Arginase Inhibitor Research Articles

Design and Synthesis of Acyclic Boronic Acid Arginase Inhibitors.

Arginase has long been a target of interest in immuno-oncology, but discovering an orally bioavailable inhibitor is severely constrained by the requisite boronic acid pharmacophore. We began our drug discovery campaign by building off the β-position of the literature inhibitor ABH (1). A divergent synthesis with an Ireland-Claisen rearrangement as the key step allowed access to numerous compounds, some of which we crystallized in the active site of arginase 2. We subsequently used structure-based drug design to further improve the potency of this series, ultimately achieving an inhibitor with an IC50 value of 12 nM. Many compounds in this series were designed to behave as prodrugs, releasing their payload with up to 4-fold improved oral exposure relative to the parent. Subtle stereochemical differences between these various inhibitors and prodrugs had substantial effects on potency and pharmacokinetics.

Abstract 4138661: Targeting Arginase I Alleviates Cardiomyopathy

Introduction: Emerging data have shown that pathological cardiac fibrosis and heart failure is driven by recruitment of CD4 + T cells to injured heart tissue. Systemic deletion of CD4 + T cells or splenectomy has been shown to attenuate CD4 + T cell heart infiltration and inflammation. We engineered cargo-less nanoparticles using a biocompatible and biodegradable polymer that target splenic macrophages to overexpress arginase I, leading to local depletion of L-arginine, an amino acid crucial for CD4 + T cell activation and expansion. Hypothesis: Cargo-less nanoparticles attenuate CD4 + T cell activation, expansion, and heart infiltration in experimental models of cardiomyopathy by regulating cross talk between macrophages and CD4 + T cells via L-arginine depletion in the spleen. Methods: Spleen-targeting, cargo-less nanoparticles were synthesized from poly(L-lactide-co-glycolide) (PLLGA) and administered to murine and human macrophages in vitro. Arginase I expression and activity were assessed via Western blotting and arginase activity assay. Epigenetic modulation was analyzed using Western blotting and CHIP-seq. Conditioned media was collected to culture CFSE-labeled T cells to assess proliferation. The nanoparticles were administered to mouse heart failure models induced by isoproterenol or angiotensin II and phenylephrine. Immune cell composition in mouse spleens and hearts was investigated by flow cytometry. Cardiac function was assessed by echocardiography and heart fibrosis was examined via immunohistochemistry and Western blotting. Results: Primary murine macrophages treated with our nanoparticles exhibited a dose-dependent T cell suppression in vitro. This effect was abrogated when an arginase inhibitor was administered together with the nanoparticles. The nanoparticles upregulated arginase I protein expression and arginase activity by increasing histone lactylation. In vivo testing with mouse heart injury models showed that the nanoparticles restored levels of effector and regulatory T cells in injured mice to non-injured levels. Additionally, the nanoparticles reduced cardiac fibrosis and restored ejection fraction. Furthermore, Western blotting of heart tissue lysate revealed that the nanoparticles downregulated the TGFb and p-SMAD signaling pathway. Conclusion: Collectively, these findings highlight a novel therapeutic strategy for heart failure, addressing the gap of fibrosis treatment by targeting upstream immunological pathways.

Liposomal Nω-hydroxy-l-norarginine, a proof-of-concept: arginase inhibitors can be incorporated in liposomes while retaining their therapeutic activity ex vivo

Cancer immunotherapy has evolved significantly over the last decade, with therapeutics targeting the adaptive immune system showing exciting effects in clinics. Yet, the modulation of the innate immune system, particularly the tumor-associated innate immune cells which are an integral part of immune responses in cancer, remains less understood. The arginase 1 (Arg1) pathway is a pivotal metabolic pathway that tumor-associated innate immune cells exploit to create an immunosuppressive tumor microenvironment, leading to the evasion of immune surveillance. The inhibition of Arg1 presents a therapeutic opportunity to reverse this immunosuppression, and Nω-hydroxy-l-norarginine (nor-NOHA) has emerged as a potent arginase inhibitor with promising in vivo efficacy. However, the rapid systemic clearance of nor-NOHA poses a significant challenge for its therapeutic application. This study pioneers the encapsulation of nor-NOHA in liposomes, aiming to enhance its bioavailability and prolong its inhibitory activity against Arg1. Historically, the extensive interaction between innate immune cells and nanoparticles has been one of the biggest drawbacks in nanomedicine. Here we seek to utilize this effect and deliver liposomal nor-NOHA to the arginase 1 expressing innate immune cells. We systematically investigated the effect of lipid composition, acyl chain length, manufacturing and loading methodology on the encapsulation efficiency (EE%) and release profile of nor-NOHA. Our results indicate that while the manufacturing method and lipid acyl chain length do not significantly impact EE%, they crucially influence the release kinetics of nor-NOHA, with longer acyl chains demonstrating a more sustained release of nor-NOHA from liposomes enabling continuous inhibition of Arg1. Our findings suggest that liposomal nor-NOHA retains its functional inhibitory activity and could offer improved pharmacokinetic properties, making it a compelling base for iterations for further innovative cancer immunotherapeutic strategies in preclinical and clinical evaluations.

Increased endothelial cell uptake of erythrocyte-derived extracellular vesicles carrying arginase-1 induces endothelial dysfunction in type 2 diabetes

Abstract Background Recently, we have demonstrated that red blood cells (RBCs) from individuals with type 2 diabetes (T2D-RBCs) induce endothelial dysfunction. However, the mechanism by which RBCs communicate with the vessel is unknown. Extracellular vesicles (EVs) are actively secreted by practically all cell types, including RBCs, and represent a novel mechanism of intercellular communication. However, the involvement of EVs from RBC in the development of endothelial dysfunction remains to be elucidated. Purpose This study was designed to test the hypothesis that EVs are key players in the communication and the transfer of signalling between RBCs and the vascular endothelium to induce endothelial dysfunction in T2D. Methods RBCs from T2D patients and age-matched healthy controls (H-RBCs) were incubated for 18h with Krebs-Henseleit buffer (20% haematocrit) for EV release. RBC-derived EVs in the conditioned medium were isolated using a membrane affinity column. The EVs were co-incubated with mouse aortae to evaluate endothelium-dependent relaxation and with endothelial cells for expression analysis. The uptake of the EVs by endothelial cells and their content of arginase-1 were determined. The functional involvement of arginase was investigated using pharmacological interventions and expression analyses. All animal experiments were performed according to the principles of laboratory animal care (NIH Publication no. 85-23 revised 1985) and human procedures according to the declaration of Helsinki with approval by the Swedish Ethical Review Authority. Results The uptake of EVs derived from T2D-RBCs by endothelial cells was 2-fold greater than that of EVs from H-RBCs (Fig. 1A-B). Inhibiting the uptake of EVs derived from T2D-RBCs by the addition of heparin during the co-incubation rescued the endothelial function (Fig. 1C). Arginase-1 was detected in RBC-derived EVs (Fig. 2A). Arginase-1 mRNA and protein levels were increased in endothelial cells following co-incubation with EVs derived from T2D-RBCs (Fig. 2B-D). Additionally, the increase in arginase-1 protein induced by EVs derived from T2D-RBCs in endothelial cells was observed also following mRNA silencing for arginase-1 (Fig. 2E-F). Finally, mouse aortae co-incubated with EVs derived from T2D-RBCs in the presence or absence of the arginase inhibitor 2(S)-amino-6-boronohexanoic acid significantly attenuated the impairment in endothelial function induced by EVs derived from T2D-RBCs (Fig. 2G). Conclusion Increased uptake of RBC-derived EVs by the endothelial cells is an important feature of the endothelial dysfunction induced by these EVs in T2D. In addition, these EVs carry arginase-1 protein to induce endothelial dysfunction. The mechanism underlying the increased uptake of EVs in target cells is of importance to identify in future studies, as it could lead to new treatment strategies.

Profiling the L-arginine/arginase 1 metabolism in early and advanced atherosclerosis

Abstract Background Atherosclerosis is a chronic inflammatory disease and the primary underlying cause of cardiovascular disease (CVD). Recently, intracellular metabolic pathways have been identified as master switches of immune cell function and thus seem promising targets for therapeutic interventions aimed at lowering inflammation and thereby atherogenesis. Decades of research have demonstrated the importance of the amino acid (AA) L-arginine (Arg) in CVD. Although most research has focused on endothelium-dependent effects of Arg by the nitric oxide synthase (NOS), Arg metabolism - mainly through its metabolizing enzyme arginase 1 (Arg1) - has also been shown to regulate immune cell responses independent of its endothelial functions. Despite these findings, the cell-specific contribution of Arg/Arg1 metabolism on atherogenesis is still largely unknown. Purpose Profiling the Arg metabolism in endothelial and immune cells to identify cell-specific changes during athero-progression. Methods To investigate Arg metabolism in atherogenesis, we fed apolipoprotein E deficient (Apoe-­/­-) mice a Western diet (WD) for 6 and 12 weeks. Chow diet-fed aged-matched Apoe-­/-­ mice were used as littermate controls and C57BL/6 mice as steady-state controls. Systemic and local Arg concentrations were measured by mass-spectrometry. Arg metabolism in organs was studied by qPCR. Arg1 expression in atherosclerotic lesions was examined by immunohistochemistry (IHC). To assess cell-specific expression of Arg-related enzymes, aortic leukocytes from WD-fed Apoe-­/-­ mice were subjected to CITE-seq analysis. The role of T cell Arg1 was determined by nor-NOHA inhibition in Jurkat cells. Results AA measurements showed that systemic Arg was reduced in early and advanced atherogenesis (p<0.02), and splenic Arg was reduced in advanced atherogenesis (p=0.006) compared with steady state. In advanced atherosclerosis, Arg1 was decreased in the liver but increased in the spleen and aorta, whereas Nos2 was increased in the liver and aorta compared with steady state. To identify the cell types driving these local changes, we performed IHC on atherosclerotic lesions. Arg1+ lesional macrophages accumulated in advanced compared to early lesions (p=0.03), whereas Arg1+ endothelial cells tended to decrease (p=0.2). Surprisingly, we also found an accumulation of Arg1+ CD4+ T cells in lesions and a further upward trend with athero-progression. CITE-seq confirmed a constitutive expression of Arg1 in lymphoid clusters. In vitro experiments with Jurkat cells showed that arginase inhibition suppressed T cell proliferation and promoted apoptosis and migration (all p<0.0001). Conclusion Our data indicate that Arg metabolism is strongly regulated during athero-progression and suggest a so far unknown role of T cell-intrinsic Arg/Arg1 metabolism in the disease. Murine atherosclerosis studies are now being performed to decipher the cell-specific contribution of Arg/Arg1 metabolism in atherosclerosis.

Biochemistry, pharmacology and in vivo function of arginases.

Arginase catalyzes the hydrolysis of L-arginine into L-ornithine and urea. The two existing isoforms Arg1 and Arg2 show different cellular localizations and metabolic functions. Arginase activity is crucial for nitrogen detoxification in the urea cycle, synthesis of polyamines, and control of l-arginine bioavailability and nitric oxide production. Despite significant progress in the understanding of the biochemistry and function of arginases, several open questions remain. Recent studies have revealed that the regulation and function of Arg1 and Arg2 are cell-type-specific, species-specific, and profoundly different in mice and humans. The main differences were found in the distribution and function of Arg1 and Arg2 in immune and erythroid cells. Contrary to what was previously thought, Arg1 activity appears to be only partially related to vascular NO signaling under homeostatic conditions in the vascular wall, but its expression is increased under disease conditions and may be targeted by treatment with arginase inhibitors. Arg2 appears to be mainly a catabolic enzyme involved in the synthesis of L-ornithine, polyamine, and proline but may play a putative role in blood pressure control, at least in mice. The immunosuppressive role of arginase-mediated arginine depletion is a promising target for cancer treatment. This review critically revises and discusses the biochemistry, pharmacology, and in vivo function of arginase, focusing on the insights gained from the analysis of cell-specific Arg1 and Arg2 knockout mice and human studies using arginase inhibitors or pegylated recombinant arginase. Significance Statement The review emphasizes the need for further research to deepen our understanding of the regulation of Arg1 and Arg 2 in different cell types under consideration of their localization, species-specificity, and multiple biochemical and physiological roles. This could lead to better pharmacological strategies to target arginase activity in liver, cardiovascular, hematological, immune/infection diseases and cancer.

Red blood cells from patients with ST-elevation myocardial infarction and elevated C-reactive protein levels induce endothelial dysfunction.

Endothelial dysfunction is an early consequence of vascular inflammation and a driver of coronary atherosclerotic disease leading to myocardial infarction. The red blood cells (RBCs) mediate endothelial dysfunction in patients at cardiovascular risk, but their role in patients with acute myocardial infarction is unknown. This study aimed to investigate if RBCs from patients with ST-elevation myocardial infarction (STEMI) induced endothelial dysfunction and the role of systemic inflammation in this effect. RBCs from patients with STEMI and aged-matched healthy controls were co-incubated with rat aortic segments for 18h followed by evaluation of endothelium-dependent (EDR) and -independent relaxation (EIDR). RBCs and aortic segments were also analyzed for arginase and oxidative stress. The patients were divided into groups depending on C-reactive protein (CRP) levels at admission. RBCs from patients with STEMI and CRP levels >2 mg/L induced impairment of EDR, but not EIDR, compared to RBCs from STEMI and CRP <2 mg/L and healthy controls. Aortic expression of arginase 1 was increased following incubation with RBCs from patients with STEMI and CRP >2, and arginase inhibition prevented the RBC-induced endothelial dysfunction. RBCs from patients with STEMI and CRP >2 had increased reactive oxygen species compared to RBCs from patients with CRP <2 and healthy controls. Vascular inhibition of NADPH oxidases and increased dismutation of superoxide improved EDR. RBCs from patients with STEMI and low-grade inflammation induce endothelial dysfunction through a mechanism involving arginase 1 as well and increased RBC and vascular superoxide by NADPH oxidases.

Tracer-based metabolomics for profiling nitric oxide metabolites in a 3D microvessels-on-chip model.

Endothelial dysfunction, prevalent in cardiovascular diseases (CVDs) and linked to conditions like diabetes, hypertension, obesity, renal failure, or hypercholesterolemia, is characterized by diminished nitric oxide (NO) bioavailability-a key signaling molecule for vascular homeostasis. Current two-dimensional (2D) invitro studies on NO synthesis by endothelial cells (ECs) lack the crucial laminar shear stress, a vital factor in modulating the NO-generating enzyme, endothelial nitric oxide synthase (eNOS), under physiological conditions. Here we developed a tracer-based metabolomics approach to measure NO-specific metabolites with mass spectrometry (MS) and show the impact of fluid flow on metabolic parameters associated with NO synthesis using 2D and 3D platforms. Specifically, we tracked the conversion of stable-isotope labeled NO substrate L-Arginine to L-Citrulline and L-Ornithine to determine eNOS activity. We demonstrated clear responses in human coronary artery endothelial cells (HCAECs) cultured with 13C6, 15N4-L-Arginine, and treated with eNOS stimulator, eNOS inhibitor, and arginase inhibitor. Analysis of downstream metabolites, 13C6, 15N3 L-Citrulline and 13C5, 15N2 L-Ornithine, revealed distinct outcomes. Additionally, we evaluated the NO metabolic status in static 2D culture and 3D microvessel models with bidirectional and unidirectional fluid flow. Our 3D model exhibited significant effects, particularly in microvessels exposed to the eNOS stimulator, as indicated by the 13C6, 15N3 L-Citrulline/13C5, 15N2 L-Ornithine ratio, compared to the 2D culture. The obtained results indicate that the 2D static culture mimics an endothelial dysfunction status, while the 3D model with a unidirectional fluid flow provides a more representative physiological environment that provides a better model to study endothelial dysfunction.

Differences in endothelial function between patients with Type 1 and Type 2 diabetes: effects of red blood cells and arginase.

The mechanisms underlying endothelial dysfunction in Type 1 and Type 2 diabetes (T1DM and T2DM) are unresolved. The red blood cells (RBCs) with increased arginase activity induce endothelial dysfunction in T2DM, but the implications of RBCs and the role of arginase inhibition in T1DM are unexplored. We aimed to investigate the differences in endothelial function in patients with T1DM and T2DM, with focus on RBCs and arginase. Thirteen patients with T1DM and twenty-six patients with T2DM, matched for HbA1c and sex were included. In vivo endothelium-dependent and -independent vasodilation (EDV and EIDV) were assessed by venous occlusion plethysmography before and after administration of an arginase inhibitor. RBCs were co-incubated with rat aortic segments for 18h followed by evaluation of endothelium-dependent (EDR) and -independent relaxation (EIDR) in isolated organ chambers. In vivo EDV, but not EIDV, was significantly impaired in patients with T2DM compared with patients with T1DM. Arginase inhibition resulted in improved EDV only in T2DM. RBCs from patients with T2DM induced impaired EDR but not EIDR in isolated aortic segments, whereas RBCs from patients with T1DM did not affect EDR nor EIDR. The present study demonstrates markedly impaired EDV in patients with T2DM in comparison with T1DM. In addition, it highlights the divergent roles of RBCs and arginase in mediating endothelial dysfunction in T1DM and T2DM. While endothelial dysfunction is mediated via RBCs and arginase in T2DM, these phenomena are not prominent in T1DM thereby indicating distinct differences in underlying mechanisms.

Macrophage-fibroblast crosstalk drives Arg1-dependent lung fibrosis via ornithine loading.

Monocyte-derived macrophages recruited to injured tissues induce a maladaptive fibrotic response characterized by excessive production of collagen by local fibroblasts. Macrophages initiate this programming via paracrine factors, but it is unknown whether reciprocal responses from fibroblasts enhance profibrotic polarization of macrophages. We identify macrophage-fibroblast crosstalk necessary for injury-associated fibrosis, in which macrophages induced interleukin 6 ( IL-6 ) expression in fibroblasts via purinergic receptor P2rx4 signaling, and IL-6, in turn, induced arginase 1 ( Arg1 ) expression in macrophages. Arg1 contributed to fibrotic responses by metabolizing arginine to ornithine, which fibroblasts used as a substrate to synthesize proline, a uniquely abundant constituent of collagen. Imaging of idiopathic pulmonary fibrosis (IPF) lung samples confirmed expression of ARG1 in myeloid cells, and arginase inhibition suppressed collagen expression in cultured precision-cut IPF lung slices. Taken together, we define a circuit between macrophages and fibroblasts that facilitates cross-feeding metabolism necessary for injury-associated fibrosis.

Three neo-Clerodane Diterpenoids from Tinospora cordifolia Stems and Their Arginase Inhibitory Activities.

Three neo-clerodane diterpenoids, including two new tinocordifoliols A (1) and B (2) and one known tinopanoid R (3), were isolated from the ethyl acetate-soluble fraction of the 70% ethanol extract of Tinospora cordifolia stems. The structures were elucidated by various spectroscopic methods, including one dimensional (1D) and 2D-NMR, high resolution-electrospray ionization (HR-ESI)-MS, and electronic circular dichroism (ECD) data. The T. cordifolia extract and all isolated compounds 1-3 possessed arginase I inhibitory activities. Among them, 3 exhibited moderate competitive inhibition of human arginase I (IC50 = 61.9 µM). Furthermore, docking studies revealed that the presence of a β-substituted furan in 3 may play a key role in the arginase I inhibitory activities.

Therapeutic Modulation of Arginase with nor-NOHA Alters Immune Responses in Experimental Mouse Models of Pulmonary Tuberculosis including in the Setting of Human Immunodeficiency Virus (HIV) Co-Infection.

L-arginine metabolism is strongly linked with immunity to mycobacteria, primarily through the antimicrobial activity of nitric oxide (NO). The potential to modulate tuberculosis (TB) outcomes through interventions that target L-arginine pathways are limited by an incomplete understanding of mechanisms and inadequate in vivo modeling. These gaps in knowledge are compounded for HIV and Mtb co-infections, where activation of arginase-1 due to HIV infection may promote survival and replication of both Mtb and HIV. We utilized in vitro and in vivo systems to determine how arginase inhibition using Nω-hydroxy-nor-L-arginine (nor-NOHA) alters L-arginine pathway metabolism relative to immune responses and disease outcomes following Mtb infection. Treatment with nor-NOHA polarized murine macrophages (RAW 264.7) towards M1 phenotype, increased NO, and reduced Mtb in RAW macrophages. In Balb/c mice, nor-NOHA reduced pulmonary arginase and increased the antimicrobial metabolite spermine in association with a trend towards reduced Mtb CFU in lung. In humanized immune system (HIS) mice, HIV infection increased plasma arginase and heightened the pulmonary arginase response to Mtb. Treatment with nor-NOHA increased cytokine responses to Mtb and Mtb/HIV in lung tissue but did not significantly alter bacterial burden or viral load. Our results suggest that L-arginine pathway modulators may have potential as host-directed therapies to augment antibiotics in TB chemotherapy.

Red blood cell-derived extracellular vesicles from type 2 diabetes patients induce endothelial dysfunction through a mechanism involving arginase 1

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Foundation for Geriatric Diseases Karolinska Institutet (2023-01860). Swedish Heart and Lung Foundation (20220210) Background The mechanisms driving the development of cardiovascular injury in type 2 diabetes (T2D) remain incompletely understood. We have recently demonstrated that red blood cells (RBCs) from patients with T2D (T2D-RBCs) act as mediators of endothelial dysfunction through the upregulation of arginase 1 and attenuation of nitric oxide bioavailability. However, the underlying mechanisms of this interaction remain unknown. It is increasingly clear that extracellular vesicles (EVs) are actively secreted by practically all cell types, including RBCs, and represent a novel mechanism of intercellular communication. However, the involvement of RBC-derived EVs in the development of endothelial dysfunction in T2D remains to be elucidated. Purpose To test the hypothesis that EVs are secreted by RBCs and transfer signalling to induce endothelial dysfunction in T2D through arginase 1. Methods EVs released from T2D-RBCs (T2D-RBCs EVs) and RBCs from age-matched healthy controls (H-RBCs EVs) were isolated using sequential ultracentrifugation or a membrane affinity column, co-incubated with mouse aortae to evaluate endothelium-dependent relaxation (EDR), and with human carotid artery endothelial cells (HCtAEC) to study the EV uptake and alteration in gene expression. EVs were characterized based on morphology, size and particle number, uptake in endothelial cells, and arginase 1 content. Functional involvement of EV uptake and arginase were investigated using pharmacological interventions. Arginase 1 was measured in EVs, HCtAEC, and mouse aortae after co-incubation with H-RBCs EVs and T2D-RBCs EVs. Results The uptake of T2D-RBCs EVs by endothelial cells was greater than that of EVs from H-RBCs (Fig. 1A, B) despite the reduced formation of EVs by T2D-RBCs (Fig. 1C). T2D-RBCs EVs significantly impaired EDR (Fig. 1D), and this impairment was prevented by inhibiting uptake of EVs with heparin (Fig. 1E). Arginase 1 was detected in RBC-derived EVs (Fig. 2A), and endothelial function was rescued by blocking arginase activity in EVs by the arginase inhibitor 2(S)-amino-6-boronohexanoic acid (ABH; Fig. 2B). Immunohistochemical staining revealed upregulation of arginase 1 in the vasculature following incubation with T2D-RBCs EVs (Fig. 2C, D). Additionally, co-incubation of HCtAEC and EVs derived from T2D-RBCs significantly increased endothelial cell arginase 1 (Fig. 2E, F). Administration of ABH to the aortae following the co-incubation also attenuated the impairment of EDR induced by T2D-RBCs EVs, suggesting the involvement of vascular arginase 1 (Fig. 2G). Conclusion T2D-RBCs EVs induce endothelial dysfunction. In addition to increased uptake of EVs in endothelial cells, the signalling behind this effect of EVs is mediated by arginase 1 to induce endothelial dysfunction. These results shed new important light on the mechanism underlying vascular injury mediated by RBCs in T2D.

Py-CoMFA, docking, and molecular dynamics simulations of Leishmania (L.) amazonensis arginase inhibitors

Leishmaniasis is a disease caused by a protozoan of the genus Leishmania, affecting millions of people, mainly in tropical countries, due to poor social conditions and low economic development. First-line chemotherapeutic agents involve highly toxic pentavalent antimonials, while treatment failure is mainly due to the emergence of drug-resistant strains. Leishmania arginase (ARG) enzyme is vital in pathogenicity and contributes to a higher infection rate, thus representing a potential drug target. This study helps in designing ARG inhibitors for the treatment of leishmaniasis. Py-CoMFA (3D-QSAR) models were constructed using 34 inhibitors from different chemical classes against ARG from L. (L.) amazonensis (LaARG). The 3D-QSAR predictions showed an excellent correlation between experimental and calculated pIC50 values. The molecular docking study identified the favorable hydrophobicity contribution of phenyl and cyclohexyl groups as substituents in the enzyme allosteric site. Molecular dynamics simulations of selected protein–ligand complexes were conducted to understand derivatives’ interaction modes and affinity in both active and allosteric sites. Two cinnamide compounds, 7g and 7k, were identified, with similar structures to the reference 4h allosteric site inhibitor. These compounds can guide the development of more effective arginase inhibitors as potential antileishmanial drugs.

Development of a quantification method for arginase inhibitors by LC-MS/MS with benzoyl chloride derivatization

Arginase is an enzyme responsible for converting arginine, a semi-essential amino acid, to ornithine and urea. Arginine depletion suppresses immunity via multiple mechanisms including inhibition of T-cell and NK cell proliferation and activity. Arginase inhibition is therefore an attractive mechanism to potentially reverse immune suppression and thus has been explored as a therapy for oncology and respiratory indications. Small molecules targeting arginase present significant bioanalytical challenges for in vitro and in vivo characterization as inhibitors of arginase are typically hydrophilic in nature. The resulting low or negative LogD characteristics are incompatible with common analytical methods such as RP-ESI-MS/MS. Accordingly, a sensitive, high-throughput bioanalytical method was developed by incorporating benzoyl chloride derivatization to increase the hydrophobic characteristics of these polar analytes. Samples were separated by reversed phase chromatography on a Waters XBridge BEH C18 3.5 μm, 30 × 3 mm column using gradient elution. The mass spec was operated in positive mode using electrospray ionization. The m/z 434.1→176.1, 439.4→181.2, 334.9→150.0 and 339.9→150.0 for AZD0011, AZD0011 IS, AZD0011-PL and AZD0011-PL IS respectively were used for quantitation. The linear calibration range of the assay was 1.00–10,000 ng/mL with QC values of 5, 50 and 500 ng/mL. The qualified method presented herein exhibits a novel, robust analytical performance and was successfully applied to evaluate the in vivo ADME properties of boronic acid-based arginase inhibitor prodrug AZD0011 and its active payload AZD0011-PL.

First-in-human phase 1 study of the arginase inhibitor INCB001158 alone or combined with pembrolizumab in patients with advanced or metastatic solid tumours

ObjectiveThe arginase inhibitor INCB001158 was evaluated for safety (primary endpoint) in locally advanced or metastatic solid tumours; pharmacokinetics, pharmacodynamics and efficacy were also assessed.Methods and analysisIn this non-randomised, open-label, three-part...

Fish arginase constrains excessive production of nitric oxide and limits mitochondrial damage during Aeromonas hydrophila infection

Bacteria-enhanced inducible nitric oxide synthase (iNOS) overproduces nitric oxide (NO) leading to mitochondrial and cellular damage. In mammals, arginase (ARG), the enzyme consuming the same substrate l-arginine with iNOS, was believed to inhibit iNOS activity by competing the substrate. But in fish, this conception has been widely challenged. In this study, the gene expression using real-time quantitative PCR (RT-qPCR) technology showed that when stimulated by Aeromonas hydrophila (A. hydrophila), grass carp (gc) iNOS was up-regulated in head kidney monocytes/macrophages (M0/MФ), and its changes were not detected in the whole tissue of liver or spleen, showing a high degree of cell-specific expression pattern. At the same time, gcARG2 had a high basal expression in tissues and was up-regulated by A. hydrophila stimulation. Next, phthalaldehyde-primaquine reaction was first used in the determination of intracellular urea in fish cells. It was found that the induced gcARG2 led to an increase in the intracellular urea content. Moreover, urea and NO production in M0/MФ were increased in a substrate dose-dependent manner from 30 to 100 μM of l-arginine and reached the highest yield at 300 and 3000 μM of l-arginine, respectively. Furthermore, head kidney M0/MФ was cultured in RPMI1640 medium containing physiological concentration (500 μM) of l-arginine to evaluate the effect of ARG. Under A. hydrophila stimulation, treatment with the arginase inhibitor S-(2-boronoethyl)-l-cysteine (BEC) showed that inhibition of arginase could further enhance the NO production stimulated by A. hydrophila. This in turn led to a cumulation in peroxynitrite (ONOO-) content and an injury of the mitochondrial membrane potential. Our study showed for the first time that fish ARG in head kidney M0/MФ can limit excessive production of NO and harmful products by iNOS to maintain mitochondrial and cellular homeostasis.

Arginase inhibitor reduces fungal dissemination in murine pulmonary cryptococcosis by promoting anti-cryptococcal immunity

Elevation of arginase enzyme activity in the lung contributes to the pathogenesis of various chronic inflammatory diseases and infections. Inhibition of arginase expression and activity is able to alleviate those effects. Here, we investigated the immunomodulatory effect of arginase inhibitor in C. neoformans infection. In the pulmonary cryptococcosis model that was shown to recapitulate human infection, we found arginase expression was excessively induced in the lung during the late stage of infection. To inhibit the activity of arginase, we administered a specific arginase inhibitor, nor-NOHA, during C. neoformans infection. Inhibition of arginase reduced eosinophil infiltration and level of IL-13 secretion in the lungs. Whole lung transcriptome RNA-sequencing analysis revealed that treatment with nor-NOHA resulted in shifting the Th2-type gene expression patterns induced by C. neoformans infection to the Th1-type immune profile, with higher expression of cytokines Ifng, Il6, Tnfa, Csf3, chemokines Cxcl9 and Cxcl10 and transcription factor Stat1. More importantly, mice treated with arginase inhibitor had more infiltrating brain leukocytes and enhanced gene expression of Th1-associated cytokines and chemokines that are known to be essential for protection against C. neoformans infection. Inhibition of arginase dramatically attenuated spleen and brain infection, with improved survival. Taken together, these studies demonstrated that inhibiting arginase activity induced by C. neoformans infection can modulate host immune response by enhancing protective type-1 immune response during C. neoformans infection. The inhibition of arginase activity could be an immunomodulatory target to enhance protective anti-cryptococcal immune responses.

PD-1 inhibition with retifanlimab and/or arginase inhibition with INCB001158 in Japanese patients with solid tumors: A phase I study.

Retifanlimab is a humanized monoclonal antibody targeting programmed death protein-1, and INCB001158 is an oral arginase inhibitor. This phase Ib study investigated retifanlimab, INCB001158, and their combination in Japanese patients with advanced solid tumors. Patients received retifanlimab (500 mg every 4 weeks [Q4W] i.v.) or escalating doses of INCB001158 (75 or 100 mg twice daily [BID]) monotherapy in Part 1 and combination of retifanlimab (500 mg Q4W) and INCB001158 (100 mg BID) in Part 2. Primary endpoints were safety, tolerability, dose-limiting toxicities (DLTs), and determination of recommended phase II doses in Japanese patients. Eighteen patients (retifanlimab or INCB001158 monotherapy and combination; n = 6 each) were enrolled at 2 sites in Japan. There were no DLTs, fatal adverse events (AEs), or discontinuations due to AEs. Rash (all grade 1) was the most common treatment-emergent AE with retifanlimab (n = 6). Treatment-related AEs were reported with retifanlimab (n = 4) or INCB001158 (n = 2) monotherapy and with combination (n = 4); an immune-related AE (thyroid disorder, grade 2) was reported with combination. Two responses were observed with retifanlimab monotherapy (1 complete, 1 partial) and 1 stable disease (SD), for an overall response rate of 33.3% (95% confidence interval [CI], 4.3-77.7) and disease control rate (DCR) of 50% (95% CI, 11.8-88.2). Three patients had SD with INCB001158 monotherapy (DCR 50%; 95% CI, 11.8-88.2). No responses or SD were observed with combination therapy. Retifanlimab, INCB001158, and their combination had acceptable safety profiles. Promising retifanlimab antitumor activity warrants further investigation in Japanese patients.

Synthesis of Mn2O3 Nanoparticles and Determination of Its Inhibition Effect On Sera of Iraqi Patients with Diabetes Mellitus Type-2 and Diabetes Nephropathy

Manganese is essential for the synthesis of antioxidant enzymes and metabolic issues in Diabetes type 2 (DMT2), which is a worldwide disease, Chronic metabolic disorders cause insulin resistance, hyperglycemia, and complications like diabetic nephropathy. Arginase converts arginine to ornithine and urea. Increased arginase activity in DMT2 and diabetes nephropathy (DN)which has been linked to kidney damage, and arginase inhibitors can increase NO which is essential to vascular function. However, the molecular mechanisms of arginased is regulationare in DMT2 and DN are still unclear. This study examined the effect of manganese oxide nanoparticles (Mn2O3NPs) on arginase activity inhibition inserum samples from DMT2 and DN patients. We hypothesized that Mn2O3NPs alter cell redox status and signaling pathways, affecting DMT2 and DN arginase activity. We used a colorimetric assay to measure arginase activity in 80 serum samples from DMT2 and DN patients treated with different MnO2 NP concentrations to test our hypothesis. The current study characterized nanoparticles using various techniques such as IR, SEM, AFM, XRD, and EDX, which found it within nanoscale nature. Our findings are that Mn2O3NPs modulate arginase activity specificity in DM2 samples. SuggestionsMn2O3NPs could be used to develop new treatments for these conditions.