Modulators of the Nuclear Receptor Retinoic Acid Receptor-Related Orphan Receptor-γ (RORγ or RORc)

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.

Identification of multiple transcription factor genes potentially involved in the development of electrosensory versus mechanosensory lateral line organs

In electroreceptive jawed vertebrates, embryonic lateral line placodes give rise to electrosensory ampullary organs as well as mechanosensory neuromasts. Previous reports of shared gene expression suggest that conserved mechanisms underlie electroreceptor and mechanosensory hair cell development and that electroreceptors evolved as a transcriptionally related "sister cell type" to hair cells. We previously identified only one transcription factor gene, Neurod4, as ampullary organ-restricted in the developing lateral line system of a chondrostean ray-finned fish, the Mississippi paddlefish (Polyodon spathula). The other 16 transcription factor genes we previously validated in paddlefish were expressed in both ampullary organs and neuromasts. Here, we used our published lateral line organ-enriched gene-set (arising from differential bulk RNA-seq in late-larval paddlefish), together with a candidate gene approach, to identify 25 transcription factor genes expressed in the developing lateral line system of a more experimentally tractable chondrostean, the sterlet (Acipenser ruthenus, a small sturgeon), and/or that of paddlefish. Thirteen are expressed in both ampullary organs and neuromasts, consistent with conservation of molecular mechanisms. Seven are electrosensory-restricted on the head (Irx5, Irx3, Insm1, Sp5, Satb2, Mafa and Rorc), and five are the first-reported mechanosensory-restricted transcription factor genes (Foxg1, Sox8, Isl1, Hmx2 and Rorb). However, as previously reported, Sox8 is expressed in ampullary organs as well as neuromasts in a catshark (Scyliorhinus canicula), suggesting the existence of lineage-specific differences between cartilaginous and ray-finned fishes. Overall, our results support the hypothesis that ampullary organs and neuromasts develop via largely conserved transcriptional mechanisms, and identify multiple transcription factors potentially involved in the formation of electrosensory versus mechanosensory lateral line organs.

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.

Lithocholic acid derivatives as potent modulators of the nuclear receptor RORγt

Retinoic acid receptor-related orphan receptor γt (RORγt) is a nuclear receptor found in various tissues that plays a crucial role in the differentiation and proliferation of T helper 17 (Th17) cells, as well as in their generation of the pro-inflammatory cytokine IL-17A. RORγt represents a promising therapeutic target for autoimmune diseases, metabolic disorders, and multiple tumors. Despite extensive research efforts focused on the development of small molecule RORγt modulators, no drug candidates have advanced to phase 3 clinical trials owing to a lack of efficacy or safety margin. This outcome highlights the unmet need to optimize small molecule drug candidates targeting RORγt to develop effective therapies for autoimmune and inflammatory diseases. In this study, we synthesized and evaluated 3-oxo-lithocholic acid amidates as a new class of RORγt modulators. Our evaluation entailed biophysical screening, cellular screening in different platforms, molecular docking, and in vitro pharmacokinetic profiling. The top compound from our study (3-oxo-lithocholic acid amidate, A2) binds to RORγt at an equilibrium dissociation constant (KD) of 16.5 ± 1.34 nM based on microscale thermophoresis (MST). Assessment of the efficacy of A2 in the cellular RORγt reporter luciferase assay revealed a half-maximal inhibitory concentration (IC50) value of 225 ± 10.4 nM. Unlike 3-oxo-lithocholic acid, A2 demonstrated the ability to reduce the IL-17A mRNA expression levels in EL4 cells with RORγt expression using quantitative reverse transcriptase PCR (RT-PCR). Validation of the desirable physicochemical properties and stability of A2 sets the stage for the preclinical evaluation of this new class of RORγt modulators in animal models of autoimmune diseases.

Validation of nuclear receptor RORγ isoform 1 as a novel host-directed antiviral target based on the modulation of cholesterol levels

Currently, the clinically approved repertoire of antiviral drugs predominantly comprises direct-acting antivirals (DAAs). However, the use of DAAs is frequently limited by adverse effects, restriction to individual virus species, or the induction of viral drug resistance. These issues will likely be resolved by the introduction of host-directed antivirals (HDAs) targeting cellular proteins crucial for viral replication. However, experiences with the development of antiviral HDAs and clinical applications are still in their infancy. With the present study, we explored the human nuclear receptor and transcription factor RORγ isoform 1 (RORγ1), a member of the retinoic acid receptor-related orphan receptor (ROR) family, as a putative target of antiviral HDAs. To this end, cell culture models were used to investigate major viral human pathogens, i.e. the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), human cytomegalovirus (HCMV), varicella zoster virus (VZV) and human immunodeficiency virus 1 (HIV-1). Our results demonstrated (i) an antiviral activity of the clinically relevant RORγ modulators cedirogant and others, (ii) that isoform RORγ1 acts as the responsible determinant and drug target in the analyzed cell culture-based models, (iii) a selectivity of the antiviral effect for RORγ1 over related receptors RORα and RORβ, (iv) a late-phase inhibition exerted by cedirogant in HCMV replication and (v) a mechanistic link to the cellular cholesterol biosynthesis. Combined, the data highlight this novel RORγ-specific antiviral targeting concept and the developmental potential of RORγ-directed small molecules.

Discovery of Biaryl Amide Derivatives as Potent, Selective, and Orally Bioavailable RORγt Agonists for Cancer Immunotherapy

The master transcription factor receptor retinoic acid receptor-related orphan receptor γt (RORγt) regulates the differentiation of T-helper 17 (Th17) cells and the production of interleukin-17 (IL-17). Activation of RORγt+ T cells in the tumor microenvironment promotes immune infiltration to more effectively inhibit tumor growth. Therefore, RORγt agonists provide a reachable approach to cancer immunotherapy. Herein, a series of biaryl amide derivatives as novel RORγt agonists were designed, synthesized, and evaluated. Starting from the reported RORγt inverse agonist GSK805 (1), "functionality switching" and structure-based drug optimization led to the discovery of a promising RORγt agonist lead compound 14, which displayed potent and selective RORγt agonist activity and significantly improved metabolic stability. With excellent in vivo pharmacokinetic profiles, compound 14 demonstrated robust efficacy in preclinical tumor models of mouse B16F10 melanoma and LLC lung adenocarcinoma. Taken together, current studies indicate that 14 deserves further investigation as a potential lead RORγt agonist for cancer immunotherapy.

Elevated profiles of peripheral Th22, Th17, Th2 cells, and decreased percentage of Th1 cells in breast cancer patients

BACKGROUND

Th22 subset is a particular type of CD4+ T helper cells subset. Our study aimed to explore the expression level of circulating Th22, Th17, Th1, and Th2 cells and the possible mechanism of these cells in breast cancer (BC) with different pathological features.

METHODS

Our study enrolled 43 newly diagnosed BC patients and 30 healthy controls. Frequencies of peripheral Th22, Th17, Th1, and Th2 cells were tested by flow cytometry. Concentrations of IL-22 cytokine in plasma were examined by enzyme-linked immunosorbent assay (ELISA). Real-time PCR was done to test aromatic hydrocarbon receptor (AHR) and RAR-associated orphan receptor C (RORC) gene expression.

RESULTS

Frequencies of Th22, Th17, Th2 subsets, and the plasma IL-22 level was obviously higher in the BC patients. A positive correlation between Th22 frequency and IL-22 concentration in plasma was detected in BC patients. Furthermore, the percentage of Th22, Th2 subsets in peripheral blood of HER2 positive BC was higher than that in HER2 negative BC patients. A negative correlation between Th1 subset and Ki-67% as well as a positive correlation between Th2 subset and Ki-67% was found in BC patients. The proportion of Th1 cells in BC patients was significantly lower than that of the control group. Expression of AHR and RORC transcription factors were also observed to be upregulated in the BC patients. Furthermore, Th22 cells were positively correlated with BC tumor stage and clinical outcomes. The BC patients with a higher percentage of Th22, Th17, Th1 cells or a lower percentage of Th1 cells showed a decreased trend of survival rate.

CONCLUSION

Th22, Th17, Th1, and Th2 subsets may play an essential role in BC patients. Th22, Th17, Th1, and Th2 cells may have potential significance to be used as clinical markers in BC patients with different molecular classification. Th22 cells may have potential value in BC patients' outcomes prediction, providing clinical value.

Silicon switch: Carbon-silicon Bioisosteric replacement as a strategy to modulate the selectivity, physicochemical, and drug-like properties in anticancer pharmacophores

Bioisosterism is one of the leading strategies in medicinal chemistry for the design and modification of drugs, consisting in replacing an atom or a substituent with a different atom or a group with similar chemical properties and an inherent biocompatibility. The objective of such an exercise is to produce a diversity of molecules with similar behavior while enhancing the desire biological and pharmacological properties, without inducing significant changes to the chemical framework. In drug discovery and development, the optimization of the absorption, distribution, metabolism, elimination, and toxicity (ADMETox) profile is of paramount importance. Silicon appears to be the right choice as a carbon isostere because they possess very similar intrinsic properties. However, the replacement of a carbon by a silicon atom in pharmaceuticals has proven to result in improved efficacy and selectivity, while enhancing physicochemical properties and bioavailability. The current review discusses how silicon has been strategically introduced to modulate drug-like properties of anticancer agents, from a molecular design strategy, biological activity, computational modeling, and structure-activity relationships perspectives.

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.

Small molecule inhibitors of RORγt for Th17 regulation in inflammatory and autoimmune diseases

As a ligand-dependent transcription factor, retinoid-associated orphan receptor γt (RORγt) that controls T helper (Th) 17 cell differentiation and interleukin (IL)-17 expression plays a critical role in the progression of several inflammatory and autoimmune conditions. An emerging novel approach to the therapy of these diseases thus involves controlling the transcriptional capacity of RORγt to decrease Th17 cell development and IL-17 production. Several RORγt inhibitors including both antagonists and inverse agonists have been discovered to regulate the transcriptional activity of RORγt by binding to orthosteric- or allosteric-binding sites in the ligand-binding domain. Some of small-molecule inhibitors have entered clinical evaluations. Therefore, in current review, the role of RORγt in Th17 regulation and Th17-related inflammatory and autoimmune diseases was highlighted. Notably, the recently developed RORγt inhibitors were summarized, with an emphasis on their optimization from lead compounds, efficacy, toxicity, mechanisms of action, and clinical trials. The limitations of current development in this area were also discussed to facilitate future research.

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.

Optimization of carbazole carboxamide RORγt agonists: Challenges in improving the metabolic stability and maintaining the agonistic activity

Based on two previously discovered carbazole carboxamide retinoic acid receptor-related orphan receptor-γt (RORγt) agonists 6 and 7 (t_1/2 = 8.7 min and 16.4 min in mouse liver microsome, respectively), new carbazole carboxamides were designed and synthesized according to the molecular mechanism of action (MOA) and metabolic site analysis with the aim of identifying novel RORγt agonists with optimal pharmacological and metabolic profiles. By modifying the "agonist lock" touching substitutions on carbazole ring, introducing heteroatoms into different parts of the molecule and attaching a side chain to the sulfonyl benzyl moiety, several potent RORγt agonists were identified with greatly improved metabolic stability. Best overall properties were achieved in compound (R)-10f with high agonistic activities in RORγt dual FRET (EC₅₀ = 15.6 nM) and Gal4 reporter gene (EC₅₀ = 141 nM) assays and greatly improved metabolic stability (t_1/2 > 145 min) in mouse liver microsome. Besides, the binding modes of (R)-10f and (S)-10f in RORγt ligand binding domain (LBD) were also studied. Altogether, the optimization of carbazole carboxamides led to the discovery of (R)-10f as a potential small molecule therapeutics for cancer immunotherapy.

Discovery of a Novel Class of Dual GPBAR1 Agonists-RORγt Inverse Agonists for the Treatment of IL-17-Mediated Disorders

Retinoic acid receptor-related orphan receptor γ-t (RORγt) and GPBAR1, a transmembrane G-protein-coupled receptor for bile acids, are attractive drug targets to develop clinically relevant small modulators as potent therapeutics for autoimmune diseases. Herein, we designed, synthesized, and evaluated several new bile acid-derived ligands with potent dual activity. Furthermore, we performed molecular docking and MD calculations of the best dual modulators in the two targets to identify the binding modes as well as to better understand the molecular basis of the inverse agonism of RORγt by bile acid derivatives. Among these compounds, 7 was identified as a GPBAR1 agonist (EC50 5.9 μM) and RORγt inverse agonist (IC50 0.107 μM), with excellent pharmacokinetic properties. Finally, the most promising ligand displayed robust anti-inflammatory activity in vitro and in vivo in a mouse model of 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis.

Analysis of the potential association between ferroptosis and immune in hepatocellular carcinoma and their relationship with prognosis

Background

The development of targeted therapy and immunotherapy has enriched the treatment of hepatocellular carcinoma (HCC), however, have had poor or no reponse, or even no response. Previous research suggested that ferroptosis and tumor immune microenvironment (TIME) may have a fundamental impact on efficacy during HCC immunotherapy and targeted therapy. Therefore, there is a clinical need to develop a signature that categorizes HCC patients in order to make more accurate clinical decisions.

Methods

Clinical data and gene expression data of HCC patients were obtained from The Cancer Genome Atlas (TCGA) portal and International Cancer Genome Consortium (ICGC) portal. To identify ferroptosis-related immune-related genes (ferroptosis-related IRGs), Pearson correlation analysis was conducted. The ferroptosis-related IRGs prognostic signature (FIPS) was constructed using Univariate Cox and LASSO Cox algorithms. The predictive effectiveness of FIPS was evaluated using Receiver Operating Characteristic (ROC) curves and survivorship curve. The correlation ship between FIPS and TIME was evaluated using single-sample Gene Set Enrichment Analysis (ssGSEA) and CIBERSORT. The relationship between FIPS and immunotherapy responsiveness was evaluated using immunophenoscore. The expression level of 10 ferroptosis-related IRGs in normal liver tissues and HCC tissues was compared using immunohistochemistry. Finally, we established a nomogram (based on FIPS, TNM stage, and age) for clinical application.

Results

The FIPS was established with ten ferroptosis-related IRGs. The high-FIPS subgroup showed a poor clinical prognosis and an obviously higher proportion of HCC patients with advanced TNM stage, high WHO grade and high alpha fetoprotein(AFP) value. Analysis of TIME indicated that patients in the high-FIPS subgroup may be in immunosuppressed state. Meanwhile, we found that ferroptosis may be inhibited in the high-FIPS subgroup and this subgroup may be impervious to immunotherapy and sorafenib.

Conclusion

We constructed a novel potential prognostic signature for HCC patients that predicts overall survival, ferroptosis and immune status, sorafenib sensitivity, and immunotherapy responsiveness.

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.

1,5-Disubstituted Acylated 2-Amino-4,5-dihydroimidazoles as a New Class of Retinoic Acid Receptor-Related Orphan Receptor (ROR) Inhibitors

A growing body of evidence suggests a pathogenic role for pro-inflammatory T helper 17 cells (Th17) in several autoimmune diseases, including multiple sclerosis, rheumatoid arthritis, inflammatory bowel disease, type I diabetes, and psoriasis-diseases for which no curative treatment is currently available. The nuclear retinoic acid receptor-related orphan receptors alpha and gamma (RORα/γ), in particular the truncated isoform RORγt that is specifically expressed in the thymus, play a critical role in the activation of a pro-inflammatory Th17 response, and RORγ inverse agonists have shown promise as negative regulators of Th17 for the treatment of autoimmune diseases. Our study underscores the screening of a large combinatorial library of 1,5-disubstituted acylated 2-amino-4,5-dihydroimidazoles using a demonstrated synthetic and screening approach and the utility of the positional scanning libraries strategy for the rapid identification of a novel class of ROR inhibitors. We identified compound 1295-273 with the highest activity against RORγ (3.3 µM IC₅₀) in this series, and almost a two-fold selectivity towards this receptor isoform, with 5.3 and 5.8 µM IC₅₀ against RORα and RORβ cells, respectively.

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.

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.

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.

Discovery of 2-(Ortho-Substituted Benzyl)-Indole Derivatives as Potent and Orally Bioavailable RORγ Agonists with Antitumor Activity

RORγ is a dual-functional drug target, which involves not only induction of inflammation but also promotion of cancer immunity. The development of agonists of RORγ promoting Th17 cell differentiation could provide a novel mechanism of action (MOA) as an immune-activating anticancer agent. Herein, we describe new 2-(ortho-substituted benzyl)-indole derivatives as RORγ agonists by scaffold hopping based on clinical RORγ antagonist VTP-43742. Interestingly, subtle structural differences of the compounds led to the opposite biological MOA. After rational optimization for structure-activity relationship and pharmacokinetic profile, we identified a potent RORγ agonist compound 17 that was able to induce the production of IL-17 and IFNγ in tumor tissues and elicit antitumor efficacy in MC38 syngeneic mouse colorectal tumor model. This is the first comprehensive work to demonstrate the in vivo antitumor efficacy of an RORγ agonist.

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.

Discovery of LYC-55716: A Potent, Selective, and Orally Bioavailable Retinoic Acid Receptor-Related Orphan Receptor-γ (RORγ) Agonist for Use in Treating Cancer

Retinoic acid receptor-related orphan receptor γ (RORc, RORγ, or NR1F3) is the nuclear receptor master transcription factor that drives the function and development of IL-17-producing T helper cells (Th17), cytotoxic T cells (Tc17), and subsets of innate lymphoid cells. Activation of RORγ+ T cells in the tumor microenvironment is hypothesized to render immune infiltrates more effective at countering tumor growth. To test this hypothesis, a family of benzoxazines was optimized to provide LYC-55716 (37c), a potent, selective, and orally bioavailable small-molecule RORγ agonist. LYC-55716 decreases tumor growth and enhances survival in preclinical tumor models and was nominated as a clinical development candidate for evaluation in patients with solid tumors.

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.

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.

Discovery of tert-amine-based RORγt agonists

The nuclear receptor retinoic acid receptor-related orphan receptor gamma-t (RORγt) is a transcription factor regulating Th17 cell differentiation and proliferation from naive CD4⁺ T cells. Since Th17 cells have demonstrated the antitumor efficacy by eliciting remarkable activation of CD8⁺ T cells, RORγt agonists could be applied as potential small molecule therapeutics for cancer immunotherapy. Based on the previously reported RORγt agonist 1 and its resolved co-crystal structure, a series of new tertiary amines were designed, synthesized and biologically evaluated, yielding optimal moieties with improved chemical properties and biological responses. The combination of these optimal moieties resulted in identification of novel RORγt agonists such as 8b with further elevated RORγt agonism responses at a target-based level as well as in cell-based assays, which provided some structural knowledge for further optimization of RORγt agonists as small molecule therapeutics for cancer immunotherapy.

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.

Cooperativity between the orthosteric and allosteric ligand binding sites of RORγt

RORγt is a nuclear receptor associated with several diseases. Various synthetic ligands have been developed that target the canonical orthosteric or a second, allosteric pocket of RORγt. We show that orthosteric and allosteric ligands can simultaneously bind to RORγt and that their potency is positively influenced by the other ligand, a phenomenon called cooperative dual ligand binding. The mechanism behind cooperative binding in proteins is poorly understood, primarily due to the lack of structural data. We solved 12 crystal structures of RORγt, simultaneously bound to various orthosteric and allosteric ligands. In combination with molecular dynamics, we reveal a mechanism responsible for the cooperative binding behavior. Our comprehensive structural studies provide unique insights into how cooperative binding occurs in proteins.

Cooperative ligand binding is an important phenomenon in biological systems where ligand binding influences the binding of another ligand at an alternative site of the protein via an intramolecular network of interactions. The underlying mechanisms behind cooperative binding remain poorly understood, primarily due to the lack of structural data of these ternary complexes. Using time-resolved fluorescence resonance energy transfer (TR-FRET) studies, we show that cooperative ligand binding occurs for RORγt, a nuclear receptor associated with the pathogenesis of autoimmune diseases. To provide the crucial structural insights, we solved 12 crystal structures of RORγt simultaneously bound to various orthosteric and allosteric ligands. The presence of the orthosteric ligand induces a clamping motion of the allosteric pocket via helices 4 to 5. Additional molecular dynamics simulations revealed the unusual mechanism behind this clamping motion, with Ala355 shifting between helix 4 and 5. The orthosteric RORγt agonists regulate the conformation of Ala355, thereby stabilizing the conformation of the allosteric pocket and cooperatively enhancing the affinity of the allosteric inverse agonists.

Discovery of novel N-sulfonamide-tetrahydroisoquinolines as potent retinoic acid receptor-related orphan receptor γt agonists

Cancer immunotherapy has become a research hotspot in recent years. A variety of targets were developed for small molecule immuno-oncology agents, including retinoic acid-related orphan receptor gamma t (RORγt), chemokine receptor, stimulator of interferon genes (Sting), indoleamine 2,3-dioxygenase (IDO), toll-like receptors (TLR), etc. Among them, the retinoic acid receptor-related orphan receptor γt (RORγt) has gradually attracted more attention in these years. In particular, LYC-55716 (cintirorgon), a small molecule RORγt agonist developed by Lycera, has entered the phase II clinical study. In this work, starting from compound 7, compound 28 was obtained after 4 rounds of compound design, synthesis and SAR studies, which had an EC₅₀ of 0.021 ± 0.002 μM in dual Fluorescence Resonance Energy Transfer (dual-FRET) assay and an EC₅₀ of 0.021 ± 0.002 μM in mouse Th17 cell differentiation assay. It indicated that compound 28 had excellent RORγt agonistic activity and was expected to be developed as a new type of small molecule drug for cancer immunotherapy. The molecular dynamic simulation revealed that the agonist 28 formed a strong HYF triplet intramolecular interaction to stabilize H12, which helped RORγt to form the protein-binding site and therefore made the receptor ready to recruit coactivator. When the inverse agonist s27 bound with RORγt, the steric hindrance between s27 and H479 caused the destruction of the HYF triplet, leading to the collapse of H12, thus the transcription function of RORγt was interrupted due to the failure of recruiting a coactivator molecule. The triplet HYF in RORγt and the rigidity of 28 and s27 were identified to be the structural determinants for the functional switch of RORγt.

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.

Azatricyclic Inverse Agonists of RORγt That Demonstrate Efficacy in Models of Rheumatoid Arthritis and Psoriasis

Structure-activity relationship studies directed toward the replacement of the fused phenyl ring of the lead hexahydrobenzoindole RORγt inverse agonist series represented by 1 with heterocyclic moieties led to the identification of three novel aza analogs 5-7. The hexahydropyrrolo[3,2-f]quinoline series 5 (X = N, Y = Z=CH) showed potency and metabolic stability comparable to series 1 but with improved in vitro membrane permeability and serum free fraction. This structural modification was applied to the hexahydrocyclopentanaphthalene series 3, culminating in the discovery of 8e as a potent and selective RORγt inverse agonist with an excellent in vitro profile, good pharmacokinetic properties, and biologic-like in vivo efficacy in preclinical models of rheumatoid arthritis and psoriasis.

Defining Target Engagement Required for Efficacy In Vivo at the Retinoic Acid Receptor-Related Orphan Receptor C2 (RORγt)

The Th17 pathway has been implicated in autoimmune diseases. The retinoic acid receptor-related orphan receptor C2 (RORγt) is a master regulator of Th17 cells and controls the expression of IL-17A. RORγt is expressed primarily in IL-17A-producing lymphoid cells. Here we describe a virtual screen of the ligand-binding pocket and subsequent screen in a binding assay that identified the 1-benzyl-4',5'-dihydrospiro[piperidine-4,7'-thieno[2,3-c]pyran]-2'-carboxamide scaffold as a starting point for optimization of binding affinity and functional activity guided by structure-based design. Compound 12 demonstrated activity in a mouse PK/PD model and efficacy in an inflammatory arthritis mouse model that were used to define the level and duration of target engagement required for efficacy in vivo. Further optimization to improve ADME and physicochemical properties with guidance from simulations and modeling provided compound 22, which is projected to achieve the level and duration of target engagement required for efficacy in the clinic.

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.

Orthosteric and Allosteric Dual Targeting of the Nuclear Receptor RORγt with a Bitopic Ligand

The RORγt nuclear receptor (NR) is of critical importance for the differentiation and proliferation of T helper 17 (Th17) cells and their production of the pro-inflammatory cytokine IL-17a. Dysregulation of RORγt has been linked to various autoimmune diseases, and small molecule inhibition of RORγt is therefore an attractive strategy to treat these diseases. RORγt is a unique NR in that it contains both a canonical, orthosteric and a second, allosteric ligand binding site in its ligand binding domain (LBD). Hence, dual targeting of both binding pockets constitutes an attractive alternative molecular entry for pharmacological modulation. Here, we report a chemical biology approach to develop a bitopic ligand for the RORγt NR, enabling concomitant engagement of both binding pockets. Three candidate bitopic ligands, Bit-L15, Bit-L9, and Bit-L4, comprising an orthosteric and allosteric RORγt pharmacophore linked via a polyethylene glycol (PEG) linker, were designed, synthesized, and evaluated to examine the influence of linker length on the RORγt binding mode. Bit-L15 and Bit-L9 show convincing evidence of concomitant engagement of both RORγt binding pockets, while the shorter Bit-L4 does not show this evidence, as was anticipated during the ligand design. As the most potent bitopic RORγt ligand, Bit-L15, antagonizes RORγt function in a potent manner in both a biochemical and cellular context. Furthermore, Bit-L15 displays an increased selectivity for RORγt over RORα and PPARγ compared to the purely orthosteric and allosteric parent compounds. Combined, these results highlight potential advantages of bitopic NR modulation over monovalent targeting strategies.

Tricyclic-Carbocyclic RORγt Inverse Agonists-Discovery of BMS-986313

SAR efforts directed at identifying RORγt inverse agonists structurally different from our clinical compound 1 (BMS-986251) led to tricyclic-carbocyclic analogues represented by 3-7 and culminated in the identification of 3d (BMS-986313), with structural differences distinct from 1. The X-ray co-crystal structure of 3d with the ligand binding domain of RORγt revealed several key interactions, which are different from 1. The in vitro and in vivo PK profiles of 3d are described. In addition, we demonstrate robust efficacy of 3d in two preclinical models of psoriasis-the IMQ-induced skin lesion model and the IL-23-induced acanthosis model. The efficacy seen with 3d in these models is comparable to the results observed with 1.

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.

Novel Tricyclic Pyroglutamide Derivatives as Potent RORγt Inverse Agonists Identified using a Virtual Screening Approach

Employing a virtual screening approach, we identified the pyroglutamide moiety as a nonacid replacement for the cyclohexanecarboxylic acid group which, when coupled to our previously reported conformationally locked tricyclic core, provided potent and selective RORγt inverse agonists. Structure-activity relationship optimization of the pyroglutamide moiety led to the identification of compound 18 as a potent and selective RORγt inverse agonist, albeit with poor aqueous solubility. We took advantage of the tertiary carbinol group in 18 to synthesize a phosphate prodrug, which provided good solubility, excellent exposures in mouse PK studies, and significant efficacy in a mouse model of psoriasis.

Possible Role of the RORC Gene in Primary and Secondary Lymphedema: Review of the Literature and Genetic Study of Two Rare Causative Variants

Background: RAR-related Orphan Receptor C (RORC) is a DNA-binding transcription factor and the key transcription factor responsible for differentiation of T helper 17 cells. The RORC gene plays a role in lymphoid organogenesis, thymopoiesis, and lymph node organogenesis. The aim of our study was to determine the possible role of RORC in the development of lymphatic system malformations by combining data from the scientific literature and next-generation sequencing of RORC in lymphedema patients negative for known causative genes. Methods and Results: We sequenced RORC in 235 lymphedema patients negative for known lymphedema-associated genes. We found two probands carrying nonsense RORC variants. Conclusions: We show that RORC is important for normal function of the lymphatic system and that a rare variant with a possible causative effect may imply predisposition for lymphedema.

Assessing the Selectivity of FXR, LXRs, CAR, and RORγ Pharmaceutical Ligands With Reporter Cell Lines

To characterize human nuclear receptor (NR) specificity of synthetic pharmaceutical chemicals we established stable cell lines expressing the ligand binding domains (LBDs) of human FXR, LXRα, LXRβ, CAR, and RORγ fused to the yeast GAL4 DNA binding domain (DBD). As we have already done for human PXR, a two-step transfection procedure was used. HeLa cells stably expressing a Gal4 responsive gene (HG5LN cell line) were transfected by Gal4-NRs expressing plasmids. At first, using these cell lines as well as the HG5LN PXR cells, we demonstrated that the basal activities varied from weak (FXR and LXRs), intermediate (PXR), to strong (CAR and RORγ), reflecting the recruitment of HeLa co-regulators in absence of ligand. Secondly, we finely characterized the activities of commercially available FXR, LXRα, LXRβ, CAR, RORγ, and PXR agonists/antagonists GW4064, feraxamine, DY268, T0901317, GW3965, WAY252623, SR9238, SR9243, GSK2033, CITCO, CINPA1, PK11195, S07662, SR1078, SR0987, SR1001, SR2211, XY018, clotrimazole, dabrafenib, SR12813, and SPA70, respectively. Among these compounds we revealed both, receptor specific agonists/antagonists, as well as less selective ligands, activating or inhibiting several nuclear receptors. FXR ligands manifested high receptor selectivity. Vice versa, LXR ligands behaved in non-selective manner, all activating at least PXR. CAR was selectively influenced by their ligands, while it also responded to several LXR ligands. Finally, although PXR was quite selectively activated or antagonized by its own ligands, it responded to several NRs ligands as well. Thus, using these reporter cell lines enabled us to precisely characterize the selectivity of pharmaceutical ligands for different nuclear receptors.

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.

Structural change of retinoic-acid receptor-related orphan receptor induced by binding of inverse-agonist: Molecular dynamics and ab initio molecular orbital simulations

To elucidate structural changes in the retinoic acid receptor-related orphan receptor gamma (RORγt) induced by the binding of an agonist or an inverse agonist, we conducted molecular dynamics (MD) simulations in explicit water. In addition, ab initio fragment molecular orbital calculations were carried out for certain characteristic structures obtained from the MD simulations to reveal important interactions between the amino acid residues of RORγt, and to distinguish the different effects in the binding of an agonist and an inverse agonist on the structure of RORγt. The results elucidate that the hydrogen bond between His479 of helix11 (H11) and Tyr502 of helix12 (H12) is important to keep the H12 conformation in the agonist-bound RORγt. In contrast, in the inverse-agonist-bound RORγt, the side chain of His479 rotates, significantly weakening the interaction between His479 and Tyr502, leading to a conformational change in H12. Therefore, the present molecular simulations clearly indicate that the conformational change in the side chain of His479 in the inverse-agonist-bound RORγt is the main reason for the H12 destabilization induced by the binding of the inverse agonist. Such a conformational change does not occur on the binding of the agonist in RORγt, owing to the strong hydrogen bond between His479 and Tyr502.

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.