NOX4 Inhibition Potentiates Immunotherapy by Overcoming Cancer-Associated Fibroblast-Mediated CD8 T-cell Exclusion from Tumors.

Determining mechanisms of resistance to αPD-1/PD-L1 immune-checkpoint immunotherapy is key to developing new treatment strategies. Cancer-associated fibroblasts (CAF) have many tumor-promoting functions and promote immune evasion through multiple mechanisms, but as yet, no CAF-specific inhibitors are clinically available. Here we generated CAF-rich murine tumor models (TC1, MC38, and 4T1) to investigate how CAFs influence the immune microenvironment and affect response to different immunotherapy modalities [anticancer vaccination, TC1 (HPV E7 DNA vaccine), αPD-1, and MC38] and found that CAFs broadly suppressed response by specifically excluding CD8+ T cells from tumors (not CD4+ T cells or macrophages); CD8+ T-cell exclusion was similarly present in CAF-rich human tumors. RNA sequencing of CD8+ T cells from CAF-rich murine tumors and immunochemistry analysis of human tumors identified significant upregulation of CTLA-4 in the absence of other exhaustion markers; inhibiting CTLA-4 with a nondepleting antibody overcame the CD8+ T-cell exclusion effect without affecting Tregs. We then examined the potential for CAF targeting, focusing on the ROS-producing enzyme NOX4, which is upregulated by CAF in many human cancers, and compared this with TGFß1 inhibition, a key regulator of the CAF phenotype. siRNA knockdown or pharmacologic inhibition [GKT137831 (Setanaxib)] of NOX4 "normalized" CAF to a quiescent phenotype and promoted intratumoral CD8+ T-cell infiltration, overcoming the exclusion effect; TGFß1 inhibition could prevent, but not reverse, CAF differentiation. Finally, NOX4 inhibition restored immunotherapy response in CAF-rich tumors. These findings demonstrate that CAF-mediated immunotherapy resistance can be effectively overcome through NOX4 inhibition and could improve outcome in a broad range of cancers. SIGNIFICANCE: NOX4 is critical for maintaining the immune-suppressive CAF phenotype in tumors. Pharmacologic inhibition of NOX4 potentiates immunotherapy by overcoming CAF-mediated CD8+ T-cell exclusion. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/9/1846/F1.large.jpg.See related commentary by Hayward, p. 1799.

Inhibition of host NOX1 blocks tumor growth and enhances checkpoint inhibitor-based immunotherapy.

NADPH oxidases catalyze the production of reactive oxygen species and are involved in physio/pathological processes. NOX1 is highly expressed in colon cancer and promotes tumor growth. To investigate the efficacy of NOX1 inhibition as an anticancer strategy, tumors were grown in immunocompetent, immunodeficient, or NOX1-deficient mice and treated with the novel NOX1-selective inhibitor GKT771. GKT771 reduced tumor growth, lymph/angiogenesis, recruited proinflammatory macrophages, and natural killer T lymphocytes to the tumor microenvironment. GKT771 treatment was ineffective in immunodeficient mice bearing tumors regardless of their NOX-expressing status. Genetic ablation of host NOX1 also suppressed tumor growth. Combined treatment with the checkpoint inhibitor anti-PD1 antibody had a greater inhibitory effect on colon carcinoma growth than each compound alone. In conclusion, GKT771 suppressed tumor growth by inhibiting angiogenesis and enhancing the recruitment of immune cells. The antitumor activity of GKT771 requires an intact immune system and enhances anti-PD1 antibody activity. Based on these results, we propose blocking of NOX1 by GKT771 as a potential novel therapeutic strategy to treat colorectal cancer, particularly in combination with checkpoint inhibition.

NADPH oxidases as drug targets and biomarkers in neurodegenerative diseases: What is the evidence?

Neurodegenerative disease are frequently characterized by microglia activation and/or leukocyte infiltration in the parenchyma of the central nervous system and at the molecular level by increased oxidative modifications of proteins, lipids and nucleic acids. NADPH oxidases (NOX) emerged as a novel promising class of pharmacological targets for the treatment of neurodegeneration due to their role in oxidant generation and presumably in regulating microglia activation. The unique function of NOX is the generation of superoxide anion (O2•-) and hydrogen peroxide (H2O2). However in the context of neuroinflammation, they present paradoxical features since O2•-/H2O2 generated by NOX and/or secondary reactive oxygen species (ROS) derived from O2•-/H2O2 can either lead to neuronal oxidative damage or resolution of inflammation. The role of NOX enzymes has been investigated in many models of neurodegenerative diseases by using either genetic or pharmacological approaches. In the present review we provide a critical assessment of recent findings related to the role of NOX in the CNS as well as how the field has advanced over the last 5 years. In particular, we focus on the data derived from the work of a consortium (Neurinox) funded by the European Commission's Programme 7 (FP7). We discuss the evidence gathered from animal models and human samples linking NOX expression/activity with neuroinflammation in neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS) and Creutzfeldt-Jakob disease as well as autoimmune demyelinating diseases like multiple sclerosis (MS) and chronic inflammatory demyelinating polyneuropathy (CIDP). We address the possibility to use measurement of the activity of the NOX2 isoform in blood samples as biomarker of disease severity and treatment efficacy in neurodegenerative disease. Finally we clarify key controversial aspects in the field of NOX, such as NOX cellular expression in the brain, measurement of NOX activity, impact of genetic deletion of NOX in animal models of neurodegeneration and specificity of NOX inhibitors.

siRNA screen identifies QPCT as a druggable target for Huntington's disease.

Huntington's disease (HD) is a currently incurable neurodegenerative condition caused by an abnormally expanded polyglutamine tract in huntingtin (HTT). We identified new modifiers of mutant HTT toxicity by performing a large-scale 'druggable genome' siRNA screen in human cultured cells, followed by hit validation in Drosophila. We focused on glutaminyl cyclase (QPCT), which had one of the strongest effects on mutant HTT-induced toxicity and aggregation in the cell-based siRNA screen and also rescued these phenotypes in Drosophila. We found that QPCT inhibition induced the levels of the molecular chaperone αB-crystallin and reduced the aggregation of diverse proteins. We generated new QPCT inhibitors using in silico methods followed by in vitro screening, which rescued the HD-related phenotypes in cell, Drosophila and zebrafish HD models. Our data reveal a new HD druggable target affecting mutant HTT aggregation and provide proof of principle for a discovery pipeline from druggable genome screen to drug development.

Genetic targeting or pharmacologic inhibition of NADPH oxidase nox4 provides renoprotection in long-term diabetic nephropathy.

Diabetic nephropathy may occur, in part, as a result of intrarenal oxidative stress. NADPH oxidases comprise the only known dedicated reactive oxygen species (ROS)-forming enzyme family. In the rodent kidney, three isoforms of the catalytic subunit of NADPH oxidase are expressed (Nox1, Nox2, and Nox4). Here we show that Nox4 is the main source of renal ROS in a mouse model of diabetic nephropathy induced by streptozotocin administration in ApoE(-/-) mice. Deletion of Nox4, but not of Nox1, resulted in renal protection from glomerular injury as evidenced by attenuated albuminuria, preserved structure, reduced glomerular accumulation of extracellular matrix proteins, attenuated glomerular macrophage infiltration, and reduced renal expression of monocyte chemoattractant protein-1 and NF-κB in streptozotocin-induced diabetic ApoE(-/-) mice. Importantly, administration of the most specific Nox1/4 inhibitor, GKT137831, replicated these renoprotective effects of Nox4 deletion. In human podocytes, silencing of the Nox4 gene resulted in reduced production of ROS and downregulation of proinflammatory and profibrotic markers that are implicated in diabetic nephropathy. Collectively, these results identify Nox4 as a key source of ROS responsible for kidney injury in diabetes and provide proof of principle for an innovative small molecule approach to treat and/or prevent chronic kidney failure.

A phenotypic screening assay for modulators of huntingtin-induced transcriptional dysregulation.

Huntington's Disease is a rare neurodegenerative disease caused by an abnormal expansion of CAG repeats encoding polyglutamine in the first exon of the huntingtin gene. N-terminal fragments containing polyglutamine (polyQ) sequences aggregate and can bind to cellular proteins, resulting in several pathophysiological consequences for affected neurons such as changes in gene transcription. One transcriptional pathway that has been implicated in HD pathogenesis is the CREB binding protein (CBP)/cAMP responsive element binding (CREB) pathway. We developed a phenotypic assay to screen for compounds that can reverse the transcriptional dysregulation of the pathway caused by induced mutated huntingtin protein (µHtt). 293/T-REx cells were stably co-transfected with an inducible full-length mutated huntingtin gene containing 138 glutamine repeats and with a reporter gene under control of the cAMP responsive element (CRE). One clone, which showed reversible inhibition of µHtt-induced reporter activity upon treatment with the neuroprotective Rho kinase inhibitor Y27632, was used for the development of a high-throughput phenotypic assay suitable for a primary screening campaign, which was performed on a library of 24,000 compounds. Several hit compounds were identified and validated further in a cell viability adenosine triphosphate assay. The assay has the potential for finding new drug candidates for the treatment of HD.

NADPH oxidase 1 plays a key role in diabetes mellitus-accelerated atherosclerosis.

BACKGROUND: In diabetes mellitus, vascular complications such as atherosclerosis are a major cause of death. The key underlying pathomechanisms are unclear. However, hyperglycemic oxidative stress derived from NADPH oxidase (Nox), the only known dedicated enzyme to generate reactive oxygen species appears to play a role. Here we identify the Nox1 isoform as playing a key and pharmacologically targetable role in the accelerated development of diabetic atherosclerosis. METHODS AND RESULTS: Human aortic endothelial cells exposed to hyperglycemic conditions showed increased expression of Nox1, oxidative stress, and proinflammatory markers in a Nox1-siRNA reversible manner. Similarly, the specific Nox inhibitor, GKT137831, prevented oxidative stress in response to hyperglycemia in human aortic endothelial cells. To examine these observations in vivo, we investigated the role of Nox1 on plaque development in apolipoprotein E-deficient mice 10 weeks after induction of diabetes mellitus. Deletion of Nox1, but not Nox4, had a profound antiatherosclerotic effect correlating with reduced reactive oxygen species formation, attenuation of chemokine expression, vascular adhesion of leukocytes, macrophage infiltration, and reduced expression of proinflammatory and profibrotic markers. Similarly, treatment of diabetic apolipoprotein E-deficient mice with GKT137831 attenuated atherosclerosis development. CONCLUSIONS: These studies identify a major pathological role for Nox1 and suggest that Nox1-dependent oxidative stress is a promising target for diabetic vasculopathies, including atherosclerosis.

Renoprotective effects of a novel Nox1/4 inhibitor in a mouse model of Type 2 diabetes.

Nox (NADPH oxidase)-derived ROS (reactive oxygen species) have been implicated in the development of diabetic nephropathy. Of the Nox isoforms in the kidney, Nox4 is important because of its renal abundance. In the present study, we tested the hypothesis that GKT136901, a Nox1/4 inhibitor, prevents the development of nephropathy in db/db (diabetic) mice. Six groups of male mice (8-week-old) were studied: (i) untreated control db/m, (ii) low-dose GKT136901-treated db/m (30 mg/kg of body weight per day), (iii) high-dose GKT136901-treated db/m (90 mg/kg of body weight per day), (iv) untreated db/db; (v) low dose GKT136901-treated db/db; and (vi) high-dose GKT136901-treated db/db. GKT136901, in chow, was administered for 16 weeks. db/db mice developed diabetes and nephropathy as evidenced by hyperglycaemia, albuminuria and renal injury (mesangial expansion, tubular dystrophy and glomerulosclerosis). GKT136901 treatment had no effect on plasma glucose or BP (blood pressure) in any of the groups. Plasma and urine TBARSs (thiobarbituric acid-reacting substances) levels, markers of systemic and renal oxidative stress, respectively, were increased in diabetic mice. Renal mRNA expression of Nox4, but not of Nox2, increased, Nox1 was barely detectable in db/db. Expression of the antioxidant enzyme SOD-1 (superoxide dismutase 1) decreased in db/db mice. Renal content of fibronectin, pro-collagen, TGFß (transforming growth factor ß) and VCAM-1 (vascular cell adhesion molecule 1) and phosphorylation of ERK1/2 (extracellular-signal-regulated kinase 1/2) were augmented in db/db kidneys, with no change in p38 MAPK (mitogen-activated protein kinase) and JNK (c-Jun N-terminal kinase). Treatment reduced albuminuria, TBARS and renal ERK1/2 phosphorylation and preserved renal structure in diabetic mice. Our findings suggest a renoprotective effect of the Nox1/4 inhibitor, possibly through reduced oxidative damage and decreased ERK1/2 activation. These phenomena occur independently of improved glucose control, suggesting GKT136901-sensitive targets are involved in complications of diabetes rather than in the disease process.

Fused 3-Hydroxy-3-trifluoromethylpyrazoles Inhibit Mutant Huntingtin Toxicity.

Here, we describe the selection and optimization of a chemical series active in both a full-length and a fragment-based Huntington's disease (HD) assay. Twenty-four thousand small molecules were screened in a phenotypic HD assay, identifying a series of compounds bearing a 3-hydroxy-3-trifluoromethylpyrazole moiety as able to revert the toxicity induced by full-length mutant Htt by up to 50%. A chemical exploration around the series led to the identification of compound 4f, which demonstrated to be active in a Htt171-82Q rat primary striatal neuron assay and a PC12-Exon-1 based assay. This compound was selected for testing in R6/2 mice, in which it was well-tolerated and showed a positive effect on body weight and a positive trend in preventing ventricular volume enlargment. These studies provide strong rationale for further testing the potential benefits of 3-hydroxy-3-trifluoromethylpyrazoles in treating HD.

Nicotinamide adenine dinucleotide phosphate oxidase in experimental liver fibrosis: GKT137831 as a novel potential therapeutic agent.

UNLABELLED: Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) generates reactive oxygen species (ROS) in hepatic stellate cells (HSCs) during liver fibrosis. In response to fibrogenic agonists, such as angiotensin II (Ang II), the NOX1 components form an active complex, including Ras-related botulinum toxin substrate 1 (Rac1). Superoxide dismutase 1 (SOD1) interacts with the NOX-Rac1 complex to stimulate NOX activity. NOX4 is also induced in activated HSCs/myofibroblast by increased gene expression. Here, we investigate the role of an enhanced activity SOD1 G37R mutation (SODmu) and the effects of GKT137831, a dual NOX1/4 inhibitor, on HSCs and liver fibrosis. To induce liver fibrosis, wild-type (WT) and SOD1mu mice were treated with CCl(4) or bile duct ligation (BDL). Then, to address the role of NOX-SOD1-mediated ROS production in HSC activation and liver fibrosis, mice were treated with a NOX1/4 inhibitor. Fibrosis and ROS generation was assessed by histology and measurement of thiobarbituric acid reactive substances and NOX-related genes. Primary cultured HSCs isolated from WT, SODmu, and NOX1 knockout (KO) mice were assessed for ROS production, Rac1 activity, and NOX gene expression. Liver fibrosis was increased in SOD1mu mice, and ROS production and Rac1 activity were increased in SOD1mu HSCs. The NOX1/4 inhibitor, GKT137831, attenuated liver fibrosis and ROS production in both SOD1mu and WT mice as well as messenger RNA expression of fibrotic and NOX genes. Treatment with GKT137831 suppressed ROS production and NOX and fibrotic gene expression, but not Rac1 activity, in SOD1mut and WT HSCs. Both Ang II and tumor growth factor beta up-regulated NOX4, but Ang II required NOX1. CONCLUSIONS: SOD1mu induces excessive NOX1 activation through Rac1 in HSCs, causing enhanced NOX4 up-regulation, ROS generation, and liver fibrosis. Treatment targeting NOX1/4 may be a new therapy for liver fibrosis.

Design, synthesis and biological activity of original pyrazolo-pyrido-diazepine, -pyrazine and -oxazine dione derivatives as novel dual Nox4/Nox1 inhibitors.

Pyrazolo-pyrido-diazepine, -pyrazine and -oxazine dione derivatives are new chemical entities with good and attractive druglikeness properties. A series of pyrazolo-pyrido-diazepine dione analogs demonstrated to be particularly amenable to lead optimization through a couple of cycles in order to improve specificity for isoforms Nox4 and Nox1 and had excellent pharmacokinetic parameters by oral route. Several molecules such as compound 7c proved to be highly potent in in vitro assays on human lung fibroblasts differentiation as well as in curative murine models of bleomycin-induced pulmonary fibrosis with superior efficiency over Pirfenidone. Pyrazolo-pyrido-diazepine dione derivatives targeting Nox4 and Nox1 isoforms appear highly promising therapeutics for the treatment of idiopathic pulmonary fibrosis.

Targeting vascular NADPH oxidase 1 blocks tumor angiogenesis through a PPARα mediated mechanism.

Reactive oxygen species, ROS, are regulators of endothelial cell migration, proliferation and survival, events critically involved in angiogenesis. Different isoforms of ROS-generating NOX enzymes are expressed in the vasculature and provide distinct signaling cues through differential localization and activation. We show that mice deficient in NOX1, but not NOX2 or NOX4, have impaired angiogenesis. NOX1 expression and activity is increased in primary mouse and human endothelial cells upon angiogenic stimulation. NOX1 silencing decreases endothelial cell migration and tube-like structure formation, through the inhibition of PPARα, a regulator of NF-κB. Administration of a novel NOX-specific inhibitor reduced angiogenesis and tumor growth in vivo in a PPARα dependent manner. In conclusion, vascular NOX1 is a critical mediator of angiogenesis and an attractive target for anti-angiogenic therapies.

First in class, potent, and orally bioavailable NADPH oxidase isoform 4 (Nox4) inhibitors for the treatment of idiopathic pulmonary fibrosis.

We describe the design, synthesis, and optimization of first-in-class series of inhibitors of NADPH oxidase isoform 4 (Nox4), an enzyme implicated in several pathologies, in particular idiopathic pulmonary fibrosis, a life-threatening and orphan disease. Initially, several moderately potent pyrazolopyridine dione derivatives were found during a high-throughput screening campaign. SAR investigation around the pyrazolopyridine dione core led to the discovery of several double-digit nanomolar inhibitors in cell free assays of reactive oxygen species (ROS) production, showing high potency on Nox4 and Nox1. The compounds have little affinity for Nox2 isoform and are selective for Nox4/1 isoforms. The specificity of these compounds was confirmed in an extensive in vitro pharmacological profile, as well as in a counterscreening assay for potential ROS scavenging. Concomitant benefits are good oral bioavailability and high plasma concentrations in vivo, allowing further clinical trials for the potential treatment of fibrotic diseases, cancers, and cardiovascular and metabolic diseases.

Small molecule drug discovery for Huntington's Disease.

Huntington's Disease (HD) is a rare neurodegenerative disease caused by mutation of the huntingtin gene that results in a protein with an expanded stretch of glutamine repeats (polyQ). Knowledge of validated targets is in its infancy, and thus, traditional target-based drug discovery strategies are of limited use. Alternative approaches are needed, and early attempts were aimed at identifying molecules that inhibited the aggregation of polyQ huntingtin fragments. More recently, phenotypic assays were used to find molecules able to reverse some of the pathogenic mechanisms of HD. Such discovery strategies have an impact on the configuration of screening cascades for effective translation of drug candidates toward clinical trials.

Drug discovery and development for Huntington's disease - an orphan indication with high medical need.

Huntington's disease (HD) is a rare neurodegenerative disorder that progressively destroys the mental capacity and motor control of patients. This loss of motor control results in abnormal body movements (chorea) - the hallmark of HD. Given that no disease-modifying therapy for HD exists and that available symptomatic treatments are not highly efficacious, the medical need for this 'orphan' disease remains high. The number of compounds that are undergoing discovery and development for the treatment of HD has increased significantly in recent years, spurred by legislative incentives for orphan drug development and by support from non-profit foundations. Thus, hope exists for patients with HD that efficacious medicines will become available.

Presence of functional oxytocin receptors in cultured human myoblasts.

In the present report, we provide for the first time evidence that functional oxytocin receptors (OTRs) are present in human myoblasts obtained from clonal cultures of postnatal satellite cells. First, binding studies performed with a non selective vasopressin (AVP) and oxytocin (OT) radioligand indicated the presence of a single class of binding sites. Second, OTR mRNA was detected by RT-PCR analysis whereas transcripts for AVP V(1a), V(1b) or V(2) receptors (V(1a)R, V(1b)R and V(2)R respectively) were not detected. Third, the presence of functional OTRs was evidenced by showing that agonist substances having a high affinity for the human OTR, namely OT, AVP and [Thr(4)Gly(7)]OT, increased the rate of myoblasts fusion and myotubes formation in the cultures, whereas F180, a V(1a)R selective agonist, and dDAVP, a V(2)R agonist had no significant effect on the fusion process. In addition, we show by RT-PCR and immunocytochemistry that the OT gene is expressed in cultured myoblasts. Taken together, our data suggest that OT may act as a paracrine/autocrine agent that stimulates the fusion of human myoblasts in vitro. In vivo, OT may be involved in the differentiation of human skeletal muscle during postnatal growth, and possibly its regeneration following injury.

Up-regulation of vasopressin and angiotensin II receptors in the thalamus and brainstem of inbred polydipsic mice.

Vasopressin (AVP), angiotensin II (Ang II) and oxytocin (OT) receptors were mapped in the brain of inbred polydipsic mice of the STR/N strain by quantitative in vitro autoradiography and receptor binding levels, compared with those found in control non-polydipsic mice of the ICR strain. A remarkable difference was evidenced in the thalamic paraventricular nucleus where AVP receptor binding was 7- to 10-fold higher in polydipsic mice than in control mice. Another disparity was observed in the hypothalamic paraventricular nucleus, which contained AVP binding sites in the control mice, but was unlabelled in the polydipsic animals. Ang II receptor binding was reduced in the hypothalamic paraventricular nucleus of the polydipsic mice, whereas it was abundant in the brainstem region, encompassing area postrema and the nucleus of the solitary tract. The distribution and amount of OT receptor binding were similar in the polydipsic and control mice. Strain-related differences of AVP and Ang II receptor binding were observed both in male and female animals. A sex-related difference was seen only for OT receptor binding in the hypothalamic ventromedial nucleus, where labelling was less intense in males than in females of both strains. Altogether, our results support the view that central AVP and Ang II systems are involved in the mechanisms responsible for polydipsia in STR/N mice.