Discovery of Biaryl Amides as Potent, Orally Bioavailable, and CNS Penetrant RORγt Inhibitors

Discovery and pharmacological characterization of 1,2,3,4-tetrahydroquinoline derivatives as RORγ inverse agonists against prostate cancer

The retinoic acid receptor-related orphan receptor γ (RORγ) is regarded as an attractive therapeutic target for the treatment of prostate cancer. Herein, we report the identification, optimization, and evaluation of 1,2,3,4-tetrahydroquinoline derivatives as novel RORγ inverse agonists, starting from high throughput screening using a thermal stability shift assay (TSA). The representative compounds 13e (designated as XY039) and 14a (designated as XY077) effectively inhibited the RORγ transcriptional activity and exhibited excellent selectivity against other nuclear receptor subtypes. The structural basis for their inhibitory potency was elucidated through the crystallographic study of RORγ LBD complex with 13e. Both 13e and 14a demonstrated reasonable antiproliferative activity, potently inhibited colony formation and the expression of AR, AR regulated genes, and other oncogene in AR positive prostate cancer cell lines. Moreover, 13e and 14a effectively suppressed tumor growth in a 22Rv1 xenograft tumor model in mice. This work provides new and valuable lead compounds for further development of drugs against prostate cancer.

Rh(III)-Catalyzed Controlled Ortho-Amidation of Arylamides with Dioxazolones Using Weakly Coordinating Native Primary Amide as the Directing Group

Herein, we report a controlled introduction of an amide unit at the ortho-position of an electron-deficient arylamide system without affording any cyclized products using user-friendly dioxazolone as an amidating reagent in the presence of a Rh(III)-catalyst. This is the first report where native primary amide has been utilized as a weakly coordinating group for site-selective C-N bond formation reaction. The developed protocol works under external auxiliary-free conditions with a wide substrate scope.

Discovery of the First-in-Class RORγ Covalent Inhibitors for Treatment of Castration-Resistant Prostate Cancer

Nuclear receptor receptor-related orphan receptor γ (RORγ) is a ligand-dependent transcription factor and has been established as a key player in castration-resistant prostate cancers (CRPC) by driving androgen receptor (AR) overexpression, representing a potential therapeutical target for advanced prostate cancers. Here, we report the identification of the first-in-class RORγ covalent inhibitor 29 via the structure-based drug design approach following structure-activity relationship (SAR) exploration. Mass spectrometry assay validated its covalent inhibition mechanism. Compound 29 significantly inhibited RORγ transcriptional activity and remarkably suppressed the expression levels of AR and AR-targeted genes. Compound 29 also exhibited much superior activity in inhibiting the proliferation and colony formation and inducing apoptosis of the CRPC cell lines relative to the positive control 2 and noncovalent control 33. Importantly, it markedly suppressed the tumor growth in a 22Rv1 mouse tumor xenograft model with good safety. These results clearly demonstrate that 29 is a highly potent and selective RORγ covalent inhibitor.

Discovery, Synthesis, and In Vitro Characterization of 2,3 Derivatives of 4,5,6,7-Tetrahydro-Benzothiophene as Potent Modulators of Retinoic Acid Receptor-Related Orphan Receptor γt

Retinoic acid receptor-related orphan receptor γt (RORγt) is a nuclear receptor that is expressed in a variety of tissues and is a potential drug target for the treatment of inflammatory and auto-immune diseases, metabolic diseases, and resistant cancer types. We herein report the discovery of 2,3 derivatives of 4,5,6,7-tetrahydro-benzothiophene modulators of RORγt. We also report the solubility in acidic/neutral pH, mouse/human/dog/rat microsomal stability, Caco-2, and MDR1-MDCKII permeabilities of a set of these derivatives. For this group of modulators, inverse agonism by steric clashes and push-pull mechanisms induce greater instability to protein conformation compared to agonist lock hydration. Independent of the two mechanisms, we observed a basal modulatory activity of the tested 2,3 derivatives of 4,5,6,7-tetrahydro-benzothiophene toward RORγt due to the interactions with the Cys320-Glu326 and Arg364-Phe377 hydrophilic regions. The drug discovery approach reported in the current study can be employed to discover modulators of nuclear receptors and other globular protein targets.

Discovery of novel triazine derivatives as potent retinoic acid receptor-related orphan receptor γt (RORγt) inverse agonists

Retinoic Acid Receptor-Related Orphan Receptor γt (RORγt) has been exploited as a promising target for the new small molecule therapeutics to treat inflammatory and autoimmune diseases via modulating the interleukin-17 (IL-17) production by T helper 17 (Th17) cells. Herein, we reported a series of triazine-based derivatives as novel RORγt inverse agonists. By screening of our in-house compound library, the hit compound 1 was identified with weak RORγt inhibitory activity. Subsequently, we engineered detailed structural modifications to explore the structure-activity relationships (SARs) of triazines derivatives, which led to discovery of a number of potent RORγt inverse agonists with IC₅₀ values in the range of 7 nM-50 nM in RORγt dual FRET assay. Among them, compound 14g displayed potent RORγt inverse agonistic activity with an IC₅₀ value of 22.9 nM in dual FRET assay. In a cell-based reporter gene assay, compound 14g showed an IC₅₀ value of 0.428 μM and maximum inhibition rate of 108.9%. Compound 14g also exhibited good metabolic stability and a decent pharmacokinetic profile with a low clearance (CL = 0.229 L/h/kg) and a reasonable oral exposure (AUC_0-Last = 5058 ng/mL*h). Most importantly, 14g alleviated the severity of imiquimod-induced psoriasis in mice. Taken together, triazine-based derivatives represent a new chemical class of RORγt inverse agonists as potential therapeutic agents against autoimmune diseases.

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.

Statistical Analysis of Protein-Ligand Interaction Patterns in Nuclear Receptor RORγ

The receptor RORγ belongs to the nuclear receptor superfamily that senses small signaling molecules and regulates at the gene transcription level. Since RORγ has a high basal activity and plays an important role in immune responses, inhibitors targeting this receptor have been a focus for many studies. The receptor-ligand interaction is complex, and often subtle differences in ligand structure can determine its role as an inverse agonist or an agonist. We examined more than 130 existing RORγ crystal structures that have the same receptor complexed with different ligands. We reported the features of receptor-ligand interaction patterns and the differences between agonist and inverse agonist binding. Specific changes in the contact interaction map are identified to distinguish active and inactive conformations. Further statistical analysis of the contact interaction patterns using principal component analysis reveals a dominant mode which separates allosteric binding vs. canonical binding and a second mode which may indicate active vs. inactive structures. We also studied the nature of constitutive activity by performing a 100-ns computer simulation of apo RORγ. Using constitutively active nuclear receptor CAR as a comparison, we identified a group of conserved contacts that have similar contact strength between the two receptors. These conserved contact interactions, especially a couple key contacts in H11–H12 interaction, can be considered essential to the constitutive activity of RORγ. These protein-ligand and internal protein contact interactions can be useful in the development of new drugs that direct receptor activity.

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.

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.

Th17 cell master transcription factor RORC2 regulates HIV-1 gene expression and viral outgrowth

HIV-1 infects CD4 T cells, and, among these, T helper 17 (Th17) cells are known to be particularly permissive for virus replication. The infection of Th17 cells is critical for AIDS pathogenesis and viral persistence. It is, however, not clear why these cells are highly permissive to HIV-1. We found that Th17 cell permissiveness depends on the expression of the hormone receptor RORC2, which is the master transcriptional regulator of Th17 cell differentiation. We identify RORC2 as a cell-specific host-dependency factor that can be targeted by small molecules. Our results suggest that RORC2 may be a cell-specific target to mitigate the loss of Th17 cells as a consequence of their preferential HIV-1 infection.

Among CD4⁺ T cells, T helper 17 (Th17) cells are particularly susceptible to HIV-1 infection and are depleted from mucosal sites, which causes damage to the gut barrier, resulting in a microbial translocation-induced systemic inflammation, a hallmark of disease progression. Furthermore, a proportion of latently infected Th17 cells persist long term in the gastrointestinal lymphatic tract where a low-level HIV-1 transcription is observed. This residual viremia contributes to chronic immune activation. Thus, Th17 cells are key players in HIV pathogenesis and viral persistence. It is, however, unclear why these cells are highly susceptible to HIV-1 infection. Th17 cell differentiation depends on the expression of the master transcriptional regulator RORC2, a retinoic acid-related nuclear hormone receptor that regulates specific transcriptional programs by binding to promoter/enhancer DNA. Here, we report that RORC2 is a key host cofactor for HIV replication in Th17 cells. We found that specific inhibitors that bind to the RORC2 ligand-binding domain reduced HIV replication in CD4⁺ T cells. The depletion of RORC2 inhibited HIV-1 infection, whereas its overexpression enhanced it. RORC2 was also found to promote HIV-1 gene expression by binding to the nuclear receptor responsive element in the HIV-1 long terminal repeats (LTR). In treated HIV-1 patients, RORC2⁺ CD4 T cells contained more proviral DNA than RORC2⁻ cells. Pharmacological inhibition of RORC2 potently reduced HIV-1 outgrowth in CD4⁺ T cells from antiretroviral-treated patients. Altogether, these results provide an explanation as to why Th17 cells are highly susceptible to HIV-1 infection and suggest that RORC2 may be a cell-specific target for HIV-1 therapy.

Discovery of N-(2-benzyl-4-oxochroman-7-yl)-2-(5-(ethylsulfonyl) pyridin-2-yl) acetamide (b12) as a potent, selective, and orally available novel retinoic acid receptor-related orphan receptor γt inverse agonist

The nuclear receptor retinoic acid receptor-related orphan receptor γ (RORγ, NR1F3, or RORc) exists in two isoforms, with one isoform (RORγ or RORc1) widely expressed in a variety of tissues, and the expression of the second isoform (RORγt or RORc2) restricted to the thymus and cells of the immune system. RORγt is a key regulator of the development and functions of T-helper 17 (Th17) cells. Clinical proof-of-concept (PoC) with small molecule inverse agonists of RORγt has been achieved with VTP-43742 (Phase II) for the treatment of psoriasis, and pre-clinical PoC for this mechanism has also been established for the treatment of autoimmune diseases. A series of aryl sulfonyl derivatives as novel RORγt inverse agonists were designed and synthesized based on VTP-43742. We conducted structural modifications that improved the activity profile. In pharmacodynamic (PD) studies, oral administration of compound b12 showed robust and dose-dependent inhibition of IL-6 and IL-17A cytokine expression. The ability of compound b12 to reduce the levels of IL-6 and IL-17A in vivo after oral dosing in mice, and a corresponding reduction in skin inflammation further supports the potential of small molecule RORγt modulation as a therapeutic target for the treatment of inflammatory diseases.

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.

The evolution paths of some reprehensive scaffolds of RORγt modulators, a perspective from medicinal chemistry

The ligand binding domain (LBD) of retinoid-related orphan nuclear receptor γt (RORγt) has been exploited as a promising target for the new small molecule therapeutics to cure autoimmune diseases via modulating the IL-17 and IL-22 production by Th17 cells. Diverse chemical scaffolds of these small molecules have been discovered by multiple groups with methods such as high throughput screening (HTS) and virtual screening. These different scaffolds are further developed by medicinal chemists to afford lead compounds the best of which enter clinical trials. In this review, we summarize these chemical scaffolds and their evolution paths according to the groups in which they have been discovered or studied. We combine the data of the chemistry, biological assays and structural biology of each chemical scaffold, in order to afford insight to develop new RORγt modulators with higher potency, less toxicity and elucidated working mechanism.

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.

Discovery and Characterization of Benzimidazole Derivative XY123 as a Potent, Selective, and Orally Available RORγ Inverse Agonist

Receptor-related orphan receptor γ (RORγ) has emerged as an attractive therapeutic target for the treatment of cancer and inflammatory diseases. Herein, we report our effort on the discovery, optimization, and evaluation of benzothiazole and benzimidazole derivatives as novel inverse agonists of RORγ. The representative compound 27h (designated as XY123) potently inhibited the RORγ transcription activity with a half-maximal inhibitory concentration (IC50) value of 64 nM and showed excellent selectivity against other nuclear receptors. 27h also potently suppressed cell proliferation, colony formation, and the expression of androgen receptor (AR)-regulated genes in AR-positive prostate cancer cell lines. In addition, 27h demonstrated good metabolic stability and a pharmacokinetic property with reasonable oral bioavailability (32.41%) and moderate half-life (t1/2 = 4.98 h). Significantly, oral administration of compound 27h achieved complete and long-lasting tumor regression in the 22Rv1 xenograft tumor model in mice. Compound 27h may serve as a new valuable lead compound for further development of drugs for the treatment of prostate cancer.

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.

Discovery of a novel RORγ antagonist with skin-restricted exposure for topical treatment of mild to moderate psoriasis

Clinical success of IL-17/IL-23 pathway biologics for the treatment of moderate to severe psoriasis suggests that targeting RORγt, a master regulator for the proliferation and function of Th17 cells, could be an effective alternative. However, oral RORγ antagonists (VTP43742, TAK828) with high systemic exposure showed toxicity in phase I/II clinical trials and terminated development. To alleviate the potential safety concerns, identifying compounds with skin-restricted exposure amenable for topical use is of great interest. Systematic structure activity relationship study and multi-parameter optimization led to the discovery of a novel RORγ antagonist (SHR168442) with desired properties for a topical drug. It suppressed the transcription of IL-17 gene, leading to reduction of IL-17 cytokine secretion. It showed high exposure in skin, but low in plasma. Topical application of SHR168442 in Vaseline exhibited excellent efficacy in the imiquimod-induced and IL-23-induced psoriasis-like skin inflammation mouse models and correlated with the reduction of Th17 pathway cytokines, IL-6, TNFα and IL-17A. This work demonstrated restricted skin exposure of RORγ antagonist may provide a new topical treatment option as targeted therapeutics for mild to moderate psoriasis patients and may be suitable for the treatment of any other inflammatory disorders that are accessible locally.

The oxysterome and its receptors as pharmacological targets in inflammatory diseases

Oxysterols have gained attention over the last decades and are now considered as fully fledged bioactive lipids. The study of their levels in several conditions, including atherosclerosis, obesity and neurodegenerative diseases, led to a better understanding of their involvement in (patho)physiological processes such as inflammation and immunity. For instance, the characterization of the cholesterol-7α,25-dihydroxycholesterol/GPR183 axis and its implication in immunity represents an important step in the oxysterome study. Besides this axis, others were identified as important in several inflammatory pathologies (such as colitis, lung inflammation and atherosclerosis). However, the oxysterome is a complex system notably due to a redundancy of metabolic enzymes and a wide range of receptors. Indeed, deciphering oxysterol roles and identifying the potential receptor(s) involved in a given pathology remain challenging. Oxysterol properties are very diverse, but most of them could be connected by a common component: inflammation. Here, we review the implication of oxysterol receptors in inflammatory diseases.

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.

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.

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.

BF3·OEt2-promoted tandem Meinwald rearrangement and nucleophilic substitution of oxiranecarbonitriles

Introducing a cyano leaving group into epoxides results in BF₃·OEt₂-promoted tandem Meinwald rearrangement and nucleophilic substitution to synthesize arylacetic derivatives from vicinal arylcyanoepoxides.

Th17 cells and their cytokines serve as potential therapeutic target in experimental autoimmune neuritis

BACKGROUND

Accumulating evidence has pointed that T helper 17 cells and their cytokines are pathogenic in Guillain-Barré syndrome (GBS). However, little is known concerning the IL-17 expression change trend during the whole course of disease, and whether drugs specially targeting Th17 cells or their cytokines have potential effects on experimental autoimmune neuritis (EAN) is uncertain.

METHODS

We explored the IL-17 and receptor-related orphan receptor-gamma-t (RORγt) expression change trends in EAN rats to identify the stage of effect of Th17 pathway in EAN, and further, we investigated the effect of RORγt inhibitors by assessing clinical score, histological staining, and IL-17 and RORγt expression change trends in serum and tissues.

RESULTS

The expression level of IL-17 and RORγt in serum and tissues increased with the progression of the disease in the EAN group and decreased after the disease reaching its peak. RORγt-IN-1 treatment strikingly reduced the neurological deficits by ameliorating inflammatory cell infiltration, deceased the serum IL-17 and RORγt levels, and further downregulated the expression of IL-17 and RORγt mRNA in spleen, lymphnodes, and sciatic nerve.

CONCLUSIONS

Th17 cells and their cytokines are closely associated with the onset of GBS and the novel RORγt inhibitors may be prospective strategies in treating GBS.

Molecular dynamics simulations on RORγt: insights into its functional agonism and inverse agonism

The retinoic acid receptor-related orphan receptor (ROR) γt receptor is a member of nuclear receptors, which is indispensable for the expression of pro-inflammatory cytokine IL-17. RORγt has been established as a drug target to design and discover novel treatments for multiple inflammatory and immunological diseases. It is important to elucidate the molecular mechanisms of how RORγt is activated by an agonist, and how the transcription function of RORγt is interrupted by an inverse agonist. In this study we performed molecular dynamics simulations on four different RORγt systems, i.e., the apo protein, protein bound with agonist, protein bound with inverse agonist in the orthosteric-binding pocket, and protein bound with inverse agonist in the allosteric-binding pocket. We found that the orthosteric-binding pocket in the apo-form RORγt was mostly open, confirming that apo-form RORγt was constitutively active and could be readily activated (ca. tens of nanoseconds scale). The tracked data from MD simulations supported that RORγt could be activated by an agonist binding at the orthosteric-binding pocket, because the bound agonist helped to enhance the triplet His479-Tyr502-Phe506 interactions and stabilized H12 structure. The stabilized H12 helped RORγt to form the protein-binding site, and therefore made the receptor ready to recruit a coactivator molecule. We also showed that transcription function of RORγt could be interrupted by the binding of inverse agonist at the orthosteric-binding pocket or at the allosteric-binding site. After the inverse agonist was bound, H12 either structurally collapsed, or reorientated to a different position, at which the presumed protein-binding site was not able to be formed.

Rationally Designed, Conformationally Constrained Inverse Agonists of RORγt-Identification of a Potent, Selective Series with Biologic-Like in Vivo Efficacy

RORγt is an important nuclear receptor that regulates the production of several pro-inflammatory cytokines such as IL-17 and IL-22. As a result, RORγt has been identified as a potential target for the treatment of various immunological disorders such as psoriasis, psoriatic arthritis, and inflammatory bowel diseases. Structure and computer-assisted drug design led to the identification of a novel series of tricyclic RORγt inverse agonists with significantly improved in vitro activity in the reporter (Gal4) and human whole blood assays compared to our previous chemotype. Through careful structure activity relationship, several potent and selective RORγt inverse agonists have been identified. Pharmacokinetic studies allowed the identification of the lead molecule 32 with a low peak-to-trough ratio. This molecule showed excellent activity in an IL-2/IL-23-induced mouse pharmacodynamic study and demonstrated biologic-like efficacy in an IL-23-induced preclinical model of psoriasis.

Discovery and pharmacological evaluation of indole derivatives as potent and selective RORγt inverse agonist for multiple autoimmune conditions

Targeting nuclear receptor RORγ is recognized to be beneficial in multiple autoimmune disorders. We disclosed new indole analogues as potent RORγ inverse agonists. RO-2 as one of the potent and orally bioavailable compounds was evaluated in various models of autoimmune disorder. It showed potent suppression of downstream markers of RORγt activity in murine and human primary cells, ex vivo PD assay and in multiple animal models of autoimmune diseases. The results indicate the potential of these indole analogues as orally bioavailable small molecule inverse agonists of RORγt, efficacious in various Th17 driven models of autoimmune disorders.

Discovery of Potent and Orally Bioavailable Inverse Agonists of the Retinoic Acid Receptor-Related Orphan Receptor C2

The further optimization of a recently disclosed series of inverse agonists of the nuclear receptor RORC2 is described. Investigations into the left-hand side of compound 1, guided by X-ray crystal structures, led to the substitution of the 4-aryl-thiophenyl residue with the hexafluoro-2-phenyl-propan-2-ol moiety. This change resulted in to compound 28, which combined improved drug-like properties with good cell potency and a significantly lower dose, using an early dose to man prediction. Target engagement in vivo was demonstrated in the thymus of mice by a reduction in the number of double positive T cells after oral dosing.

ILC3-derived OX40L is essential for homeostasis of intestinal Tregs in immunodeficient mice

OX40L is one of the co-stimulatory molecules that can be expressed by splenic lymphoid tissue inducer (Lti) cells, a subset of group 3 innate lymphoid cells (ILC3s). OX40L expression in subsets of intestinal ILC3s and the molecular regulation of OX40L expression in ILC3s are unknown. Here, we showed intestinal ILC3s marked as an OX40L^high population among all the intestinal leukocytes and were the dominant source of OX40L in Rag1^-/- mice. All ILC3 subsets expressed OX40L, and NCR^-ILC3s were the most abundant source of OX40L. The expression of OX40L in ILC3s could be upregulated during inflammation. In addition to tumor necrosis factor (TNF)-like cytokine 1A (TL1A), which has been known as a trigger for OX40L, we found that Poly (I:C) representing viral stimulus promoted OX40L expression in ILC3s via a cell-autonomous manner. Furthermore, we demonstrated that IL-7-STAT5 signaling sustained OX40L expression by ILC3s. Intestinal regulatory T cells (Tregs), most of which expressed OX40, had defective expansion in chimeric mice, in which ILC3s were specifically deficient for OX40L expression. Consistently, co-localization of Tregs and ILC3s was found in the cryptopatches of the intestine, which suggests the close interaction between ILC3s and Tregs. Our study has unveiled the crosstalk between Tregs and ILC3s in mucosal tissues through OX40-OX40L signaling, which is crucial for the homeostasis of intestinal Tregs.

Analysis of the Transcriptional Activity of Retinoic Acid-Related Orphan Receptors (RORs) and Inhibition by Inverse Agonists

Here, we describe several assays to analyze the transcriptional activity of retinoic acid-related orphan receptors (RORs) and the effect of inverse agonists on their activity. One assay measures the effect of an inverse agonist on the transcriptional activation of a luciferase reporter by RORs in a Tet-On cell system. A mammalian two-hybrid assay analyzes the interaction of the ROR ligand binding domain with a coactivator peptide. Two additional assays examine the effect of an inverse agonist on the activation of a luciferase reporter under control of the promoter of the ROR target gene, IL17, and on ROR-mediated activation using a mammalian monohybrid assay.

Molecular Mechanism of Action of RORγt Agonists and Inverse Agonists: Insights from Molecular Dynamics Simulation

As an attractive drug-target, retinoic acid receptor-related orphan receptor-gamma-t (RORγt) has been employed widely to develop clinically relevant small molecular modulators as potent therapy for autoimmune disease and cancer, but its molecular mechanism of action (MOA) remains unclear. In the present study, we designed and discovered two novel RORγt ligands that are similar in structure, but different in efficacy. Using fluorescence resonance energy transfer (FRET) assay, compound 1 was identified as an agonist with an EC₅₀ of 3.7 μM (max. act.: 78%), while compound 2 as an inverse agonist with an IC₅₀ value of 2.0 μM (max. inh.: 61%). We performed molecular dynamics (MD) simulations, and elucidated the MOA of RORγt agonist and inverse agonist. Through the analyses of our MD results, we found that, after RORγt is bound with the agonist 1, the side chain of Trp317 stays in the gauche- conformation, and thus helps to form the hydrogen bond, His479-Trp502, and a large hydrophobic network among H11, H11′, and H12. All these interactions stabilize the H12, and helps the receptor recruit the coactivator. When the RORγt is bound with the inverse agonist 2, the side chain of Trp317 is forced to adopt the trans conformation, and these presumed interactions are partially destroyed. Taken together, the critical role of residue Trp317 could be viewed as the driving force for the activation of RORγt.

Ternary crystal structure of human RORγ ligand-binding-domain, an inhibitor and corepressor peptide provides a new insight into corepressor interaction

Retinoic acid-related orphan receptor gamma (RORγ) plays pivotal roles in autoimmune diseases by controlling the lineage of interleukin 17 (IL-17)-producing CD4⁺ T cells (Th17 cells). Structure-based drug design has proven fruitful in the development of inhibitors targeting the ligand binding domain (LBD) of RORγ. Here, we present the crystal structure of a novel RORγ inhibitor co-complex, in the presence of a corepressor (CoR) peptide. This ternary complex with compound T reveals the structural basis for an inhibitory mechanism different from the previously reported inverse agonist. Compared to the inverse agonist, compound T induces about 2 Å shift of helix 5 (H5) backbone and side-chain conformational changes of Met365 on H5. These conformational changes correlate to reduced CoR peptide binding to RORγ-LBD in the presence of compound T, which suggests that the shift of H5 is responsible. This crystal structure analysis will provide useful information for the development of novel and efficacious drugs for autoimmune disorders.

Discovery of carbazole carboxamides as novel RORγt inverse agonists

A novel series of carbazole carboxamides was discovered as potent RORγt inverse agonists using a scaffold hybridization strategy. Structure-activity relationship exploration on the amide linker, carbazole ring and arylsulfone moiety of the hybrid amide 3a led to identification of potent RORγt inverse agonists. Compound 6c was found to have a good RORγt activity with an IC₅₀ of 58.5 nM in FRET assay, and reasonable inhibitory activity in mouse Th17 cell differentiation assay (58.8% inhibition at 0.3 μM). The binding mode of carbazole carboxamides in RORγt ligand binding domain was discussed.

From RORγt Agonist to Two Types of RORγt Inverse Agonists

Biaryl amides as new RORγt modulators were discovered. The crystal structure of biaryl amide agonist 6 in complex with RORγt ligand binding domain (LBD) was resolved, and both "short" and "long" inverse agonists were obtained by removing from 6 or adding to 6 a proper structural moiety. While "short" inverse agonist (8) recruits a corepressor peptide and dispels a coactivator peptide, "long" inverse agonist (9) dispels both. The two types of inverse agonists can be utilized as potential tools to study mechanisms of Th17 transcriptional network inhibition and related disease biology.