Miguel Guerrero

Full Pharmacological Efficacy of a Novel S1P1 Agonist That Does Not Require S1P-Like Headgroup Interactions

Strong evidence exists for interactions of zwitterionic phosphate and amine groups in sphingosine-1 phosphate (S1P) to conserved Arg and Glu residues present at the extracellular face of the third transmembrane domain of S1P receptors. The contribution of Arg120 and Glu121 for high-affinity ligand-receptor interactions is essential, because single-point R120A or E121A S1P1 mutants neither bind S1P nor transduce S1P function. Because S1P receptors are therapeutically interesting, identifying potent selective agonists with different binding modes and in vivo efficacy is of pharmacological importance. Here we describe a modestly water-soluble highly selective S1P1 agonist [2-(4-(5-(3,4-diethoxyphenyl)-1,2,4-oxadiazol-3-yl)-2,3-dihydro-1H-inden-1-yl amino) ethanol (CYM-5442)] that does not require Arg120 or Glu121 residues for activating S1P1-dependent p42/p44 mitogen-activated protein kinase phosphorylation, which defines a new hydrophobic pocket in S1P1. CYM-5442 is a full agonist in vitro for S1P1 internalization, phosphorylation, and ubiquitination. It is noteworthy that CYM-5442 was a full agonist for induction and maintenance of S1P1-dependent blood lymphopenia, decreasing B lymphocytes by 65% and T lymphocytes by 85% of vehicle. Induction of CYM-5442 lymphopenia was dose- and time-dependent, requiring serum concentrations in the 50 nM range. In vitro measures of S1P1 activation by CYM-5442 were noncompetitively inhibited by a specific S1P1 antagonist [(R)-3-amino-(3-hexylphenylamino)-4-oxobutylphosphonic acid (W146)], competitive for S1P, 2-amino-2-(4-octylphenethyl)propane-1,3-diol (FTY720-P), and 5-[4-phenyl-5-(trifluoromethyl)-2-thienyl]-3-[3-(trifluoromethyl)phenyl]-1,2, 4-oxadiazole (SEW2871). In addition, lymphopenia induced by CYM-5442 was reversed by W146 administration or upon pharmacokinetic agonist clearance. Pharmacokinetics in mice also indicated that CYM-5442 partitions significantly in central nervous tissue. These data show that CYM-5442 activates S1P1-dependent pathways in vitro and to levels of full efficacy in vivo through a hydrophobic pocket separate from the orthosteric site of S1P binding that is headgroup-dependent.

Evidence that vasopressin V1b receptors mediate the transition to excessive drinking in ethanol-dependent rats.

Alcoholism is a devastating condition that represents a progression from initial alcohol use to dependence. Although most individuals are capable of consuming alcohol in a limited fashion, the development of alcohol dependence in a subset of individuals is often associated with negative emotional states (including anxiety and depression). Since the alleviation of this negative motivational state via excessive alcohol consumption often becomes a central goal of alcoholics, the transition from initial use to dependence is postulated to be associated with a transition from positive to negative reinforcement mechanisms. Vasopressin is a neuropeptide known to potentiate the effects of CRF on the HPA axis, and emerging evidence also suggests a role for centrally located vasopressin acting on V1b receptors in the regulation of stress‐ and anxiety‐like behaviors in rodents. The present study determined state‐dependent alterations in vasopressin/V1bR signaling in an animal model of ethanol dependence. The V1bR antagonist SSR149415 dose‐dependently reduced excessive levels of ethanol self‐administration observed in dependent animals without affecting the limited levels of ethanol drinking in non‐dependent animals. Ethanol self‐administration reduced V1b receptor levels in the basolateral amygdala of non‐dependent animals, a neuroadaptation that could theoretically facilitate the positive reinforcing effects of alcohol. In contrast, V1bR levels were seemingly restored in ethanol‐dependent rats, a switch that may in part underlie a transition from positive to negative reinforcement mechanisms with dependence. Together, our data suggest a key role for vasopressin/V1bR signaling in the transition to ethanol dependence.

Local not systemic modulation of dendritic cell S1P receptors in lung blunts virus-specific immune responses to influenza

The mechanism by which locally delivered sphingosine analogs regulate host response to localized viral infection has never been addressed. In this report, we show that intratracheal delivery of the chiral sphingosine analog (R)-2-amino-4-(4-heptyloxyphenyl)-2-methylbutanol (AAL-R) or its phosphate ester inhibits the T-cell response to influenza virus infection. In contrast, neither intraperitoneal delivery of AAL-R nor intratracheal instillation of the non-phosphorylatable stereoisomer AAL-S suppressed virus-specific T-cell response, indicating that in vivo phosphorylation of AAL-R and sphingosine 1-phosphate (S1P) receptor modulation in lungs is essential for immunomodulation. Intratracheal delivery of water-soluble S1P1 receptor agonist at doses sufficient to induce systemic lymphopenia did not inhibit virus-specific T-cell response, indicating that S1P1 is not involved in the immunosuppressive activities of AAL-R and that immunosuppression acts independently of naive lymphocyte recirculation. Accumulation of dendritic cells (DCs) in draining lymph nodes was inhibited by intratracheal but not intraperitoneal delivery of AAL-R. Direct modulation of DCs is demonstrated by the impaired ability of virus-infected bone marrow-derived DCs treated in vitro with AAL-R to trigger in vivo T-cell response after adoptive transfer to the airways. Thus, our results suggest that locally delivered sphingosine analogs induce immunosuppression by modulating S1P receptors other than S1P1 or S1P2 on dendritic cells in the lungs after influenza virus infection.

Sphingosine 1-phosphate receptor agonists: a patent review (2010 – 2012)

Introduction: The sphingosine-1-phosphate (S1P)-driven signaling regulates fundamental biological functions, including cell proliferation, angiogenesis, endothelial cell chemotaxis, immune cell trafficking and mitogenesis. A large body of research has been focusing on the development of immunosuppressive S1P1 receptor (S1P1-R) agonist molecules. The S1P1,3 – 5-R pan-agonist fingolimod (FTY720) has been approved by the FDA for the treatment of relapsing–remitting multiple sclerosis. However, FTY720 is now contraindicated in patients with compromised cardiac function. Although the main adverse effect bradycardia has been linked to the S1P3-R activation, cardiovascular liabilities persist with more selective S1P1-R agonists that have entered clinical trials. In contrast to the S1P1-R, the therapeutic application of the S1P2 – 5-Rs remains poorly explored. Areas covered: This review provides the patent literature from 2010 to date on S1P-R agonist molecules and their relevant biological properties. Expert opinion: Limited progress has been made on agonists at S1P4,5-R subtypes, with some families of S1P5-R agonists showing promising results in animal models of age-related cognitive disorders. A discrete number of reviewed molecules are S1P1-R agonists with a promising clinical outlook in transplantation, inflammation, cancer and autoimmune settings. Further preclinical and clinical studies will determine whether the new developed S1P1-R agonists do indeed improve the safety profile of FTY720.

Novel Selective Allosteric and Bitopic Ligands for the S1P3 Receptor

Sphingosine 1-phosphate (S1P) is a lysophospholipid signaling molecule that regulates important biological functions, including lymphocyte trafficking and vascular development, by activating G protein-coupled receptors for S1P, namely, S1P(1) through S1P(5). Here, we map the S1P(3) binding pocket with a novel allosteric agonist (CYM-5541), an orthosteric agonist (S1P), and a novel bitopic antagonist (SPM-242). With a combination of site-directed mutagenesis, ligand competition assay, and molecular modeling, we concluded that S1P and CYM-5541 occupy different chemical spaces in the ligand binding pocket of S1P(3). CYM-5541 allowed us to identify an allosteric site where Phe263 is a key gate-keeper residue for its affinity and efficacy. This ligand lacks a polar moiety, and the novel allosteric hydrophobic pocket permits S1P(3) selectivity of CYM-5541 within the highly similar S1P receptor family. However, a novel S1P(3)-selective antagonist, SPM-242, in the S1P(3) pocket occupies the ligand binding spaces of both S1P and CYM-5541, showing its bitopic mode of binding. Therefore, our coordinated approach with biochemical data and molecular modeling, based on our recently published S1P(1) crystal structure data in a highly conserved set of related receptors with a shared ligand, provides a strong basis for the successful optimization of orthosteric, allosteric, and bitopic modulators of S1P(3).

Modulators of the Sphingosine 1-phosphate receptor 1.

The Sphingosine 1-phosphate receptor (S1P-R) signaling system has proven to be of biological and medical importance in autoimmune settings. S1P1-R is a validated drug target for multiple sclerosis (MS) for which FTY720 (Fingolimod), a S1P1,3-5-R pan-agonist, was recently approved as the first orally active drug for the treatment of relapsing-remitting MS. Transient bradycardia and long half-life are the FTY720 critical pitfalls. This review provides the latest advances on next-generation S1P1-R modulators from 2012 up to date, with an overview of the chemical structures, structure-activity relationships, and relevant biological and clinical properties.

Antagonists of the kappa opioid receptor.

The research community has increasingly focused on the development of OPRK antagonists as pharmacotherapies for the treatment of depression, anxiety, addictive disorders and other psychiatric conditions produced or exacerbated by stress. Short-acting OPRK antagonists have been recently developed as a potential improvement over long-acting prototypic ligands including nor-BNI and JDTic. Remarkably the short-acting LY2456302 is undergoing phase II clinical trials for the augmentation of the antidepressant therapy in treatment-resistant depression. This Letter reviews relevant chemical and pharmacological advances in the identification and development of OPRK antagonists.

A Sphingosine 1-phosphate receptor 2 selective allosteric agonist

Molecular probe tool compounds for the Sphingosine 1-phosphate receptor 2 (S1PR2) are important for investigating the multiple biological processes in which the S1PR2 receptor has been implicated. Amongst these are NF-κB-mediated tumor cell survival and fibroblast chemotaxis to fibronectin. Here we report our efforts to identify selective chemical probes for S1PR2 and their characterization. We employed high throughput screening to identify two compounds which activate the S1PR2 receptor. SAR optimization led to compounds with high nanomolar potency. These compounds, XAX-162 and CYM-5520, are highly selective and do not activate other S1P receptors. Binding of CYM-5520 is not competitive with the antagonist JTE-013. Mutation of receptor residues responsible for binding to the zwitterionic headgroup of sphingosine 1-phosphate (S1P) abolishes S1P activation of the receptor, but not activation by CYM-5520. Competitive binding experiments with radiolabeled S1P demonstrate that CYM-5520 is an allosteric agonist and does not displace the native ligand. Computational modeling suggests that CYM-5520 binds lower in the orthosteric binding pocket, and that co-binding with S1P is energetically well tolerated. In summary, we have identified an allosteric S1PR2 selective agonist compound.

Discovery, Design and Synthesis of the First Reported Potent and Selective Sphingosine-1-Phosphate 4 (S1P4) Receptor Antagonists

Selective S1P(4) receptor antagonists could be novel therapeutic agents for the treatment of influenza infection in addition to serving as a useful tool for understanding S1P(4) receptor biological functions. 5-(2,5-Dichlorophenyl)-N-(2,6-dimethylphenyl)furan-2-carboxamide was identified from screening the Molecular Libraries-Small Molecule Repository (MLSMR) collection and selected as a promising S1P(4) antagonist hit with moderate in vitro potency and high selectivity against the other family receptor subtypes (S1P(1-3,5)). Rational chemical modifications of the hit allowed the disclosure of the first reported highly selective S1P(4) antagonists with low nanomolar activity and adequate physicochemical properties suitable for further lead-optimization studies.

SAR Analysis of Innovative Selective Small Molecule Antagonists of Sphingosine-1-Phosphate 4 (S1P4) Receptor

Recent evidence suggests an innovative application of chemical modulators targeting the S1P(4) receptor as novel mechanism-based drugs for the treatment of influenza virus infection. Modulation of the S1P(4) receptor may also represent an alternative therapeutic approach for clinical conditions where reactive thrombocytosis is an undesired effect or increased megakaryopoiesis is required. With the exception of our recent research program disclosure, we are not aware of any selective S1P(4) antagonists reported in the literature to date. Herein, we describe complementary structure-activity relationships (SAR) of the high-throughput screening (HTS)-derived hit 5-(2,5-dichlorophenyl)-N-(2,6-dimethylphenyl)furan-2-carboxamide and its 2,5-dimethylphenyl analog. Systematic structural modifications of the furan ring showed that both steric and electronic factors in this region have a significant impact on the potency. The furan moiety was successfully replaced with a thiophene or phenyl ring maintaining potency in the low nanomolar range and high selectivity against the other S1P receptor subtypes. By expanding the molecular diversity within the hit-derived class, our SAR study provides innovative small molecule potent and selective S1P(4) antagonists suitable for in vivo pharmacological validation of the target receptor.