Non-peptide Antagonist Research Articles

Pharmacokinetics, bioavailability and metabolism of cligosiban, an antagonist of oxytocin receptor, in rat by liquid chromatography hyphenated with electrospray ionization tandem mass spectrometry

Cligosiban is a highly-affinity nonpeptide oxytocin receptor antagonist. In this study, a simple an sensitive LC–MS/MS method was developed and validated for the determination of cligosiban in rat plasma. The plasma samples were pretreated with acetonitrile as precipitant and then separated on an ACQUITY BEH C18 column (2.1 × 50 mm, 1.7 μm) with 0.1% formic acid in water and acetonitrile as mobile phase. The analytes were monitored using selected reaction monitoring (SRM) mode with transitions at m/z 420.1→248.1 for cligosiban and m/z 304.1→161.1 for IS. The developed method showed good linearity over the concentration range of 1–1000 ng/mL with coefficient of correlation > 0.996. The lower limit of quantification (LLOQ) is 1 ng/mL. The method was validated for selectivity, precision, accuracy, recovery, and stability in accordance with FDA’s guidance. The validated assay has been successfully applied to the pharmacokinetic study of cligosiban in rat plasma after intravenous and oral administration. According to the current results, the oral bioavailability of cligosiban was 63.82%. Furthermore, the metabolites present in rat liver microsomes (RLM), human liver microsomes (HLM) and rat plasma were analyzed by UHPLC-LTQ-Orbitrap-MS method, and four metabolites structurally identified based on their accurate masses, and fragment ions. The proposed metabolic pathways of cligosiban were demethylation and glucuronidation. This study is the first report on the pharmacokinetic and metabolic information of cligosiban, which would provide insights into the effectiveness and toxicity of cligosiban.

Differential consequences of neurokinin receptor 1 and 2 antagonists in metastatic breast carcinoma cells; Effects independent of Substance P.

The biological action of Substance P (SP) is mediated mainly by NK-1 receptors (NK1R) followed by NK2 receptors (NK2R). Aberrant expression of NK1R and NK2R has been identified in various carcinomas. The role of Substance P and its receptors, especially NK2R in cancer progression is not entirely known and there are conflicting results in the literature demonstrating the need for further investigation. In the current study, we examined the effects of SP and antagonists selective for the NK1R and NK2R in breast carcinoma cells metastasize to vital organs. The effects of highly potent and selective non-peptide mouse NK1R and NK2R antagonists RP 67,580 and GR 159897, respectively, as well as SP and SP methyl ester, on both metastatic (4THM, 4TBM, 4TLM, 4T1) and non-metastatic (67NR) breast cancer cells were determined. NK1R and NK2R were over expressed in metastatic breast cells compared to non-metastatic cells. The NK1R antagonist at a 30 μM dose inhibited cell growth and induced cell death in metastatic cells while enhancing phosphorylation of Akt, the latter response not observed in the non-metastatic 67NR cells. Blocking the action of SP at the NK2R (30 μM antagonist) suppressed cellular proliferation in all the cell lines examined, with a response less prominent than that of the NK1R antagonist. Differently, the NK2R antagonist increased phosphorylation of p38 and enhanced MIP-2 secretion. SP and the SP methyl ester neither altered cell proliferation nor the effects of NK1R and NK2R antagonists in the metastatic cell lines. Increased sensitivity of metastatic breast carcinoma cells to NK1R and NK2R antagonists suggest potential therapeutic value of antagonists in metastatic disease. NK1R and NK2R in metastatic breast carcinoma cells react differently to agonists and antagonists. These findings together with previously published data demonstrate that differential consequences of receptor antagonists and SP may inhibit breast cancer growth and metastasis.

Binding mode of AIF(370-394) peptide to CypA: insights from NMR, label-free and molecular docking studies.

The complex formation between the proteins apoptosis-inducing factor (AIF) and cyclophilin A (CypA) following oxidative stress in neuronal cells has been suggested as a main target for reverting ischemia-stroke damage. Recently, a peptide encompassing AIF residues 370-394 has been developed to target the AIF-binding site on CypA, to prevent the association between the two proteins and suppress glutamate-induced cell death in neuronal cells. Using a combined approach based on NMR spectroscopy, synthesis and in vitro testing of all Ala-scan mutants of the peptide and molecular docking/molecular dynamics, we have generated a detailed model of the AIF (370-394)/CypA complex. The model suggests us that the central region of the peptide spanning residues V374-K384 mostly interacts with the protein and that for efficient complex inhibition and preservation of CypA activity, it is bent around amino acids F46-G75 of the protein. The model is consistent with experimental data also from previous works and supports the concept that the peptide does not interfere with other CypA activities unrelated to AIF activation; therefore, it may serve as an ideal template for generating future non-peptidic antagonists.

Abstract LB-064: The discovery of novel small molecular CXCR2 antagonist by using ligand-based pharmacophore model

Abstract Tumor metastasis has become a fatal disease progress which greatly influence cancer treatment and prognosis. Generally, the metastatic progression can be classified into three main processes: the cancer cells leave the original “tumor home”, travel through “vessel highway”, and settle down in a new “tissue house”. Many agents with various machnisms have been developed for the treatment of cancer cell metastasis, including VEGFR inhibitors, integrin inhibitors, or MMP (matrix metallo protease) inhibitors. Recently a growing interest has been shown for the CXC chemokine receptor 2 (CXCR2), due to their involvement in metastasis physiology. Once CXCR2 is triggered by upstream effectors, it can cause the activation of downstream signals such as serine/threonine kinases, tyrosine kinases. Its essential role in influencing tumor microenvironment makes CXCR2 an important target for anti-tumor metastasis treatment. The first non-peptide CXCR2 antagonist SB225002 was discovered in the mid-1990s by GSK Company. To date, four drug candidates are in clinical trials, including Danirixin, AZD5069, Reparixin and Ladarixin. The clinical indications of AZD5069 were expanded to metastatic head & neck cancer and metastatic pancreatic cancer, in combination with MEDI4736 (a PDL-1 inhibitor). As an excellent computational tool, the pharmacophore model, has been rapidly developed for the identification of novel hit/lead compounds for various targets, especially for proteins without crystal structures. An extensive effort has been made in the attempt to apply pharmacophore model to identify novel VEGFR inhibitors, MMP inhibitors as anti-cancer metastasis agents, revealing that ligand-based pharmacophore model is the best approach when the target geometry is not available, or the binding mode is not elucidated. At present, the binding mode of CXCR2 with its antagonists has not been fully discovered, however, the group of N. Neamati have been trying to establishing a ligand-based pharmacophore model which could be applied for virtual screening to find novel scaffolds of CXCR2 antagonist; this work, for the first time, indicated the feasibility of applying pharmacophore model for the discovery of CXCR2 antagonist. Although a bunch of CXCR2 antagonists have been identified, the anti-tumor metastasis effect of CXCR2 antagonists is not considered in most cases. In our study, a convenient pharmacophore model was built with HipHop program, by screening a mini-database contained compounds which were designed based on the known structure-activity relationship (SAR) of the diarylurea series CXCR2 antagonists. Several novel skeletons with moderate to potent CXCR2 antigonitic activiites were identified. Following optimization resulted in the discovery of compound D45 which showed not only potent CXCR2 antagonist activity with an IC50 value of 10 nM and 910-fold selectivity against CXCR1, but also good in vitro anti-tumor metastatic effect in wound healing assay. Moreover, compound D45 exhibitored promising druglikeness with more than 90% bioavailability in rat. Citation Format: Wen-Hai Huang, Zhi-Long Wang, Jin-Xin Che, Hai-Chao Sheng, Feng Huang, Yong-Zhou Hu, You-Hong Hu, Xin Xie, Xiao-Wu Dong. The discovery of novel small molecular CXCR2 antagonist by using ligand-based pharmacophore model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-064.

Orthosteric and allosteric action of the C5a receptor antagonists.

The C5a receptor (C5aR) is a G-protein-coupled receptor (GPCR) that can induce strong inflammatory response to the anaphylatoxin C5a. Targeting C5aR has emerged as a novel anti-inflammatory therapeutic method. However, developing potent C5aR antagonists as drugs has proven difficult. Here, we report two crystal structures of human C5aR in ternary complexes with the peptide antagonist PMX53 and a non-peptide antagonist, either avacopan or NDT9513727. The structures, together with other biophysical, computational docking and cell-based signaling data, reveal the orthosteric action of PMX53 and its effect of stabilizing the C5aR structure, as well as the allosteric action of chemically diverse non-peptide C5aR antagonists with different binding poses. Structural comparison analysis suggests the presence of similar allosteric sites in other GPCRs. We also discuss critical structural features of C5aR in activation, including a novel conformation of helix 8. On the basis of our results, we suggest novel strategies for developing C5aR-targeting drugs.

Binding, Thermodynamics, and Selectivity of a Non-peptide Antagonist to the Melanocortin-4 Receptor.

The melanocortin-4 receptor (MC4R) is a potential drug target for treatment of obesity, anxiety, depression, and sexual dysfunction. Crystal structures for MC4R are not yet available, which has hindered successful structure-based drug design. Using microsecond-scale molecular-dynamics simulations, we have investigated selective binding of the non-peptide antagonist MCL0129 to a homology model of human MC4R (hMC4R). This approach revealed that, at the end of a multi-step binding process, MCL0129 spontaneously adopts a binding mode in which it blocks the agonistic-binding site. This binding mode was confirmed in subsequent metadynamics simulations, which gave an affinity for human hMC4R that matches the experimentally determined value. Extending our simulations of MCL0129 binding to hMC1R and hMC3R, we find that receptor subtype selectivity for hMC4R depends on few amino acids located in various structural elements of the receptor. These insights may support rational drug design targeting the melanocortin systems.

Targeted Tubulysin B Hydrazide Conjugate for the Treatment of Luteinizing Hormone-Releasing Hormone Receptor-Positive Cancers.

The targeted delivery of chemotherapeutic agents to receptors that are overexpressed on cancer cells has become an attractive strategy to concentrate drugs in cancer cells while avoiding uptake by healthy cells. Luteinizing hormone-releasing hormone receptor (LHRH-R) has attracted considerable interest for this application, since LHRH-R is upregulated in ∼86% of prostate cancers, ∼80% of endometrial cancers, ∼80% of ovarian cancers, and ∼50% of breast cancers, but virtually absent from normal tissues. Although LHRH and related peptides have been used to deliver cytotoxic drugs to LHRH-R overexpressing cancer cells, they have suffered from off-target delivery of the therapeutic agents to the liver and kidneys. To reduce such unwanted uptake by peptide scavenger receptors in the liver and kidneys, we have explored the use of a nonpeptidic LHRH-R antagonist (NBI42902) to construct an LHRH-R targeted tubulysin conjugate (BOEPL-L3-TubBH). In vitro studies with BOEPL-L3-TubBH demonstrate that the conjugate can kill LHRH-R expressing triple-negative breast cancer cells (MDA-MB-231 cells) with low nanomolar IC50. Related studies on tumor-bearing mice further reveal that the same conjugate can eradicate MDA-MB-231 solid tumors without any measurable side-effects, yielding mice that gain weight during therapy and show no evidence of tumor recurrence for at least 5 weeks after termination of treatment. That these complete responses are LHRH-R targeted was then established by showing that identical treatment of receptor-negative (SKOV3) tumors yields no antitumor response. Overall, these data provide a proof-of-concept that LHRH-R specific targeting of an extremely toxic drug like tubulysin B can treat LHRH-R positive tumors without causing significant toxicity to healthy cells.

UPLC/MS-MS assay development for estimation of mozavaptan in plasma and its pharmacokinetic study in rats.

Mozavaptan is a nonpeptide vasopressin receptor antagonist approved for the treatment of ectopic antidiuretic hormone secretion syndrome. A simple, rapid and fully validated UPLC/MS-MS method was developed for the quantitation of mozavaptan in rat plasma. The chromatographic separation was conducted on an Acquity UPLC BEH™ C18 column with an optimum mobile phase of 10mM ammonium acetate buffer and 0.1% formic acid in acetonitrile (30:70 v/v) at a flow rate of 0.3ml/min. The multiple reaction monitoring transitions were performed at m/z 428.16→119.03 for mozavaptan and m/z 237.06→179.10 for carbamazepine (internal standard). The method was effectively applied for the determination of mozavaptan pharmacokinetic parameters after the oral administration of 3mg/kg mozavaptan in rats.

Potentiation of capsaicin-induced neurogenic inflammation by 5-HT7 receptors in the rat hind paw: Involvement of calcitonin gen-related peptide

A decrease in the activation threshold of primary sensory neurons to transient receptor potential V1 (TRPV1) stimulation by serotonin 5-HT7 receptors has been reported but no confirmation if this might translate into facilitation of neurogenic inflammation has been provided. We analysed the modulation of capsaicin (CAP)-induced neurogenic inflammation in the rat hind paw by the selective 5-HT7 receptor agonist, LP-44, and the involvement of calcitonin gen-related peptide (CGRP) in this effect. Animals received intra-plantar injections (30 μL) of vehicle, CAP (0.05%, 0.1% and 0.2%), LP-44 (7.5 and 15 nmol) and the combination of LP–44 + CAP; then, the time course of the inflammatory responses was measured. The effect of the 5-HT7 receptor antagonist, SB-269970 (3 mg/kg, s.c.), on responses produced by LP-44 alone and combined with CAP was tested. As expected, CAP produced concentration- and time-dependent inflammatory responses in the hind paw. Interestingly, LP-44 by itself also produced inflammation in a concentration- and time-dependent manner, and magnified CAP-induced responses. Systemic pre-treatment with SB-269970 significantly blunted LP-44 (15 nmol)-induced inflammation as well as magnified inflammatory responses produced by the combination of LP-44 (7.5 and 15 nmol) + CAP (0.1%) thus confirming the involvement of 5-HT7 receptors. Finally, the non-peptide CGRP receptor antagonist, BIBN4096 (3 mg/kg, s.c.), strongly inhibited the potentiated inflammatory responses induced by LP-44 (7.5 and 15 nmol) + CAP (0.1%) thus substantiating their neurogenic nature. Thus, sensitization of CAP-sensitive primary sensory neurons by 5-HT7 receptors may result in facilitation of neurogenic inflammation involving CGRP in the rat hind paw.

Long-term Effect of Elagolix on Bone Mineral Density in Women with Endometriosis-Associated Pain [38G

INTRODUCTION: To evaluate the long-term effect of elagolix, an oral, non-peptide GnRH antagonist, on bone mineral density (BMD) in two 6-month (M) extension studies (Elaris EM-III and IV) of the pivotal, 6M, phase 3 studies (12M overall treatment with 150mg once daily [QD] or 200mg twice daily [BID]). METHODS: Women with moderate/severe endometriosis-associated pain and a baseline BMD Z-score >-1.5 were randomized to receive elagolix in the pivotal studies and continued elagolix treatment in the extension studies (treated: Elaris EM-III, n=287; Elaris EM-IV, n=282). Total hip BMD was measured by dual energy X-ray absorptiometry and reviewed/evaluated by a blinded central reader. Baseline was before dosing in pivotal studies. RESULTS: After 6M of elagolix treatment in the pivotal studies, the proportion of women with a decrease in total hip BMD ≥8% ranged 0–1.1% across doses/studies; these women were not eligible for extension study. Following 12M treatment, the proportion of women with a total hip BMD decrease from baseline ≥8% was 1.8% (n=2) at 150mg QD and 0.9% (n=1) at 200mg BID in Elaris EM-III and 0% (n=0) at 150mg QD and 4.6% (n=5) at 200mg BID in Elaris EM-IV. For total hip, the mean BMD Z-score at extension-M6 was within the normal range of -2.0 to +2.0 across doses/studies; no women had a total hip BMD Z-score ≤-2. CONCLUSION: In women with endometriosis-associated pain, long-term elagolix treatment was associated with decreases in total hip BMD, while the mean total hip BMD Z-score was within the normal range and no women had a total hip BMD Z-score ≤-2.

Baseline Burden of Endometriosis-Associated Pain among Women in Two Phase 3 Elagolix Studies [10Q

INTRODUCTION: Few data exist on the extent of symptoms in women with endometriosis. This analysis examined baseline pain burden among women with moderate to severe endometriosis pain in two phase 3 studies of elagolix (an oral, non-peptide GnRH antagonist) for the management of endometriosis-associated pain. METHODS: Elaris EM-I and Elaris EM-II were two double-blind, randomized, 6-month, placebo-controlled phase 3 studies evaluating two elagolix doses (150 mg once daily and 200 mg twice daily) in women with endometriosis-associated pain. This analysis included randomized women pooled across studies and treatment groups. Dysmenorrhea (DYS) and non-menstrual pelvic pain (NMPP) scores were recorded in a daily electronic-diary and characterized as ‘none’, ‘mild’, ‘moderate’, and ‘severe’, with definitions that incorporated daily functioning. Days with DYS or NMPP and severity of pain are summarized. Baseline was defined as the average of the last 35 days during the screening period. RESULTS: At baseline, the mean [SD] number of days women reported DYS and NMPP was 8.0 [3.0] days (97.6% of menstruating days) and 20.5 days [5.4] (90.3% of non-menstruating days), respectively (N=1686 for the combined studies). Enrolled women reported moderate/severe DYS and NMPP most days during the baseline phase (mean [SD]: DYS, 80.5% [21.2] of menstruating days; NMPP, 57% [29.0] of non-menstruating days). CONCLUSION: On average in these two phase 3 studies, women with endometriosis-associated pain experienced DYS or NMPP > 90% of days during the baseline phase and moderate/severe pain was reported for a majority of the days when pain was reported.

Long-Term Safety and Efficacy of Elagolix Treatment in Women With Endometriosis-Associated Pain [11OP

INTRODUCTION: Long-term safety and efficacy of elagolix, an oral, non-peptide GnRH antagonist for the management of endometriosis-associated pain, was evaluated in two 6-month (M) extension studies (Elaris EM-III and IV) of the pivotal, 6M, phase 3 studies (12M-overall treatment with 150 mg once daily [QD] or 200 mg twice daily [BID]). METHODS: Women with moderate/severe endometriosis-associated pain, randomized to receive elagolix in the pivotal studies, continued treatment during the extension studies (treated: Elaris EM-III, n=287; Elaris EM-IV, n=282). Baseline was before dosing in pivotal studies. Dysmenorrhea (DYS), non-menstrual pelvic pain (NMPP), and dyspareunia (DYSP) scores were recorded in a daily electronic-diary. Adverse events (AE), bone mineral density (BMD), and endometrium were assessed. RESULTS: DYS, NMPP and DYSP scores across dose groups were significantly decreased compared to placebo at M6 in the pivotal studies (P<.05; exception-DYSP 150 mg), and improvements in scores were maintained after 12M of treatment in Elaris EM-III (Extension-M6 mean percent change from baseline: DYS, 150 mg QD=−49%, 95% CI [−57,−41], 200 mg BID=−82%, 95% CI [−88,−76], NMPP, 150 mg QD=−49, 95% CI [−57,−41], 200 mg BID=−57%, 95% CI [−64,−49]; DYSP, 150 mg QD=−31%, 95% CI [−46,−16], 200 mg BID=−42%, 95% CI [−58,−25]). Hot flush was the most common AE over 12M of treatment (150 mg QD=29.5%; 200 mg BID=52.2%). At extension M6, there was a dose-dependent decrease in BMD from baseline, while mean lumbar spine BMD Z-score was within normal range (−2.0–+2.0). Mean change in endometrial thickness ranged 0.6 to −0.8 mm across doses. Elaris EM-IV results were generally similar. CONCLUSION: In women with endometriosis-associated pain, long-term elagolix treatment was associated with reductions in DYS, NMPP, and DYSP. No new safety concerns were identified with long-term elagolix use.

Antileukemic effects of neurokinin-1 receptor inhibition on hematologic malignant cells: a novel therapeutic potential for aprepitant.

Genetic and laboratory studies have remodeled the conventional understanding of cancer pathogenesis by identifying different molecular alterations. Intrigued by the contribution of neurokinin-1 receptor (NK1R) network in cancer pathogenesis, we investigated the antileukemic effects of aprepitant, a nonpeptide antagonist of NK1R, in a panel of hematological cell lines. In this study, we found that aprepitant decreased the survival of all the tested cells; however, as compared with NB4, viability of the other cell lines was inhibited at higher concentrations. By increasing both p21 and p73 along with suppressing c-Myc and hTERT, aprepitant probably disordered cell distribution in the cell cycle, decreased DNA replication rate, and, thereby, impeded the proliferative capability of NB4 cells. Moreover, exposing cells to this agent led to activation of the caspase-3-dependent apoptotic pathway through altering the expression of apoptosis-related genes. Noteworthy, aprepitant also sensitized NB4 cells to the cytotoxic effects of arsenic trioxide and vincristine. Overall, it seems that pharmaceutical targeting of NK1R using aprepitant, either as a single agent or in combination, possesses novel promising potential for leukemia treatment strategies.

Antagonism of corticotropin-releasing factor CRF1 receptors blocks the enhanced response to cocaine after social stress

Numerous studies have shown that social defeat stress induces an increase in the rewarding effects of cocaine. In this study we have investigated the role played by the main hypothalamic stress hormone, corticotropin-releasing factor (CRF), in the effects that repeated social defeat (RSD) induces in the conditioned rewarding effects and locomotor sensitization induced by cocaine. A total of 220 OF1 mice were divided into experimental groups according to the treatment received before each social defeat: saline, 5 or 10 mg/kg of the nonpeptidic corticotropin-releasing factor CRF1 receptor antagonist CP-154,526, or 15 or 30 µg/kg of the peptidic corticotropin-releasing factor CRF2 receptor antagonist Astressin2-B. Three weeks after the last defeat, conditioned place preference (CPP) induced by 1 mg/kg of cocaine was evaluated. Motor response to 10 mg/kg of cocaine was also studied after a sensitization induction. Blockade of corticotropin-releasing factor CRF1 receptor reversed the increase in cocaine CPP induced by social defeat. Conversely, peripheral corticotropin-releasing factor CRF2 receptor blockade produced similar effects to those observed in socially stressed animals. The effect of RSD on cocaine sensitization was again blocked by the corticotropin-releasing factor CRF1 receptor antagonist, while peripheral CRF2 receptor antagonist did not show effect. Acute administration of Astressin2-B induced an anxiogenic response. Our results confirm that CRF modulates the effects of social stress on reinforcement and sensitization induced by cocaine in contrasting ways. These findings highlight CRF receptors as potential therapeutic targets to be explored by research about stress-related addiction problems.

18F]RPS-544: A PET tracer for imaging the chemokine receptor CXCR4

IntroductionCXCR4 specific [18F]-labeled positron emission tomography (PET) imaging agents are needed which would enable general distribution of the radiotracer for clinical investigation. We sought to synthesize, radiolabel and evaluate [18F]RPS-544, a novel non-peptide CXCR4 antagonist as a CXCR4 specific probe. We compared [18F]RPS-544 with the previously published [18F]-3 ([18F]RPS-510 in this paper) in a bi-lateral tumor model of differential CXCR4 expression for its ability to selectively target CXCR4 expression. MethodsRadiolabeling of [18F]RPS-544 and [18F]RPS-510 was performed by aromatic substitution on a 6-nitropyridyl group using no-carrier-added [18F]fluoride under basic conditions. 18F incorporation was determined by radioHPLC. Semi-preparative HPLC was used to purify the final product prior to reformulation. Imaging and biodistribution was performed in nude mice with bilateral PC3 (CXCR4+ and WT) xenograft tumors at 1, 2 and 4 h post injection. ResultsRPS-544 bound CXCR4 with an IC50 of 4.9 ± 0.3 nM. [18F]RPS-544 showed preferential uptake in CXCR4+ tumors, with a CXCR4/WT ratio of 3.3 ± 1.3 at 1 h p.i. and 2.3 ± 0.5 at 2 h p.i. Maximum uptake in the CXCR4+ tumors was 3.4 ± 1.2%ID/g at 1 h p.i., significantly greater (p = 0.003) than the uptake in the WT tumor. Tumor/blood ratios were 2.5 ± 0.4 and 3.6 ± 0.3 at 1 and 2 h p.i. Tumor/muscle ratios were >4 at all time-points. Tumor/lung ratios were >2 at 1 h and 2 h p.i. Substantial uptake was observed in the liver (15–25%ID/g), kidneys (25–35%ID/g), the small intestine (1–7%ID/g) and the large intestine (1–12%ID/g). Blood concentrations varied over time (0.5–2%ID/g). All other organs showed uptake of <1%ID/g at all time points studied with clearance profiles similar to blood clearance. ConclusionsHere we present, to the best of our knowledge, the first high affinity [18F]-labeled tracer, suitable for in vivo PET imaging of CXCR4. [18F]RPS-544 displayed high affinity for CXCR4 and good tumor uptake with a maximum uptake at 1 h p.i.. CXCR4 dependent uptake was demonstrated using bilateral tumors with differential CXCR4 expression as well as pharmacological blockade using the known CXCR4 antagonist, AMD-3100. Tissue contrast as judged by tumor to normal tissue ratios was positive in several key tissues. The structural and pharmacological similarities between [18F]RPS-544 and the approved drug AMD-3465, combined with the ease of synthesis and high molar activity (>185 GBq/μmol) achieved during radiosynthesis could lead to accelerated translation into the clinic.

Studies on Glucagon Receptor and Antagonists of Glucagon Receptor for the Management of Diabetes Mellitus

Glucagon receptor plays an important role in the glucose homeostasis and thus is drug target for the management of hyperglycemia in type-2 diabetes mellitus. The suppression of glucagon secretion from the alpha-cells is the key to control hyperglycemic condition. The identification of non-peptide antagonists of glucagon receptor is an effective therapeutic approach to inhibit the glucagon secretion to achieve normal glucose index.

Activation of NPY-Y2 receptors ameliorates disease pathology in the R6/2 mouse and PC12 cell models of Huntington's disease

Huntington's disease (HD) is a monogenic inherited polyglutamine-mediated neurodegenerative disorder for which effective therapies are currently unavailable. Neuropeptide Y (NPY) has been implicated as a potential therapeutic target in several neurodegenerative diseases, including HD. However, its mechanisms of action in the context of HD pathology remain unknown. Here, we investigated the beneficial effects of Y2 receptor (Y2R) activation with NPY or Y2R selective agonist NPY13–36 in the R6/2 mouse and PC12 cell models of HD. Also, we explored the effects of selective pharmacological blockage of Y2R using selective non-peptide small molecule Y2R antagonist SF31 in vivo and in vitro.Our results showed that activation of Y2R with intranasal NPY or NPY13–36 led to an improved motor function in R6/2 mice as revealed by rotarod performance, vertical pole test, and hindlimb clasping behaviour. Also, intranasal NPY or NPY13–36 led to a decrease in aggregated mHtt and mediated increase in dopamine and cAMP-regulated phosphoprotein, 32kDa (DARPP-32), brain-derived neurotrophic factor (BDNF), and activated extracellular signal-regulated protein kinases (pERK1/2) levels in R6/2 mice. Intranasal NPY or NPY13–36 had no effect on body weight but showed positive effects on survival in R6/2 mice. Furthermore, intranasal NPY or NPY13–36 attenuated induction of proinflammatory cytokine and inflammatory mediators in R6/2 mice. In contrast, antagonizing by using SF31 exacerbates phenotypic severity in R6/2 mice and treatment effects with either intranasal NPY or NPY13–36 were significantly blocked.In vitro, using inducible PC12/HttQ103-EGFP cells, treatment with NPY or NPY13–36 protected against mHtt-mediated neuromorphological defects (neurite length and soma area) and neurotoxicity but had no effect on mHtt inclusion body formation. Conversely, co-treatment with SF31 significantly inhibited these effects. Together, our findings extend previous evidence of the beneficial effects of NPY in R6/2 mice, and more importantly, suggest that targeted activation of Y2R receptor might be a promising disease-modifying target for HD and other neurodegenerative diseases.

Recent Development of Non-Peptide GnRH Antagonists.

The decapeptide gonadotropin-releasing hormone, also referred to as luteinizing hormone-releasing hormone with the sequence (pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2) plays an important role in regulating the reproductive system. It stimulates differential release of the gonadotropins FSH and LH from pituitary tissue. To date, treatment of hormone-dependent diseases targeting the GnRH receptor, including peptide GnRH agonist and antagonists are now available on the market. The inherited issues associate with peptide agonists and antagonists have however, led to significant interest in developing orally active, small molecule, non-peptide antagonists. In this review, we will summarize all developed small molecule GnRH antagonists along with the most recent clinical data and therapeutic applications.

Structure and Function of Small Non-Peptide CRF Antagonists and their Potential Clinical Use.

Corticotropin-releasing factor (CRF) can be considered a very important hormone or a chemical mediator. It works closely with other systems to regulate the manner through which the body may respond to stress. Thus it affects many biological processes associated with stress. Dysfunction of this system has also been correlated with various diseases such as major depression, anxiety, drug addiction and eating disorders. Rationally, this means that interfering with binding of CRF to its intended receptors can be an attractive target for drug design aiming at developing new medications for many ailments that are associated with stress such as depression, anxiety and stress-induced relapse in drug addiction. Hundreds of accounts of small molecule antagonists have appeared in the literature and the preclinical and clinical pharmacology have been reported for many of these agents. Several classes of small molecule CRF receptor antagonists which belong to the non-peptide class have been developed with many being widely used for research purposes. Currently several major pharmaceutical companies are pursuing development of small non-peptide CRF1 receptor antagonists. In this review article we explain the importance of development of non-peptide CRF antagonists and their clinical relevance with emphasis on those members that showed great promise or those that were advanced to clinical trials.

The Arg-Phe-amide peptide 26RFa/glutamine RF-amide peptide and its receptor: IUPHAR Review 24.

The RFamide neuropeptide 26RFa was first isolated from the brain of the European green frog on the basis of cross-reactivity with antibodies raised against bovine neuropeptide FF (NPFF). 26RFa and its N-terminally extended form glutamine RF-amide peptide (QRFP) have been identified as cognate ligands of the former orphan receptor GPR103, now renamed glutamine RF-amide peptide receptor (QRFP receptor). The 26RFa/QRFP precursor has been characterized in various mammalian and non-mammalian species. In the brain of mammals, including humans, 26RFa/QRFP mRNA is almost exclusively expressed in hypothalamic nuclei. The 26RFa/QRFP transcript is also present in various organs especially in endocrine glands. While humans express only one QRFP receptor, two isoforms are present in rodents. The QRFP receptor genes are widely expressed in the CNS and in peripheral tissues, notably in bone, heart, kidney, pancreas and testis. Structure-activity relationship studies have led to the identification of low MW peptidergic agonists and antagonists of QRFP receptor. Concurrently, several selective non-peptidic antagonists have been designed from high-throughput screening hit optimization. Consistent with the widespread distribution of QRFP receptor mRNA and 26RFa binding sites, 26RFa/QRFP exerts a large range of biological activities, notably in the control of energy homeostasis, bone formation and nociception that are mediated by QRFP receptor or NPFF2. The present report reviews the current knowledge concerning the 26RFa/QRFP-QRFP receptor system and discusses the potential use of selective QRFP receptor ligands for therapeutic applications.