Retinoic acid receptor-related orphan receptor gamma-t (RORγt) inhibitors in clinical development for the treatment of autoimmune diseases: a patent review (2016-present)

Tumor mitochondrial oxidative phosphorylation stimulated by the nuclear receptor RORγ represents an effective therapeutic opportunity in osteosarcoma

Osteosarcoma (OS) is the most common malignant bone tumor with a poor prognosis. Here, we show that the nuclear receptor RORγ may serve as a potential therapeutic target in OS. OS exhibits a hyperactivated oxidative phosphorylation (OXPHOS) program, which fuels the carbon source to promote tumor progression. We found that RORγ is overexpressed in OS tumors and is linked to hyperactivated OXPHOS. RORγ induces the expression of PGC-1β and physically interacts with it to activate the OXPHOS program by upregulating the expression of respiratory chain component genes. Inhibition of RORγ strongly inhibits OXPHOS activation, downregulates mitochondrial functions, and increases ROS production, which results in OS cell apoptosis and ferroptosis. RORγ inverse agonists strongly suppressed OS tumor growth and progression and sensitized OS tumors to chemotherapy. Taken together, our results indicate that RORγ is a critical regulator of the OXPHOS program in OS and provides an effective therapeutic strategy for this deadly disease.

Small-molecule agents for treating skin diseases

Skin diseases are a class of common and frequently occurring diseases that significantly impact daily lives. Currently, the limited effective therapeutic drugs are far from meeting the clinical needs; most drugs typically only provide symptomatic relief rather than a cure. Developing small-molecule drugs with improved efficacy holds paramount importance for treating skin diseases. This review aimed to systematically introduce the pathogenesis of common skin diseases in daily life, list related drugs applied in the clinic, and summarize the clinical research status of candidate drugs and the latest research progress of candidate compounds in the drug discovery stage. Also, it statistically analyzed the number of publications and global attention trends for the involved skin diseases. This review might provide practical information for researchers engaged in dermatological drugs and further increase research attention to this disease area.

Bibliometric analysis and description of research trends on T cells in psoriasis over the past two decades (2003-2022)

Background

It is now understood that T cells play a key role in the occurrence and development of psoriasis. Herein, a bibliometric analysis was conducted to summarize the content and trends of T cell-related research in psoriasis.

Methods

A bibliometric analysis was conducted on publications pertaining to T cells in psoriasis between 2003 and 2022 retrieved from the Web of Science Core Collection (WoSCC) database using tools such as CiteSpace, the Bibliometrix R package, and VOSviewer.

Results

The study included a total of 3595 articles authored by 14,188 individuals, including all coauthors in article bylines. The Laboratory for Investigative Dermatology at Rockefeller University, led by James G Krueger, has made significant contributions to this field through focusing on the pathogenesis of psoriasis and exploring the potential of using biological agents to treat psoriasis. Furthermore, targeted inhibitors have significantly impacted the treatment of psoriasis, with researchers focusing on small-molecule targeted drugs as a new area of research that could potentially replace biological agents.

Conclusions

Research has established the efficacy and long-term safety of targeted inhibition of T cell-related targets. Deucravacitinib, a psoriasis treatment drug targeting TYK2 as an allosteric inhibitor, has attracted significant attention and raised high expectations.

Molecular components of the circadian clock regulate HIV-1 replication

Human immunodeficiency virus 1 (HIV-1) causes major health burdens worldwide and still lacks curative therapies and vaccines. Circadian rhythms are endogenous daily oscillations that coordinate an organism's response to its environment and invading pathogens. Peripheral viral loads of HIV-1 infected patients show diurnal variation; however, the underlying mechanisms remain unknown. Here, we demonstrate a role for the cell-intrinsic clock to regulate rhythmic HIV-1 replication in circadian-synchronized systems. Silencing the circadian activator Bmal1 abolishes this phenotype, and we observe BMAL1 binding to the HIV-1 promoter. Importantly, we show differential binding of the nuclear receptors REV-ERB and ROR to the HIV-long terminal repeat at different circadian times, demonstrating a dynamic interplay in time-of-day regulation of HIV-1 transcription. Bioinformatic analysis shows circadian regulation of host factors that control HIV-1 replication, providing an additional mechanism for rhythmic viral replication. This study increases our understanding of the circadian regulation of HIV-1, which can ultimately inform new therapies.

Development and therapeutic potential of allosteric retinoic acid receptor-related orphan receptor γt (RORγt) inverse agonists for autoimmune diseases

The transcription factor retinoic acid receptor-related orphan receptor γt (RORγt) is an attractive drug target for some autoimmune diseases owing to its roles in the differentiation of human T helper 17 (Th17) cells which produce pro-inflammatory cytokine interleukin (IL)-17. RORγt agonists and inverse agonists are classically targeted to the hydrophobic and highly conserved orthosteric binding pocket of RORγt ligand binding domain (LBD). Although successful, this approach also brings some challenges, including off-target effects due to lack of selectivity over other nuclear receptors (NRs). Allosteric regulation of RORγt by synthetic small molecules has recently emerged as novel research interests for its interesting modes of action (MOA), satisfying bioactivity profile and improved selectivity. In this review, we delineated the discovery and identification of the allosteric pocket of RORγt. Subsequently, we focused on examples of small molecules that allosterically inhibit RORγt, with a central attention on structural-activity-relationship (SAR) information, biological activity, pharmacokinetic (PK) property, and the ligand binding mode of these compounds. We also discussed the potential role of RORγt allosteric inverse agonists as small molecule therapeutics for autoimmune diseases.

Discovery, structural optimization, and anti-tumor bioactivity evaluations of betulinic acid derivatives as a new type of RORγ antagonists

Betulinic acid (BA) is a natural pentacyclic triterpenoid that has a wide range of biological and pharmacological effects. Here, computational methods such as pharmacophore screening and reverse docking were used to predict the potential target for BA. Retinoic acid receptor-related orphan receptor gamma (RORγ) was confirmed as its target by several molecular assays as well as crystal complex structure determination. RORγ has been the focus of metabolic regulation, but its potential role in cancer treatment has only recently come to the fore. In this study, rationale optimization of BA was performed and several new derivatives were generated. Among them, the compound 22 showed stronger binding affinity with RORγ (K_D = 180 nM), good anti-proliferative activity against cancer cell lines, and potent anti-tumor efficacy with a TGI value of 71.6% (at a dose of 15 mg/kg) in the HPAF-II pancreatic cancer xenograft model. Further RNA-seq analysis and cellular validation experiments supported that RORγ antagonism was closely related to the antitumor activity of BA and 22, resulting in suppression of the RAS/MAPK and AKT/mTORC1 pathway and inducing caspase-dependent apoptosis in pancreatic cancer cells. RORγ was highly expressed in cancer cells and tissues and positively correlated with the poor prognosis of cancer patients. These results suggest that BA derivatives are potential RORγ antagonists worthy of further exploration.

Virtual Screening Strategy to Identify Retinoic Acid-Related Orphan Receptor γt Modulators

Molecular docking is a key method used in virtual screening (VS) campaigns to identify small-molecule ligands for drug discovery targets. While docking provides a tangible way to understand and predict the protein-ligand complex formation, the docking algorithms are often unable to separate active ligands from inactive molecules in practical VS usage. Here, a novel docking and shape-focused pharmacophore VS protocol is demonstrated for facilitating effective hit discovery using retinoic acid receptor-related orphan receptor gamma t (RORγt) as a case study. RORγt is a prospective target for treating inflammatory diseases such as psoriasis and multiple sclerosis. First, a commercial molecular database was flexibly docked. Second, the alternative docking poses were rescored against the shape/electrostatic potential of negative image-based (NIB) models that mirror the target's binding cavity. The compositions of the NIB models were optimized via iterative trimming and benchmarking using a greedy search-driven algorithm or brute force NIB optimization. Third, a pharmacophore point-based filtering was performed to focus the hit identification on the known RORγt activity hotspots. Fourth, free energy binding affinity evaluation was performed on the remaining molecules. Finally, twenty-eight compounds were selected for in vitro testing and eight compounds were determined to be low μM range RORγt inhibitors, thereby showing that the introduced VS protocol generated an effective hit rate of ~29%.

Modes of action insights from the crystallographic structures of retinoic acid receptor-related orphan receptor-γt (RORγt)

RORγt plays an important role in mediating IL-17 production and some tumor cells. It has four functional domains, of which the ligand-binding domain (LBD) is responsible for binding agonists to recruit co-activators or inverse agonists to prevent co-activator recruiting the agonists. Thus, potent ligands targeting the LBD of this protein could provide novel treatments for cancer and autoimmune diseases. In this perspective, we summarized and discussed various modes of action (MOA) of RORγt-ligand binding structures. The ligands can bind with RORγt at either orthosteric site or the allosteric site, and the binding modes at these two sites are different for agonists and inverse agonist. At the orthosteric site, the binding of agonist is to stabilize the H479-Y502-F506 triplet interaction network of RORγt. The binding of inverse agonist features as these four apparent ways: (1) blocking the entrance of the agonist pocket in RORγt; (2) directly breaking the H479-Y502 pair interactions; (3) destabilizing the triplet H479-Y502-F506 interaction network through perturbing the conformation of the side chain in M358 at the bottom of the binding pocket; (4) and destabilizing the triplet H479-Y502-F506 through changing the conformation of the side chain of residue W317 side chain. At the allosteric site of RORγt, the binding of inverse agonist was found recently to inhibit the activation of protein by interacting directly with H12, which results in unfolding of helix 11' and orientation of H12 to directly block cofactor peptide binding. This overview of recent advances in the RORγt structures is expected to provide a guidance of designing more potent drugs to treat RORγt-related diseases.

Synthesis of A-9758, an Inverse Agonist of Retinoic Acid-Related Orphan Receptor γt

A-9758 is an inverse agonist of retinoic acid-related orphan receptor γt with well-characterized in vitro and in vivo anti-inflammatory activity. A chromatography-free decagram-scale synthesis of this compound was developed to support pre-clinical research activities. This route was designed to enable late-stage structure-activity relationship studies of the amide moiety and convergently uses a reductive alkylation sequence between indole and benzaldehyde intermediates. A key advantage of this strategy is the fact that the indole precursor can be alkylated at C2, as required for A-9758, or at C3 to provide access to an isomeric chemical series. Access to the critical indole fragment was expedited via an underutilized SnAr/reductive cyclization cascade sequence, and the benzaldehyde fragment was prepared in two steps from inexpensive 2,4-dichlorobenzoic acid.

RORγt expression in mature TH17 cells safeguards their lineage specification by inhibiting conversion to TH2 cells

RORγt is the lineage-specific transcription factor for T helper 17 (T_H17) cells and an attractive drug target for treating T_H17-associated diseases. Although the critical role of RORγt in early T_H17 cell differentiation has been well recognized, its function in mature T_H17 cell maintenance remains largely unknown. Here, we show that genetic deletion of Rorc in mature T_H17 cells inhibited their pathogenic functions. Mechanistically, loss of RORγt led to a closed chromatin configuration at key T_H17-specific gene loci, particularly at the "super-enhancer" regions. Unexpectedly, RORγt directly bound and inhibited Il4 transcription, whereas pharmaceutically or genetically targeting RORγt caused spontaneous conversion of T_H17 cells to T_H2-like cells in vitro and in vivo. Our results thus reveal dual crucial functions of RORγt in effector T_H17 cells in maintaining T_H17 cell program and constraining T_H2 cell conversion, offering previously unidenified considerations in therapeutic targeting of RORγt.

Deregulation of Cholesterol Homeostasis by a Nuclear Hormone Receptor Crosstalk in Advanced Prostate Cancer

Metastatic castration-resistant prostate cancer (mCRPC) features high intratumoral cholesterol levels, due to aberrant regulation of cholesterol homeostasis. However, the underlying mechanisms are still poorly understood. The retinoid acid receptor-related orphan receptor gamma (RORγ), an attractive therapeutic target for cancer and autoimmune diseases, is strongly implicated in prostate cancer progression. We demonstrate in this study that in mCRPC cells and tumors, RORγ plays a crucial role in deregulation of cholesterol homeostasis. First, we found that RORγ activates the expression of key cholesterol biosynthesis proteins, including HMGCS1, HMGCR, and SQLE. Interestingly, we also found that RORγ inhibition induces cholesterol efflux gene program including ABCA1, ABCG1 and ApoA1. Our further studies revealed that liver X receptors (LXRα and LXRβ), the master regulators of cholesterol efflux pathway, mediate the function of RORγ in repression of cholesterol efflux. Finally, we demonstrated that RORγ antagonist in combination with statins has synergistic effect in killing mCRPC cells through blocking statin-induced feedback induction of cholesterol biosynthesis program and that the combination treatment also elicits stronger anti-tumor effects than either alone. Altogether, our work revealed that in mCRPC, RORγ contributes to aberrant cholesterol homeostasis by induction of cholesterol biosynthesis program and suppression of cholesterol efflux genes. Our findings support a therapeutic strategy of targeting RORγ alone or in combination with statin for effective treatment of mCRPC.

2', 4'-Dihydroxy-2,3-dimethoxychalcone: A pharmacological inverse agonist of RORγt ameliorating Th17-driven inflammatory diseases by regulating Th17/Treg

Multiple sclerosis, inflammatory bowel disease and organ transplant rejection are related to Th17 cell development and inflammatory respond. RORγt, a specific transcription factor regulating Th17 cell differentiation, is a pivotal target for the treatment of diseases. However, the clinical application of RORγt inverse agonists reported so far has been hindered due to limited efficacy and toxic side effects. Plant-derived natural products with drug-like properties and safety are wide and valuable resources for candidate drug discovery. Herein, structure-based virtual screening was used to find out 2',4'-Dihydroxy-2,3-dimethoxychalcone (DDC), a chalcone derivative rich in plants and food, located in the binding pocket of RORγt and targeted to inhibit RORγt activity. DDC repressed murine Th17 differentiation and promoted Treg differentiation remarkably in a dose-dependent manner. In addition, DDC treatment improved experimental autoimmune encephalomyelitis recovery, ameliorated experimental colitis severity, and prevented graft rejection significantly. Mechanically, DDC indirectly stabilized Foxp3 expression by inhibiting RORγt activity and the expression of its target gene profile in vitro and in vivo, which realized its regulation of Th17/Treg balance. In conclusion, our study provides a scientific basis that DDC, as an inverse agonist of RORγt with simple structure, rich sources, low cost, high efficiency, and low toxicity, has great potential for the development of a novel effective immunomodulator for the treatment of Th17-mediated inflammatory diseases.

Targeting Nuclear Receptors for TH17-Mediated Inflammation: REV-ERBerations of Circadian Rhythm and Metabolism

Since their discovery, a significant amount of progress has been made understanding T helper 17 (T_H17) cells' roles in immune homeostasis and disease. Outside of classical cytokine signaling, environmental and cellular intrinsic factors, including metabolism, have proven to be critical for non-pathogenic vs pathogenic T_H17 cell development, clearance of infections, and disease. The nuclear receptor RORγt has been identified as a key regulator of T_H17-mediated inflammation. Nuclear receptors regulate a variety of physiological processes, ranging from reproduction to the circadian rhythm, immunity to metabolism. Outside of RORγt, the roles of other nuclear receptors in T_H17-mediated immunity are not as well established. In this mini-review we describe recent studies that revealed a role for a different member of the nuclear receptor superfamily, REV-ERBα, in the regulation of T_H17 cells and autoimmunity. We highlight similarities and differences between reports, potential roles beyond T_H17-mediated cytokine regulation, unresolved questions in the field, as well as the translational potential of targeting REV-ERBα.

Activation of retinoic acid-related orphan receptor γ(t) by parabens and benzophenone UV-filters

Retinoic acid-related orphan receptor γt (RORγt) regulates immune responses and its impaired function contributes to inflammatory and autoimmune diseases and may promote skin cancer. Synthetic inverse RORγt agonists block the production of Th17-associated cytokines including interleukin (IL)-17A and IL-22 and are under investigation for treatment of such pathologies. Unintentional RORγt activation in skin, following exposure to environmental chemicals, may promote inflammatory skin disease. Parabens and UV-filters, frequently used as additives in cosmetics and body care products, are intensively inspected for endocrine disrupting properties. This study assessed whether such compounds can interfere with RORγ activity using a previously established tetracycline-inducible reporter gene assay in CHO cells. These transactivation experiments revealed hexylparaben, benzylparaben and benzophenone-10 as RORγ agonists (EC50 values: 144 ± 97 nM, 3.39 ± 1.74 µM and 1.67 ± 1.04 µM, respectively), and they could restore RORγ activity after suppression by an inverse agonist. Furthermore, they enhanced RORγt-dependent transcription of the pro-inflammatory IL-17A and/or IL-22 genes in the murine T-cell model EL4. Virtual screening of a cosmetics database for structurally similar chemicals and in vitro testing of the most promising hits revealed benzylbenzoate, benzylsalicylate and 4-methylphenylbenzoate as RORγ agonists (low micromolar EC50 values). Moreover, an analysis of mixtures of the newly identified RORγ agonists suggested additive effects. This study presents novel RORγ(t) agonistic structural scaffolds. By activating RORγ(t) the identified parabens and UV-filters may potentially aggravate pathophysiological conditions, especially skin diseases where highest exposure of such chemicals can be expected. Follow-up studies should assess whether such compounds, either alone or as mixtures, can reach relevant concentrations in tissues and target cells to activate RORγ(t) in vivo.

Discovery of 2H-chromone-4-one based sulfonamide derivatives as potent retinoic acid receptor-related orphan receptor γt inverse agonists

Retinoic acid receptor related orphan receptor γt (RORγt), identified as the essential functional regulator of IL-17 producing Th17 cells, is an attractive drug target for treating autoimmune diseases. Starting from the reported GSK2981278 (Phase II), we structurally modified and synthesized a series of 2H-chromone-4-one based sulfonamide derivatives as novel RORγt inverse agonists, which significantly improved their human metabolic stabilities while maintaining a potent RORγt inverse agonist profile. Efforts in reducing the lipophilicity and improving the LLE values led to the discovery of c9, which demonstrated potent RORγt inverse agonistic activity and consistent metabolic stability. During in vivo studies, oral administration of compound c9 exhibited a robust and dose-dependent inhibition of IL-17A cytokine expression and significantly lessened the skin inflammatory symptoms in the mouse imiquimod-induced skin inflammation model. Docking analysis of the binding mode revealed that c9 can suitably occupy the active pocket, and the introduction of the morpholine pyridine group can interact with Leu396, His479, and Cys393. Thus, compound c9 was selected as a preclinical compound for treating Th17-driven autoimmune diseases.

Development of novel Gemini-cholesterol analogues for Retinoid-related Orphan Receptor

Retinoic-acid-related Orphan Receptors (RORs) regulate maintenance of the circadian rhythm and immune response among others and are involved in increasing number of pathologies including autoimmune diseases, cancer and neurological disorders...

Discovery of Orally Available Retinoic Acid Receptor-Related Orphan Receptor γ-t/Dihydroorotate Dehydrogenase Dual Inhibitors for the Treatment of Refractory Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a multifactorial autoimmune disease, representing a major clinical challenge. Herein, a strategy of dual-targeting approach employing retinoic acid receptor-related orphan receptor γ-t (RORγt) and dihydroorotate dehydrogenase (DHODH) was proposed for the treatment of IBD. Dual RORγt/DHODH inhibitors are expected not only to reduce RORγt-driven Th17 cell differentiation but also to mitigate the expansion and activation of T cells, which may enhance anti-inflammatory effects. Starting from 2-aminobenzothiazole hit 1, a series of 2-aminotetrahydrobenzothiazoles were discovered as potent dual RORγt/DHODH inhibitors. Compound 14d stands out with IC₅₀ values of 0.110 μM for RORγt and of 0.297 μM for DHODH. With acceptable mouse pharmacokinetic profiles, 14d exhibited remarkable in vivo anti-inflammatory activity and dose-dependently alleviated the severity of dextran sulfate sodium (DSS)-induced acute colitis in mice. Taken together, the present study provides a novel framework for the development of therapeutic agents for the treatment of IBD.

Rationalizing heptadecaphobia: TH 17 cells and associated cytokines in cancer and metastasis

Cancer is one of the leading causes of death worldwide. When cancer patients are diagnosed with metastasis, meaning that the primary tumor has spread to at least one different site, their life expectancy decreases dramatically. In the past decade, the immune system´s role in fighting cancer and metastasis has been studied extensively. Importantly, immune cells and inflammatory reactions generate potent antitumor responses but also contribute to tumor development. However, the molecular and cellular mechanisms underlying this dichotomic interaction between the immune system and cancer are still poorly understood. Recently, a spotlight has been cast on the distinct subsets of immune cells and their derived cytokines since evidence has implicated their crucial impact on cancer development. T helper 17 cell (TH 17) cells, which express the master transcriptional factor Retinoic acid-receptor-related orphan receptor gamma t, are among these critical cell subsets and are defined by their production of type 3 cytokines, such as IL-17A, IL-17F, and IL-22. Depending on the tumor microenvironment, these cytokines can also be produced by other immune cell sources, such as T cytotoxic 17 cell, innate lymphoid cells, NKT cells, or γδ T cells. To date, a lot of data have been collected describing the divergent functions of IL-17A, IL-17F, and IL-22 in malignancies. In this comprehensive review, we discuss the role of these TH 17- and non-TH 17-derived type 3 cytokines in different tumor entities. Furthermore, we will provide a structured insight into the strict regulation and subsequent downstream mechanisms of these cytokines in cancer and metastasis.

Crystallographic landscape provides molecular insights into the modes of action of diverse ROR-γt modulators

ROR-γt, the master regulator of Th-17 cells, is activated by the binding of small molecules at its orthosteric site, followed by the recruitment of co-activators or co-repressors in the ligand binding domain (LBD). Th-17 cells provide immune-dependent protection against cancers and pathogens. Their dysregulation causes inflammation and is therefore implicated in various autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, and psoriasis. Consequently, there is enormous interest in the development of ROR-γt modulators, both agonist and inverse-agonists. Here, we review advances in the development of ROR-γt modulators that have been made over the past decade, focusing on the rich crystallography landscape for ROR-γt co-crystals that has delineated the relationship between the binding patterns of modulators and the resulting biological activities.

Discovery of Chromane-6-Sulfonamide Derivative as a Potent, Selective, and Orally Available Novel Retinoic Acid Receptor-Related Orphan Receptor γt Inverse Agonist

Interleukin-17 (IL-17) is a proinflammatory cytokine that plays a dominant role in inflammation, autoimmunity, and host defense. RORγt is a key transcription factor mediating T helper 17 (Th17) cell differentiation and IL-17 production, which is able to activate CD8⁺ T cells and elicit antitumor efficacy. A series of sulfonamide derivatives as novel RORγt inverse agonists were designed and synthesized. Using GSK2981278 (phase II) as a starting point, we engineered structural modifications that significantly improved the activity and pharmacokinetic profile. In animal studies, oral administration of compound d3 showed a robust and dose-dependent inhibition of the IL-17A cytokine expression in a mouse imiquimod-induced skin inflammation model. Docking analysis of the binding mode revealed that the compound d3 occupied the active pocket suitably. Thus, compound d3 was selected as a clinical compound for the treatment of Th17-driven autoimmune diseases.

Conformational Changes of RORγ During Response Element Recognition and Coregulator Engagement

The retinoic acid receptor-related orphan receptor γ (RORγ) is a ligand-dependent transcription factor of the nuclear receptor super family that underpins metabolic activity, immune function, and cancer progression. Despite being a valuable drug target in health and disease, our understanding of the ligand-dependent activities of RORγ is far from complete. Like most nuclear receptors, RORγ must recruit coregulatory protein to enact the RORγ target gene program. To date, a majority of structural studies have been focused exclusively on the RORγ ligand-binding domain and the ligand-dependent recruitment of small peptide segments of coregulators. Herein, we examine the ligand-dependent assembly of full length RORγ:coregulator complexes on cognate DNA response elements using structural proteomics and small angle x-ray scattering. The results from our studies suggest that RORγ becomes elongated upon DNA recognition, preventing long range interdomain crosstalk. We also determined that the DNA binding domain adopts a sequence-specific conformation, and that coregulatory protein may be able to 'sense' the ligand- and DNA-bound status of RORγ. We propose a model where ligand-dependent coregulator recruitment may be influenced by the sequence of the DNA to which RORγ is bound. Overall, the efforts described herein will illuminate important aspects of full length RORγ and monomeric orphan nuclear receptor target gene regulation through DNA-dependent conformational changes.

RORγt protein modifications and IL-17-mediated inflammation

RORγt, the master transcription factor for cytokine interleukin (IL)-17, is expressed explicitly in Th17 cells, γδT cells, and type 3 innate lymphoid cells in mice and humans. Since dysregulated IL-17 expression is strongly linked to several human inflammatory diseases, the RORγt-IL-17 axis has been the focus of intense research. Recently, several studies have shown that RORγt is modified by multiple post-translational mechanisms, including ubiquitination, acetylation, SUMOylation, and phosphorylation. This review discusses how post-translational modifications modulate RORγt function and its turnover to regulate IL-17-driven inflammation. Broad knowledge of these pathways is crucial for a clear understanding of the pathogenic role of RORγt+IL-17+ cells and for the development of putative therapeutic strategies to target IL-17-driven diseases such as multiple sclerosis, psoriasis, rheumatoid arthritis, systemic lupus erythematosus, and inflammatory bowel disease.

AZD0284, a Potent, Selective, and Orally Bioavailable Inverse Agonist of Retinoic Acid Receptor-Related Orphan Receptor C2

Inverse agonists of the nuclear receptor RORC2 have been widely pursued as a potential treatment for a variety of autoimmune diseases. We have discovered a novel series of isoindoline-based inverse agonists of the nuclear receptor RORC2, derived from our recently disclosed RORC2 inverse agonist 2. Extensive structure-activity relationship (SAR) studies resulted in AZD0284 (20), which combined potent inhibition of IL-17A secretion from primary human TH17 cells with excellent metabolic stability and good PK in preclinical species. In two preclinical in vivo studies, compound 20 reduced thymocyte numbers in mice and showed dose-dependent reduction of IL-17A containing γδ-T cells and of IL-17A and IL-22 RNA in the imiquimod induced inflammation model. Based on these data and a favorable safety profile, 20 was progressed to phase 1 clinical studies.

Diastereoselective Synthesis of a cis-1,3-Disubstituted Cyclobutane Carboxylic Acid Scaffold for TAK-828F, a Potent Retinoic Acid Receptor-Related Orphan Receptor (ROR)-γt Inverse Agonist

A scalable synthesis of the cis-1,3-disubstituted cyclobutane carboxylic acid scaffold of TAK-828F (1) has been developed, featuring the diastereoselective reduction of a cyclobutylidene Meldrum's acid derivative with NaBH₄. Controlling acidic impurities was crucial for improving the diastereomeric ratio by recrystallization. Furthermore, reaction optimization and the streamlining of several steps established a scalable synthetic method free from column chromatography purification with an overall yield improved from 23 to 39%.

Crystallography-guided discovery of carbazole-based retinoic acid-related orphan receptor gamma-t (RORγt) modulators: insights into different protein behaviors with "short" and "long" inverse agonists

A series of 6-substituted carbazole-based retinoic acid-related orphan receptor gamma-t (RORγt) modulators were discovered through 6-position modification guided by insights from the crystallographic profiles of the "short" inverse agonist 6. With the increase in the size of the 6-position substituents, the "short" inverse agonist 6 first reversed its function to agonists and then to "long" inverse agonists. The cocrystal structures of RORγt complexed with the representative "short" inverse agonist 6 (PDB: 6LOB), the agonist 7d (PDB: 6LOA) and the "long" inverse agonist 7h (PDB: 6LO9) were revealed by X-ray analysis. However, minor differences were found in the binding modes of "short" inverse agonist 6 and "long" inverse agonist 7h. To further reveal the molecular mechanisms of different RORγt inverse agonists, we performed molecular dynamics simulations and found that "short" or "long" inverse agonists led to different behaviors of helixes H11, H11', and H12 of RORγt. The "short" inverse agonist 6 destabilizes H11' and dislocates H12, while the "long" inverse agonist 7h separates H11 and unwinds H12. The results indicate that the two types of inverse agonists may behave differently in downstream signaling, which may help identify novel inverse agonists with different regulatory mechanisms.

RORγ is a context-specific master regulator of cholesterol biosynthesis and an emerging therapeutic target in cancer and autoimmune diseases

Aberrant cholesterol metabolism and homeostasis in the form of elevated cholesterol biosynthesis and dysregulated efflux and metabolism is well recognized as a major feature of metabolic reprogramming in solid tumors. Recent studies have emphasized on major drivers and regulators such as Myc, mutant p53, SREBP2, LXRs and oncogenic signaling pathways that play crucial roles in tumor cholesterol metabolic reprogramming. Therapeutics such as statins targeting the mevalonate pathway were tried at the clinic without showing consistent benefits to cancer patients. Nuclear receptors are prominent regulators of mammalian metabolism. Their de-regulation often drives tumorigenesis. RORγ and its immune cell-specific isoform RORγt play important functions in control of mammalian metabolism, circadian rhythm and immune responses. Although RORγ, together with its closely related members RORα and RORβ were identified initially as orphan receptors, recent studies strongly support the conclusion that specific intermediates and metabolites of cholesterol pathways serve as endogenous ligands of RORγ. More recent studies also reveal a critical role of RORγ in tumorigenesis through major oncogenic pathways including acting a new master-like regulator of tumor cholesterol biosynthesis program. Importantly, an increasing number of RORγ orthosteric and allosteric ligands are being identified that display potent activities in blocking tumor growth and autoimmune disorders in preclinical models. This review summarizes the recent preclinical and clinical progress on RORγ with emphasis on its role in reprogramming tumor cholesterol metabolism and its regulation. It will also discuss RORγ functional mechanisms, context-specificity and its value as a therapeutic target for effective cancer treatment.

Agonist Lock Touched and Untouched Retinoic Acid Receptor-Related Orphan Receptor-γt (RORγt) Inverse Agonists: Classification Based on the Molecular Mechanisms of Action

Retinoic acid receptor-related orphan receptor-gamma-t (RORγt) is a potential drug target for autoimmune diseases with a clear biological mechanism in the Th17/IL-17 pathway. The "agonist lock", which is formed by residues His479-Tyr502-Phe506 in RORγt, makes H12 tightly contact H11 in a suitable conformation for coactivator binding and, thus, is related to RORγt transcriptional activation. The inverse agonism of RORγt is complex because not all RORγt inverse agonists directly break the agonist lock to interfere with coactivator recruitment and the transcription of RORγt. Here, we analyze the complex structures, binding modes, and biological activities of various RORγt inverse agonists and classify them as "agonist lock touched" and "agonist lock untouched" RORγt inverse agonists according to whether they infringe on the agonist lock directly or not. We aim at providing a comprehensive review and insights into drug discovery of RORγt inverse agonists.

Retinoic acid-related orphan receptor gamma t (RORγt) inverse agonists/antagonists for the treatment of inflammatory diseases - where are we presently?

Introduction: The transcription factor retinoic acid-related orphan receptor gamma t (RORγt) has been identified as the master regulator of T_H17 cell differentiation and IL-17/22 production and is therefore an attractive target for the treatment of inflammatory diseases. Several orally or topically administered small molecule RORγt inverse agonists (RIAs) have progressed up to the end of clinical Phase 2.Areas covered: Based on publications and patent evaluations this review summarizes the evolution of the chemical matter for all 16 pharmaceutical companies, who develop(ed) a clinical-stage RIAs (until March 2021). Structure proposals for some clinical stage RIAs are presented and the outcome of the clinical trials is discussed.Expert opinion: So far, the clinical trials have been plagued with a high attrition rate. Main reasons were lack of efficacy (topical) or safety signals (oral) as well as, amongst other things, thymic lymphomas as seen with BMS-986251 in a preclinical study and liver enzyme elevations in humans with VTP-43742. Possibilities to mitigate these risks could be the use of RIAs with different chemical structures not interfering with thymocytes maturation and no livertox-inducing properties. With new frontrunners (e.g., ABBV-157 (cedirogant), BI 730357 or IMU-935) this is still an exciting time for this treatment approach.

Circadian clock genes as promising therapeutic targets for autoimmune diseases

Circadian rhythm is a natural, endogenous process whose physiological functions are controlled by a set of clock genes. Disturbance of the clock genes have detrimental effects on both innate and adaptive immunity, which significantly enhance pro-inflammatory responses and susceptibility to autoimmune diseases via strictly controlling the individual cellular components of the immune system that initiate and perpetuate the inflammation pathways. Autoimmune diseases, especially rheumatoid arthritis (RA), often exhibit substantial circadian oscillations, and circadian rhythm is involved in the onset and progression of autoimmune diseases. Mounting evidence indicate that the synthetic ligands of circadian clock genes have the property of reducing the susceptibility and clinical severity of subjects. This review supplies an overview of the roles of circadian clock genes in the pathology of autoimmune diseases, including BMAL1, CLOCK, PER, CRY, REV-ERBα, and ROR. Furthermore, summarized some circadian clock genes as candidate genes for autoimmune diseases and current advancement on therapy of autoimmune diseases with synthetic ligands of circadian clock genes. The existing body of knowledge demonstrates that circadian clock genes are inextricably linked to autoimmune diseases. Future research should pay attention to improve the quality of life of patients with autoimmune diseases and reduce the effects of drug preparation on the normal circadian rhythms.

Preclinical and clinical characterization of the RORγt inhibitor JNJ-61803534

The nuclear receptor retinoid-related orphan receptor gamma t (RORγt) plays a critical role in driving Th17 cell differentiation and expansion, as well as IL-17 production in innate and adaptive immune cells. The IL-23/IL-17 axis is implicated in several autoimmune and inflammatory diseases, and biologics targeting IL-23 and IL-17 have shown significant clinical efficacy in treating psoriasis and psoriatic arthritis. JNJ-61803534 is a potent RORγt inverse agonist, selectively inhibiting RORγt-driven transcription versus closely-related family members, RORα and RORβ. JNJ-61803534 inhibited IL-17A production in human CD4⁺ T cells under Th17 differentiation conditions, but did not inhibit IFNγ production under Th1 differentiation conditions, and had no impact on in vitro differentiation of regulatory T cells (Treg), nor on the suppressive activity of natural Tregs. In the mouse collagen-induced arthritis model, JNJ-61803534 dose-dependently attenuated inflammation, achieving ~ 90% maximum inhibition of clinical score. JNJ-61803534 significantly inhibited disease score in the imiquimod-induced mouse skin inflammation model, and dose-dependently inhibited the expression of RORγt-regulated genes, including IL-17A, IL-17F, IL-22 and IL-23R. Preclinical 1-month toxicity studies in rats and dogs identified doses that were well tolerated supporting progression into first-in-human studies. An oral formulation of JNJ-61803534 was studied in a phase 1 randomized double-blind study in healthy human volunteers to assess safety, pharmacokinetics, and pharmacodynamics. The compound was well tolerated in single ascending doses (SAD) up to 200 mg, and exhibited dose-dependent increases in exposure upon oral dosing, with a plasma half-life of 164 to 170 h. In addition, dose-dependent inhibition of ex vivo stimulated IL-17A production in whole blood was observed, demonstrating in vivo target engagement. In conclusion, JNJ-61803534 is a potent and selective RORγt inhibitor that exhibited acceptable preclinical safety and efficacy, as well as an acceptable safety profile in a healthy volunteer SAD study, with clear evidence of a pharmacodynamic effect in humans.

Structure-Activity Relationship Studies of Trisubstituted Isoxazoles as Selective Allosteric Ligands for the Retinoic-Acid-Receptor-Related Orphan Receptor γt

The inhibition of the nuclear receptor retinoic-acid-receptor-related orphan receptor γt (RORγt) is a promising strategy in the treatment of autoimmune diseases. RORγt features an allosteric binding site within its ligand-binding domain that provides an opportunity to overcome drawbacks associated with orthosteric modulators. Recently, trisubstituted isoxazoles were identified as a novel class of allosteric RORγt inverse agonists. This chemotype offers new opportunities for optimization into selective and efficacious allosteric drug-like molecules. Here, we explore the structure–activity relationship profile of the isoxazole series utilizing a combination of structure-based design, X-ray crystallography, and biochemical assays. The initial lead isoxazole (FM26) was optimized, resulting in compounds with a ∼10-fold increase in potency (low nM), significant cellular activity, promising pharmacokinetic properties, and a good selectivity profile over the peroxisome-proliferated-activated receptor γ and the farnesoid X receptor. We envisage that this work will serve as a platform for the accelerated development of isoxazoles and other novel chemotypes for the effective allosteric targeting of RORγt.

Covalent Occlusion of the RORγt Ligand Binding Pocket Allows Unambiguous Targeting of an Allosteric Site

The nuclear receptor RORγt is a key positive regulator in the differentiation and proliferation of T helper 17 (Th17) cells and the production of proinflammatory cytokines like IL-17a. Dysregulation of this pathway can result in the development of various autoimmune diseases, and inhibition of RORγt with small molecules thus holds great potential as a therapeutic strategy. RORγt has a unique allosteric ligand binding site in the ligand binding domain, which is distinct from the canonical, orthosteric binding site. Allosteric modulation of RORγt shows high potential, but the targeted discovery of novel allosteric ligands is highly challenging via currently available methods. Here, we introduce covalent, orthosteric chemical probes for RORγt that occlude the binding of canonical, orthosteric ligands but still allow allosteric ligand binding. Ultimately, these probes could be used to underpin screening approaches for the unambiguous and rapid identification of novel allosteric RORγt ligands.

Nrf2 through Aryl Hydrocarbon Receptor Regulates IL-22 Response in CD4+ T Cells

IL-17A and IL-22 derived from Th17 cells play a significant role in mucosal immunity and inflammation. TGF-β and IL-6 promote Th17 differentiation; however, these cytokines have multiple targets. The identification and screening of additional molecules that regulate IL-17A and IL-22 responses in certain inflammatory conditions is of great clinical significance. In this study, we show that CDDO-Im, a specific Nrf2 activator, promotes IL-17A and IL-22 responses in murine Th17 cells. In contrast, CDDO-Im inhibits IL-17A response in multiple sclerosis patient-derived PBMCs. However, Nrf2 specifically regulates IL-22 response in vivo. Nrf2 acts through the regulation of antioxidant response element (ARE) binding motifs in target genes to induce or repress transcription. Promoter analysis revealed that Il17a, Rorc, and Ahr genes have several ARE motifs. We showed that Nrf2 bound to ARE repressor (ARE-R2) of Rorc and inhibited Rorc-dependent IL-17A transactivation. The luciferase reporter assay data showed that CDDO-Im regulated Ahr promoter activity. Chromatin immunoprecipitation quantitative PCR data showed that Nrf2 bound to ARE of AhR. Finally, we confirmed that the CDDO-Im-mediated induction of IL-22 production in CD4+ T cells was abrogated in CD4-specific Ahr knockout mice (AhrCD4 ). CH-223191, a specific AhR antagonist, inhibits CDDO-Im-induced IL-22 production in CD4+ T cells, which further confirmed the AhR-dependent regulation. Collectively, our data showed that Nrf2 via AhR pathways regulated IL-22 response in CD4+ T cells.

Discovery of 6-Oxo-4-phenyl-hexanoic acid derivatives as RORγt inverse agonists showing favorable ADME profile

The retinoic acid receptor-related orphan nuclear receptor gamma t (RORγt), which is a promising therapeutic target for immune diseases, is a major transcription factor of genes related to psoriasis pathogenesis, such as interleukin (IL)-17A, IL-22, and IL-23R. Inspired by the co-crystal structure of RORγt, a 6-oxo-4-phenyl-hexanoic acid derivative 6a was designed, synthesized, and identified as a ligand of RORγt. The structure-activity relationship (SAR) studies in 6a, which focus on the improvement of its membrane permeability profile by introducing chlorine atoms, led to finding 12a, which has a potent RORγt inhibitory activity and a favorable pharmacokinetic profile.

Monocyclic beta-lactams for therapeutic uses: a patent overview (2010-2020)

INTRODUCTION

Monocyclic beta-lactams are four-membered cyclic amides with various structural modifications of the nucleus that determine their chemical reactivity and target specificity. Their historical use is based on their antibacterial activity, but they have recently appeared in other areas as well.

AREAS COVERED

This review summarizes the relevant patent development on monocyclic beta-lactams in various therapeutic areas over the last 10 years. The majority of patents describe compounds with antibacterial activity, while there are some recent patents describing the neuroprotective, anti-inflammatory, anti-cancer, anticoagulant and antihyperlipidemic effects of 2-azetidinones.

EXPERT OPINION

Monocyclic beta-lactams can be considered safe and nontoxic drugs, as they have been used in the clinic for almost half of the century. Recently, monocyclic beta-lactams have been increasingly recognized for their non-antibiotic activity, which has led to some promising new clinical candidates in the field of neurodegenerative diseases and coagulation therapy. With regard to their antibacterial activity, there is still room for improvement of their activity and broadening of their spectrum of action, especially in Gram-positive bacteria and on drug-insensitive penicillin-binding proteins, and in increasing their beta-lactamase stability.

Natural products as modulators of retinoic acid receptor-related orphan receptors (RORs)

Covering: 1994 to 2020 Retinoic acid receptor-related orphan receptors (RORs) belong to a subfamily of the nuclear receptor superfamily and possess prominent roles in circadian rhythm, metabolism, inflammation, and cancer. They have been subject of research for over two decades and represent attractive but challenging drug targets. Natural products were among the first identified ligands of RORs and continue to be of interest to this day. This review focuses on ligands and indirect modulators of RORs from natural sources and explores their roles in a therapeutic context.

Targeting castration-resistant prostate cancer with a novel RORγ antagonist elaiophylin

Prostate cancer (PCa) patients who progress to metastatic castration-resistant PCa (mCRPC) mostly have poor outcomes due to the lack of effective therapies. Our recent study established the orphan nuclear receptor RORγ as a novel therapeutic target for CRPC. Here, we reveal that elaiophylin (Elai), an antibiotic from Actinomycete streptomyces, is a novel RORγ antagonist and showed potent antitumor activity against CRPC in vitro and in vivo. We demonstrated that Elai selectively binded to RORγ protein and potently blocked RORγ transcriptional regulation activities. Structure–activity relationship studies showed that Elai occupied the binding pocket with several key interactions. Furthermore, Elai markedly reduced the recruitment of RORγ to its genomic DNA response element (RORE), suppressed the expression of RORγ target genes AR and AR variants, and significantly inhibited PCa cell growth. Importantly, Elai strongly suppressed tumor growth in both cell line based and patient-derived PCa xenograft models. Taken together, these results suggest that Elai is novel therapeutic RORγ inhibitor that can be used as a drug candidate for the treatment of human CRPC.

Current perspectives on the immunopathogenesis of sarcoidosis

Sarcoidosis is an inflammatory systemic disease that commonly affects the lungs or lymph nodes but can manifest in other organs. Herein, we review the latest evidence establishing how innate and adaptive immune responses contribute to the pathogenesis and clinical course of sarcoidosis. We discuss the possible role of microbial organisms as etiologic agents in sarcoidosis and the evidence supporting sarcoidosis as an autoimmune disease. We also discuss how animal and in vitro human models have advanced our understanding of the immunopathogenesis of sarcoidosis. Finally, we discuss therapeutics for sarcoidosis and the effects on the immune system.

Retinoid-Related Orphan Receptor RORγt in CD4+ T-Cell-Mediated Intestinal Homeostasis and Inflammation

Retinoic acid-related orphan receptor (ROR)-γt, the master transcription factor of the Th17 subset of CD4⁺ Th cells, is a promising target for treating a host of autoimmune diseases. RORγt plays a vital role in the pathogenesis of inflammatory bowel diseases-Crohn disease and ulcerative colitis-caused by untoward reactivity of the immune system to the components of the intestinal microbiome. The mammalian intestinal tract is a highly complex and compartmentalized organ with specialized functions, and is a privileged site for the generation of both peripherally induced regulatory CD4⁺ T cells (Tregs) and effector Th17 cells. As Th17 cells can be proinflammatory in nature, the equilibrium between effector Th17 and Treg cells is crucial for balancing intestinal homeostasis and inflammation. Recent findings suggest that RORγt, in addition to Th17 cells, is also expressed in peripherally induced, colonic regulatory CD4⁺ T cells. Therefore, RORγt is expressed in both effector and regulatory subsets of CD4⁺ T cells in the intestine. The present review discusses the role of RORγt in cellular and molecular differentiation of Th17 and Treg, and examines how targeting RORγt in inflammatory bowel disease therapy could influence the development of these two diverse subsets of immune cells with opposing functions.

RORγ Structural Plasticity and Druggability

Retinoic acid receptor-related orphan receptor γ (RORγ) is a transcription factor regulating the expression of the pro-inflammatory cytokine IL-17 in human T helper 17 (Th17) cells. Activating RORγ can induce multiple IL-17-mediated autoimmune diseases but may also be useful for anticancer therapy. Its deep immunological functions make RORɣ an attractive drug target. Over 100 crystal structures have been published describing atomic interactions between RORɣ and agonists and inverse agonists. In this review, we focus on the role of dynamic properties and plasticity of the RORɣ orthosteric and allosteric binding sites by examining structural information from crystal structures and simulated models. We discuss the possible influences of allosteric ligands on the orthosteric binding site. We find that high structural plasticity favors the druggability of RORɣ, especially for allosteric ligands.

Discovery of (3S,4S)-3-methyl-3-(4-fluorophenyl)-4-(4-(1,1,1,3,3,3-hexafluoro-2-hydroxyprop-2-yl)phenyl)pyrrolidines as novel RORγt inverse agonists

A novel series of cis-3,4-diphenylpyrrolidines were designed as RORγt inverse agonists based on the binding conformation of previously reported bicyclic sulfonamide 1. Preliminary synthesis and structure-activity relationship (SAR) study established (3S,4S)-3-methyl-3-(4-fluorophenyl)-4-(4-(1,1,1,3,3,3-hexafluoro-2-hydroxyprop-2-yl)phenyl)pyrrolidine as the most effective scaffold. Subsequent SAR optimization led to identification of a piperidinyl carboxamide 31, which was potent against RORγt (EC₅₀ of 61 nM in an inverse agonist assay), selective relative to RORα, RORβ, LXRα and LXRβ, and stable in human and mouse liver microsomes. Furthermore, compound 31 exhibited considerably lower PXR Y_max (46%) and emerged as a promising lead. The binding mode of the diphenylpyrrolidine series was established with an X-ray co-crystal structure of 10A/RORγt.

Discovery of carboxyl-containing biaryl ureas as potent RORγt inverse agonists

GSK805 (1) is a potent RORγt inverse agonist, but a drawback of 1 is its low solubility, leading to a limited absorption in high doses. We have explored detailed structure-activity relationship on the amide linker, biaryl and arylsulfonyl moieties of 1 trying to improve solubility while maintaining RORγt activity. As a result, a novel series of carboxyl-containing biaryl urea derivatives was discovered as potent RORγt inverse agonists with improved drug-like properties. Compound 3i showed potent RORγt inhibitory activity and subtype selectivity with an IC₅₀ of 63.8 nM in RORγ FRET assay and 85 nM in cell-based RORγ-GAL4 promotor reporter assay. Reasonable inhibitory activity of 3i was also achieved in mouse Th17 cell differentiation assay (76% inhibition at 0.3 μM). Moreover, 3i had greatly improved aqueous solubility at pH 7.4 compared to 1, exhibited decent mouse PK profile and demonstrated some in vivo efficacy in an imiquimod-induced psoriasis mice model.

Substituted benzyloxytricyclic compounds as retinoic acid-related orphan receptor gamma t (RORγt) agonists

Substituted benzyloxy aryl compound 2 was identified as an RORγt agonist. Structure based drug design efforts resulted in a potent and selective tricyclic compound 19 which, when administered orally in an MC38 mouse tumor model, demonstrated a desired pharmacokinetic profile as well as a dose-dependent pharmacodynamic response. However, no perceptible efficacy was observed in this tumor model at the doses investigated.

Discovery of BMS-986251: A Clinically Viable, Potent, and Selective RORγt Inverse Agonist

Novel tricyclic analogues were designed, synthesized, and evaluated as RORγt inverse agonists. Several of these compounds were potent in an IL-17 human whole blood assay and exhibited excellent oral bioavailability in mouse pharmacokinetic studies. This led to the identification of compound 5, which displayed dose-dependent inhibition of IL-17F production in a mouse IL-2/IL-23 stimulated pharmacodynamic model. In addition, compound 5 was studied in mouse acanthosis and imiquimod-induced models of skin inflammation, where it demonstrated robust efficacy comparable to a positive control. As a result of this excellent overall profile, compound 5 (BMS-986251) was selected as a clinically viable developmental candidate.

Discovery of [1,2,4]Triazolo[1,5-a]pyridine Derivatives as Potent and Orally Bioavailable RORγt Inverse Agonists

The retinoic acid receptor-related orphan nuclear receptor γt (RORγt), a promising therapeutic target, is a major transcription factor of genes related to psoriasis pathogenesis such as interleukin (IL)-17A, IL-22, and IL-23R. On the basis of the X-ray cocrystal structure of RORγt with 1a, an analogue of the known piperazine RORγt inverse agonist 1, triazolopyridine derivatives of 1 were designed and synthesized, and analogue 3a was found to be a potent RORγt inverse agonist. Structure-activity relationship studies on 3a, focusing on the treatment of its metabolically unstable cyclopentyl ring and the central piperazine core, led to a novel analogue, namely, 6-methyl-N-(7-methyl-8-(((2S,4S)-2-methyl-1-(4,4,4-trifluoro-3-(trifluoromethyl)butanoyl)piperidin-4-yl)oxy)[1,2,4]triazolo[1,5-a]pyridin-6-yl)nicotinamide (5a), which exhibited strong RORγt inhibitory activity and a favorable pharmacokinetic profile. Moreover, the in vitro and in vivo evaluation of 5a in a human whole-blood assay and a mouse IL-18/23-induced cytokine expression model revealed its robust and dose-dependent inhibitory effect on IL-17A production.

Elucidation of an Allosteric Mode of Action for a Thienopyrazole RORγt Inverse Agonist

The demand for allosteric targeting of nuclear receptors is high, but examples are limited, and structural information is scarce. The retinoic acid-related orphan receptor gamma t (RORγt) is an important transcriptional regulator for the differentiation of T helper 17 cells for which the first, and some of the most promising, examples of allosteric nuclear receptor modulation have been reported and structurally proven. In a 2015 patent, filed by the pharmaceutical company Glenmark, a new class of small molecules was reported that act as potent inverse agonists for RORγt. A compound library around the central thienopyrazole scaffold captured a clear structure-activity relationship, but the binding mechanism of this new class of RORγt modulators has not been elucidated. Using a combination of biochemical and X-ray crystallography studies, here the allosteric mechanism for the inverse agonism for the most potent compound, classified in the patent as "example 13", is reported, providing a strongly desired additional example of allosteric nuclear receptor targeting.

Transcriptional Regulators of T Helper 17 Cell Differentiation in Health and Autoimmune Diseases

T helper (Th) 17 cells are a subtype of CD4 T lymphocytes characterized by the expression of retinoic acid-receptor (RAR)-related orphan receptor (ROR)γt transcription factor, encoded by gene Rorc. These cells are implicated in the pathology of autoimmune inflammatory disorders as well as in the clearance of extracellular infections. The main function of Th17 cells is the production of cytokine called interleukin (IL)-17A. This review highlights recent advances in mechanisms regulating transcription of IL-17A. In particular, we described the lineage defining transcription factor RORγt and other factors that regulate transcription of Il17a or Rorc by interacting with RORγt or by binding their specific DNA regions, which may positively or negatively influence their expression. Moreover, we reported the eventual involvement of those factors in Th17-related diseases, such as multiple sclerosis, rheumatoid arthritis, psoriasis, and Crohn's disease, characterized by an exaggerated Th17 response. Finally, we discussed the potential new therapeutic approaches for Th17-related diseases targeting these transcription factors. The wide knowledge of transcriptional regulators of Th17 cells is crucial for the better understanding of the pathogenic role of these cells and for development of therapeutic strategies aimed at fighting Th17-related diseases.