Discovery of indoximod prodrugs and characterization of clinical candidate NLG802

A. M. Subbaiah M., Mandlekar S., Desikan S., Ramar T., Subramani L., Annadurai M., Desai S.D., Sinha S., Jenkins S.M., Krystal M.R., Subramanian M., Sridhar S., Padmanabhan S., Bhutani P., Arla R., et. al.

Phosphate and amino acid prodrugs of the HIV-1 protease inhibitor (PI) atazanavir (1) were prepared and evaluated to address solubility and absorption limitations. While the phosphate prodrug failed to release 1 in rats, the introduction of a methylene spacer facilitated prodrug activation, but parent exposure was lower than that following direct administration of 1. Val amino acid and Val-Val dipeptides imparted low plasma exposure of the parent, although the exposure of the prodrugs was high, reflecting good absorption. Screening of additional amino acids resulted in the identification of an l-Phe ester that offered an improved exposure of 1 and reduced levels of the circulating prodrug. Further molecular editing focusing on the linker design culminated in the discovery of the self-immolative l-Phe-Sar dipeptide derivative 74 that gave four-fold improved AUC and eight-fold higher Ctrough values of 1 compared with oral administration of the drug itself, demonstrating a successful prodrug approach to the oral delivery of 1.

Ambrosio L.F., Insfran C., Volpini X., Acosta Rodriguez E., Serra H.M., Quintana F.J., Cervi L., Motrán C.C.

Resistance to Trypanosoma cruzi infection is dependent on a rapid induction of Th1-type and CD8+ T cell responses that should be promptly balanced to prevent immunopathology. T. cruzi-infected B6 mice are able to control parasite replication but show a limited expansion of Foxp3+regulatory T (Treg) cells that results in the accumulation of effector immune cells and the development of acute liver pathology. AhR is a ligand-activated transcription factor that promotes Treg cell development and suppression of pro-inflammatory cytokine production in dendritic cells, altering the course of adaptive immune response and the development of immunopathology. Here, we used different AhR-dependent activation strategies aiming to improve the Treg response, and B6 congenic mice carrying a mutant AhR variant with low affinity for its ligands (AhRd) to evaluate the role of AhR activation by natural ligands during experimental T. cruzi infection. The outcome of TCDD or 3-HK plus ITE treatments indicated that strong or weak AhR activation before or during T. cruzi infection was effective to regulate inflammation improving the Treg cell response and regularizing the ratio between CD4+ CD25- to Treg cells. However, AhR activation shifted the host-parasite balance to the parasite replication. Weak AhR activation resulted in Treg promotion while strong activation differentially modulated the susceptibility and resistance of cell death in activated T and Treg cells and the increase in TGF-β-producing Treg cells. Of note, T. cruzi-infected AhRd mice showed low levels of Treg cells associated with strong Th1-type response, low parasite burden and absence of liver pathology. These mice developed a Treg- and Tr1-independent mechanism of Th1 constriction showing increased levels of systemic IL-10 and IL-10-secreting CD4+ splenocytes. In addition, AhR activation induced by exogenous ligands had negative effects on the development of memory CD8+ T cell subsets while the lack/very weak activation in AhRd mice showed opposite results, suggesting that AhR ligation restricts the differentiation of memory CD8+T cell subsets. We propose a model in which a threshold of AhR activation exists and may explain how activation or inhibition of AhR-derived signals by infection/inflammation-induced ligands, therapeutic interventions or exposure to pollutants can modulate infections/diseases outcomes or vaccination efficacy

Vale N., Ferreira A., Matos J., Fresco P., Gouveia M.

Although drugs currently used for the various types of diseases (e.g., antiparasitic, antiviral, antibacterial, etc.) are effective, they present several undesirable pharmacological and pharmaceutical properties. Most of the drugs have low bioavailability, lack of sensitivity, and do not target only the damaged cells, thus also affecting normal cells. Moreover, there is the risk of developing resistance against drugs upon chronic treatment. Consequently, their potential clinical applications might be limited and therefore, it is mandatory to find strategies that improve those properties of therapeutic agents. The development of prodrugs using amino acids as moieties has resulted in improvements in several properties, namely increased bioavailability, decreased toxicity of the parent drug, accurate delivery to target tissues or organs, and prevention of fast metabolism. Herein, we provide an overview of models currently in use of prodrug design with amino acids. Furthermore, we review the challenges related to the permeability of poorly absorbed drugs and transport and deliver on target organs.

Brincks E.L., Adams J., Essmann M., Turner B.A., Wang L., Ke J., Marcinowicz A., Vahanian N., Link C.J., Mautino M.R.

Abstract The IDO pathway mediates immunosuppressive effects by metabolizing tryptophan (Trp) into kynurenine (Kyn). The depletion of Trp stimulates downstream signaling through nutrient sensors GCN2 and mTOR, while the production of Kyn stimulates signaling through the aryl-hydrocarbon receptor (AHR) transcription factor. The activation of these signaling pathways has pleiotropic effects on immune cells, including influencing the differentiation of dendritic cells (DCs), helper T cells, and regulatory T cells (Treg) as well as enhancing the proliferation of effector T cells and Treg. Indoximod has been demonstrated to relieve IDO-mediated immunosuppression in vitro and in vivo, by creating an artificial Trp-sufficiency signal that bypasses activation of GCN2 and inhibition of mTOR in conditions of Trp deprivation. We hypothesized that indoximod's activity could also include the disruption of AHR activation by Kyn and other Trp catabolites, causing differential AHR signaling and transcriptional activity, resulting in an augmented antitumor immune response. We observed that indoximod activates AHR-dependent transcriptional activity in HepG2 cells as evidenced by increased AHR-driven luciferase and endogenous CYP1A1 activity. AHR activation by indoximod was also observed in primary human T cells, as measured by the induction of CYP1A1 mRNA. In a Kyn-driven Treg differentiation assay, indoximod altered transcription of genes associated with T helper and Treg phenotypes. Indoximod induced upregulation of Rorc expression, a TH17-associated transcription factor, while concurrently downregulating transcription of Foxp3, the master transcription factor of Treg cells. These effects were reverted by an AHR inhibitor. Consistent with the gene expression profiles, indoximod shifted the cellular phenotype from Foxp3+ Treg toward Th17-producing CD4 helper T cells. Transcription of Ido1 is controlled by IFNγ and AHR-response elements in its promoter. Consistent with the role of indoximod in blocking the IDO pathway, we observed that indoximod downregulated the expression and function of IDO in in vitro derived plasmacytoid DC that normally would express IDO under the same differentiation conditions. When these in vitro differentiated human pDCs were used in an MLR culture, the indoximod-induced downregulation of IDO resulted in decreased Kyn production and increased T cell proliferation. Moreover, indoximod treatment of tumor-bearing mice decreased expression of IDO in the pDC in tumor-draining LN. Together, these data suggest that indoximod modulates AHR signaling to exert multiple immunomodulatory effects, including a shift from suppressive Foxp3+ Treg toward TH17 helper T cells as well as the downregulation of IDO expression in pDC, contributing to enhanced antitumor immunity. Citation Format: Erik L. Brincks, James Adams, Michael Essmann, Benjamin A. Turner, Lifu Wang, Jiyuan Ke, Agnieszka Marcinowicz, Nicholas Vahanian, Charles J. Link, Mario R. Mautino. Indoximod modulates AhR-driven transcription of genes that control immune function [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3753.

Wang W., Huang L., Jin J., Jolly S., Zang Y., Wu H., Yan L., Pi W., Li L., Mellor A.L., Kong F.(.

Abstract Host immunity influences the impact of radiotherapy (RT) in cancer, but mechanistic connections remain obscure. In this study, we investigated the relationship of indoleamine 2,3-dioxygenase (IDO) systemic activity on clinical outcomes in RT-treated non–small cell lung cancer (NSCLC). IDO-mediated production of kynurenine and the kynurenine:tryptophan ratio in patient blood serum were determined for stage III NSCLC patients at times before, during, and after RT administration and then correlated to overall survival (OS), progression-free survival, and disease progression rate in patients. We found the impact of RT on these serum IDO markers to be heterogeneous in patients. On average, kynurenine:tryptophan ratios were reduced during RT but restored after RT. Notably, both baseline levels of kynurenine:tryptophan and changes in the levels of kynurenine after RT were significantly associated with OS. When combined, favorable change and favorable baseline corresponded with very long-term OS (median OS was not reached after 57 months of median follow-up). Favorable change combined with unfavorable baseline still corresponded with a lack of distant metastases. Our results suggest that RT alters IDO-mediated immune status in NSCLC patients and that changes in this serum biomarker may be useful to predict outcomes and perhaps personalize RT dosage to improve survival. Significance: Radiotherapy appears to influence systemic IDO activity and to exert a significant impact on metastatic risk and overall survival, with possible implications for defining a biomarker to optimize radiation dose in patients to improve outcomes. Cancer Res; 78(3); 809–16. ©2017 AACR.

Gutiérrez-Vázquez C., Quintana F.J.

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that is activated by small molecules provided by the diet, microorganisms, metabolism, and pollutants. AhR is expressed by a number of immune cells, and thus AhR signaling provides a molecular pathway that integrates the effects of the environment and metabolism on the immune response. Studies have shown that AhR signaling plays important roles in the immune system in health and disease. As its activity is regulated by small molecules, AhR also constitutes a potential target for therapeutic immunomodulation. In this review we discuss the role of AhR in the regulation of the immune response in the context of autoimmunity, infection, and cancer, as well as the potential opportunities and challenges of developing AhR-targeted therapeutics.

Li Q., Harden J.L., Anderson C.D., Egilmez N.K.

Abstract Previous studies demonstrated that IL-12–driven antitumor activity is short-circuited by a rapid switch in dendritic cell (DC) function from immunogenic to tolerogenic activity. This process was dependent on IFN-γ and the tolerogenic phenotype was conferred by IDO. Extended monitoring of IDO+ DC in the tumor-draining lymph nodes of IL-12 plus GM-CSF–treated tumor-bearing mice revealed that whereas IFN-γ induction was transient, IDO expression in DC was maintained long-term. An in vitro system modeling the IFN-γ–mediated change in DC function was developed to dissect the molecular basis of persistent IDO expression in post–IL-12 DC. Stimulation of DC with IFN-γ and CD40L resulted in rapid induction of IDO1 and IDO2 transcription and recapitulated the in vivo switch from immunogenic to tolerogenic activity. Long-term maintenance of IDO expression was found to be independent of exogenous and autocrine IFN-γ, or the secondary cytokines TGF-β, TNF-α, and IL-6. In contrast, both IDO enzymatic activity and IFN-γ–induced AhR expression were required for continued IDO transcription in vitro and in vivo. Addition of the tryptophan catabolite kynurenine to DC cultures in which IDO activity was blocked restored long-term IDO expression in wild-type DC but not in AhR-deficient DC, establishing the central role of the kynurenine–AhR pathway in maintaining IDO expression in tolerogenic DC. These findings shed further light on the cellular and molecular biology of the post–IL-12 regulatory rebound and provide insight into how feedback inhibitory mechanisms dominate in the long-term.

Soliman H.H., Minton S.E., Han H.S., Ismail-Khan R., Neuger A., Khambati F., Noyes D., Lush R., Chiappori A.A., Roberts J.D., Link C., Vahanian N.N., Mautino M., Streicher H., Sullivan D.M., et. al.

Indoximod is an oral inhibitor of the indoleamine 2,3-dioxygenase pathway, which causes tumor-mediated immunosuppression. Primary endpoints were maximum tolerated dose (MTD) and toxicity for indoximod in patients with advanced solid tumors. Secondary endpoints included response rates, pharmacokinetics, and immune correlates.Our 3+3 phase I trial comprised 10 dose levels (200, 300, 400, 600, and 800 mg once/day; 600, 800, 1200, 1600, and 2000 mg twice/day). Inclusion criteria were measurable metastatic solid malignancy, age ≥18 years, and adequate organ/marrow function. Exclusion criteria were chemotherapy ≤ 3 weeks prior, untreated brain metastases, autoimmune disease, or malabsorption.In 48 patients, MTD was not reached at 2000 mg twice/day. At 200 mg once/day, 3 patients previously treated with checkpoint inhibitors developed hypophysitis. Five patients showed stable disease >6 months. Indoximod plasma AUC and Cmax plateaued above 1200mg. Cmax (~12 μM at 2000 mg twice/day) occurred at 2.9 hours, and half-life was 10.5 hours. C reactive protein (CRP) levels increased across multiple dose levels.Indoximod was safe at doses up to 2000 mg orally twice/day. Best response was stable disease >6 months in 5 patients. Induction of hypophysitis, increased tumor antigen autoantibodies and CRP levels were observed.

Munn D.H., Mellor A.L.

Indoleamine 2,3-dioxygenase (IDO) has immunoregulatory roles associated with tryptophan metabolism. These include counter-regulation (controlling inflammation) and acquired tolerance in T cells. Recent findings reveal that IDO can be triggered by innate responses during tumorigenesis, and also by attempted T cell activation, either spontaneous or due to immunotherapy. Here we review the current understanding of mechanisms by which IDO participates in the control of inflammation and in peripheral tolerance. Focusing on the tumor microenvironment, we examine the role of IDO in response to apoptotic cells and the impact of IDO on Treg cell function. We discuss how the counter-regulatory and tolerogenic functions of IDO can be targeted for cancer immunotherapy and present an overview of the current clinical progress in this area.

Théate I., van Baren N., Pilotte L., Moulin P., Larrieu P., Renauld J., Hervé C., Gutierrez-Roelens I., Marbaix E., Sempoux C., Van den Eynde B.J.

Abstract Tryptophan catabolism by indoleamine 2,3-dioxygenase 1 (IDO1) plays a key role in tumoral resistance to immune rejection. In humans, constitutive expression of IDO1 has been observed in several tumor types. However, a comprehensive analysis of its expression in normal and tumor tissues is still required to anticipate the risks and potential benefits of IDO1 inhibitors. Using a newly validated monoclonal antibody to human IDO1, we performed an extensive immunohistochemical analysis of IDO1 expression in normal and tumor tissues. In normal tissues, IDO1 was expressed by endothelial cells in the placenta and lung and by epithelial cells in the female genital tract. In lymphoid tissues, IDO1 was expressed in mature dendritic cells with a phenotype (CD83+, DC-LAMP+, langerin−, CD123−, CD163−) distinct from plasmacytoid dendritic cells. Importantly, IDO1-expressing dendritic cells were not enriched in tumor-draining lymph nodes, in contrast with previously reported findings. IDO1-expressing cells were observed in a large fraction (382/624, 61%) of human tumors. They comprised tumor cells, endothelial cells, and stromal cells in proportions that varied depending on the tumor type. Tumors showing the highest proportions of IDO1-immunolabeled samples were carcinomas of the cervix, followed by endometrium, bladder, kidney, and lung. This hierarchy of IDO1 expression was confirmed by gene expression data mined from The Cancer Genome Atlas database. Expression of IDO1 may be used to select tumors likely to benefit from targeted therapy with IDO1 inhibitors.

Julliard W., Fechner J.H., Mezrich J.D.

The aryl hydrocarbon receptor (AHR) has long been studied by toxicologists as a ligand-activated transcription factor that is activated by dioxin and other environmental pollutants such as polycyclic aromatic hydrocarbons. The hallmark of AHR activation is the upregulation of the cytochrome P450 enzymes that metabolize many of these toxic compounds. However, recent findings demonstrate that both exogenous and endogenous AHR ligands can alter innate and adaptive immune responses including effects on T-cell differentiation. Kynurenine, a tryptophan breakdown product, is one such endogenous ligand of the AHR. Expression of indoleamine 2,3-dioxygenase by dendritic cells causes accumulation of kynurenine and results in subsequent tolerogenic effects including increased regulatory T cell activity. At the same time, polycyclic aromatic hydrocarbons found in pollution enhance Th17 differentiation in the lungs of exposed mice via the AHR. In this perspective, we will discuss the importance of the AHR in the immune system and the role this might play in normal physiology and response to disease.

Soliman H.H., Jackson E., Neuger T., Dees E.C., Harvey R.D., Han H., Ismail-Khan R., Minton S., Vahanian N.N., Link C., Sullivan D.M., Antonia S.

Indoleamine 2,3-dioxygenase (IDO) is an enzyme that tumors use to create a state of immunosuppression. Indoximod is an IDO pathway inhibitor. Preclinical studies demonstrated that indoximod combined with chemotherapy was synergistic in a mouse model of breast cancer. A phase I 3+3 trial was designed to study the combination of docetaxel and indoximod.Docetaxel was administered at 60 mg/m2 intravenously every 3 weeks dose levels 1-4 and 75 mg/m2 for dose level 5. Indoximod was given at 300, 600, 1000, 2000, and 1200 mg PO twice daily continuously for levels 1-5, respectively. Serum drug levels were measured.Twenty-seven patients were treated, with 22 evaluable for response. DLTs included grade 3 dehydration (level 1), hypotension(level 4), mucositis (level 4) and grade 5 enterocolitis (level 2). Dose level 5 is the recommended phase II dose. The most frequent adverse events were fatigue (58.6%), anemia (51.7%), hyperglycemia (48.3%), infection (44.8%), and nausea (41.4%). There were 4 partial responses (2 breast, 1 NSCLC, 1 thymic tumor). No drug-drug interactions were noted.Docetaxel plus indoximod was well tolerated with no increase in expected toxicities or pharmacokinetic interactions. It was active in a pretreated population of patients with metastatic solid tumors.

Lee K., Venkateswararao E., Sharma V.K., Jung S.

The amino acid-conjugates (1a-k) with eleven amino acids attached to primary amine of (S)-1-[1-(4-aminobenzoyl)-2,3-dihydro-1H-indol-6-sulfonyl]-4-phenyl-imidazolidin-2-one (DW2282, 1) were prepared and studied for their prodrug characteristics and anti-cancer activity against SW620 cell line. All the amino acid derivatives showed not only improved water solubility but also displayed potent anti-cancer activity in vitro. Among these amino acid-conjugates the compounds, DW2282-L-Ala (1b), DW2282-L-Phe (1e), DW2282-L-Leu (1g) and DW2282-L-Met (1h) showed good reconversion within 8 h (104.76%, 84.03%, 95.02% and 78.34%, respectively) to the parent drug in human plasma. In addition, the compounds 1e, 1g and 1j also showed good bioavailability profile along with potent in vivo anticancer activity.

Diez-Torrubia A., Cabrera S., de Castro S., García-Aparicio C., Mulder G., De Meester I., Camarasa M., Balzarini J., Velázquez S.

We herein report for the first time the successful use of the dipeptidyl peptidase IV (DPPIV/CD26) prodrug approach to guanine derivatives such as the antiviral acyclovir (ACV). The solution- and solid-phase synthesis of the tetrapeptide amide prodrug 3 and the tripeptide ester conjugate 4 of acyclovir are reported. The synthesis of the demanding tetrapeptide amide prodrug of ACV 3 was first established in solution and successfully transferred onto solid support by using Ellman's dihydropyran (DHP) resin. In contrast with the valyl ester prodrug (valacyclovir, VACV), the tetrapeptide amide prodrug 3 and the tripeptide ester conjugate 4 of ACV proved fully stable in PBS. Both prodrugs converted to VACV (for 4) or ACV (for 3) upon exposure to purified DPPIV/CD26 or human or bovine serum. Vildagliptin, a potent inhibitor of DPPIV/CD26 efficiently inhibited the DPPIV/CD26-catalysed hydrolysis reaction. Both amide and ester prodrugs of ACV showed pronounced anti-herpetic activity in cell culture and significantly improved the water solubility in comparison with the parent drug.

Quintana F.J., Sherr D.H.

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that belongs to the family of basic helix-loop-helix transcription factors. Although the AhR was initially recognized as the receptor mediating the pathologic effects of dioxins and other pollutants, the activation of AhR by endogenous and environmental factors has important physiologic effects, including the regulation of the immune response. Thus, the AhR provides a molecular pathway through which environmental factors modulate the immune response in health and disease. In this review, we discuss the role of AhR in the regulation of the immune response, the source and chemical nature of AhR ligands, factors controlling production and degradation of AhR ligands, and the potential to target the AhR for therapeutic immunomodulation.

Wang F., Du R., Shang Y.

Backgroundd-Tryptophan is recognised for its unique physiological properties. In this study, we aimed to explore the dynamic trends and emerging topics in d-tryptophan research to offer fresh perspectives for future studies.MethodsEmploying bibliometric analysis, we examined the literature on d-tryptophan indexed in the Web of Science Core Collection from January 1987 to December 2023. The “Bibliometrix” R package and CiteSpace were utilised for data processing.ResultsAnalyses of 865 publications revealed 2209 keywords, 4068 authors, 2094 institutions, and contributors from 302 regions. The USA was at the forefront of publications concerning d-tryptophan, but the European Journal of Pharmacology, Journal of Biological Chemistry, and Journal of Medicinal Chemistry were notable for their contributions, co-citations, and impact, respectively. This literature review reveals that since 1987, studies have developed from a focus on d-tryptophan metabolism to the exploration of its functions in organic and medicinal chemistry and food science. Recent findings highlight the potential of d-tryptophan as a non-nutritional sweetener and food preservative as well as its role in inhibiting the growth of bacterial biofilms. Additionally, its immunomodulatory properties are being investigated in relation to allergic diseases. Furthermore, d-tryptophan plays a role in the therapy of atherosclerosis, osteoporosis, tuberculosis, and cancer.ConclusionThe results of bibliometric analysis highlight that future research should focus on the biological functions of d-tryptophan as a food preservative and its use in immunomodulation and drug development, providing strong guidance for future research.

Li H., Liu J., Wang J., Li Z., Yu J., Huang X., Wan B., Meng X., Zhang X.

Background: CY1-4, 9-nitropyridine [2′,3′:4,5] pyrimido [1,2-α] indole -5,11- dione, is an indoleamine 2,3-dioxygenase (IDO) inhibitor and a poorly water-soluble substance. It is very important to increase the solubility of CY1-4 to improve its bioavailability and therapeutic effect. In this study, the mesoporous silica nano-skeleton carrier material Sylysia was selected as the carrier to load CY1-4, and then the CY1-4 nano-skeleton drug delivery system (MSNM@CY1-4) was prepared by coating the hydrophilic polymer material Hydroxypropyl methylcellulose (HPMC) and the lipid material Distearoylphosphatidyl-ethanolamine-poly(ethylene glycol)2000 (DSPE-PEG2000) to improve the anti-tumor effect of CY1-4. Methods: The solubility and dissolution of MSNM@CY1-4 were investigated, and its bioavailability, anti-tumor efficacy, IDO inhibitory ability and immune mechanism were evaluated in vivo. Results: CY1-4 was loaded in MSNM@CY1-4 in an amorphous form, and MSNM@CY1-4 could significantly improve the solubility (up to about 200 times) and dissolution rate of CY1-4. In vivo studies showed that the oral bioavailability of CY1-4 in 20 mg/kg MSNM@CY1-4 was about 23.9-fold more than that in 50 mg/kg CY1-4 suspension. In B16F10 tumor-bearing mice, MSNM@CY1-4 significantly inhibited tumor growth, prolonged survival time, significantly inhibited IDO activity in blood and tumor tissues, and reduced Tregs in tumor tissues and tumor-draining lymph nodes to improve anti-tumor efficacy. Conclusions: The nano-skeleton drug delivery system (MSNM@CY1-4) constructed in this study is a potential drug delivery platform for improving the anti-tumor effect of oral poorly water-soluble CY1-4.

Chen X., Xu D., Yu J., Song X., Li X., Cui Y.

Background: Tryptophan is widely present in foods such as peanuts, milk, and bananas, playing a crucial role in maintaining metabolic homeostasis in health and disease. Tryptophan metabolism is involved in the development and progression of immune, nervous, and digestive system diseases. Although some excellent reviews on tryptophan metabolism exist, there has been no systematic scientometric study as of yet. Methods: This review provides and summarizes research hotspots and potential future directions by analyzing annual publications, topics, keywords, and highly cited papers sourced from Web of Science spanning 1964 to 2022. Results: This review provides a scientometric overview of tryptophan metabolism disorder-triggered diseases, mechanisms, and therapeutic strategies. Conclusions: The gut microbiota regulates gut permeability, inflammation, and host immunity by directly converting tryptophan to indole and its derivatives. Gut microbial metabolites regulate tryptophan metabolism by activating specific receptors or enzymes. Additionally, the kynurenine (KYN) pathway, activated by indoleamine-2, 3-dioxygenase (IDO) and tryptophan 2, 3-dioxygenase, affects the migration and invasion of glioma cells and the development of COVID-19 and depression. The research and development of IDO inhibitors help to improve the effectiveness of immunotherapy. Tryptophan metabolites as potential markers are used for disease therapy, guiding clinical decision-making. Tryptophan metabolites serve as targets to provide a new promising strategy for neuroprotective/neurotoxic imbalance affecting brain structure and function. In summary, this review provides valuable guidance for the basic research and clinical application of tryptophan metabolism.

Ye D., Chen Y., Xu H., Zheng M., Liu Z., Tang Z.

Tumor blood vessels have always been a popular target for anti-tumor therapy, and several vascular disrupting agents (VDAs) with potent anti-tumor vascular functions have entered clinical trials. Although VDAs can selectively destroy immature tumor blood vessels, clinical trials have still observed dose-limiting toxicity, and the efficacy is not satisfactory. This article reviews small molecule prodrugs, polymer nanoparticles, and various tumor-targeted delivery systems based on VDAs, as well as the anti-tumor mechanisms of these delivery systems. In addition, the anti-tumor mechanisms of these delivery systems are discussed, along with the prospects and potential research directions for developing VDAs based on our current understanding.

Jiang K., Wang Q., Chen X., Wang X., Gu X., Feng S., Wu J., Shang H., Ba X., Zhang Y., Tang K.

Kumar N., Murti K., Meenakshi S., Maharana K.C., Nama L., Kumar V.U., Dhingra S., Ravichandiran V.

Abstract: Despite little progress in survival rates with regular therapies, which do not provide com- plete care for curing pediatric brain tumors (PBTs), there is an urgent need for novel strategies to overcome the toxic effects of conventional therapies to treat PBTs. The co-inhibitory immune check- point molecules, e.g., CTLA-4, PD-1/PD-L1, etc., and epigenetic alterations in histone variants, e.g., H3K27me3 that help in immune evasion at tumor microenvironment have not gained much attention in PBTs treatment. However, key epigenetic mechanistic alterations, such as acetylation, methylation, phosphorylation, sumoylation, poly (ADP)-ribosylation, and ubiquitination in histone protein, are greatly acknowledged. The crucial checkpoints in pediatric brain tumors are cytotoxic T lymphocyte antigen-4 (CTLA-4), programmed cell death protein-1 (PD-1) and programmed death-ligand 1 (PD- L1), OX-2 membrane glycoprotein (CD200), and indoleamine 2,3-dioxygenase (IDO). This review covers the state of knowledge on the role of multiple co-inhibitory immunological checkpoint proteins and histone epigenetic alterations in different cancers. We further discuss the processes behind these checkpoints, cell signalling, the current scenario of clinical and preclinical research and potential fu- turistic opportunities for immunotherapies in the treatment of pediatric brain tumors. Conclusively, this article further discusses the possibilities of these interventions to be used for better therapy options.

Gonçalves M., Rodrigues-Santos P., Januário C., Cosentino M., Pereira F.C.

Parkinson's Disease (PD) is the second most common neurodegenerative disease where central and peripheral immune dysfunctions have been pointed out as a critical component of susceptibility and progression of this disease. Dendritic cells (DCs) and monocytes are key players in promoting immune response regulation and can induce the enzyme indoleamine 2,3-dioxygenase 1 (IDO1) under pro-inflammatory environments. This enzyme with catalytic and signaling activity supports the axis IDO1-KYN-aryl hydrocarbon receptor (AhR), promoting disease-specific immunomodulatory effects. IDO1 is a rate-limiting enzyme of the kynurenine pathway (KP) that begins tryptophan (Trp) catabolism across this pathway. The immune functions of the pathway, which are extensively described in cancer, have been forgotten so far in neurodegenerative diseases, where a chronic inflammatory environment underlines the progression of the disease. Despite dysfunctions of KP have been described in PD, these are mainly associated with neurotoxic functions. With this review, we aim to focus on the immune properties of IDO1+DCs and IDO1+monocytes as a possible strategy to balance the pro-inflammatory profile described in PD. We also highlight the importance of exploring the role of dopaminergic therapeutics in IDO1 modulation to possibly optimize current PD therapeutic strategies.

Subbaiah M.A., Rautio J., Meanwell N.A.

Recent tactical applications of prodrugs as effective tools in drug discovery and development to resolve issues associated with drug delivery of lead and drug candidates are reviewed as a reflection of the approval of 53 prodrugs during 2012–2022.

Kwiatkowska I., Hermanowicz J.M., Czarnomysy R., Surażyński A., Kowalczuk K., Kałafut J., Przybyszewska-Podstawka A., Bielawski K., Rivero-Müller A., Mojzych M., Pawlak D.

(1) Background: The purpose of the given study was to examine the antitumor activity of the simultaneous administration of MM-129, a 1,2,4-triazine derivative, and indoximod (IND), the kynurenine pathway inhibitor, toward colon cancer. (2) Methods: The efficiency of the co-administration of the studied compounds was assessed in xenografted zebrafish embryos. Then, the effects of the combined administration of compounds on cellular processes such as cell viability, apoptosis, and intracellular signaling pathways were evaluated. In vitro studies were performed using two colorectal cancer cell lines, namely, DLD-1 and HT-29. (3) Results: The results indicated that the simultaneous application of MM-129 and indoximod induced a stronger inhibition of tumor growth in zebrafish xenografts. The combination of these compounds intensified the process of apoptosis by lowering the mitochondrial potential, enhancing the externalization of phosphatidylserine (PS) and activation of caspases. Additionally, the expression of protein kinase B (AKT) and indoleamine 2,3-dioxygenase-(1IDO1) was disrupted under the applied compound combination. (4) Conclusions: Simultaneous targeting of ongoing cell signaling that promotes tumor progression, along with inhibition of the kynurenine pathway enzyme IDO1, results in the enhancement of the antitumor effect of the tested compounds against the colon cancer cells.

Das N.M., Prusty B.M., Pradhan N., Gupta A., Carmena-Bargueño M., Karn R., Pérez-Sánchez H., Kumar S., Manna D.

Herein, we report the development of synthetically simpler analogs of 4,7-dichloroquinoline (DCQ) as apo-indoleamine 2,3-dioxygenase 1(IDO1) protein targeting ligand to inhibit the activity of IDO1 enzyme. Derivatization of the DCQ moiety improved the IDO1 inhibitory activity both against purified enzyme and the cellular environment without any significant cytotoxicity, leading to the identification of piperazine containing DCQ derivative DCQ4 as a potent IDO1 inhibitor. A series of biophysical studies, including UV–Vis spectroscopy of the Soret band, docking, as well as protoporphyrin IX binding studies, suggested that the IDO1 inhibitory activity of potent compound could be due to its direct binding to apo-IDO1 protein and formation of DCQ4-heme complex. This simple strategy of developing apo-IDO1 targeting molecules having DCQ, piperazine, and amino acid moieties as potent IDO1 inhibitors could be useful in fighting against immune-related diseases.

Davarzani Z., Salehi P., Asghari S.M., Bararjanian M., Hamrahi Mohsen A., Dehghan Harati H.

Cherney E.C., Williams D.K., Zhang L., Nara S.J.

Zheng Y., Yao Y., Ge T., Ge S., Jia R., Song X., Zhuang A.

AbstractMetabolic reprogramming of amino acids has been increasingly recognized to initiate and fuel tumorigenesis and survival. Therefore, there is emerging interest in the application of amino acid metabolic strategies in antitumor therapy. Tremendous efforts have been made to develop amino acid metabolic node interventions such as amino acid antagonists and targeting amino acid transporters, key enzymes of amino acid metabolism, and common downstream pathways of amino acid metabolism. In addition to playing an essential role in sustaining tumor growth, new technologies and studies has revealed amino acid metabolic reprograming to have wide implications in the regulation of antitumor immune responses. Specifically, extensive crosstalk between amino acid metabolism and T cell immunity has been reported. Tumor cells can inhibit T cell immunity by depleting amino acids in the microenvironment through nutrient competition, and toxic metabolites of amino acids can also inhibit T cell function. In addition, amino acids can interfere with T cells by regulating glucose and lipid metabolism. This crucial crosstalk inspires the exploitation of novel strategies of immunotherapy enhancement and combination, owing to the unprecedented benefits of immunotherapy and the limited population it can benefit. Herein, we review recent findings related to the crosstalk between amino acid metabolism and T cell immunity. We also describe possible approaches to intervene in amino acid metabolic pathways by targeting various signaling nodes. Novel efforts to combine with and unleash potential immunotherapy are also discussed. Hopefully, some strategies that take the lead in the pipeline may soon be used for the common good.

Qu X., Wang Y., Jiang Q., Ren T., Guo C., Hua K., Qiu J.

AbstractBackgroundCervical cancer (CC) is the fourth most common cancer in women worldwide. Although immunotherapy has been applied in clinical practice, its therapeutic efficacy remains far from satisfactory, necessitating further investigation of the mechanism of CC immune remodeling and exploration of novel treatment targets. This study aimed to investigate the mechanism of CC immune remodeling and explore potential therapeutic targets.MethodsWe conducted single‐cell RNA sequencing on a total of 17 clinical specimens, including normal cervical tissues, high‐grade squamous intraepithelial lesions, and CC tissues. To validate our findings, we conducted multicolor immunohistochemical staining of CC tissues and constructed a subcutaneous tumorigenesis model in C57BL/6 mice using murine CC cell lines (TC1) to evaluate the effectiveness of combination therapy involving indoleamine 2,3‐dioxygenase 1 (IDO1) inhibition and immune checkpoint blockade (ICB). We used the unpaired two‐tailed Student's t‐test, Mann‐Whitney test, or Kruskal‐Wallis test to compare continuous data between two groups and one‐way ANOVA with Tukey's post hoc test to compare data between multiple groups.ResultsMalignant cervical epithelial cells did not manifest noticeable signs of tumor escape, whereas lysosomal‐associated membrane protein 3‐positive (LAMP3+) dendritic cells (DCs) in a mature state with immunoregulatory roles were found to express IDO1 and affect tryptophan metabolism. These cells interacted with both tumor‐reactive exhausted CD8+ T cells and CD4+ regulatory T cells, synergistically forming a vicious immunosuppressive cycle and mediating CC immune escape. Further validation through multicolor immunohistochemical staining showed co‐localization of neoantigen‐reactive T cells (CD3+, CD4+/CD8+, and PD‐1+) and LAMP3+ DCs (CD80+ and PD‐L1+). Additionally, a combination of the IDO1 inhibitor with an ICB agent significantly reduced tumor volume in the mouse model of CC compared with an ICB agent alone.ConclusionsOur study suggested that a combination treatment consisting of targeting IDO1 and ICB agent could improve the therapeutic efficacy of current CC immunotherapies. Additionally, our results provided crucial insights for designing drugs and conducting future clinical trials for CC.

Lizcano-Meneses S., Hernández-Pando R., García-Aguirre I., Bonilla-Delgado J., Alvarado-Castro V.M., Cisneros B., Gariglio P., Cortés-Malagón E.M.

Cervical cancer is a public health problem diagnosed in advanced stages, and its main risk factor is persistent high-risk human papillomavirus infection. Today, it is necessary to study new treatment strategies, such as immunotherapy, that use different targets of the tumor microenvironment. In this study, the K14E7E2 mouse was used as a cervical cancer model to evaluate the inhibition of indolamine-2,3-dioxygenase 1 (IDO-1) and C-X-C chemokine receptor type 2 (CXCR-2) as potential anti-tumor targets. DL-1MT and SB225002 were administered for 30 days in two regimens (R1 and R2) based on combination and single therapy approaches to inhibit IDO-1 and CXCR-2, respectively. Subsequently, the reproductive tracts were resected and analyzed to determine the tumor areas, and IHCs were performed to assess proliferation, apoptosis, and CD8 cellular infiltration. Our results revealed that combined inhibition of IDO-1 and CXCR-2 significantly reduces the areas of cervical tumors (from 196.0 mm2 to 58.24 mm2 in R1 and 149.6 mm2 to 52.65 mm2 in R2), accompanied by regions of moderate dysplasia, decreased papillae, and reduced inflammation. Furthermore, the proliferation diminished, and apoptosis and intra-tumoral CD8 T cells increased. In conclusion, the combined inhibition of IDO-1 and CXCR-2 is helpful in the antitumor response against preclinical cervical cancer.