syndrome (R/R MDS): Updated enrollment and results of a phase 1 dose-escalation and expansion substudy.

7053 Background: Mutations in isocitrate dehydrogenase 1 ( IDH1) occur in ̃3% of patients (pts) with MDS and are associated with increased transformation to acute myeloid leukemia (AML). Ivosidenib (IVO), an oral, potent, targeted inhibitor of the mutant IDH1 (mIDH1) enzyme, is FDA approved for m IDH1 R/R AML and m IDH1 newly diagnosed AML in pts ≥75 years old or with comorbidities precluding the use of intensive induction chemotherapy. In the first-in-human study of IVO in pts with m IDH1 advanced hematologic malignancies (NCT02074839), 12 pts with R/R MDS received IVO 500 mg once daily (QD). Based on encouraging safety and efficacy findings, including an investigator-assessed overall response rate (ORR) of 75%, with median response duration of 21.4 months, the FDA granted Breakthrough Therapy designation to IVO in m IDH1 R/R MDS and the study was amended to enroll additional pts. We report updated results. Methods: This substudy of the single-arm, open-label study of IVO evaluated pts with R/R MDS after documented failure or relapse following prior standard therapy including intensive chemotherapy and hypomethylating agents. Other key eligibility criteria included: high disease burden based on IPSS or IPSS-R risk at baseline; an Eastern Cooperative Oncology Group performance status score of 0–2; and no prior IDH1 inhibitor therapy. Pts received IVO 500 mg QD orally on days 1–28 of 28-day cycles. Results: As of 08May2021, 16 pts with R/R MDS were enrolled: 5 (31%) pts remained on treatment and free from leukemic transformation; 11 (69%) had discontinued including 6 for disease progression, 1 for allogeneic stem cell transplantation, and 1 owing to an adverse event (AE) of sepsis (the only fatal AE; reported by investigator as not related to IVO). AEs are summarized in the Table. 2 pts each experienced differentiation syndrome (grade 2) and QTcF prolongation (grade 1 and 2). 7/16 pts achieved complete response (CR, 44%; 95% CI, 20%, 70%), 1 achieved partial response (6%), and 5 achieved marrow CR (31%), resulting in an ORR of 81% (95% CI, 54%, 96%). Hematologic improvement in ≥1 lineages was achieved by 11/16 (69%) pts. The Kaplan-Meier estimate of duration of CR+PR at 12 months was 60%. 3 pts experienced CRs lasting 24.0, 63.7, and 65.4 months, which remain ongoing. 5/7 pts (71%) who were transfusion dependent at baseline became independent of red blood cell or platelet transfusions for 56 or more consecutive days on treatment. Additional translational data are being analyzed. Conclusions: In pts with m IDH1 R/R MDS, IVO monotherapy was tolerable and induced durable remissions and transfusion independence. These findings support the role of IVO as an effective, oral, targeted treatment for pts with m IDH1 R/R MDS. Clinical trial information: NCT02074839. [Table: see text]

Molecular characterization of clinical response in patients with newly diagnosed acute myeloid leukemia treated with ivosidenib + azacitidine compared to placebo + azacitidine.

7019 Background: Acute myeloid leukemia (AML) is a disease with a dynamic mutational landscape; 6–10% of patients (pts) have somatic mutations in isocitrate dehydrogenase 1 ( IDH1), which can drive oncogenesis. Ivosidenib (IVO) is a potent oral targeted inhibitor of mutant IDH1 (mIDH1). IVO 500 mg QD + azacitidine (AZA) 75 mg/m2 SC or IV for 7 days in 28-day cycles was shown to significantly improve event-free survival (HR = 0.33 [95% CI 0.16, 0.69], p = 0.0011), median overall survival (24.0 vs 7.9 months), and complete remission + partial hematologic recovery rates (CR/CRh; 52.8% vs 17.6%) vs placebo (PBO) + AZA in the double-blind phase 3 AGILE study (NCT03173248) in pts with newly diagnosed IDH1-mutated AML (ND-AML). IDH1-mutation clearance ( IDH1-MC) and baseline co-mutation analysis from AGILE is reported. Methods: Genomic DNA from bone marrow mononuclear cells (BMMCs) or peripheral blood mononuclear cells (PBMCs), and/or bone marrow aspirate (BMA) were used for molecular studies. IDH1-MC analysis on BMMCs was performed by BEAMing digital PCR (limit of detection 0.02%-0.04%). BMA, BMMCs and PBMCs were utilized for co-mutational analysis by next-generation sequencing, ACE Extended Cancer Panel (detection limit 2%). Results: 146 pts were randomized: 72 to IVO+AZA; 74 to PBO+AZA. Median (range) baseline m IDH1 variant allele frequency in BMMCs was 36.7% (3.1–50.5) in the IVO+AZA arm and 35.5% (3.0–48.6) in the PBO+AZA arm. Updated IDH1-MC data (October 2021) from 47 IVO+AZA and 32 PBO+AZA treated pts with at least 1 on-treatment sample demonstrated IDH1-MC in 21/35 (60%) IVO+AZA pts achieving CR/CRh vs 4/11 (36%) PBO+AZA pts. In CR/CRh pts with time points available after IDH1-MC, suppression of the m IDH1 was durable and IDH1-MC maintained in all subsequent samples in 17/17 (100%) IVO+AZA treated pts and 1/3 (33%) PBO+AZA pts. Further analysis of baseline co-mutations on 120 pts (IVO+AZA: n = 58; PBO+AZA: n = 62) showed that DNMT3A, SRSF2, and RUNX1 were the most frequent in both treatment arms. Importantly, comparison of CR/CRh and non CR/CRh responses by cohort did not identify any single gene or pathway associated with an inferior outcome in IVO+AZA pts compared to PBO+AZA pts (p &lt; 0.05, Fisher’s Exact test). Several genes ( DNMT3A, RUNX1, SRSF2, STAG2) and pathways (Differentiation, Epigenetics, Splicing) were associated with improved outcomes with IVO+AZA, including the RTK pathway, which was previously reported to be associated with primary resistance to IVO monotherapy. Further analysis of patient subgroups, including R132 variants (i.e., R132C vs R132S), will be presented. Conclusions: These data suggest that improved clinical outcomes with IVO+AZA are associated with sustained clearance of the m IDH1 clone including pts with disease that harbor mutations implicated in resistance to IVO monotherapy (e.g., with RTK pathway mutations). Clinical trial information: NCT03173248.

Molecular and clinical characteristics of IDH mutations in Chinese NSCLC patients and potential treatment strategies.

Isocitrate dehydrogenase (IDH) is an appealing target for anticancer therapy, and IDH (IDH1/2) inhibitors have been approved for targeted therapy of acute myeloid leukemia (AML) and Cholangiocarcinoma. The therapeutic potential of IDH inhibitors for non-small-cell lung cancer (NSCLC) patients is under active clinical investigation. Thus, it would be necessary and meaningful to study the molecular and clinical characteristics of IDH mutation in NSCLC patients, especially in the Chinese population. A total of 17,978 Chinese patients with NSCLC who underwent next -generation sequencing (NGS) testing were retrospectively reviewed. We identified 161 unique IDH mutations in 361 of 17,978 patients (2.01%). Common active-site mutations, including IDH1R100 , IDH1R132 , IDH2R140 , and IDH2R172 , were detected in 154 patients (0.86%) and were associated with male sex (p=0.004) and older age (p=0.02). The IDH mutation spectra observed in NSCLC were quite different from those in glioma or AML. Patients with IDH active-site mutations exhibited significantly higher coalterations in KRAS (p. G12/13/61, 22.1% vs. 8.2%, p < 0.001) or BRAF (p. V600E, 6.5% vs. 1.0%, p < 0.001), but significantly lower coalterations in activating EGFR (e18-e20, 22.7 vs. 37.9%, p < 0.001) than IDH wild-type patients. Furthermore, we found that active-site IDH mutations were correlated with a short PFS (2-5.6 months) and short OS (2-9.5 months), which may arise as a resistance mechanism against common targeted drugs. In vitro, we experimentally observed that the combination of an IDH inhibitor and EGFR TKI could better inhibit lung cancer cell proliferation than an EGFR TKI alone. Taken together, this study reveals the molecular and clinical characteristics of IDH mutations in Chinese NSCLC patients and provides a theoretical basis for IDH-directed treatment. The potential of IDH mutations as response markers for targeted therapy warrants further investigation.

Monitoring of Dynamic Changes and Clonal Evolution in Circulating Tumor DNA From Patients With IDH-Mutated Cholangiocarcinoma Treated With Isocitrate Dehydrogenase Inhibitors.

IDH mutations occur in about 30% of patients with cholangiocarcinoma. Analysis of mutations in circulating tumor DNA (ctDNA) can be performed by droplet digital polymerase chain reaction (ddPCR). The analysis of ctDNA is a feasible approach to detect IDH mutations. We isolated ctDNA from the blood of patients with IDH-mutated advanced cholangiocarcinoma collected at baseline, on therapy, and at progression to isocitrate dehydrogenase (IDH) inhibitors. Of 31 patients with IDH1R132 (n = 26) or IDH2R172 mutations (n = 5) in the tumor, IDH mutations were detected in 84% of ctDNA samples analyzed by ddPCR and in 83% of ctDNA samples analyzed by next-generation sequencing (NGS). Patients with a low variant allele frequency of ctDNA detected by NGS at baseline had a longer median time to treatment failure compared to patients with high variant allele frequency of ctDNA (3.6 v 1.5 months; P = .008). Patients with a decrease in IDH-mutated ctDNA on therapy by ddPCR compared with no change/increase had a trend to a longer median survival (P = .07). Most frequent emergent alterations in ctDNA by NGS at progression were ARID1A (n = 3) and TP53 mutations (n = 3). Detection of IDH mutations in ctDNA in patients with advanced cholangiocarcinoma is feasible, and dynamic changes in ctDNA can correspond with the clinical course and clonal evolution.

Isocitrate Dehydrogenase-Mutated Cholangiocarcinoma: Natural History and Clinical Outcomes.

Clinical-pathologic features and natural history of patients with isocitrate dehydrogenase (IDH)-mutant intrahepatic cholangiocarcinoma (CCA) are not well characterized. Here, we sought to describe the natural history, clinical phenotype, and prognostic impact of advanced, IDH-mutated CCA. We conducted a multicentric, retrospective analysis of patients with IDH-mutated (IDH1 or IDH2) CCA between 2010 and 2020. Median overall survival (OS) and progression-free survival (PFS) analyses were performed using the Kaplan-Meier method. Chi-square test was used to analyze disease control rate (DCR) and overall response rate (ORR). Matched controls were used for comparing survival between patients with and without IDH mutations (mIDH). Sixty-five patients with IDH-mutated CCA were included. All patients had intrahepatic CCA. On first-line chemotherapy, median OS and median PFS were 21.2 months and 8.3 months, respectively. Notably, median OS (32.4 v 19.5 months, P = .12) and PFS (18.0 v 8.0 months, P = .12) were not significantly affected by disease status at presentation (locally advanced v metastatic, respectively). Median OS was significantly longer in patients with mIDH (21.2 v 10.5 months; P < .01). First-line gemcitabine-containing regimens had a significantly higher DCR and ORR than non-gemcitabine-containing regimens (DCR: 75% v 33%, P = .01; ORR: 39% v 0%, P = .02). In patients receiving IDH inhibitor therapy, median PFS was 4.6 months with a DCR of 29%. CCA with mIDH confers a unique subtype resulting in a better survival compared with that of counterparts. IDH inhibitors represent a promising therapeutic option in later lines of therapy in this subgroup.

Inhibition of D-2HG leads to upregulation of a proinflammatory gene signature in a novel HLA-A2/HLA-DR1 transgenic mouse model of IDH1R132H-expressing glioma

BackgroundLong-term prognosis of WHO grade II, isocitrate dehydrogenase (IDH)-mutated low-grade glioma (LGG) is poor due to high risks of recurrence and malignant transformation into high-grade glioma. Immunotherapy strategies are attractive...

Clinical usefulness of 2-hydroxyglutarate as a biomarker in IDH-mutant chondrosarcoma

BackgroundChondrosarcoma is a common form of malignant bone tumor with limited treatment options. Approximately half of chondrosarcomas harbor gain-of-function mutations in isocitrate dehydrogenase (IDH), and mutant IDH produces 2-hydroxyglutarate (2-HG), which is an oncometabolite that contributes to malignant transformation. Therefore, inhibiting 2-HG production is a novel and promising treatment for advanced chondrosarcoma. 2-HG is also expected to be a useful biomarker for the diagnosis and treatment of IDH-mutant tumors. However, few studies have confirmed this using chondrosarcoma clinical specimens. Non-invasive monitoring of 2-HG levels is useful to infer that mutant IDH inhibitors reach therapeutic targets and to confirm their therapeutic efficacy in clinical practice. MethodsTo evaluate the clinical utility of 2-HG as a surrogate biomarker for diagnosis and therapeutic efficacy, we measured intra-tumor and serum levels of 2-HG using frozen tissues and peripheral blood from patients with chondrosarcoma. We also developed a non-invasive method to detect intra-tumor 2-HG signals in vivo using magnetic resonance spectroscopy (MRS) ResultsBoth intratumoral and serum 2-HG levels were significantly elevated in IDH-mutant tumors, and these levels correlated with decreased survival. Furthermore, we detected intratumoral 2-HG peaks using MR spectroscopy in a xenograft model of IDH-mutant chondrosarcoma, and observed that 2-HG peak signals disappeared after administering an inhibitor of mutant IDH1. ConclusionsOur findings suggest that both intratumoral and serum 2-HG levels represent potentially useful biomarkers for IDH-mutant tumors and that the 2-HG signal in MR spectra has potential value as a non-invasive biomarker. Taken together, these findings may positively impact the clinical development of mutant IDH inhibitors for the treatment of advanced chondrosarcoma.