Recent Progress in the Discovery of Allosteric Inhibitors of Kidney-Type Glutaminase

Glycogenesis and glyconeogenesis from glutamine, lactate and glycerol support human macrophage functions

Macrophages fight infection and ensure tissue repair, often operating at nutrient-poor wound sites. We investigated the ability of human macrophages to metabolize glycogen. We observed that the cytokines GM-CSF and M-CSF plus IL-4 induced glycogenesis and the accumulation of glycogen by monocyte-derived macrophages. Glyconeogenesis occurs in cells cultured in the presence of the inflammatory cytokines GM-CSF and IFNγ (M1 cells), via phosphoenolpyruvate carboxykinase 2 (PCK2) and fructose-1,6-bisphosphatase 1 (FBP1). Enzyme inhibition with drugs or gene silencing techniques and 13C-tracing demonstrate that glutamine (metabolized by the TCA cycle), lactic acid, and glycerol were substrates of glyconeogenesis only in M1 cells. Tumor-associated macrophages (TAMs) also store glycogen and can perform glyconeogenesis. Finally, macrophage glycogenolysis and the pentose phosphate pathway (PPP) support cytokine secretion and phagocytosis regardless of the availability of extracellular glucose. Thus, glycogen metabolism supports the functions of human M1 and M2 cells, with inflammatory M1 cells displaying a possible dependence on glyconeogenesis.

Cellular metabolism: A key player in cancer ferroptosis

Cellular metabolism is the fundamental process by which cells maintain growth and self-renewal. It produces energy, furnishes raw materials, and intermediates for biomolecule synthesis, and modulates enzyme activity to sustain normal cellular functions. Cellular metabolism is the foundation of cellular life processes and plays a regulatory role in various biological functions, including programmed cell death. Ferroptosis is a recently discovered form of iron-dependent programmed cell death. The inhibition of ferroptosis plays a crucial role in tumorigenesis and tumor progression. However, the role of cellular metabolism, particularly glucose and amino acid metabolism, in cancer ferroptosis is not well understood. Here, we reviewed glucose, lipid, amino acid, iron and selenium metabolism involvement in cancer cell ferroptosis to elucidate the impact of different metabolic pathways on this process. Additionally, we provided a detailed overview of agents used to induce cancer ferroptosis. We explained that the metabolism of tumor cells plays a crucial role in maintaining intracellular redox homeostasis and that disrupting the normal metabolic processes in these cells renders them more susceptible to iron-induced cell death, resulting in enhanced tumor cell killing. The combination of ferroptosis inducers and cellular metabolism inhibitors may be a novel approach to future cancer therapy and an important strategy to advance the development of treatments.

Synthesis of 1,3,4-Thiadiazole Derivatives and Their Anticancer Evaluation

Thiadiazole derivatives have garnered significant attention in the field of medicinal chemistry due to their diverse pharmacological activities, including anticancer properties. This article presents the synthesis of a series of thiadiazole derivatives and investigates their chemical characterization and potential anticancer effects on various cell lines. The results of the nuclear magnetic resonance (NMR) analyses confirmed the successful formation of the target compounds. The anticancer potential was evaluated through in silico and in vitro cell-based assays using LoVo and MCF-7 cancer lines. The assays included cell viability, proliferation, apoptosis, and cell cycle analysis to assess the compounds' effects on cancer cell growth and survival. Daphnia magna was used as an invertebrate model for the toxicity evaluation of the compounds. The results revealed promising anticancer activity for several of the synthesized derivatives, suggesting their potential as lead compounds for further drug development. The novel compound 2g, 5-[2-(benzenesulfonylmethyl)phenyl]-1,3,4-thiadiazol-2-amine, demonstrated good anti-proliferative effects, exhibiting an IC50 value of 2.44 µM against LoVo and 23.29 µM against MCF-7 after a 48-h incubation and little toxic effects in the Daphnia test.

Biomolecular condensates in kidney physiology and disease

The regulation and preservation of distinct intracellular and extracellular solute microenvironments is crucial for the maintenance of cellular homeostasis. In mammals, the kidneys control bodily salt and water homeostasis. Specifically, the urine-concentrating mechanism within the renal medulla causes fluctuations in extracellular osmolarity, which enables cells of the kidney to either conserve or eliminate water and electrolytes, depending on the balance between intake and loss. However, relatively little is known about the subcellular and molecular changes caused by such osmotic stresses. Advances have shown that many cells, including those of the kidney, rapidly (within seconds) and reversibly (within minutes) assemble membraneless, nano-to-microscale subcellular assemblies termed biomolecular condensates via the biophysical process of hyperosmotic phase separation (HOPS). Mechanistically, osmotic cell compression mediates changes in intracellular hydration, concentration and molecular crowding, rendering HOPS one of many related phase-separation phenomena. Osmotic stress causes numerous homo-multimeric proteins to condense, thereby affecting gene expression and cell survival. HOPS rapidly regulates specific cellular biochemical processes before appropriate protective or corrective action by broader stress response mechanisms can be initiated. Here, we broadly survey emerging evidence for, and the impact of, biomolecular condensates in nephrology, where initial concentration buffering by HOPS and its subsequent cellular escalation mechanisms are expected to have important implications for kidney physiology and disease.

Kidney-type glutaminase is a biomarker for the diagnosis and prognosis of hepatocellular carcinoma: a prospective study

PURPOSE

The pathological diagnosis and prognosis prediction of hepatocellular carcinoma (HCC) is challenging due to the lack of specific biomarkers. This study aimed to validate the diagnostic and prognostic efficiency of Kidney-type glutaminase (GLS1) for HCC in prospective cohorts with a large sample size.

METHODS

A total of 1140 HCC patients were enrolled in our prospective clinical trials. Control cases included 114 nontumour tissues. The registered clinical trial (ChiCTR-DDT-14,005,102, chictr.org.cn) was referred to for the exact protocol. GLS1 immunohistochemistry was performed on the whole tumour section. The diagnostic and prognostic performances of GLS1 was evaluated by the receiver operating characteristic curve and Cox regression model.

RESULTS

The sensitivity, specificity, positive predictive value, negative predictive value, Youden index, and area under the curve of GLS1 for the diagnosis of HCC were 0.746, 0.842, 0.979, 0.249, 0.588, and 0.814, respectively, which could be increased to 0.846, 0.886, 0.987,0.366, 0.732, and 0.921 when combined with glypican 3 (GPC3) and alpha-fetoprotein (AFP), indicating better diagnostic performance. Further, we developed a nomogram with GPC3 and GLS1 for identifying HCC which showed good discrimination and calibration. GLS1 expression was also related with age, T stage, TNM stage, Edmondson-Steiner grade, microvascular invasion, Ki67, VEGFR2, GPC3, and AFP expression in HCC. GLS1 expression was negatively correlated with disease-free survival (P < 0.001) probability of patients with HCC.

CONCLUSIONS

It was validated that GLS1 was a sensitive and specific biomarker for pathological diagnosis of HCC and had prognostic value, thus having practical value for clinical application.

Enhancing the affinity of novel GLS1 allosteric inhibitors by targeting key residue Lys320

Aim: A series of novel GLS1 irreversible allosteric inhibitors targeting Lys320 might have robust enzyme inhibitory activity and potent antitumor activity. Materials & methods: Novel GLS1 allosteric inhibitors targeting Lys320 were synthesized and their anticancer activity was assessed. Moreover, GLS1 protein was used as a model system to analyze the reactivity of these electrophilic groups in GLS1 irreversible allosteric inhibitors with other amino acids, including tyrosine, histidine, serine and threonine, using biochemical and biophysical assays. Results: AC16 exhibited robust GLS1 inhibitory activity, antiproliferative effect in vitro, good plasma stability and potential covalent addition with GLS1 K320. Conclusion: This study opens a novel avenue for the design of robust irreversible GLS1 inhibitors targeting the allosteric site K320.

Diselenide Covalent Allosteric Inhibitors of Glutaminase with Strong In Vivo Anticancer Activity

Allosteric glutaminase inhibitors demonstrate inhibition of glutamine-dependent cancer cells with low general drug toxicity, but have issues with efficacy in vivo. Here, we designed a series of diselenide compounds with 6 atoms in the middle, aiming to target the allosteric site of kidney type glutaminase (KGA) with a covalent linkage to strengthen the interaction. Proteomic analysis demonstrated that the diselenide compounds cross-linked with the Lys320 residue at the KGA allosteric site; this was confirmed by the KGA K320A mutant which showed essentially no binding to the diselenide. Further, structure-activity relationship (SAR) analysis demonstrated that growth inhibition correlated well with KGA inhibition and was enhanced by thioredoxin reductase (TrxR) inhibition. Interestingly, diselenide compounds showed no inhibition of glutamate dehydrogenase (GDH), indicating some enzyme selectivity. Importantly, the designed novel diselenides are glutaminase allosteric inhibitors that showed in vivo efficacy and survival in the xenograft animal model.

Targeting glutaminase 1 (GLS1) by small molecules for anticancer therapeutics

Glutaminase-1 (GLS1) is a critical enzyme involved in several cellular processes, and its overexpression has been linked to the development and progression of cancer. Based on existing research, GLS1 plays a crucial role in the metabolic activities of cancer cells, promoting rapid proliferation, cell survival, and immune evasion. Therefore, targeting GLS1 has been proposed as a promising cancer therapy strategy, with several GLS1 inhibitors currently under development. To date, several GLS1 inhibitors have been identified, which can be broadly classified into two types: active site and allosteric inhibitors. Despite their pre-clinical effectiveness, only a few number of these inhibitors have advanced to initial clinical trials. Hence, the present medical research emphasizes the need for developing small molecule inhibitors of GLS1 possessing significantly high potency and selectivity. In this manuscript, we aim to summarize the regulatory role of GLS1 in physiological and pathophysiological processes. We also provide a comprehensive overview of the development of GLS1 inhibitors, focusing on multiple aspects such as target selectivity, in vitro and in vivo potency and structure-activity relationships.

The pyridazine heterocycle in molecular recognition and drug discovery

The pyridazine ring is endowed with unique physicochemical properties, characterized by weak basicity, a high dipole moment that subtends π-π stacking interactions and robust, dual hydrogen-bonding capacity that can be of importance in drug-target interactions. These properties contribute to unique applications in molecular recognition while the inherent polarity, low cytochrome P450 inhibitory effects and potential to reduce interaction of a molecule with the cardiac hERG potassium channel add additional value in drug discovery and development. The recent approvals of the gonadotropin-releasing hormone receptor antagonist relugolix (24) and the allosteric tyrosine kinase 2 inhibitor deucravacitinib (25) represent the first examples of FDA-approved drugs that incorporate a pyridazine ring. In this review, the properties of the pyridazine ring are summarized in comparison to the other azines and its potential in drug discovery is illustrated through vignettes that explore applications that take advantage of the inherent physicochemical properties as an approach to solving challenges associated with candidate optimization.

Graphical Abstract

Methanodibenzo[b,f][1,5]dioxocins as Novel Glutaminase Inhibitor with Anti-Glioblastoma Potential

Glutamine metabolism is an important hallmark of several cancers with demonstrated antitumor activity in glioblastoma cancer cells (GBM). GBM cells regulate glutamine and use it as a major energy source for their proliferation through the glutaminolysis process. Enzymes, such as glutaminase in glutaminolysis, can be targeted by small-molecule inhibitors, thus exhibiting promising anticancer properties. The resistance to glutaminolysis demands the development of new therapeutic molecules to overcome drug resistance. Herein, we have reported a novel library of constrained methanodibenzo[b,f][1,5]dioxocin derivatives as glutaminase (GLS) inhibitors and their anti-GBM potential. The library consisting of seven molecules was obtained through self-condensation of 2'-hydroxyacetophenones, out of which three molecules, namely compounds 3, 5, and 6, were identified with higher binding energy values ranging between -10.2 and -9.8 kcal/mol with GLS (PDB ID; 4O7D). Pharmacological validation of these compounds also showed a higher growth inhibition effect in GBM cells than the standard drug temozolomide (TMZ). The most promising compound, 6, obeyed Lipinski's rule of five and was identified to interact with key residues Arg³⁰⁷, Asp³²⁶, Lys³²⁸, Lys³⁹⁹, and Glu⁴⁰³ of GLS. This compound exhibited the best cytotoxic effect with IC₅₀ values of 63 µM and 83 µM in LN229 and SNB19 cells, respectively. The potential activation of GLS by the best-constrained dibenzo[b,f][1,5]dioxocin in the tested series increased apoptosis via reactive oxygen species production in both GBM cells, and exhibited anti-migratory and anti-proliferative properties over time in both cell lines. Our results highlight the activation mechanism of a dibenzo[b,f][1,5]dioxocin from the structural basis and demonstrate that inhibition of glutaminolysis may facilitate the pharmacological intervention for GBM treatment.

Design, synthesis, and biological evaluation of novel glutaminase 1 allosteric inhibitors with an alkane chain tail group

Tumor cells often exhibit metabolic reprogramming to maintain their rapid growth and proliferation. Glutaminase 1 (GLS1) has been viewed as a promising target in the glutamine metabolism pathway for the treatment of malignant tumors. Using structure-based drug design approaches, a novel series of GLS1 allosteric inhibitors were designed and synthesized. Compound 41a (LWG-301) with an alkane chain "tail" group had potent biochemical and cellular GLS1 activity, and improved metabolic stability. LWG-301 exhibited moderate antitumor effects in HCT116 xenograft model, with TGI of 38.9% in vivo. Mechanistically, LWG-301 could significantly block glutamine metabolism, resulting in changes in the corresponding amino acid levels in cells, induce a concentration-dependent increase in intracellular ROS levels, and induce apoptosis. Taken together, this paper provides more structural references and new design strategy for the development of GLS1 allosteric inhibitors.

An updated patent review of glutaminase inhibitors (2019-2022)

INTRODUCTION

Kidney-type glutaminase (GLS1), a key enzyme controlling the hydrolysis of glutamine to glutamate to resolve the 'glutamine addiction' of cancer cells, has been shown to play a central role in supporting cancer growth and proliferation. Therefore, the inhibition of GLS1 as a novel cancer treating strategy is of great interest.

AREAS COVERED

This review covers recent patents (2019-present) involving GLS1 inhibitors, which are mostly focused on their chemical structures, molecular mechanisms of action, pharmacokinetic properties, and potential clinical applications.

EXPERT OPINION

Currently, despite significant efforts, the search for potent GLS1 inhibitors has not resulted in the development of compounds for therapeutic applications. Most recent patents and literature focus on GLS1 inhibitors IPN60090 and DRP104, which have entered clinical trials. While other patent disclosures during this period have not generated any drug candidates, the clinical update will inform the potential of these inhibitors as promising therapeutic agents either as single or as combination interventions.

Novel Allosteric Glutaminase 1 Inhibitors with Macrocyclic Structure Activity Relationship Analysis

Glutamine-addicted cancer metabolism is recently recognized as novel cancer target especially for KRAS and KEAP1 co-occurring mutations. Selective glutaminase1 (GLS1) inhibition was reported using BPTES which has novel mode of allosteric inhibition. However, BPTES is a highly hydrophobic and symmetric molecule with very poor solubility which results in suboptimal pharmacokinetic parameters and hinders its further development. As an ongoing effort to identify more drug-like GLS1 inhibitors via systematic structure-activity relationship (SAR) analysis of BPTES analogs, we disclose our novel macrocycles for GLS1 inhibition with conclusive SAR analysis on the core, core linker, and wing linker, respectively. Selected molecules resulted in reduction in intracellular glutamate levels in LR (LDK378-resistant) cells which is consistent to cell viability result. Finally, compounds 13 selectively reduced the growth of A549 and H460 cells which have co-occurring mutations including KRAS and KEAP1.

Metabolic intervention liposome for targeting glutamine-addiction of breast cancer

The growth and rapid proliferation of tumor cells depend on both glycolysis and glutamine metabolism, leading to metabolic compensation. Here, dual inhibition on the metabolic plasticity by Glucose oxidase and Telaglenastat loaded liposome (Lip@GOx&Tel) were studied for intervening metabolic pathway on energy and material against breast cancer. Lip@GOx&Tel targeting inhibited the two nutrient supply mechanisms employed by tumor cells, reducing the supply of ATP production and biosynthesis precursors essential necessary for tumor, thereby eliciting anti-tumor and anti-metastasis effect. Meanwhile, Lip@GOx&Tel ingeniously amplify the therapeutic effect by up-regulating ROS and down-regulating GSH to disrupt redox homeostasis, thus resulting in inspiring 82% tumor suppression rate on 4 T1 tumor model. Moreover, our study solved the limitation of combination between protein drugs and small molecule drugs in vivo by using liposome nanoparticles with clinical translation value. In short, this work provides a unique perspective of nanomedicine for treating diseases from metabolic intervention.

An Insight into the Medicinal Chemistry Perspective of Macrocyclic Derivatives with Antitumor Activity: A Systematic Review

The profound pharmacological properties of macrocyclic compounds have led to their development as drugs. In conformationally pre-organized ring structures, the multiple functions and stereochemical complexity provided by the macrocycle result in high affinity and selectivity of protein targets while maintaining sufficient bioavailability to reach intracellular locations. Therefore, the construction of macrocycles is an ideal choice to solve the problem of “undruggable” targets. Inspection of 68 macrocyclic drugs on the market showed that 10 of them were used to treat cancer, but this structural class still has been poorly explored within drug discovery. This perspective considers the macrocyclic compounds used for anti-tumor with different targets, their advantages and disadvantages, and the various synthetic methods of them.

Ginsenoside Rk1 regulates glutamine metabolism in hepatocellular carcinoma through inhibition of the ERK/c-Myc pathway

Hepatocellular carcinoma (HCC) is one of the most prevalent and deadly cancers in the world. Recently, suppression of glutamine metabolism has become one of the hottest therapy targets for cancer treatment. There is a growing amount of research that indicates that ginsenosides possess good anti-tumor activity. However, the effect of ginsenoside Rk1 on glutamine metabolism in HCC is unclear. In this study, Rk1 was demonstrated to be effective at inhibiting the proliferation of HCC through the induction of cell cycle arrest and apoptosis. Especially, Rk1 was shown for the first time to inhibit glutamine metabolism in HCC. Rk1 downregulates GLS1 expression, and consequently decreases the GSH production, stimulating ROS accumulation to induce apoptosis. In addition, transcriptomic results showed that the ERK/c-Myc signaling pathway was enriched in HepG2. Rk1 exerts an inhibitory effect on glutamine metabolism in HCC by regulating the ERK/c-Myc signaling pathway, and inducing apoptosis in vitro and in vivo with less toxicity. Therefore, ginsenoside Rk1 could be a promising candidate for the clinical treatment of HCC.

Prognostic value of glutaminase 1 in breast cancer depends on H3K27me3 expression and menopausal status

Glutaminase 1 (GLS) is a therapeutic target for breast cancer; although GLS inhibitors have been developed, only a few subjects responded well to the therapy. Considering that the expression of histone H3 lysine 27 trimethylation (H3K27me3) and menopausal status was closely linked to GLS, we examined the effects of H3K27me3 and menopausal status on GLS to breast cancer prognosis. Data for 962 women diagnosed with primary invasive breast cancer were analyzed. H3K27me3 and GLS expression in tumors were evaluated with tissue microarrays by immunohistochemistry. Hazard ratios (HRs) and their 95% confidence intervals (CIs) for overall survival and progression-free survival were estimated using Cox regression models. Statistical interaction was assessed on multiplicative scale. There was a beneficial prognostic effect of GLS expression on overall survival for those with low H3K27me3 level (HR = 0.50, 95% CI: 0.20-1.28) but an adverse prognostic effect for those with high H3K27me3 level (HR = 3.90, 95% CI: 1.29-11.78) among premenopausal women, and the statistical interaction was significant (P_interaction = 0.003). Similar pattern was further observed for progression-free survival (HR = 0.44, 95% CI: 0.20-0.95 for low H3K27me3 level, HR = 1.35, 95% CI: 0.74-2.48 for high H3K27me3 level, P_interaction = 0.024). The statistical interaction did not occur among postmenopausal women. Our study showed that the prognostic effects of GLS on breast cancer correlated to the expression level of H3K27me3 and menopausal status, which would help optimize the medication strategies of GLS inhibitors.

Structure-Enabled Discovery of Novel Macrocyclic Inhibitors Targeting Glutaminase 1 Allosteric Binding Site

The inhibition of glutaminase 1 (GLS1) represents a potential treatment of malignant tumors. Structural analysis led to the design of a novel series of macrocyclic GLS1 allosteric inhibitors. Through extensive structure-activity relationship studies, a promising candidate molecule 13b (LL202) was identified with robust GLS1 inhibitory activity (IC₅₀ = 6 nM) and high GLS1 binding affinity (SPR, K_d = 24 nM; ITC, K_d = 37 nM). The X-ray crystal structure of the 13b-GLS1 complex was resolved, revealing a unique binding mode and providing a novel structural scaffold for GLS1 allosteric inhibitors. Importantly, 13b clearly adjusted the cellular metabolites and induced an increase in the ROS level by blocking glutamine metabolism. Furthermore, 13b exhibited a similar in vivo antitumor activity as CB839. This study adds to the growing body of evidence that macrocyclization provides an alternative and complementary approach for the design of small-molecule inhibitors, with the potential to improve the binding affinity to the targets.

Host cell glutamine metabolism as a potential antiviral target

A virus minimally contains a nucleic acid genome packaged by a protein coat. The genome and capsid together are known as the nucleocapsid, which has an envelope containing a lipid bilayer (mainly phospholipids) originating from host cell membranes. The viral envelope has transmembrane proteins that are usually glycoproteins. The proteins in the envelope bind to host cell receptors, promoting membrane fusion and viral entry into the cell. Virus-infected host cells exhibit marked increases in glutamine utilization and metabolism. Glutamine metabolism generates ATP and precursors for the synthesis of macromolecules to assemble progeny viruses. Some compounds derived from glutamine are used in the synthesis of purines and pyrimidines. These latter compounds are precursors for the synthesis of nucleotides. Inhibitors of glutamine transport and metabolism are potential candidate antiviral drugs. Glutamine is also an essential nutrient for the functions of leukocytes (lymphocyte, macrophage, and neutrophil), including those in virus-infected patients. The increased glutamine requirement for immune cell functions occurs concomitantly with the high glutamine utilization by host cells in virus-infected patients. The development of antiviral drugs that target glutamine metabolism must then be specifically directed at virus-infected host cells to avoid negative effects on immune functions. Therefore, the aim of this review was to describe the landscape of cellular glutamine metabolism to search for potential candidates to inhibit glutamine transport or glutamine metabolism.

Targeting the Proline-Glutamine-Asparagine-Arginine Metabolic Axis in Amino Acid Starvation Cancer Therapy

Proline, glutamine, asparagine, and arginine are conditionally non-essential amino acids that can be produced in our body. However, they are essential for the growth of highly proliferative cells such as cancers. Many cancers express reduced levels of these amino acids and thus require import from the environment. Meanwhile, the biosynthesis of these amino acids is inter-connected but can be intervened individually through the inhibition of key enzymes of the biosynthesis of these amino acids, resulting in amino acid starvation and cell death. Amino acid starvation strategies have been in various stages of clinical applications. Targeting asparagine using asparaginase has been approved for treating acute lymphoblastic leukemia. Targeting glutamine and arginine starvations are in various stages of clinical trials, and targeting proline starvation is in preclinical development. The most important obstacle of these therapies is drug resistance, which is mostly due to reactivation of the key enzymes involved in biosynthesis of the targeted amino acids and reprogramming of compensatory survival pathways via transcriptional, epigenetic, and post-translational mechanisms. Here, we review the interactive regulatory mechanisms that control cellular levels of these amino acids for amino acid starvation therapy and how drug resistance is evolved underlying treatment failure.

Metabolic Reprogramming of Cancer by Chemicals that Target Glutaminase Isoenzymes

BACKGROUND

Metabolic reprogramming of tumours is a hallmark of cancer. Among the changes in the metabolic network of cancer cells, glutaminolysis is a key reaction altered in neoplasms. Glutaminase proteins control the first step in glutamine metabolism and their expression correlates with malignancy and growth rate of a great variety of cancers. The two types of glutaminase isoenzymes, GLS and GLS2, differ in their expression patterns and functional roles: GLS has oncogenic properties and GLS2 has been described as a tumour suppressor factor.

RESULTS

We have focused on glutaminase connections with key oncogenes and tumour suppressor genes. Targeting glutaminase isoenzymes includes different strategies aimed at deactivating the rewiring of cancer metabolism. In addition, we found a long list of metabolic enzymes, transcription factors and signalling pathways dealing with glutaminase. On the other hand, a number of chemicals have been described as isoenzyme-specific inhibitors of GLS and/or GLS2 isoforms. These molecules are being characterized as synergic and therapeutic agents in many types of tumours.

CONCLUSION

This review states the metabolic pathways that are rewired in cancer, the roles of glutaminase isoforms in cancer, as well as the metabolic circuits regulated by glutaminases. We also show the plethora of anticancer drugs that specifically inhibit glutaminase isoenzymes for treating several sets of cancer.

Discovery of IPN60090, a Clinical Stage Selective Glutaminase-1 (GLS-1) Inhibitor with Excellent Pharmacokinetic and Physicochemical Properties

Inhibition of glutaminase-1 (GLS-1) hampers the proliferation of tumor cells reliant on glutamine. Known glutaminase inhibitors have potential limitations, and in vivo exposures are potentially limited due to poor physicochemical properties. We initiated a GLS-1 inhibitor discovery program focused on optimizing physicochemical and pharmacokinetic properties, and have developed a new selective inhibitor, compound 27 (IPN60090), which is currently in phase 1 clinical trials. Compound 27 attains high oral exposures in preclinical species, with strong in vivo target engagement, and should robustly inhibit glutaminase in humans.

Thiadiazole derivatives as anticancer agents

In spite of substantial progress made toward understanding cancer pathogenesis, this disease remains one of the leading causes of mortality. Thus, there is an urgent need to develop novel, more effective anticancer therapeutics. Thiadiazole ring is a versatile scaffold widely studied in medicinal chemistry. Mesoionic character of this ring allows thiadiazole-containing compounds to cross cellular membrane and interact strongly with biological targets. Consequently, these compounds exert a broad spectrum of biological activities. This review presents the current state of knowledge on thiadiazole derivatives that demonstrate in vitro and/or in vivo efficacy across the cancer models with an emphasis on targets of action. The influence of the substituent on the compounds' activity is depicted. Furthermore, the results from clinical trials assessing thiadiazole-containing drugs in cancer patients are summarized.

Allosteric kidney-type glutaminase (GLS) inhibitors with a mercaptoethyl linker

A series of allosteric kidney-type glutaminase (GLS) inhibitors possessing a mercaptoethyl (SCH₂CH₂) linker were synthesized in an effort to further expand the structural diversity of chemotypes derived from bis-2-(5-phenylacetamido-1,3,4-thiadiazol-2-yl)ethyl sulfide (BPTES), a prototype allosteric inhibitor of GLS. BPTES analog 3a with a mercaptoethyl linker between the two thiadiazole rings was found to potently inhibit GLS with an IC₅₀ value of 50 nM. Interestingly, the corresponding derivative with an n-propyl (CH₂CH₂CH₂) linker showed substantially lower inhibitory potency (IC₅₀ = 2.3 μM) while the derivative with a dimethylsulfide (CH₂SCH₂) linker showed no inhibitory activity at concentrations up to 100 μM, underscoring the critical role played by the mercaptoethyl linker in the high affinity binding to the allosteric site of GLS. Additional mercaptoethyl-linked compounds were synthesized and tested as GLS inhibitors to further explore SAR within this scaffold including derivatives possessing a pyridazine as a replacement for one of the two thiadiazole moiety.

BPTES inhibits anthrax lethal toxin-induced inflammatory response

Bacillus anthracis is a lethal agent of anthrax disease and the toxins are required in anthrax pathogenesis. The anthrax lethal toxin can trigger NLRP1b inflammasome activation and pyroptosis. Although the underlying mechanism is well understood, the medications targeting the NLRP1b inflammasome are not available in the clinic. Herein, we describe that BPTES, a known Glutaminase (GLS) inhibitor, is an effective NLRP1b inflammasome inhibitor. BPTES could effectively and specifically suppress NLRP1b inflammasome activation in macrophages but have no effects on NLRP3, NLRC4 and AIM2 inflammasome activation. Mechanistically, BPTES alleviated the UBR2 mediated proteasomal degradation pathway of the NLRP1b N terminus, thus blocking the release of the CARD domain for subsequent caspase-1 processing. Furthermore, BPTES could prevent disease progression in mice challenged with the anthrax lethal toxin. Taken together, our studies indicate that BPTES can be a promising pharmacological inhibitor to treat anthrax lethal toxin-related inflammatory diseases.

Catalytic Approaches for the Direct Heterofunctionalization of Aliphatic Carboxylic Acids and Their Equivalents with Group 16 Elements

In contrast to traditional multistep synthesis, modern organic synthesis extensively depends on the direct functionalization of unactivated C-H bonds for the construction of various C-C and C-heteroatom bonds in atom- and step-economic manner. Common aliphatic substrates, e. g. carboxylic acids and their synthetic equivalents, are regiospecifically functionalized based on either a directed approach, in which the polar directing group assists to functionalize a specific C-H bond positioned at β- and γ-carbon centers, or a non-directed approach typically leading to α-functionalization. While numerous reviews on catalytic C-H functionalization have appeared, a concise review on the direct C(sp³ )-H heterofunctionalization of carboxylic acid synthons with Group 16 elements has been awaited. The recent advances on the direct oxy-functionalization and chalcogenation of aliphatic carboxylic acid synthons enabled by transition metal, organo- and photocatalysts are described herein.

PdII-Catalyzed methoxylation of C(sp3)-H bonds adjacent to benzoxazoles and benzothiazoles

The Pd(OAc)2/PhI(OAc)2 catalyst system promotes the highly regioselective dehydrogenative methoxylation of a C(sp3)-H bond adjacent to benzoxazole and benzothiazole rings. The title transformation constitutes the first example of a Pd-catalyzed C(sp3)-H activating methoxylation at the proximal-selective α-position with regard to a directing auxiliary and provides expedient access to an important class of azole-decorated methyl ethers (up to 90% isolated yield). The synthetic practicality of the methodology was demonstrated by achieving α-methoxyacetic acids via the elimination of the benzoxazole auxiliaries and by obtaining the precursor of an O-methylated Breslow intermediate.

The Emerging Role of l-Glutamine in Cardiovascular Health and Disease

Emerging evidence indicates that l-glutamine (Gln) plays a fundamental role in cardiovascular physiology and pathology. By serving as a substrate for the synthesis of DNA, ATP, proteins, and lipids, Gln drives critical processes in vascular cells, including proliferation, migration, apoptosis, senescence, and extracellular matrix deposition. Furthermore, Gln exerts potent antioxidant and anti-inflammatory effects in the circulation by inducing the expression of heme oxygenase-1, heat shock proteins, and glutathione. Gln also promotes cardiovascular health by serving as an l-arginine precursor to optimize nitric oxide synthesis. Importantly, Gln mitigates numerous risk factors for cardiovascular disease, such as hypertension, hyperlipidemia, glucose intolerance, obesity, and diabetes. Many studies demonstrate that Gln supplementation protects against cardiometabolic disease, ischemia-reperfusion injury, sickle cell disease, cardiac injury by inimical stimuli, and may be beneficial in patients with heart failure. However, excessive shunting of Gln to the Krebs cycle can precipitate aberrant angiogenic responses and the development of pulmonary arterial hypertension. In these instances, therapeutic targeting of the enzymes involved in glutaminolysis such as glutaminase-1, Gln synthetase, glutamate dehydrogenase, and amino acid transaminase has shown promise in preclinical models. Future translation studies employing Gln delivery approaches and/or glutaminolysis inhibitors will determine the success of targeting Gln in cardiovascular disease.

GAC inhibitors with a 4-hydroxypiperidine spacer: Requirements for potency

Allosteric inhibitors of glutaminase (GAC), such as BPTES, CB-839 and UPGL00019, have great promise as inhibitors of cancer cell growth, but potent inhibitors with drug-like qualities have been difficult to achieve. Here, a small library of GAC inhibitors based on the UPGL00019 core is described. This set of derivatives was designed to assess if one or both of the phenylacetyl groups flanking the UPGL00019 core can be replaced by smaller simple aliphatic acyl groups without loss in potency. We found that one of the phenylacetyl moieties can be replaced by a set of small aliphatic moieties without loss in potency. We also found that enzymatic potency co-varies with the VDW volume or the maximum projection area of the groups used as replacements of the phenylacetyl moiety and used literature X-ray data to provide an explanation for this finding.

Design and synthesis of biotinylated Hexylselen as a probe to identify KGA allosteric inhibitors by a convenient biomolecular interaction assay

Hexylselen is a novel submicromolar dual KGA/GDH inhibitor, which demonstrates potent inhibition of cancer cells with minimal toxicity. To further investigation its mechanism of action, we designed and synthesized its biotinylated derivative 2 as a novel probe. From commercially available starting material, 2 was obtained in 6 steps with 13.4% overall yield. It is notable that this practical synthetic route give a template for the preparation of unsymmetrical di-benzo[d][1,2]selenazol-3(2H)-ones. Based on probe 2, we developed a novel biomolecular interaction assay for convenient and reliable test of KGA allosteric inhibitors and confirmed that hexylselen as an allosteric inhibitor of KGA sharing the same binding pocket with BPTES but not with Ebselen via competitive experiments.

Inhibition of cancer metabolism: a patent landscape

Cancer metabolism is currently a hot topic. Since it was first realized that cancer cells rely upon an altered metabolic program to sustain their rapid proliferation, the enzymes that support those metabolic changes have appeared to be good targets for pharmacological intervention. Here, we discuss efforts pertaining to targets in cancer metabolism, focusing upon the tricarboxylic acid cycle and the mechanisms which feed nutrients into it. We describe a broad landscape of small-molecule inhibitors, targeting a dozen different proteins, each implicated in cancer progression. We hope that this will serve as a reference both to the areas being most highly examined today and, relatedly, the areas that are still ripe for novel intervention.