Potent Agonist Research Articles

Decoding Molecular Mechanism Underlying Human Olfactory Receptor OR8D1 Activation by Sotolone Enantiomers.

Sotolone, a chiral compound, plays an important role in the food industry. Herein, (R)-/(S)-sotolone were separated to determine their odor characteristics and thresholds in air (R-form: smoky, burned, herb, and green aroma, 0.0514 μg/m3; S-form: sweet, milk, acid, and nutty aroma, 0.0048 μg/m3). OR8D1 responses to (R)-/(S)-sotolone were detected in a HEK293 cell-based luminescence assay. (S)-Sotolone was a more potent agonist than (R)-sotolone (EC50 values of 84.98 ± 1.05 and 167.20 ± 0.25 μmol/L, respectively). Molecular dynamics simulations and molecular mechanics Poisson-Boltzmann surface area analyses confirmed that the combination of (S)-sotolone and OR8D1 was more stable than that of (R)-sotolone. Odorant docking, multiple sequence alignments, site-directed mutagenesis, and functional studies with recombinant odorant receptors (ORs) in a cell-based luminescence assay identified 11 amino-acid residues that influence the enantioselectivity of OR8D1 toward sotolone significantly and that N2065.46 was indispensable to the activation of OR8D1 by (S)-sotolone.

Structure-Activity Relationship Studies and Optimization of 4-Hydroxypyridones as GPR84 Agonists.

GPR84 is a putative medium-chain fatty acid receptor that is implicated in regulation of inflammation and fibrogenesis. Studies have indicated that GPR84 agonists may have therapeutic potential in diseases such as Alzheimer's disease, atherosclerosis, and cancer, but there is a lack of quality tool compounds to explore this potential. The fatty acid analogue LY237 (4a) is the most potent GPR84 agonist disclosed to date but has unfavorable physicochemical properties. We here present a SAR study of 4a. Several highly potent agonists were identified with EC50 down to 28 pM, and with SAR generally in excellent agreement with structure-based modeling. Proper incorporation of rings and polar groups resulted in the identification of TUG-2099 (4s) and TUG-2208 (42a), both highly potent GPR84 agonists with lowered lipophilicity and good to excellent solubility, in vitro permeability, and microsomal stability, which will be valuable tools for exploring the pharmacology and therapeutic prospects of GPR84.

In vitro EVALUATION of THE EFFECTS of POTENTIAL GSK-3β INHIBITORS TERBUTALINE and ORCIPRENALINE

Lung cancer is a type of cancer that is mostly diagnosed at an advanced stage and has a short survival time despite standard chemotherapy and targeted therapies. Terbutaline and Orciprenaline are bronchodilator agent that are potent and selective β2 receptor agonists. The purpose of this study was to investigate by continuous monitoring to assay the effects of Terbutaline and Orciprenaline on human lung carcinoma cell line. Cells were treated 1, 10, 100, 200, 400 µM concentrations with Terbutaline/Orciprenaline. MTT assay and xCELLigence real-time cell analyzer were used to determine these compounds effect on cell viability. The cell index was monitored continuously by visualizing the impedance of the E-plate wells. Because of GSK3β roles in a diverse range of cellular processes like metabolism, cell proliferation, differentiation and survival and its key position at several signaling pathways, GSK3β inhibition was investigated of these molecules. It has been determined that Terbutaline and Orciprenaline inhibits GSK-3β.
 This is the first known study to demonstrate the effects of Terbutaline and Orciprenaline on A549 and the human bronchial epithelial cell line Beas-2b in real time. In this study, it was detected that Terbutaline and especially Orciprenaline may have potential therapeutic effects in lung carcinoma.

Are carfentanil and acrylfentanyl naloxone resistant?

The rapid rise in deaths since 2012 due to opioid poisoning is correlated with the proliferation of potent synthetic opioid agonists such as fentanyl, acrylfentanyl, and carfentanil. The efficacy of frontline antidotes such as naloxone in reversing such poisoning events has been questioned, and the possibility of naloxone-resistant synthetic opioids has been raised. In this manuscript, we applied in vitro techniques to establish the median effective inhibitory concentrations for fentanyl, acrylfentanyl, and carfentanil and subsequently evaluate naloxone's ability to reverse agonist-receptor interactions.

Heterocyclic-Modified Imidazoquinoline Derivatives: Selective TLR7 Agonist Regulates Tumor Microenvironment against Melanoma.

Immunotherapy targeting the toll-like receptor 7 (TLR7) is a promising strategy for cancer treatment. Herein, we describe the design and synthesis of a series of imidazoquinoline-based TLR7 agonists and assess NF-κB pathway activation using HEK-Blue hTLR7 cells to identify the most potent small-molecule TLR7 agonist, SMU-L11 (EC50 = 0.024 ± 0.002 μM). In vitro experiments demonstrated that SMU-L11 specifically activated TLR7, resulting in recruitment of the MyD88 adaptor protein and activation of the NF-κB and MAPK signaling pathways. Moreover, SMU-L11 was found to exert immune-enhancing effects by significantly inducing the secretion of proinflammatory cytokines in murine dendritic cells, macrophages, and human peripheral blood mononuclear cells while promoting M1 macrophage polarization. In vivo studies using a B16-F10 mouse tumor model showed that SMU-L11 significantly enhanced immune cell activation and augmented CD4+ T and CD8+ T-cell proliferation, directly killing tumor cells and inhibiting tumor growth.

6-Formylindolo[3,2-b]carbazole, a potent ligand for the aryl hydrocarbon receptor, attenuates concanavalin-induced hepatitis by limiting T-cell activation and infiltration of proinflammatory CD11b+ Kupffer cells.

FICZ (6-formylindolo[3,2-b]carbazole) is a potent aryl hydrocarbon receptor agonist that has a poorly understood function in the regulation of inflammation. In this study, we investigated the effect of aryl hydrocarbon receptor activation by FICZ in a murine model of autoimmune hepatitis induced by concanavalin A. High-throughput sequencing techniques such as single-cell RNA sequencing and assay for transposase accessible chromatin sequencing were used to explore the mechanisms through which FICZ induces its effects. FICZ treatment attenuated concanavalin A-induced hepatitis, evidenced by decreased T-cell infiltration, decreased circulating alanine transaminase levels, and suppression of proinflammatory cytokines. Concanavalin A revealed an increase in natural killer T cells, T cells, and mature B cells upon concanavalin A injection while FICZ treatment reversed the presence of these subsets. Surprisingly, concanavalin A depleted a subset of CD55+ B cells, while FICZ partially protected this subset. The immune cells showed significant dysregulation in the gene expression profiles, including diverse expression of migratory markers such as CCL4, CCL5, and CXCL2 and critical regulatory markers such as Junb. Assay for transposase accessible chromatin sequencing showed more accessible chromatin in the CD3e promoter in the concanavalin A-only group as compared to the naive and concanavalin A-exposed, FICZ-treated group. While there was overall more accessible chromatin of the Adgre1 (F4/80) promoter in the FICZ-treated group, we observed less open chromatin in the Itgam (CD11b) promoter in Kupffer cells, supporting the ability of FICZ to reduce the infiltration of proinflammatory cytokine producing CD11b+ Kupffer cells. Taken together, these data demonstrate that aryl hydrocarbon receptor activation by FICZ suppresses liver injury through the limitation of CD3+ T-cell activation and CD11b+ Kupffer cell infiltration.

TC14012 enhances the anti-fibrosis effects of UC-MSCs on the liver by reducing collagen accumulation and ameliorating inflammation

BackgroundMesenchymal stem cells (MSCs) are attracting attention as a promising cell-based therapy for the treatment of liver fibrosis or cirrhosis. However, the strategies and potential mechanisms of MSCs therapy need further investigation. The CXCL12/CXCR4/CXCR7 chemokine axis is well known to regulate cell migration and is involved in the regulation of liver fibrosis. This study aims to treat MSCs with a CXCR7-specific agonist to evaluate its therapeutic effects on hepatic fibrosis and potential mechanisms.MethodsTC14012, a potent agonist of CXCR7, has been used to pretreat human umbilical cord-derived MSCs (UC-MSCs) and assess its effect on proliferation, apoptosis, migration, immunoregulation, and gene regulatory network. Then, CCl4-induced liver fibrosis mice models were used to evaluate the therapeutic effect and mechanism of TC14012-treated UC-MSCs for treating hepatic fibrosis.ResultsTC14012 increased CXCR7 expression in UC-MSCs. Notably, co-culture of liver sinusoidal endothelial cells (LSEC) with TC14012-pretreated UC-MSCs increased CXCR7 expression in LSEC. Additionally, TC14012 promoted cell migration and mediated the immunoregulation of UC-MSCs. Compared to UC-MSCs without TC14012 pretreatment, UC-MSCs treated with TC14012 ameliorated live fibrosis by restoring CXCR7 expression, reducing collagen fibril accumulation, inhibiting hepatic stellate cells activation, and attenuating the inflammatory response.ConclusionThis study suggests that TC14012 pretreatment can enhance the therapeutic effects of UC-MSCs on liver fibrosis, mainly by promoting the migration and immunoregulation of MSCs.

Discovery and Identification of Novel 5-Hydroxy-4H-benzo[1,4]oxazin-3-one Derivatives as Potent β2-Adrenoceptor Agonists through Structure-Based Design, Synthesis, and Biological Evaluation.

Although β2-agonists are crucial for treatment of chronic respiratory diseases, optimizing β2-agonistic activity and selectivity remains essential for achieving favorable therapeutic outcomes. A structure-based molecular design workflow was employed to discover a novel class of β2 agonists featuring a 5-hydroxy-4H-benzo[1,4]oxazin-3-one scaffold, which potently stimulated β2 adrenoceptors (β2-ARs). Screening for the β2-agonistic activity and selectivity led to the identification of compound A19 (EC50 = 3.7 pM), which functioned as a partial β2-agonist in HEK-293 cells containing endogenous β2-ARs. Compound A19 exhibited significant relaxant effects, rapid onset time (Ot50 = 2.14 min), and long duration of action (>12 h) on isolated guinea pig tracheal strips, as well as advantageous pharmacokinetic characteristics in vivo, rendering A19 suitable for inhalation administration. Moreover, A19 suppressed the upregulation of inflammatory cytokines and leukocytes and improved lung function in a rat model of COPD, thereby indicating that A19 is a potential β2 agonist candidate for further study.

Pharmacological Characterization and Radiolabeling of VUF15485, a High-Affinity Small-Molecule Agonist for the Atypical Chemokine Receptor ACKR3.

Atypical chemokine receptor 3 (ACKR3), formerly referred to as CXCR7, is considered to be an interesting drug target. In this study, we report on the synthesis, pharmacological characterization and radiolabeling of VUF15485, a new ACKR3 small-molecule agonist, that will serve as an important new tool to study this β-arrestin-biased chemokine receptor. VUF15485 binds with nanomolar affinity (pIC50 = 8.3) to human ACKR3, as measured in [125I]CXCL12 competition binding experiments. Moreover, in a bioluminescence resonance energy transfer-based β-arrestin2 recruitment assay VUF15485 acts as a potent ACKR3 agonist (pEC50 = 7.6) and shows a similar extent of receptor activation compared with CXCL12 when using a newly developed, fluorescence resonance energy transfer-based ACKR3 conformational sensor. Moreover, the ACKR3 agonist VUF15485, tested against a (atypical) chemokine receptor panel (agonist and antagonist mode), proves to be selective for ACKR3. VUF15485 labeled with tritium at one of its methoxy groups ([3H]VUF15485), binds ACKR3 saturably and with high affinity (K d = 8.2 nM). Additionally, [3H]VUF15485 shows rapid binding kinetics and consequently a short residence time (<2 minutes) for binding to ACKR3. The selectivity of [3H]VUF15485 for ACKR3, was confirmed by binding studies, whereupon CXCR3, CXCR4, and ACKR3 small-molecule ligands were competed for binding against the radiolabeled agonist. Interestingly, the chemokine ligands CXCL11 and CXCL12 are not able to displace the binding of [3H]VUF15485 to ACKR3. The radiolabeled VUF15485 was subsequently used to evaluate its binding pocket. Site-directed mutagenesis and docking studies using a recently solved cryo-EM structure propose that VUF15485 binds in the major and the minor binding pocket of ACKR3. SIGNIFICANCE STATEMENT: The atypical chemokine receptor atypical chemokine receptor 3 (ACKR3) is considered an interesting drug target in relation to cancer and multiple sclerosis. The study reports on new chemical biology tools for ACKR3, i.e., a new agonist that can also be radiolabeled and a new ACKR3 conformational sensor, that both can be used to directly study the interaction of ACKR3 ligands with the G protein-coupled receptor.

Comparative Pharmacological Effects of Lisuride and Lysergic Acid Diethylamide Revisited.

Lisuride is a non-psychedelic serotonin (5-HT) 2A receptor (5-HT2A) agonist and analogue of the psychedelic lysergic acid diethylamide (LSD). Lisuride also acts as an agonist at the serotonin 1A receptor (5-HT1A), a property known to counter psychedelic effects. Here, we tested whether lisuride lacks psychedelic activity due to a dual mechanism: (1) partial agonism at 5-HT2A and (2) potent agonism at 5-HT1A. The in vitro effects of lisuride, LSD, and related analogues on 5-HT2A signaling were characterized by using miniGαq and β-arrestin 2 recruitment assays. The 5-HT1A- and 5-HT2A-mediated effects of lisuride and LSD were also compared in male C57BL/6J mice. The in vitro results confirmed that LSD is an agonist at 5-HT2A, with high efficacy and potency for recruiting miniGαq and β-arrestin 2. By contrast, lisuride displayed partial efficacy for both functional end points (6-52% of 5-HT or LSD Emax) and antagonized the effects of LSD. The mouse experiments demonstrated that LSD induces head twitch responses (HTRs)(ED50 = 0.039 mg/kg), while lisuride suppresses HTRs (ED50 = 0.006 mg/kg). Lisuride also produced potent hypothermia and hypolocomotion (ED50 = 0.008-0.023 mg/kg) that was blocked by the 5-HT1A antagonist WAY100635 (3 mg/kg). Blockade of 5-HT1A prior to lisuride restored basal HTRs, but it failed to increase HTRs above baseline levels. HTRs induced by LSD were blocked by lisuride (0.03 mg/kg) or the 5-HT1A agonist 8-OH-DPAT (1 mg/kg). Overall, our findings show that lisuride is an ultrapotent 5-HT1A agonist in C57BL/6J mice, limiting its use as a 5-HT2A ligand in mouse studies examining acute drug effects. Results also indicate that the 5-HT2A partial agonist-antagonist activity of lisuride explains its lack of psychedelic effects.

Ginsenoside Rg5, a potent agonist of Nrf2, inhibits HSV-1 infection-induced neuroinflammation by inhibiting oxidative stress and NF-κB activation

BackgroundHerpes simplex virus type 1 (HSV-1), known to latently infect the host’s trigeminal ganglion, can lead to severe herpes encephalitis or asymptomatic infection, potentially contributing to neurodegenerative diseases like Alzheimer’s. The virus generates reactive oxygen species (ROS) that significantly impact viral replication and induce chronic inflammation through NF-κB activation. Nuclear factor E2-related factor 2 (Nrf2), an oxidative stress regulator, can prevent and treat HSV-1 infection by activating the passive defense response in the early stages of infection. Methods and resultsOur study investigated the antiviral effects of ginsenoside Rg5, an Nrf2 activator, on HSV-1 replication and several host cell signaling pathways. We found that HSV-1 infection inhibited Nrf2 activity in host cells, induced ROS/NF-κB signaling, and triggered inflammatory cytokines. However, treatment with ginsenoside Rg5 inhibited ROS/NF-κB signaling and reduced inflammatory cytokines through NRF2 induction. Interestingly, the Nrf2 inhibitor ML385 suppressed the expression of NAD(P)H quinone oxidoreductase 1(NQO1) and enhanced the expression of KEAP1 in HSV-1 infected cells. This led to the reversal of VP16 expression inhibition, a protein factor associated with HSV-1 infection, thereby promoting HSV-1 replication. ConclusionThese findings suggest for the first time that ginsenoside Rg5 may serve as an antiviral against HSV-1 infection and could be a novel therapeutic agent for HSV-1-induced neuroinflammation.

Computational Insights on Migraine and Anxiety in Association with BDNF

Background:: Migraine is an unusual piercing headache on one side of the head. It is due to the dysregulation of epigenetic factors associated with the brain. Migraine affects about one percent of the general population. Despite the recent implementation of worldwide diagnostic criteria for migraine, this disorder remains relatively unknown and is frequently underdiagnosed. Migrainous conditions are also associated with anxiety and stress. This pathologic condition affects the daily life and productivity of the patients. Objective:: Hence, there is a need to develop proper treatment and management strategies to cope with migraine and associated anxiety. Through in silico approaches, this work elucidates to identify the effective lead compounds for migraine and anxiety. Methods:: Brain-derived neurotrophic factor (BDNF) was identified as a possible target for treating migraine and anxiety using computational analysis. Virtual screening and molecular dynamics simulation were used to find potential agonists with high affinities for BDNF. Results:: Based on the results of computational analysis (glide XP score, number of interactions, glide energy, and pharmacokinetic factors), four top hit molecules (Asinex_35922, Enamine_44630, Maybridge_1999, and SMMDB_17457) were identified and taken for further analysis. The hydrogen bond interactions between the agonists and the BDNF protein were verified by dynamics analysis Conclusion:: Computational studies support that BDNF agonist molecules could be effective regulating molecules for migraine and anxiety. For further evidence of the effectiveness of lead compounds in treating migraine and related anxiety, more experimental studies are necessary.

Association of microbial metabolism of tryptophan with resistance to immune checkpoint (ICB) therapy in renal cell cancer (RCC).

452 Background: Metastatic RCC has a poor prognosis. Despite improvement in treatment outcomes with ICB and targeted therapy, many patients fail to respond to first line therapy and durable responses remain elusive. The tryptophan metabolite kynurenine, an agonist of the immunosuppressive aryl hydrocarbon receptor (AhR), is associated with resistance to ICB. However, IDO (Indole 2,3 dioxygenase) blockers which inhibit tryptophan metabolism to kynurenine failed to show benefit in clinical trials, suggesting the presence of alternate AhR activation. We hypothesize that microbial metabolism of tryptophan to indole metabolites may be associated with AhR activation and ICB resistance. Methods: We prospectively collected paired stool and blood samples of treatment naïve metastatic RCC patients, treated with ICB +/- Tyrosine kinase inhibitors (TKI) at treatment initiation and at time of first response assessment (12+/-3 weeks). We evaluated stool metagenomics and untargeted stool and plasma metabolomics among responders (R) and non-responders (NR). We focused on kynurenine/tryptophan and indoles/tryptophan ratio to evaluate differential host and microbial metabolism of tryptophan. A responder was classified as progression free survival (PFS) greater than 6 months. We also performed global metabolomics on tumor and plasma of germ-free (GF) &amp; specific pathogen free (SPF) mice to identify microbial &amp; host metabolites. Results: Among 120 patients accrued, baseline paired samples were analyzed from 99 patients, 39 were treated with combination ICB, while 60 patients were treated with ICB + TKI. Median follow up was 15 months. 65% of patients had PFS &gt; 6 months. Using unpaired t test comparing baseline relative abundance of metabolites between R vs NR - plasma Kynurenine/tryptophan ratio was significantly higher in NR vs R, at baseline and at 3 months (baseline-0.042 vs 0.01, p=0.01, 3 months-0.058 vs 0.02, p=0.02). Microbial metabolites of Tryptophan -Indole pyruvic acid (IPA), Indole carboxylic acid (IcA), and Indole acetaldehyde (IAAld) were differentially associated with ICB resistance and was significantly higher in NR (IcA: 8.0 vs 5.2, p=0.03; IPA: 82.4 vs 64.9, p=0.01; IAAld: 78.7 vs 64.6, p=0.03). We also noted differential enrichment of microbial KEGG enzymes associated with IPA, IAAld and IcA production in the stool of NR patients compared to R. Microbial origin of these metablites was confirmed by its absence in tumor of GF mice. Conclusions: This is first study in metastatic RCC which shows the association of indoles (microbial metabolites of tryptophan) with resistance to ICB. These indoles are known to be potent AhR agonists and are associated with immunosuppression suggesting that microbial metabolism of tryptophan may represent a novel pathway for ICB resistance in RCC patients.

Identification of novel PPAR-γ agonist ameliorating triple negative breast cancer by in silico methods

Triple negative breast cancer (TNBC) is still considered a medical challenge as it is an aggressive cancer characterized by poor prognosis, frequent metastasis, distinct clinical and pathological features and lack of proper treatment options. In TNBC, estrogen, progesterone and Her2 neu receptors are absent, which are usually present in otherwise breast cancers. So, hormonal therapy cannot be given in case of TNBC, leaving chemotherapy as the mainstay for treatment. However, chemotherapy is an infamous therapeutic option due to several aweful side effects like loss of appetite, extreme weight loss, hair loss, vomiting, fatigue etc. Several reports have highlighted role of Peroxisome Proliferated Activated Receptor gamma (PPAR-γ) in ameliorating breast cancer, but it is still less explored receptor for TNBC. Moreover, synthetic PPAR gamma agonists like thiazolidinediones, have good capability of activating PPAR-γ receptor, but these are also gloomy therapeutic agent due to their dreadful side effects like hepatotoxicity, bladder cancer, congestive heart failure etc. So, there is serious urge among researchers to find safer therapeutic option for TNBC. Phytochemicals are nowadays grabbing attention worldwide to treat several diseases due to their fewer or no side effects. This in silico study was performed after thorough review to select a natural, potent PPAR-γ agonist Gallotanin, as a query compound for ligand based similarity searching in PubChem database with 80% filter. Top 10 obtained compounds having highest similarity index were chosen for molecular docking in AutoDock Vina, with PPAR-γ receptor (3V9T) to know their binding patterns. Further, top 5 compounds having highest dock scores underwent ADME studies in SwissADME to assess pharmacokinetic profile of these compounds. Finally, this in silico study resulted in discovery of compound called Chamuvaritin which is still not known as a PPAR-γ agonist, efficient enough to act as potent therapeutic agent against TNBC.

Novel orexin receptor agonists based on arene- or pyridine-fused 1,3-dihydro-2H-imidazole-2-imines

A structurally novel class of benzo- or pyrido-fused 1,3-dihydro-2H-imidazole-2-imines was designed and evaluated in an inositol phosphate accumulation assay for Gq signaling to measure agonistic activation of the orexin receptor type 2 (OX2R). These compounds were synthesized in 4–9 steps overall from readily available starting materials. Analogs that contain a stereogenic methyl or cyclopropyl substituent at the benzylic center, and a correctly configured alkyl ether, alkoxyalkyl ether, cyanoalkyl ether, or α-hydroxyacetamido substituted homobenzylic sidechain were identified as the most potent activators of OX2R coupled Gq signaling. Our results also indicate that agonistic activity was stereospecific at both the benzylic and homobenzylic stereogenic centra. We identified methoxyethoxy-substituted pyrido-fused dihydroimidazolimine analog 63c containing a stereogenic benzylic methyl group was the most potent agonist, registering a respectable EC50 of 339 nM and a maximal response (Emax) of 96 % in this assay. In vivo pharmacokinetic analysis indicated good brain exposure for several analogs. Our combined results provide important information towards a structurally novel class of orexin receptor agonists distinct from current chemotypes.

QSAR and docking based lead optimization of nitrogen heterocycles for enhanced prostaglandin EP2 receptor agonistic potency

In the existing effort, a dataset of 309 experimentally screened molecules for in vitro (Ki) agonist potential for Prostaglandin E2 (PGE2) receptor 2 subtype (EP2), which is a metabolite of arachidonic acid that binds with and regulates cellular responses to PGE2, was investigated in the QSAR (Quantitative structure–activity relationship) study. A six-parameter QSAR model was developed that meets the specified values ​​for internal and external validation as well as random parameters such as R2tr = 0.808, Q2LMO = 0.794, R2ex = 0.781. Insightful and quantitative opinion reveals several underappreciated and distinct structural features that are responsible for the agonist potency of these molecules on Prostaglandin EP2 receptor such as; the hydrogen atom is correct 2 bonds from the donor atom, the sp2 hybridized carbon atom is correct 2 bonds from the cyclic nitrogen atom, and so on. The developed QSAR model captures the narrative as well as the novel pharmacophoric features. The QSAR effect was further demonstrated using the reported crystalline buildings of CP533536 with the Prostaglandin EP2 receptor activity. The evaluation led to the identification of valuable new pharmacophoric properties that will be used to optimize lead compounds in the future.

Synthesis and pharmacological characterization of conformationally restricted 2-amino-Adipic acid analogs and carboxycyclopropyl glycines as selective metabotropic glutamate 2 receptor agonists

The metabotropic glutamate (Glu) receptors (mGluRs) are G-protein coupled receptors, which play a central role in modulating excitatory neurotransmission in the central nervous system (CNS). Thus, the development of tool compounds thereto, continues to interest the scientific community. In this study, we report the design and synthesis of new conformationally restricted 2-aminoadipic acid (2AA) 2–4, and glutamic acid 5, 6 analogs, which share the cyclopropane ring as the restrictor. The analogs were characterized at rat mGlu1−8 in an IP-One functional assay. While the 2AA analogs 3a, 4a and CCG-I analog 5a were shown to be selective mGlu2 agonists with low micromolar potencies, CCG-II analog 5b was shown to be a potent full agonist at mGlu2 (EC50 = 82 nM) with ∼15-fold selectivity over mGlu3, >25-fold selectivity over group III, and >60-fold selectivity over group I subtypes. An in silico study was performed to address this significant change (>3500 fold) in potency upon introduction of this methyl group (L-CCG-II vs 5b).

Structure-Guided Design of a Highly Potent Partial RXR Agonist with Superior Physicochemical Properties.

Retinoid X receptors (RXRs, NR2B1-3) hold therapeutic potential in oncology, neurodegeneration, and metabolic diseases, but traditional RXR agonists mimicking the natural ligand 9-cis retinoic acid exhibit poor physicochemical properties, pharmacokinetics, and safety profiles. Improved RXR ligands are needed to exploit RXR modulation as a promising therapeutic concept in various indications beyond its current role in second-line cancer treatment. Here, we report the co-crystal structure of RXR in complex with a novel pyrimidine-based ligand and the structure-informed optimization of this scaffold to highly potent and highly soluble RXR agonists. Focused structure-activity relationship elucidation and rigidization resulted in a substantially optimized partial RXR agonist with low nanomolar potency, no cytotoxic activity, and very favorable physicochemical properties highlighting this promising scaffold for the development of next-generation RXR targeting drugs.

Abstract PR15: Adenosine inhibits STING driven anti-tumor immunity in pancreatic cancer

Abstract Pancreatic ductal adenocarcinoma (PDAC) is characterized by an immunosuppressed tumor immune microenvironment (TIME) where combinations of chemotherapy and immune checkpoint blockade (ICB) have shown limited efficacy. Standard of care FOLFIRINOX chemotherapy promotes replication stress associated cell death leading to an increase in extracellular ATP in the TIME and subsequent inflammation that favors anti-tumor immunity. Concomitantly, replication stress from chemotherapy also generates aberrant cytosolic DNA, which stimulates the production of 2’-3’ cGAMP, an immunotransmitter that activates STING in cells in the TIME. STING activation leads to the induction of Type 1 Interferon and a host of anti-tumor immune responses. Moreover, ATP augments leukocyte uptake of cGAMP, further increasing STING activation and promoting tumor immunity. However, acute ATP-dependent inflammation is self-limiting when ATP is inevitably converted to immunosuppressive adenosine (Ado) by extracellular ectonucleotidases (notably, CD39 and CD73) which are highly expressed in PDAC. As evidence of the tumor-promoting role of Ado in PDAC, we show in a Phase I neoadjuvant clinical trial for borderline resectable tumors (n=20) that resistance to neoadjuvant FOLFIRINOX and PD-1 inhibition is associated with an increase in adenosine-related gene expression. We deciphered a novel mechanism of adenosine-mediated immunosuppression whereby signaling through Ado receptors interrupts STING activation by cGAMP. Specifically, we show that NECA, a potent adenosine receptor agonist, inhibits phosphorylation of IRF3 downstream of STING activation and consequently blocks transcription of STING-driven IFNB1 in RAW264.7 macrophages, murine bone marrow-derived macrophages, and CD14+ human PBMCs. Under these same conditions, NECA increases IL-6 and IL-1B, highlighting a complex cytokine milieu controlled by ATP metabolism and STING signaling. These effects are reversed with the addition of AB928, an adenosine receptor antagonist. We considered that boosting cGAMP in the PDAC TIME might be sufficient to offset the effects of Ado signaling. In support of this approach, we show that blocking hydrolysis of cGAMP by inhibiting ENPP1 augments the efficacy of FOLFIRINOX against syngeneic murine PDAC tumors, despite the likely presence of adenosine. These findings support the conclusion that adenosine signaling interrupts anti-tumor STING signaling and demonstrate that ENPP-1 inhibition may provide therapeutic benefits by boosting STING and reducing adenosine during chemotherapy treatment in PDAC patients. Citation Format: Alykhan Premji, Jason Link, Takanobu Yamao, Khalid Rashid, Evan Abt, Amanda Labora, Charlotte Chan, Thuc Le, Zev Wainberg, Caius Radu, Timothy Donahue. Adenosine inhibits STING driven anti-tumor immunity in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr PR15.

Targeting CD38/ ADP-ribosyl cyclase as a novel therapeutic strategy for identification of three potent agonists for leukopenia treatment

Leukopenia is the most common side effect of chemotherapy and radiotherapy. It potentially deteriorates into a life-threatening complication in cancer patients. Despite several agents being approved for clinical administration, there are still high incidences of pathogen-related disease due to a lack of functional immune cells. ADP-ribosyl cyclase of CD38 displays a regulatory effect on leukopoiesis and the immune system. To explore whether the ADP-ribosyl cyclase was a potential therapeutic target of leukopenia. We established a drug screening model based on an ADP-ribosyl cyclase-based pharmacophore generation algorithm and discovered three novel ADP-ribosyl cyclase agonists: ziyuglycoside II (ZGSII), brevifolincarboxylic acid (BA), and 3,4-dihydroxy-5-methoxybenzoic acid (DMA). Then, in vitro experiments demonstrated that these three natural compounds significantly promoted myeloid differentiation and antibacterial activity in NB4 cells. In vivo, experiments confirmed that the compounds also stimulated the recovery of leukocytes in irradiation-induced mice and zebrafish. The mechanism was investigated by network pharmacology, and the top 12 biological processes and the top 20 signaling pathways were obtained by intersecting target genes among ZGSII, BA, DMA, and leukopenia. The potential signaling molecules involved were further explored through experiments. Finally, the ADP-ribosyl cyclase agonists (ZGSII, BA, and DMA) has been found to regenerate microbicidal myeloid cells to effectively ameliorate leukopenia-associated infection by activating CD38/ADP-ribosyl cyclase-Ca2+-NFAT. In summary, this study constructs a drug screening model to discover active compounds against leukopenia, reveals the critical roles of ADP-ribosyl cyclase in promoting myeloid differentiation and the immune response, and provides a promising strategy for the treatment of radiation-induced leukopenia.