Epithelial-mesenchymal transition (EMT) is a fundamental biological process involved in normal functions such as embryonic development and tissue repair, as well as in pathological conditions including cancer progression, metastasis, and fibrosis. TGF-β1 is a key inducer of EMT, activating pathways that alter cell morphology and gene expression (e.g., downregulation of E-cadherin, upregulation of α-smooth muscle actin (α-SMA)). EMT contributes to fibrotic tissue remodeling in idiopathic pulmonary fibrosis (IPF), a chronic and progressive lung disease characterized by excessive scarring of lung tissue.To achieve a comprehensive evaluation of EMT in respiratory epithelial cells (A549), we employed the standard Operetta CLS platform to assess morphological changes and protein expression of key biomarkers (E-cadherin, α-SMA), alongside an advanced approach that monitored cellular dynamics using the xCELLigence Real-Time Cell Analysis (RTCA) system and quantified biomarker gene expression via RT-qPCR.In Operetta experiments, TGF-β1 reduced cell roundness and E-cadherin protein levels, while it increased cell length and α-SMA protein levels. In xCELLigence RTCA experiments, TGF-β1 reduced the cellular index and E-cadherin gene expression while increasing α-SMA expression. SB-525334 blocked all effects of TGF-β1, whereas nintedanib was more effective in counteracting the stimulatory effects of TGF-β1 on cell length and α-SMA. Interestingly, nintedanib, per se, evoked small but consistent effects opposite to those of TGF-β1.In conclusion, integrating these experimental approaches provides a powerful platform for detailed investigation of EMT mechanisms and for the identification of novel drug candidates that counteract EMT.

The nociceptin/orphanin FQ (N/OFQ) receptor (NOP) ligands are drug candidates for different diseases, but peptide ligands are often limited by rapid enzymatic degradation and short in vivo duration of action. Here, we applied a multiple D-amino acid substitution strategy to the peptide template [Arg14 Lys15]N/OFQ(1-15)-NH2 to improve metabolic stability while preserving receptor activity. Progressive substitutions revealed marked positional tolerance within the C-terminal address domain and identified [d-Lys13,15d-Arg14]N/OFQ(1-15)-NH2 (compound 1c) as the most promising compound. This led to the Cha1-containing analogue 3a, which retained full agonist efficacy and high selectivity at the NOP receptor in vitro and ex vivo. In vivo, compound 3a induced a long-lasting loss of the righting reflex in mice, closely overlapping the pharmacological profile of the potent and long-acting agonist UFP-112. These findings define the stereochemical tolerance of the NOP receptor toward multiple d-amino acid substitutions within the N/OFQ peptide and demonstrate that this information can be exploited as a rational design strategy to generate NOP receptor agonists with prolonged in vivo activity.

BACKGROUND AND PURPOSE:The nociceptin/orphanin FQ (N/OFQ) peptide receptor (NOP) is an opioid receptor family member with distinct pharmacology and broad therapeutic potential. NOP receptors regulate functions such as nociception, stress reactivity, reward, mood, autonomic tone, immunity and sleep/wake cycle. Biased signalling has been proposed to enhance efficacy and minimise adverse effects at many G protein-coupled receptors (GPCRs), yet the transducer coupling preferences of NOP remain poorly defined. EXPERIMENTAL APPROACH:We applied the (TRansdUcer PATHways) BRET-based G protein profiling platform (TRUPATH) biosensor suite to resolve NOP receptor coupling. Human NOP receptor was expressed in HEK293 cells and challenged with 20 chemically diverse ligands, including the endogenous neuropeptide, as well as peptide and non-peptide agonists. We compared TRUPATH data with those obtained in validated assays, that is, calcium mobilisation (via Gαqi5), NOP-G protein and NOP-β-Arrestin 2 interaction. KEY RESULTS:N/OFQ activated six inhibitory G proteins (Gi1, Gi2, Gi3, GoA, GoB, Gz) with high potency (pEC50 9.08-10.49) but modest signal amplitude (15-30% of basal). Ligands UFP-113 and Comp 26 showed the most pronounced deviations across G protein isoforms. CONCLUSIONS AND IMPLICATIONS:This study provides a comprehensive fingerprint of NOP receptor pharmacology at the single-transducer level. The lack of marked G protein bias at the NOP receptor, more pronounced than for the classical opioid receptors, may reflect a combination of intrinsic receptor properties and assay limitations. These findings underscore the need for innovative chemotypes and complementary experimental strategies to fully resolve potential transducer bias at the NOP receptor.

Sleep-related disorders affect a significant portion of the global population. The nociceptin/orphanin FQ (N/OFQ) peptide (NOP) receptor has become a promising candidate for the development of innovative drugs to treat sleep disorders. In this study, we conducted an in-depth pharmacological characterization of sunobinop, a selective NOP receptor partial agonist already under clinical evaluation for treating multiple conditions including insomnia, using a wide range of in vitro and ex vivo methodologies. Sunobinop exhibited partial agonist activity in calcium mobilization, NOP - G protein interaction, label-free bioimpedance, and cAMP inhibition assays. Notably, it demonstrated competitive antagonism in the NOP - β-Arrestin 2 recruitment and ex vivo electrically stimulated mouse Vas Deferens, assays characterized by low amplification. The findings reported here confirm and extend the characterization of sunobinop as a tool for studying NOP receptor pharmacology providing new insights into its mode of action, relevant to its clinical evaluation.

BACKGROUND AND PURPOSE:Migraine is a neurovascular disorder largely mediated by calcitonin gene-related peptide (CGRP). This study explores the role of the nociceptin/orphanin FQ (N/OFQ)-N/OFQ receptor (NOP) system in CGRP-induced periorbital mechanical allodynia (PMA) in mice. EXPERIMENTAL APPROACH:Male or female wild type (NOP(+/+)) and NOP receptor knockout (NOP(-/-)) mice and CD-1 mice were used. The brain penetrant, AT-403, and the peripherally restricted, UFP-112, NOP agonists were tested for PMA prevention. To identify a potential site of action at the cellular level, the ability of N/OFQ to signal at membrane and endosomal level in NOP-expressing HEK293 cells, and to inhibit the increase in cyclic adenosine monophosphate (cAMP) induced by CGRP in human Schwann cells (hSCs) was investigated. KEY RESULTS:CGRP-induced PMA was comparable in NOP(+/+) and NOP(-/-) mice. AT-403 and UFP-112 equally reduced CGRP-evoked PMA in CD-1 mice. In NOP-expressing cells, activation of NOP resulted in the internalisation and movement of NOP away from the plasma membrane marker CAAX and to early endosomes marker Rab5a. N/OFQ stimulated Gαi recruitment to NOP at the plasma membrane and from the endosomal compartment. N/OFQ attenuated cAMP increase elicited by CGRP in hSCs. CONCLUSIONS AND IMPLICATIONS:The peripherally restricted NOP agonist showed efficacy similar to the brain-penetrant compound, indicating that peripheral NOP activation is sufficient to alleviate CGRP-evoked PMA. Despite NOP ability to halt Gαi recruitment and cAMP increase in cells, further studies are required to confirm that SCs are the cellular site where N/OFQ operates to attenuate the CGRP pro-migraine action.

Background and Purpose: Fentanyl analogues have been implicated in many cases of intoxication and death with overdose worldwide. The aim of this study is to investigate the pharmaco-toxicology of two fentanyl analogues: butyrylfentanyl (BUF) and 4-fluorobutyrylfentanyl (4F-BUF). Experimental Approach: In vitro, we measured agonist opioid receptor efficacy, potency, and selectivity and ability to promote interaction of the mu receptor with G protein and beta-arrestin 2. In vivo, we evaluated thermal antinociception, stimulated motor activity and cardiorespiratory changes in female and male CD-1 mice injected with BUF or 4F-BUF (0.1-6 mgkg(-1)). Opioid receptor specificity was investigated using naloxone (6 mgkg(-1)). We investigated the possible role of stress in increasing cardiorespiratory toxicity using the corticotropin-releasing factor 1 (CRF1) antagonist antalarmin (10 mgkg(-1)). Key Results: Agonists displayed the following rank of potency at mu receptors: fentanyl > 4F-BUF > BUF. Fentanyl and BUF behaved as partial agonists for the beta-arrestin 2 pathway, whereas 4F-BUF did not promote beta-arrestin 2 recruitment. In vivo, we revealed sex differences in motor and cardiorespiratory impairments but not antinociception induced by BUF and 4F-BUF. Antalarmin alone was effective in blocking respiratory impairment induced by BUF in both sexes but not 4F-BUF. The combination of naloxone and antalarmin significantly enhanced naloxone reversal of the cardiorespiratory impairments induced by BUF and 4F-BUF in mice. Conclusion and Implications: In this study, we have uncovered a novel mechanism by which synthetic opioids induce respiratory depression, shedding new light on the role of CRF1 receptors in cardiorespiratory impairments by mu agonists.

Opioid and opioid-like receptors are activated by a variety of endogenous peptides including [Met]enkephalin (met), [Leu]enkephalin (leu), β-endorphin (β-end), α-neodynorphin, dynorphin A (dynA), dynorphin B (dynB), big dynorphin (Big dyn), nociceptin/orphanin FQ (N/OFQ); endomorphin-1 and endomorphin-2 are also potential endogenous peptides. The Greek letter nomenclature for the opioid receptors, μ, δ and κ, is well established, and NC-IUPHAR considers this nomenclature appropriate, along with the symbols spelled out (mu, delta, and kappa), and the acronyms, MOP, DOP, and KOP [126, 103, 94]. However the acronyms MOR, DOR and KOR are still widely used in the literature. The human N/OFQ receptor, NOP, is considered 'opioid-related' rather than opioid because, while it exhibits a high degree of structural homology with the conventional opioid receptors [310], it displays a distinct pharmacology. Currently there are numerous clinically used drugs, such as morphine and many other opioid analgesics, as well as antagonists such as naloxone. The majority of clinically used opiates are relatively selective μ agonists or partial agonists, though there are some μ/κ compounds, such as butorphanol, in clinical use. κ opioid agonists, such as the alkaloid nalfurafine and the peripherally acting peptide difelikefalin, are in clinical use for itch.

The Concise Guide to Pharmacology 2025/26 marks the seventh edition in this series of biennial publications in the British Journal of Pharmacology. Presented in landscape format, the guide provides a comparative overview of the pharmacology of drug target families. The concise nature of the Concise Guide refers to the style of presentation, being clear, accessible, and well-structured, rather than the scope of the content, which spans approximately 500 pages. The Concise Guide summarises the key pharmacological properties of around 1900 human drug targets, and nearly 7000 interactions, involving around 4400 ligands. While the content is a substantially condensed version of the more detailed information and links available at the www.guidetopharmacology.org website, the printed guide serves as a permanent, citable, point-in-time record, that remains stable despite ongoing updates to the online database. The full contents of this publication can be found at https://bpspubs.onlinelibrary.wiley.com/doi/10.1111/bph.70230. The Concise Guides provide expert-curated recommendations of 'Gold Standard' selective pharmacological tools, available either commercially or as donations, which enable the identification of individual drug targets or families of drug targets. While the Concise Guide offers a more streamlined overview, more comprehensive information, including detailed pharmacological profiles and links to multiple online databases, is available through the Guide to Pharmacology website. The 2025/26 edition of the Concise Guide is based on material current as of mid-2025, and supersedes all previous editions, including the 2023/24 Guide, and earlier Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), and as such provides official IUPHAR classification and nomenclature for human drug targets, where applicable. G protein-coupled receptors are one of the six major pharmacological targets into which the Guide is divided, with the others being: ion channels, nuclear hormone receptors, catalytic receptors, enzymes and transporters. Each section includes nomenclature guidance, concise summaries, information of the best available pharmacological tools, key references, and suggestions for further reading.

Opioid and opioid-like receptors are activated by a variety of endogenous peptides including [Met]enkephalin (met), [Leu]enkephalin (leu), β-endorphin (β-end), α-neodynorphin, dynorphin A (dynA), dynorphin B (dynB), big dynorphin (Big dyn), nociceptin/orphanin FQ (N/OFQ); endomorphin-1 and endomorphin-2 are also potential endogenous peptides. The Greek letter nomenclature for the opioid receptors, μ, δ and κ, is well established, and NC-IUPHAR considers this nomenclature appropriate, along with the symbols spelled out (mu, delta, and kappa), and the acronyms, MOP, DOP, and KOP [127, 103, 94]. However the acronyms MOR, DOR and KOR are still widely used in the literature. The human N/OFQ receptor, NOP, is considered 'opioid-related' rather than opioid because, while it exhibits a high degree of structural homology with the conventional opioid receptors [313, 94], it displays a distinct pharmacology. Currently there are numerous clinically used drugs, such as morphine and many other opioid analgesics, as well as antagonists such as naloxone. The majority of clinically used opiates are relatively selective μ agonists or partial agonists, though there are some μ/κ compounds, such as butorphanol, in clinical use. κ opioid agonists, such as the alkaloid nalfurafine and the peripherally acting peptide difelikefalin, are in clinical use for itch.

The neuropeptide nociceptin/orphanin FQ (N/OFQ) plays a key role in regulating several physiological functions and pathological states, which makes its receptor (NOP) a promising target for therapeutic interventions. In this study, we synthesized homodimeric N/OFQ-NH2 derivatives linked by disulfide bonds between cysteines appropriately introduced in the addressing region of the native peptide in place of the original amino acids. The in vitro activity of the compounds was evaluated using both an NOP-G protein interaction BRET assay and a calcium mobilization assay. The most potent compound, 1h (pEC50 > 9), was obtained by coupling two monomeric precursors via a Leu14-to-Cys substitution. In vivo, 1h demonstrated 3-fold greater potency than N/OFQ in eliciting loss of the righting reflex in mice and produced a long-lasting effect monitored for up to 7 h, supporting multimerization as a viable approach to developing long-acting peptide-based NOP ligands.

Ghrelin modulates several biological functions via selective activation of the growth hormone secretagogue receptor (GHSR). GHSR agonists may be useful for the treatment of anorexia and cachexia, while antagonists and inverse agonists may represent new drugs for the treatment of metabolic and substance use disorders. Thus, the identification and pharmacodynamic characterization of new GHSR ligands is of high interest. In the present work the label-free dynamic mass redistribution (DMR) assay has been used to evaluate the pharmacological activity of a panel of GHSR ligands. This includes the endogenous peptides ghrelin, desacyl-ghrelin and LEAP2 (1-14). Among synthetic compounds, the agonists anamorelin and HM01, the antagonists HM04 and YIL-781, and the inverse agonist PF-05190457 have been tested, together with HM03, R011, and H1498 from patent literature. The DMR results have been compared to those obtained in parallel experiments with the calcium mobilization assay. Ghrelin, anamorelin, HM01, and HM03 behaved as potent full GHSR agonists. YIL-781 behaved as a partial GHSR agonist and R011 as antagonist in both the assays. LEAP2(1-14) resulted a GHSR inverse agonist in DMR but not in calcium mobilization assay. PF-05190457, HM04, and H1498 behaved as GHSR inverse agonists in DMR experiments, while they acted as antagonists in calcium mobilization studies. In conclusion, this study provided a systematic pharmacodynamic characterization of several GHSR ligands in two different pharmacological assays. It demonstrated that the DMR assay can be successfully used particularly to discriminate between antagonists and inverse agonists. This study may be useful for the selection of the most appropriate compounds to be used in future studies.

The N/OFQ-NOP receptor is a fascinating peptidergic system with the potential to be exploited for the development of analgesic drugs devoid of side effects associated with classical opioid signalling modulation. To date, up to four X-ray and cryo-EM structures of the NOP receptor in complex with the endogenous peptide agonist N/OFQ and three small molecule antagonists have been solved and released. Despite the available structural information, the details of selective small molecule agonist binding to the NOP receptor in the active state remain elusive. In this study, by leveraging the available structural information and using N/OFQ(1-13)-NH2 as a reference compound, we developed a computational protocol based on docking followed by short molecular dynamics (MD) simulations that can suggest small molecule agonist binding modes at the NOP receptor that are reproducible and stable over time in the solvated membrane-embedded receptor active state and in agreement with known structure-activity relationship (SAR) data.

With nearly 700 structures solved and a growing number of customized structure prediction algorithms being developed at a fast pace, G protein-coupled receptors (GPCRs) are an optimal test case for validating new approaches for the prediction of receptor active state and ligand bioactive conformation complexes. In this study, we leveraged the availability of hundreds of peptide GPCRs in the active state and both classical homology and artificial intelligence (AI) based protein modeling combined with docking and AI-based peptide structure prediction approaches to predict the nociceptin/orphanin FQ-NOP receptor active state complex (N/OFQ-NOPa). The In Silico generated hypotheses were validated via the design, synthesis, and pharmacological characterization of novel linear N/OFQ(1-13)-NH2 analogues, leading to the discovery of a novel antagonist (3B; pK(B) = 6.63) bearing a single ring-constrained residue in place of the Gly(2)-Gly(3) motif of the N/OFQ message sequence (FGGF). While the experimental validation was ongoing, the availability of the Cryo-EM structure of the predicted complex enabled us to unambiguously validate the generated hypotheses. To the best of our knowledge, this is the first example of a peptide-GPCR complex predicted with atomistic accuracy (full complex C alpha RMSD < 1.0 & Aring;) and of the N/OFQ message moiety being successfully modified with a rigid scaffold.

The Concise Guide to PHARMACOLOGY 2023/24 is the sixth in this series of biennial publications. The Concise Guide provides concise overviews, mostly in tabular format, of the key properties of approximately 1800 drug targets, and about 6000 interactions with about 3900 ligands. There is an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (), which provides more detailed views of target and ligand properties. Although the Concise Guide constitutes almost 500 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at . G protein-coupled receptors are one of the six major pharmacological targets into which the Guide is divided, with the others being: ion channels, nuclear hormone receptors, catalytic receptors, enzymes and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2023, and supersedes data presented in the 2021/22, 2019/20, 2017/18, 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

Opioid and opioid-like receptors are activated by a variety of endogenous peptides including [Met]enkephalin (met), [Leu]enkephalin (leu), β-endorphin (β-end), α-neodynorphin, dynorphin A (dynA), dynorphin B (dynB), big dynorphin (Big dyn), nociceptin/orphanin FQ (N/OFQ); endomorphin-1 and endomorphin-2 are also potential endogenous peptides. The Greek letter nomenclature for the opioid receptors, μ, δ and κ, is well established, and NC-IUPHAR considers this nomenclature appropriate, along with the symbols spelled out (mu, delta, and kappa), and the acronyms, MOP, DOP, and KOP [124, 101, 92]. However the acronyms MOR, DOR and KOR are still widely used in the literature. The human N/OFQ receptor, NOP, is considered 'opioid-related' rather than opioid because, while it exhibits a high degree of structural homology with the conventional opioid receptors [304], it displays a distinct pharmacology. Currently there are numerous clinically used drugs, such as morphine and many other opioid analgesics, as well as antagonists such as naloxone. The majority of clinically used opiates are relatively selective μ agonists or partial agonists, though there are some μ/κ compounds, such as butorphanol, in clinical use. κ opioid agonists, such as the alkaloid nalfurafine and the peripherally acting peptide difelikefalin, are in clinical use for itch.

The mu opioid receptor agonists are the most efficacious pain controlling agents but their use is accompanied by severe side effects. More recent developments indicate that some ligands can differentially activate receptor downstream pathways, possibly allowing for dissociation of analgesia mediated through the G protein from the opioid-related side effects mediated by β-arrestin pathway. In an effort to identify such biased ligands, here we present a series of thirteen endomorphin-2 (EM-2) analogs with modifications in positions 1, 2, and/or 3. All obtained analogs behaved as mu receptor selective agonists in calcium mobilization assay carried out on cells expressing opioid receptors and chimeric G proteins. A Bioluminescence Resonance Energy Transfer (BRET) approach was employed to determine the ability of analogs to promote the interaction of the mu opioid receptor with G protein or β-arrestin 2. Nearly half of the developed analogs showed strong bias towards G protein, in addition four compounds were nearly inactive towards β-arrestin 2 recruitment while blocking the propensity of EM-2 to evoke mu-β-arrestin 2 interaction. The data presented here contribute to our understanding of EM-2 interaction with the mu opioid receptor and of the transductional propagation of the signal. In addition, the generation of potent and selective mu receptor agonists strongly biased towards G protein provides the scientific community with novel tools to investigate the in vivo consequences of biased agonism at this receptor.

The enormous influence in terms of bioactivity, affinity, and selectivity represented by the replacement of (L)-2,6-dimethyl tyrosine (Dmt) instead of Phenylalanine (Phe) into Nociceptin/orphanin (N/OFQ) neuropeptide analogues has been well documented in the literature. More recently, the non-natural amino acid (L)-2-methyl tyrosine (Mmt), with steric hindrance included between Tyr and Dmt, has been studied because of the modulation of steric effects in opioid peptide chains. Here, we report a new synthetic strategy to obtain Mmt based on the well-known Pd-catalyzed ortho-C(sp2)–H activation approach, because there is a paucity of other synthetic routes in the literature to achieve it. The aim of this work was to force only the mono-ortho-methylation process over the double ortho-methylation one. In this regard, we are pleased to report that the introduction of the dibenzylamine moiety on a Tyr aromatic nucleus is a convenient and traceless solution to achieve such a goal. Interestingly, our method provided the aimed Mmt either as N-Boc or N-Fmoc derivatives ready to be inserted into peptide chains through solid-phase peptide synthesis (SPPS). Importantly, the introduction of Mmt in place of Phe1 in the sequence of N/OFQ(1-13)-NH2 was very well tolerated in terms of pharmacological profile and bioactivity.