IDO1 inhibitors are synergistic with CXCL10 agonists in inhibiting colon cancer growth.

Indoleamine 2,3-dioxygenase 1 (IDO1) is an immune checkpoint that degrades L-tryptophan to kynurenine (Kyn) and enhance immunosuppression, which can be an attractive target for treating colon cancer. IDO1 inhibitors have limited efficacy when used as monotherapies, and their combination approach has been shown to provide synergistic benefits. Many studies have shown that targeting chemokines can promote the efficacy of immune checkpoint inhibitors. Therefore, this study explored the use of IDO1 inhibitors with multiple chemokines to develop a new combination regimen for IDO1 inhibitors. We found that IDO1 inhibitors reduce the secretion of C-X-C motif ligand 10(CXCL10) in cancer cells, and CXCL10 supplementation significantly improved the anticancer effect of IDO1 inhibitors. The combination of the IDO1 inhibitor with CXCL10 or its agonist axitinib had a synergistic inhibitory effect on the growth of colon cancer cells and transplanted CT26 tumors. This synergistic effect may be achieved by inhibiting cancer cell proliferation, promoting cancer cell apoptosis, promoting CD8+T cell differentiation and decreasing Tregs. Two downstream pathways of IDO1 affect CXCL10 secretion. One being the Kyn-aryl hydrocarbon receptor (AHR) pathway, the other is the general control nonderepressible 2(GCN2). Our study provides a new reference for combination regimens of IDO1 inhibitors.

mRNA-delivery of IDO1 suppresses T cell-mediated autoimmunity.

Indoleamine-2,3-dioxygenase (IDO)1 degrades tryptophan, obtained through dietary intake, into immunoregulatory metabolites of the kynurenine pathway. Deficiency or blockade of IDO1 results in the enhancement of autoimmune severity in rodent models and increased susceptibility to developing autoimmunity in humans. Despite this, therapeutic modalities that leverage IDO1 for the treatment of autoimmunity remain limited. Here, we use messenger (m)RNA formulated in lipid nanoparticles (LNPs) to deliver a human IDO1 variant containing the myristoylation site of Src to anchor the protein to the inner face of the plasma membrane. This membrane-anchored IDO1 has increased protein production, leading to increased metabolite changes, and ultimately ameliorates disease in three models of T cell-mediated autoimmunity: experimental autoimmune encephalomyelitis (EAE), rat collagen-induced arthritis (CIA), and acute graft-versus-host disease (aGVHD). The efficacy of IDO1 is correlated with hepatic expression and systemic tryptophan depletion. Thus, the delivery of membrane-anchored IDO1 by mRNA suppresses the immune response in several well-characterized models of autoimmunity.

Tryptophan Metabolism in Obesity: The Indoleamine 2,3-Dioxygenase-1 Activity and Therapeutic Options.

Obesity activates both innate and adaptive immune responses in adipose tissue. Adipose tissue macrophages are functional antigen-presenting cells that promote the proliferation of interferon-gamma (IFN-γ)-producing cluster of differentiation (CD)4+ T cells in adipose tissue of obese subjects. The increased formation of neopterin and degradation of tryptophan may result in decreased T-cell responsiveness and lead to immunodeficiency. The activity of inducible indoleamine 2,3-dioxygenase-1 (IDO1) plays a major role in pro-inflammatory, IFN-γ-dominated settings. The expression of several kynurenine pathway enzyme genes is significantly increased in obesity. IDO1 in obesity shifts tryptophan metabolism from serotonin and melatonin synthesis to the formation of kynurenines and increases the ratio of kynurenine to tryptophan as well as with neopterin production. Reduction in serotonin (5-hydroxytryptamine; 5-HT) production provokes satiety dysregulation that leads to increased caloric uptake and obesity. According to the monoamine-deficiency hypothesis, a deficiency of cerebral serotonin is involved in neuropsychiatric symptomatology of depression, mania, and psychosis. Indeed, bipolar disorder (BD) and related cognitive deficits are accompanied by a higher prevalence of overweight and obesity. Furthermore, the accumulation of amyloid-ß in Alzheimer's disease brains has several toxic effects as well as IDO induction. Hence, abdominal obesity is associated with vascular endothelial dysfunction. kynurenines and their ratios are prognostic parameters in coronary artery disease. Increased kynurenine/tryptophan ratio correlates with increased intima-media thickness and represents advanced atherosclerosis. However, after bariatric surgery, weight reduction does not lead to the normalization of IDO1 activity and atherosclerosis. IDO1 is involved in the mechanisms of immune tolerance and in the concept of tumor immuno-editing process in cancer development. Serum IDO1 activity is still used as a parameter in cancer development and growth. IDO-producing tumors show a high total IDO immunostaining score, and thus, using IDO inhibitors, such as Epacadostat, Navoximod, and L isomer of 1-methyl-tryptophan, seems an important modality for cancer treatment. There is an inverse correlation between serum folate concentration and body mass index, thus folate deficiency leads to hyperhomocysteinemia-induced oxidative stress. Immune checkpoint blockade targeting cytotoxic T-lymphocyte-associated protein-4 synergizes with imatinib, which is an inhibitor of mitochondrial folate-mediated one-carbon (1C) metabolism. Antitumor effects of imatinib are enhanced by increasing T-cell effector function in the presence of IDO inhibition. Combining IDO targeting with chemotherapy, radiotherapy and/or immunotherapy, may be an effective tool against a wide range of malignancies. However, there are some controversial results regarding the efficacy of IDO1 inhibitors in cancer treatment.

Macrophage Activation Syndrome in Coinciding Pandemics of Obesity and COVID-19: Worse than Bad.

Epigenetic changes have long-lasting impacts, which influence the epigenome and are maintained during cell division. Thus, human genome changes have required a very long timescale to become a major contributor to the current obesity pandemic. Whereas bidirectional effects of coronavirus disease 2019 (COVID-19) and obesity pandemics have given the opportunity to explore, how the viral microribonucleic acids (miRNAs) use the human's transcriptional machinery that regulate gene expression at a posttranscriptional level. Obesity and its related comorbidity, type 2 diabetes (T2D), and new-onset diabetes due to severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) are additional risk factors, which increase the severity of COVID-19 and its related mortality. The higher mortality rate of these patients is dependent on severe cytokine storm, which is the sum of the additional cytokine production by concomitant comorbidities and own cytokine synthesis of COVID-19. Patients with obesity facilitate the SARS-CoV-2 entry to host cell via increasing the host's cell receptor expression and modifying the host cell proteases. After entering the host cells, the SARS-CoV-2 genome directly functions as a messenger ribonucleic acid (mRNA) and encodes a set of nonstructural proteins via processing by the own proteases, main protease (Mpro), and papain-like protease (PLpro) to initiate viral genome replication and transcription. Following viral invasion, SARS-CoV-2 infection reduces insulin secretion via either inducing ß-cell apoptosis or reducing intensity of angiotensin-converting enzyme 2 (ACE2) receptors and leads to new-onset diabetes. Since both T2D and severity of COVID-19 are associated with the increased serum levels of pro-inflammatory cytokines, high glucose levels in T2D aggravate SARS-CoV-2 infection. Elevated neopterin (NPT) value due to persistent interferon gamma (IFN-γ)-mediated monocyte-macrophage activation is an indicator of hyperactivated pro-inflammatory phenotype M1 macrophages. Thus, NPT could be a reliable biomarker for the simultaneously occurring COVID-19-, obesity- and T2D-induced cytokine storm. While host miRNAs attack viral RNAs, viral miRNAs target host transcripts. Eventually, the expression rate and type of miRNAs also are different in COVID-19 patients with different viral loads. It is concluded that specific miRNA signatures in macrophage activation phase may provide an opportunity to become aware of the severity of COVID-19 in patients with obesity and obesity-related T2D.

Nanodelivery Optimization of IDO1 Inhibitors in Tumor Immunotherapy: Challenges and Strategies.

Tryptophan (Trp) metabolism plays a vital role in cancer immunity. Indoleamine 2.3-dioxygenase 1 (IDO1), is a crucial enzyme in the metabolic pathway by which Trp is degraded to kynurenine (Kyn). IDO1-mediated Trp metabolites can inhibit tumor immunity and facilitate immune evasion by cancer cells; thus, targeting IDO1 is a potential tumor immunotherapy strategy. Recently, numerous IDO1 inhibitors have been introduced into clinical trials as immunotherapeutic agents for cancer treatment. However, drawbacks such as low oral bioavailability, slow onset of action, and high toxicity are associated with these drugs. With the continuous development of nanotechnology, medicine is gradually entering an era of precision healthcare. Nanodrugs carried by inorganic, lipid, and polymer nanoparticles (NPs) have shown great potential for tumor therapy, providing new ways to overcome tumor diversity and improve therapeutic efficacy. Compared to traditional drugs, nanomedicines offer numerous significant advantages, including a prolonged half-life, low toxicity, targeted delivery, and responsive release. Moreover, based on the physicochemical properties of these nanomaterials (eg, photothermal, ultrasonic response, and chemocatalytic properties), various combination therapeutic strategies have been developed to synergize the effects of IDO1 inhibitors and enhance their anticancer efficacy. This review is an overview of the mechanism by which the Trp-IDO1-Kyn pathway acts in tumor immune escape. The classification of IDO1 inhibitors, their clinical applications, and barriers for translational development are discussed, the use of IDO1 inhibitor-based nanodrug delivery systems as combination therapy strategies is summarized, and the issues faced in their clinical application are elucidated. We expect that this review will provide guidance for the development of IDO1 inhibitor-based nanoparticle nanomedicines that can overcome the limitations of current treatments, improve the efficacy of cancer immunotherapy, and lead to new breakthroughs in the field of cancer immunotherapy.

The effects of chronic, continuous ß-funaltrexamine pre-treatment on lipopolysaccharide-induced inflammation and behavioral deficits in C57BL/6J mice.

BACKGROUND: Inflammation and neuroinflammation are integral to the progression and severity of many diseases and are strongly associated with cardiovascular disease, cancer, autoimmune disorders, neurodegenerative disease, and neuropsychiatric disorders. These diseases can be difficult to treat without addressing the underlying inflammation, and, as such, a growing need has arisen for pharmaceutical treatments that target inflammatory mediators and signaling pathways. Our lab has investigated the therapeutic potential of the irreversible µ-opioid antagonist ß-funaltrexamine (ß-FNA) and discovered that acute treatment ameliorates inflammation in astrocytes in vitro and inhibits central and peripheral inflammation and reduces anxiety- and sickness-like behavior in male C57BL/6J mice. Now, our investigation has expanded to investigate the chronic pre-treatment effects of ß-FNA on lipopolysaccharide (LPS)-induced inflammation and behavior in male C57BL/6J mice. RESULTS: Micro-osmotic drug pumps were surgically inserted into the subcutaneous intrascapular space of male C57BL/6J mice. ß-FNA or saline vehicle was continuously administered for seven days. On the sixth day, mice were given intraperitoneal injections of LPS or saline. An elevated plus maze test, followed by a forced swim test, were administered 24 h post-injection to measure sickness-, anxiety- and depressive-like behavior. Immediately after testing, frontal cortex, hippocampus, spleen, and plasma were collected. Levels of inflammatory chemokines C-C motif chemokine ligand 2 (CCL2) and C-X-C motif chemokine ligand 10 (CXCL10) were measured in tissues by enzyme-linked immunosorbent assay (ELISA). Quantitative reverse transcription polymerase chain reaction (RT-qPCR) was used to assess expression of the enzyme indoleamine 2, 3-dioxygenase 1 (IDO1) and the NLR family pyrin domain-containing protein 3 (NRLP3) inflammasome in frontal cortex and spleen tissues. Chronic pre-treatment robustly decreased inflammation in the hippocampus, frontal cortex, and spleen and reduced or abolished anxiety- and sickness-like behavior (e.g., increased time spent motionless, increased time spent in a contracted position, and reduced distance moved). However, treatment with ß-FNA alone increased both inflammation in the frontal cortex and anxiety-like behavior. CONCLUSION: These findings provide novel insights into the anti-inflammatory and behavior-modifying effects of chronic ß-FNA pre-treatment and continue to support the therapeutic potential of ß-FNA under inflammatory conditions.

Transformable self-delivered supramolecular nanomaterials combined with anti-PD-1 antibodies alleviate tumor immunosuppression to treat breast cancer with bone metastasis.

Breast cancer is the most common malignant tumor that threatens women's life and health, and metastasis often occurs in the advanced stage of breast cancer, leading to pathological bone destruction and seriously reducing patient quality of life. In this study, we coupled chlorin e6 (Ce6) with mono-(6-amino-6-deoxy)-beta-cyclodextrin (ß-CD) to form Ce6-CD, and combined ferrocene with the FFVLG3C peptide and PEG chains to form the triblock molecule Fc-pep-PEG. In addition, the IDO-1 inhibitor NLG919 was loaded with Ce6-CD and Fc-pep-PEG to construct the supramolecular nanoparticle NLG919@Ce6-CD/Fc-pep-PEG (NLG919@CF). After laser irradiation, Ce6 produced robust reactive oxidative species to induce tumor cell apoptosis. Simultaneously, ferrocene became charged, and Fc-pep-PEG dissociated from the spherical nanoparticles, enabling their transformation into nanofibers, which increased both the retention effect and the induction of ferroptosis. The released NLG919 reduced the number of regulatory T cells (Tregs) and restored the function of cytotoxic T lymphocytes (CTLs) by inhibiting the activity of IDO-1. Moreover, combined administration with an anti-PD-1 antibody further relieved immune suppression in the tumor microenvironment. This article presents a new strategy for the clinical treatment of breast cancer with bone metastasis and osteolysis.

Integrated metabolic-transcriptomic network identifies immunometabolic modulations in human macrophages.

Macrophages exhibit diverse phenotypes and respond flexibly to environmental cues through metabolic remodeling. In this study, we present a comprehensive multi-omics dataset integrating intra- and extracellular metabolomes with transcriptomic data to investigate the metabolic impact on human macrophage function. Our analysis establishes a metabolite-gene correlation network that characterizes macrophage activation. We find that the concurrent inhibition of tryptophan catabolism by IDO1 and IL4I1 inhibitors suppresses the macrophage pro-inflammatory response, whereas single inhibition leads to pro-inflammatory activation. We find that a subset of anti-inflammatory macrophages activated by Fc receptor signaling promotes glycolysis, challenging the conventional concept of reduced glycolysis preference in anti-inflammatory macrophages. We demonstrate that cholesterol accumulation suppresses macrophage IFN-γ responses. Our integrated network enables the discovery of immunometabolic features, provides insights into macrophage functional metabolic reprogramming, and offers valuable resources for researchers exploring macrophage immunometabolic characteristics and potential therapeutic targets for immune-related disorders.

Targeting amino acid-metabolizing enzymes for cancer immunotherapy.

Despite the immune system's role in the detection and eradication of abnormal cells, cancer cells often evade elimination by exploitation of various immune escape mechanisms. Among these mechanisms is the ability of cancer cells to upregulate amino acid-metabolizing enzymes, or to induce these enzymes in tumor-infiltrating immunosuppressive cells. Amino acids are fundamental cellular nutrients required for a variety of physiological processes, and their inadequacy can severely impact immune cell function. Amino acid-derived metabolites can additionally dampen the anti-tumor immune response by means of their immunosuppressive activities, whilst some can also promote tumor growth directly. Based on their evident role in tumor immune escape, the amino acid-metabolizing enzymes glutaminase 1 (GLS1), arginase 1 (ARG1), inducible nitric oxide synthase (iNOS), indoleamine 2,3-dioxygenase 1 (IDO1), tryptophan 2,3-dioxygenase (TDO) and interleukin 4 induced 1 (IL4I1) each serve as a promising target for immunotherapeutic intervention. This review summarizes and discusses the involvement of these enzymes in cancer, their effect on the anti-tumor immune response and the recent progress made in the preclinical and clinical evaluation of inhibitors targeting these enzymes.

Interstitial Foci Expression of Indoleamine 2,3-Dioxygenase 1: A Potential Biomarker for Kidney Transplant Rejection.

(1) Background: Kidney transplantation is the best therapy for patients with end-stage renal disease, but the risk of rejection complicates it. Indoleamine 2,3-dioxygenase 1 (IDO1), an enzyme involved in immune response modulation, has been suggested to play a role in transplant immunological injury. The aim of the study was to explore the expression of IDO1 in the interstitial foci of transplanted kidneys and its potential association with rejection episodes. (2) Methods: This retrospective study analysed kidney transplant biopsies from 121 patients, focusing on IDO1 expression in interstitial foci. Immunohistochemistry was used to detect IDO1, and patients were categorised based on IDO1 presence (IDO1-IF positive or negative). The incidence of rejection was compared between these groups. (3) Results: Patients with IDO1 expression in interstitial foci (IDO1-IF(+)) exhibited higher incidences of rejection 46/80 (57.5%) vs. 10/41 (24.34%) patients compared to IDO1-IF(-) patients, which was statistically significant with p = 0.0005. The analysis of antibody-mediated rejection showed that IDO1-IF(+) patients developed AMR at 12/80 (15%), while only 1 IDO1-IF(-) negative patient did (2,44%), with p = 0.035. T-cell-mediated rejection was also more common in IDO1-IF(+) patients 43/80 (53.75%) than in IDO1-IF(-) patients 7/41 (17.07%), with p = 0.0001. (4) Conclusions: IDO1 expression in interstitial foci of renal transplant biopsies is associated with a higher incidence of rejection, suggesting that IDO1 could serve as a potential biomarker for transplant rejection. These findings highlight the importance of IDO1 in immune regulation and its potential utility in improving the management of kidney transplant recipients.

Immunohistochemical Detection of Indoleamine 2,3-Dioxygenase in Spontaneous Mammary Carcinomas of 96 Pet Rabbits.

For mammary carcinomas in pet rabbits, prognostic biomarkers are poorly defined, and treatment is limited to surgical excision. Additional treatment options are needed for rabbit patients for which surgery is not a suitable option. In human breast cancer, the immunosuppressive enzyme indoleamine 2,3-dioxygenase 1 (IDO1) represents a prognostic biomarker and possible therapeutic target. This retrospective immunohistochemical study examined IDO1 in 96 pet rabbit mammary carcinomas with known mitotic count, hormone receptor status, and percentage of stromal tumor infiltrating lymphocytes (TILs). Tumors were obtained from 96 pet rabbits with an average of 5.5 years. All rabbits with reported sex (n = 88) were female or female-spayed. Of the carcinomas, 94% expressed IDO1, and 86% had sparse TILs consistent with cold tumors. Statistically significant correlations existed between a higher percentage of IDO1-positive tumor cells, lower mitotic counts, and increased estrogen receptor expression. The threshold for significance was IDO1 staining in >10% of tumor cells. These results lead to the assumption that IDO1 expression contributes to tumorigenesis and may represent a prognostic biomarker and possible therapeutic target also in pet rabbit mammary carcinomas. They also support the value of rabbits for breast cancer research.

Exploring the Surface: Sampling of Potential Skin Cancer Biomarkers Kynurenine and Tryptophan, Studied on 3D Melanocyte and Melanoma Models.

Early detection of cancer via biomarkers is vital for improving patient survival rates. In the case of skin cancers, low-molecular-weight biomarkers can penetrate the skin barrier, enabling non-invasive sampling at an early stage. This study focuses on detecting tryptophan (Trp) and kynurenine (Kyn) on the surface of reconstructed 3D melanoma and melanocyte models. This is examined in connection with IDO-1 and IL-6 expression in response to IFN-γ or UVB stimulation, both crucial factors of the melanoma tumor microenvironment (TME). Using a polystyrene scaffold, full-thickness human skin equivalents containing fibroblasts, keratinocytes, and melanocytes or melanoma cells were developed. The samples were stimulated with IFN-γ or UVB, and Trp and Kyn secretion was measured using HPLC-PDA and HPLC-MS. The expression of IDO-1 and IL-6 was measured using RT-qPCR. Increased Trp catabolism to Kyn was observed in IFN-γ-stimulated melanoma and melanocyte models, along with higher IDO-1 expression. UVB exposure led to significant changes in Kyn levels but only in the melanoma model. This study demonstrates the potential of skin surface Trp and Kyn monitoring to capture TME metabolic changes. It also lays the groundwork for future in vivo studies, aiding in understanding and monitoring skin cancer progression.

TRIM28 Regulates Proliferation of Gastric Cancer Cells Partly Through SRF/IDO1 Axis.

Background: Gastric cancer (GC) is one of the most common malignancies worldwide, with high incidence and mortality rate. Tripartite motif-containing 28 (TRIM28) is an important molecule that affects the occurrence and development of tumors, but its function in GC has not been elucidated clearly. The purpose of this study is to explore the molecular mechanism by which TRIM28 affect the GC. Methods: TRIM28 expression was tested in RNA-seq data from TCGA database, tumor tissue samples from patients and GC cell lines. Genes were silenced or overexpressed by siRNA, lentivirus-mediated shRNA, or plasmids. Cell Counting Kit-8 (CCK-8) and colony formation assays were performed to explore the proliferation of GC cells after TRIM28 knockdown. RNA-seq and TCGA database were used to identify target genes. Luciferase report assay was employed to detect the possible mechanism between TRIM28 and Indoleamine 2,3-dioxygenase (IDO1). Tryptophan concentration in cell supernatant was measured using a fluorometric assay kit. MGC-803 and 746T cells were injected into mice to establish xenograft animal models. Results: The expression of TRIM28 was positively correlated with tumor size and poorer prognosis. Upregulation of TRIM28 was observed in GC tissues and cells. In vitro, we proved that knockdown of TRIM28 significantly inhibited the proliferation of GC cells. Then TRIM28 was found to be positively correlated with the expression of IDO1 in GC cells. In accordance with this, tryptophan levels in cell supernatants were increased in TRIM28 knockdown GC cells and overexpression of IDO1 could reverse this phenotype. Serum response factor (SRF), a reported regulator of IDO1, was also regulated by TRIM28 in GC cells. And decreased expression of IDO1 induced by TRIM28 knockdown could be partly reversed through overexpression of serum response factor (SRF) in GC cells. Functional research demonstrated that the expression of IDO1 was increased in GC and IDO1 knockdown could also inhibited the proliferation of GC cells. Furthermore, overexpression of IDO1 could partly reverse proliferation inhibited by TRIM28 knockdown in GC cells. In vivo, knockdown of TRIM28 significantly inhibited the tumor growth and overexpression of IDO1 and SRF both could reverse proliferation inhibited by TRIM28 knockdown. Conclusions: TRIM28 is crucial in the development of GC, and may regulate IDO1 through SRF. TRIM28 promote GC cell proliferation through SRF/IDO1 axis.

Corrigendum: HSA-nanobinders crafted from bioresponsive prodrugs for combined cancer chemoimmunotherapy-an in vitro exploration.

[This corrects the article DOI: 10.3389/fchem.2024.1378233.].

Expression and Function of Long Non-coding RNA in Endemic Cretinism.

Endemic cretinism (EC) is one of the most severe iodine deficiency disorders, leading to typical symptoms such as neurodevelopmental impairments or mental deficits. In addition to environmental factors, the pathogenesis of its genetic contribution remains unclear. The study revealed the differential expression profiles of long non-coding RNA(lncRNA) and messenger RNA(mRNA) based on high-throughput RNA-seq. GO and KEGG analyses were used to annotate the function and pathway of differentially expressed (DE) mRNA and co-expressed mRNA. The protein-protein interaction(PPI) network was established. The expression levels of three lncRNAs and six mRNAs were validated by quantitative real-time PCR analysis (qRT-PCR) and subjected to correlation analysis. Compared to controls, a total of 864 lncRNAs and 393 mRNAs were differentially expressed. The PPI network had 149 nodes and 238 edges, and three key protein-coding genes were observed. Levels of LINC01220 and target mRNA IDO1 were statistically elevated in EC patients. Differentially expressed lncRNA may be a new potential player in EC. LINC01220 and IDO1 might interact with each other to participate in EC. The biological process of regulation of postsynaptic membrane potential and the Rap1 signaling pathway might exert a regulating role in the pathophysiological process of EC. Our findings could provide more theoretical and experimental evidence for investigating the pathophysiological mechanisms of EC.

A randomized, open-label, phase 3 trial of pembrolizumab plus epacadostat versus sunitinib or pazopanib as first-line treatment for metastatic renal cell carcinoma (KEYNOTE-679/ECHO-302).

BACKGROUND: Immunotherapy-based combinations have emerged as standard therapies for patients with metastatic renal cell carcinoma (mRCC). Pembrolizumab, a PD-1 inhibitor, combined with epacadostat, an indoleamine 2,3-deoxygenase 1 selective inhibitor, demonstrated promising antitumor activity in a phase 1 study in advanced solid tumors, including mRCC. METHODS: KEYNOTE-679/ECHO-302 was a randomized, open-label, parallel-group, multicenter, phase 3 study (NCT03260894) that compared pembrolizumab plus epacadostat with sunitinib or pazopanib as first-line treatment for mRCC. Eligible patients had histologically confirmed locally advanced or metastatic clear cell RCC and had not received systemic therapy. Patients were randomly assigned 1:1 to pembrolizumab 200 mg IV every 3 weeks plus epacadostat 100 mg orally twice daily versus sunitinib 50 mg orally once daily (4 weeks on treatment followed by 2 weeks off treatment) or pazopanib 800 mg orally once daily. Original dual primary end points were progression-free survival and overall survival. Enrollment was stopped when a phase 3 study in melanoma of pembrolizumab plus epacadostat compared with pembrolizumab monotherapy did not meet its primary end point. This protocol was amended, and primary end point was changed to investigator-assessed objective response rate (ORR) per RECIST 1.1. RESULTS: One-hundred-twenty-nine patients were randomly assigned to receive pembrolizumab plus epacadostat (n = 64) or sunitinib/pazopanib (n = 65). Median (range) follow-up, defined as time from randomization to data cutoff, was 10.3 months (2.2-14.3) and 10.3 months (2.7-13.8) in the pembrolizumab plus epacadostat and sunitinib/pazopanib arms, respectively. ORRs were similar between pembrolizumab plus epacadostat (31.3% [95% CI 20.2-44.1] and sunitinib/pazopanib (29.2% [18.6-41.8]). Grade 3-5 treatment-related adverse events occurred in 34.4% and 42.9% of patients in the pembrolizumab plus epacadostat and sunitinib/pazopanib arms, respectively. One patient in the sunitinib/pazopanib arm died of septic shock (not treatment-related). Circulating kynurenine levels decreased in the pembrolizumab plus epacadostat arm, but not to levels observed in healthy subjects. CONCLUSIONS: ORRs were similar between pembrolizumab plus epacadostat and sunitinib/pazopanib as first-line treatment in patients with mRCC. Safety and tolerability appeared similar between treatment arms; no new safety concerns were identified. Antitumor responses observed in patients with RCC receiving pembrolizumab plus epacadostat may be driven primarily by pembrolizumab. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov; NCT03260894 .

Artesunate induces melanoma cell ferroptosis and augments antitumor immunity through targeting Ido1.

Artesunate (ART), a natural product isolated from traditional Chinese plant Artemisia annua, has not been extensively explored for its anti-melanoma properties. In our study, we found that ART inhibited melanoma cell proliferation and induced melanoma cell ferroptosis. Mechanistic study revealed that ART directly targets Ido1, thereby suppressing Hic1-mediated transcription suppression of Hmox1, resulting in melanoma cell ferroptosis. In CD8+ T cells, ART does not cause cell ferroptosis due to the low expression of Hmox1. It also targets Ido1, elevating tryptophan levels, which inhibits NFATc1-mediated PD1 transcription, consequently activating CD8+ T cells. Our study uncovered a potent and synergistic anti-melanoma efficacy arising from ART-induced melanoma cell ferroptosis and concurrently enhancing CD8+ T cell-mediated immune response both in vivo and in vitro through directly targeting Ido1. Our study provides a novel mechanistic basis for the utilization of ART as an Ido1 inhibitor and application in clinical melanoma treatment.

Epacadostat plus pembrolizumab versus placebo plus pembrolizumab for advanced urothelial carcinoma: results from the randomized phase III ECHO-303/KEYNOTE-698 study.

BACKGROUND: Indoleamine 2,3-dioxygenase 1 (IDO1) levels correlate with poor outcomes in urothelial carcinoma (UC). IDO1 and programmed death-ligand 1 (PD-L1) are often co-expressed. Epacadostat is a potent and highly selective inhibitor of IDO1. In a subgroup analysis of patients with advanced UC participating in a phase I/II study, epacadostat-pembrolizumab treatment produced an objective response rate (ORR) of 35%. METHODS: ECHO-303/KEYNOTE-698 was a double-blinded, randomized phase III study of adults with metastatic or unresectable locally advanced UC with recurrence or progression following first-line platinum-based chemotherapy. Participants were randomized to epacadostat 100 mg twice daily (BID) plus pembrolizumab or placebo plus pembrolizumab until completion of 35 pembrolizumab infusions, disease progression, or unacceptable toxicity. The primary endpoint was investigator-assessed ORR per Response Evaluation Criteria in Solid Tumors version 1.1. RESULTS: Target enrollment was 648 patients; enrollment was halted early based on efficacy results from the phase III ECHO-301/KEYNOTE-252 study in metastatic melanoma. Forty-two patients were randomized to each treatment arm. Median duration of follow-up was 62 days in each arm. The investigator-assessed ORR (unconfirmed) was 26.2% (95% CI 16.35-48.11) for epacadostat plus pembrolizumab and 11.9% (95% CI 4.67-29.50) for placebo plus pembrolizumab. Two complete responses were reported, both in the placebo-plus-pembrolizumab arm. Circulating kynurenine levels increased from C1D1 to C2D1 in the placebo-plus-pembrolizumab arm and numerically decreased in the epacadostat-plus-pembrolizumab arm. The safety profile of epacadostat plus pembrolizumab was similar to that of pembrolizumab monotherapy, although a numerically greater proportion of patients in the combination vs. control arm experienced treatment-related grade ≥ 3 adverse events (16.7% vs. 7.3%). One patient in each arm died due to cardiovascular events, which were not deemed drug-related. No new safety concerns were identified for either agent. CONCLUSIONS: Epacadostat plus pembrolizumab demonstrated anti-tumor activity and was generally tolerable as second-line treatment of patients with unresectable locally advanced or recurrent/progressive metastatic UC. Epacadostat 100 mg BID, when administered with pembrolizumab, did not normalize circulating kynurenine in most patients. Further study of combined IDO1/PD-L1 inhibition in this patient population, particularly with epacadostat doses that result in durable normalization of circulating kynurenine, may be warranted. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03374488. Registered 12/15/2017.

Pembrolizumab plus either epacadostat or placebo for cisplatin-ineligible urothelial carcinoma: results from the ECHO-307/KEYNOTE-672 study.

BACKGROUND: Indoleamine 2,3- dioxygenase 1 (IDO1) is an immunosuppressive enzyme that has been correlated with shorter disease-specific survival in patients with urothelial carcinoma (UC). IDO1 may counteract the antitumor effects of immune checkpoint inhibitors. Epacadostat is a potent and highly selective inhibitor of IDO1. In the phase I/II ECHO-202/KEYNOTE-037 study, epacadostat plus pembrolizumab resulted in a preliminary objective response rate (ORR) of 35% in a cohort of patients with advanced UC. METHODS: ECHO-307/KEYNOTE-672 was a double-blinded, randomized, phase III study. Eligible adults had confirmed locally advanced/unresectable or metastatic UC of the urinary tract and were ineligible to receive cisplatin-based chemotherapy. Participants were randomly assigned (1:1) to receive epacadostat (100 mg twice daily) plus pembrolizumab (200 mg every 3 weeks) or placebo plus pembrolizumab for up to 35 pembrolizumab infusions. The primary endpoint was investigator-assessed ORR per Response Evaluation Criteria in Solid Tumors (version 1.1). RESULTS: A total of 93 patients were randomized (epacadostat plus pembrolizumab, n = 44; placebo plus pembrolizumab, n = 49). Enrollment was stopped early due to emerging data from the phase III ECHO-301/KEYNOTE-252 study. The median duration of follow-up was 64 days in both arms. Based on all available data at cutoff, ORR (unconfirmed) was 31.8% (95% CI, 22.46-55.24%) for epacadostat plus pembrolizumab and 24.5% (95% CI, 15.33-43.67%) for placebo plus pembrolizumab. Circulating kynurenine levels numerically increased from C1D1 to C2D1 in the placebo-plus-pembrolizumab arm and decreased in the epacadostat-plus-pembrolizumab arm. Epacadostat-plus-pembrolizumab combination treatment was well tolerated with a safety profile similar to the placebo arm. Treatment discontinuations due to treatment-related adverse events were more frequent with epacadostat (11.6% vs. 4.1%). CONCLUSIONS: Treatment with epacadostat plus pembrolizumab resulted in a similar ORR and safety profile as placebo plus pembrolizumab in cisplatin-ineligible patients with previously untreated locally advanced/unresectable or metastatic UC. At a dose of 100 mg twice daily, epacadostat did not appear to completely normalize circulating kynurenine levels when administered with pembrolizumab. Larger studies with longer follow-up and possibly testing higher doses of epacadostat, potentially in different therapy settings, may be warranted. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT03361865, retrospectively registered December 5, 2017.