Production of the Bengamide Class of Marine Natural Products in Myxobacteria: Biosynthesis and Structure-Activity Relationships.

The bengamides, sponge-derived natural products that have been characterized as inhibitors of methionine aminopeptidases (MetAPs), have been intensively investigated as anticancer compounds. We embarked on a multidisciplinary project to supply bengamides by fermentation of the terrestrial myxobacterium M. virescens, decipher their biosynthesis, and optimize their properties as drug leads. The characterization of the biosynthetic pathway revealed that bacterial resistance to bengamides is conferred by Leu 154 of the myxobacterial MetAP protein, and enabled transfer of the entire gene cluster into the more suitable production host M. xanthus DK1622. A combination of semisynthesis of microbially derived bengamides and total synthesis resulted in an optimized derivative that combined high cellular potency in the nanomolar range with high metabolic stability, which translated to an improved half-life in mice and antitumor efficacy in a melanoma mouse model.

SAR156497, an exquisitely selective inhibitor of aurora kinases.

The Aurora family of serine/threonine kinases is essential for mitosis. Their crucial role in cell cycle regulation and aberrant expression in a broad range of malignancies have been demonstrated and have prompted intensive search for small molecule Aurora inhibitors. Indeed, over 10 of them have reached the clinic as potential anticancer therapies. We report herein the discovery and optimization of a novel series of tricyclic molecules that has led to SAR156497, an exquisitely selective Aurora A, B, and C inhibitor with in vitro and in vivo efficacy. We also provide insights into its mode of binding to its target proteins, which could explain its selectivity.

The selective intravenous inhibitor of the MET tyrosine kinase SAR125844 inhibits tumor growth in MET-amplified cancer.

Activation of the MET/HGF pathway is common in human cancer and is thought to promote tumor initiation, metastasis, angiogenesis, and resistance to diverse therapies. We report here the pharmacologic characterization of the triazolopyridazine derivative SAR125844, a potent and highly selective inhibitor of the MET receptor tyrosine kinase (RTK), for intravenous administration. SAR125844 displayed nanomolar activity against the wild-type kinase (IC50 value of 4.2 nmol/L) and the M1250T and Y1235D mutants. Broad biochemical profiling revealed that SAR125844 was highly selective for MET kinase. SAR125844 inhibits MET autophosphorylation in cell-based assays in the nanomolar range, and promotes low nanomolar proapoptotic and antiproliferative activities selectively in cell lines with MET gene amplification or pathway addiction. In two MET-amplified human gastric tumor xenograft models, SNU-5 and Hs 746T, intravenous treatment with SAR125844 leads to potent, dose- and time-dependent inhibition of the MET kinase and to significant impact on downstream PI3K/AKT and RAS/MAPK pathways. Long duration of MET kinase inhibition up to 7 days was achieved with a nanosuspension formulation of SAR125844. Daily or every-2-days intravenous treatment of SAR125844 promoted a dose-dependent tumor regression in MET-amplified human gastric cancer models at tolerated doses without treatment-related body weight loss. Our data demonstrated that SAR125844 is a potent and selective MET kinase inhibitor with a favorable preclinical toxicity profile, supporting its clinical development in patients with MET-amplified and MET pathway-addicted tumors.

Preparation and optimization of new 4-(2-(indolin-1-yl)-2-oxoethyl)-2-morpholinothiazole-5-carboxylic acid and amide derivatives as potent and selective PI3Kß inhibitors.

In our continuous efforts to identify and develop novel targeted cancer treatments, a new morpholino-thiazole scaffold active against PI3Kß has been identified. This Letter reports the optimization of this compound class to develop PI3Kß isoform-selective inhibitors with suitable pharmacological properties.

Discovery and optimization of pyrimidone indoline amide PI3Kß inhibitors for the treatment of phosphatase and tensin homologue (PTEN)-deficient cancers.

Compelling molecular biology publications have reported the implication of phosphoinositide kinase PI3Kß in PTEN-deficient cell line growth and proliferation. These findings supported a scientific rationale for the development of PI3Kß-specific inhibitors for the treatment of PTEN-deficient cancers. This paper describes the discovery of 2-[2-(2,3-dihydro-indol-1-yl)-2-oxo-ethyl]-6-morpholin-4-yl-3H-pyrimidin-4-one (7) and the optimization of this new series of active and selective pyrimidone indoline amide PI3Kß inhibitors. 2-[2-(2-Methyl-2,3-dihydro-indol-1-yl)-2-oxo-ethyl]-6-morpholin-4-yl-3H-pyrimidin-4-one (28), identified following a carefully designed methyl scan, displayed improved physicochemical and in vitro pharmacokinetic properties. Structural biology efforts enabled the acquisition of the first X-ray cocrystal structure of p110ß with the selective inhibitor compound 28 bound to the ATP site. The nonplanar binding mode described herein is consistent with observed structure-activity relationship for the series. Compound 28 demonstrated significant in vivo activity in a UACC-62 xenograft model in mice, warranting further preclinical investigation. Following successful development, compound 28 entered phase I/Ib clinical trial in patients with advanced cancer.

Preparation and optimization of new 4-(morpholin-4-yl)-(6-oxo-1,6-dihydropyrimidin-2-yl)amide derivatives as PI3Kß inhibitors.

From a HTS campaign, a new series of pyrimidone anilides exemplified by compound 1 has been identified with good inhibitory activity for the PI3Kß isoform. The structure of compound 1 in PI3Kγ was solved revealing a binding mode in agreement with the SAR observed on PI3Kß. These compounds displayed inhibition in the nanomolar range in the biochemical assay and were also potent p-Akt inhibitors in a PTEN-deficient PC3 prostate cancer cell line. Optimization of in vitro pharmocokinetic properties led to compound 25 exhibiting 52% bioavailability in mice and target engagement in an acute PK/PD study.

Discovery and optimization of new benzimidazole- and benzoxazole-pyrimidone selective PI3Kß inhibitors for the treatment of phosphatase and TENsin homologue (PTEN)-deficient cancers.

Most of the phosphoinositide-3 kinase (PI3K) kinase inhibitors currently in clinical trials for cancer treatment exhibit pan PI3K isoform profiles. Single PI3K isoforms differentially control tumorigenesis, and PI3Kß has emerged as the isoform involved in the tumorigenicity of PTEN-deficient tumors. Herein we describe the discovery and optimization of a new series of benzimidazole- and benzoxazole-pyrimidones as small molecular mass PI3Kß-selective inhibitors. Starting with compound 5 obtained from a one-pot reaction via a novel intermediate 1, medicinal chemistry optimization led to the discovery of compound 8, which showed a significant activity and selectivity for PI3Kß and adequate in vitro pharmacokinetic properties. The X-ray costructure of compound 8 in PI3Kδ showed key interactions and structural features supporting the observed PI3Kß isoform selectivity. Compound 8 achieved sustained target modulation and tumor growth delay at well tolerated doses when administered orally to SCID mice implanted with PTEN-deficient human tumor xenografts.

Functional characterization of human neuropeptide Y receptor subtype five specific antagonists using a luciferase reporter gene assay.

Neuropeptide Y (NPY) has several receptors; one of them, the neuropeptide Y5 receptor (NPY5) seems involved in feeding behavior in mammals. Although this particular receptor has been extensively studied in the literature, the difficulties encountered to obtain a stable cell line expressing this recombinant receptor have impaired the development of tools necessary to establish its molecular pharmacology. We thus established a method for the functional study of new ligands. It is based upon the cotransfection in human melatonin receptor 1 (MT1)-overexpressing HEK293 cells of three plasmids encoding melanocortin receptor (MC5), neuropeptide Y5 receptor (NPY5) and a cyclic AMP response element-controlled luciferase. Once challenged with alphaMSH, the MC5 receptor activates the cyclic AMP response, through the coupling protein subunit G(s). In contrast, NPY5 agonists, through the NPY5 receptor which is negatively coupled to the same pathway, counteract the alphaMSH-mediated effect on cyclic AMP level. Using appropriate controls, this method can pinpoint compounds with antagonistic activity. Simple and straightforward, this system permits reproducible measurements of agonist or antagonist effects in the presence of neuropeptide Y, the natural agonist. This method has the advantage over already existing methods and beyond its apparent complexity, to enhance the cyclic AMP concentration at a 'physiological' level, by opposition to a forskolin-induced adenylate cyclase activation. Finally, to further validate this assay, we showed results from (1) a series of natural peptidic agonists that permitted the standardization and (2) a series of potent nonpeptidic antagonists (affinity >10(-9) M) that form a new class of active NPY5 receptor antagonists.

Synthesis of new arylalkoxy amido derivatives as melatoninergic ligands.

Amido derivatives 10-18 of the corresponding oxyamines were synthesised as melatoninergic ligands by the reaction of hydroxyphtalimide with the halogeno derivatives or the corresponding alcohols using Mitsunobu reaction conditions. The affinity of the compounds for chicken brain melatonin receptors and recombinant human MT(1) and MT(2) receptors was evaluated using 2-[125I]-iodomelatonin as the radioligand. Overall, the introduction of an oxygen atom in the amido chain was not a favourable parameter as the compounds were less potent than the corresponding deoxy derivatives. However, nanomolar compounds were obtained with the arylethyloxy derivatives (13c (R'=nPr), chicken brain, hMT(1), hMT(2), K(i) values: 4.8, 3.86, 2.4 nM, respectively) and the 2,7-dimethoxynaphthalene derivatives (17c (R'=nPr), chicken brain, hMT(1), hMT(2), K(i) values: 0.04, 0.13, 0.1 nM, respectively). The functional activity of these compounds was evaluated by the aggregation of melanophores in Xenopus laevis tadpoles and the potency was related to the affinity of the molecules for melatonin receptors. The compounds were found to be full agonists and compound 17a was 20-fold more potent than melatonin in this bioassay.

Molecular identification of the long isoform of the human neuropeptide Y Y5 receptor and pharmacological comparison with the short Y5 receptor isoform.

The neuropeptide Y Y5 receptor gene generates two splice variants, referred to here as Y5(L) (long isoform) and Y5(S) (short isoform). Y5(L) mRNA differs from Y5(S) mRNA in its 5' end, generating a putative open reading frame with 30 additional nucleotides upstream of the initiator AUG compared with the Y5(S) mRNA. The purpose of the present work was to investigate the existence of the Y5(L) mRNA. The authenticity of this transcript was confirmed by isolating part of its 5' untranslated region through 5' rapid amplification of cDNA ends and analysing its tissue distribution. To study the initiation of translation on Y5(L) mRNA, we cloned the Y5(L) cDNA and two Y5(L) cDNA mutants lacking the first or the second putative initiation start codon. Transient expression of the three plasmids in COS-7 cells and saturation binding experiments using (125)I-labelled polypeptide YY (PYY) as a ligand showed that initiation of translation on Y5(L) mRNA could start at the first AUG, giving rise to a Y5(L) receptor with an N-terminal 10-amino-acid extension when compared with the Y5(S) receptor. The human Y5(L) and Y5(S) receptor isoforms displayed similar affinity constants (1.3 nM and 1.5 nM respectively). [(125)I]PYY binding to COS-7 cells expressing either the Y5(L) or the Y5(S) isoform was inhibited with the same rank order of potency by a selection of six chemically diverse compounds: PYY>neuropeptide Y>pancreatic polypeptide>CGP71683A>Synaptic 34>Banyu 6. Comparison of the tissue distribution of Y5(L) and Y5(S) mRNAs, as determined by reverse transcription-PCR analysis, indicated that expression of Y5(L) mRNA occurs in a tissue-specific manner. Finally, we have shown that the two AUG triplets contained in the 5' untranslated region of Y5(L) mRNA did not affect receptor expression.

Effects of EGIS-7625, a selective and competitive 5-HT2B receptor antagonist.

Our aim was to specify the 5-HT(2) subtype selectivity of EGIS-7625 (1-benzyl-4-[(2-nitro-4-methyl-5-amino)-phenyl]-piperazine), a new 5-HT(2B) ligand, in receptor binding studies and characterize its pharmacology at 5-HT(2A), 5-HT(2B) and 5-HT(2C) receptors in in vivo experiments and in isolated organs, in vitro. EGIS-7625 had high affinity for recombinant human 5-HT(2B) receptors (pK(i) = 9.0) but much weaker affinity for 5-HT(2A) and 5-HT(2C) receptors (pK(i) = 6.2 and 7.7, respectively). In the classic 5-HT(2B) test, EGIS-7625 produced a concentration-related parallel rightward shift in the concentration-response relationship for the 5-HT-induced smooth muscle constriction in rat stomach fundus strips with a pA(2) of 9.4. On the other hand, EGIS-7625 was a weak competitive antagonist at 5-HT(2A) receptors as it shifted 5-HT-induced concentration-response curves to the right at high concentrations (pA(2) = 6.7) in rabbit pulmonary artery strips. The m-chlorophenylpiperazine-induced hypomotility and hypophagia was only partially attenuated by EGIS-7625 even at a dose of 30 mg/kg i.p. while mianserin, a non-selective 5-HT antagonist was almost fully effective in these tests at 3 mg/kg i.p., suggesting weak antagonistic effect of EGIS-7625 at neuronal 5-HT(2C) receptors, in vivo. In conclusion, EGIS-7625 is a potent, selective and competitive 5-HT(2B) antagonist that seems to be a good research tool for the separation of the functional roles of vascular 5-HT(2A) and 5-HT(2B) receptors.

Differential actions of antiparkinson agents at multiple classes of monoaminergic receptor. II. Agonist and antagonist properties at subtypes of dopamine D(2)-like receptor and alpha(1)/alpha(2)-adrenoceptor.

The accompanying multivariate analysis of the binding profiles of antiparkinson agents revealed contrasting patterns of affinities at diverse classes of monoaminergic receptor. Herein, we characterized efficacies at human (h)D(2SHORT(S)), hD(2LONG(L)), hD(3), and hD(4.4) receptors and at halpha(2A)-, halpha(2B)-, halpha(2C)-, and halpha(1A)-adrenoceptors (ARs). As determined by guanosine 5'-O-(3-[(35)S]thio)triphosphate ([(35)S]GTPgammaS) binding, no ligand displayed "full" efficacy relative to dopamine (100%) at all "D(2)-like" sites. However, at hD(2S) receptors quinpirole, pramipexole, ropinirole, quinerolane, pergolide, and cabergoline were as efficacious as dopamine (E(max)100%); TL99, talipexole, and apomorphine were highly efficacious (79-92%); piribedil, lisuride, bromocriptine, and terguride showed intermediate efficacy (40-55%); and roxindole displayed low efficacy (11%). For all drugs, efficacies were lower at hD(2L) receptors, with terguride and roxindole acting as antagonists. At hD(3) receptors, efficacies ranged from 33% (roxindole) to 94% (TL99), whereas, for hD(4) receptors, highest efficacies (approximately 70%) were seen for quinerolane, quinpirole, and TL99, whereas piribedil and terguride behaved as antagonists and bromocriptine was inactive. Although efficacies at hD(2S) versus hD(2L) sites were highly correlated (r = 0.79), they correlated only modestly to hD(3)/hD(4) sites (r = 0.44-0.59). In [(35)S]GTPgammaS studies of halpha(2A)-ARs, TL99 (108%), pramipexole (52%), talipexole (51%), pergolide (31%), apomorphine (16%), and quinerolane (11%) were agonists and ropinirole and roxindole were inactive, whereas piribedil and other agents were antagonists. Similar findings were obtained at halpha(2B)- and halpha(2C)-ARs. Using [(3)H]phosphatidylinositol depletion, roxindole, bromocriptine, lisuride, and terguride displayed potent antagonist properties at halpha(1A)-ARs. In conclusion, antiparkinson agents display diverse agonist and antagonist properties at multiple subtypes of D(2)-like receptor and alpha(1)/alpha(2)-AR, actions, which likely contribute to their contrasting functional profiles.

SVK14 cells express an MCH binding site different from the MCH1 or MCH2 receptor.

Melanin-concentrating hormone (MCH) is a cyclic peptide, mainly involved in the regulation of skin pigmentation in teleosts and feeding behavior in mammals. The human keratinocyte SVK14 cell line has been previously shown to express binding sites for the MCH analog [125I]-[Phe13,3-iodo-Tyr19]MCH. We report here that: (1) this binding site similarly recognized [125I]-[3-iodo-Tyr13]MCH; (2) its pharmacological profile clearly differed from those observed at the two human MCH receptor subtypes, MCH1-R and MCH2-R; (3) MCH did not induce any effect on second messenger systems (including cAMP, calcium, and MAP kinase signaling pathways), and (4) no mRNAs corresponding to the MCH receptors were found. In conclusion, the binding site characterized in the SVK14 cell line is distinct from the MCH1 and MCH2 receptors and deserves therefore further investigation.

Ligand modulation of [35S]GTPgammaS binding at human alpha(2A), alpha(2B) and alpha(2C) adrenoceptors.

Affinities and efficacies of chemically diverse ligands--some of them used as clinical agents--were examined, employing [3H]RX821,002 and [35S]GTPgammaS binding assays, respectively, at human (h) cloned, halpha(2A), halpha(2B) and halpha(2C) adrenoceptors (AR) expressed in Chinese hamster ovary (CHO) cells. As compared to noradrenaline (NA, efficacy defined as 100%), the majority of the 13 agonists tested generally behaved as partial agonists. Amongst 18 antagonists, pK(B) and pK(i) values, which were highly correlated for each alpha(2)-AR subtype, failed to reveal any strikingly selective agents. Inverse agonist properties were not detected for any antagonist, consistent with a lack of constitutive activity suggested by the monophasic inhibition of [35S]GTPgammaS binding by GTPgammaS. These data should facilitate interpretation of experimental and clinical actions of adrenergic agonists. Moreover, they emphasize the continuing need for alpha(2)-AR subtype-selective antagonists in order to define further the roles and therapeutic relevance of halpha(2A)-, halpha(2B)-, and halpha(2C)-AR.

Melanin-concentrating hormone and its receptors: state of the art.

Melanin-concentrating hormone (MCH) is a cyclic neuropeptide of nineteen amino acids in mammals. Its involvement in the feeding behaviour has been well established during the last few years. A first receptor subtype, now termed MCHIR, was discovered in 1999, following the desorphanisation of the SLCI orphan receptor, using either reverse pharmacology or systematic screening of agonist candidates. A second MCH receptor, MCH2R, has been discovered recently, by several groups working on data mining of genomic banks. The molecular pharmacology of these two receptors is only described on the basis of the action of peptides derived from MCH. The present review tentatively summarizes the knowledge on these two receptors and presents the first attempts to discover new classes of antagonists that might have major roles in the control of obesity and feeding behaviour.

Synthesis and structure-affinity-activity relationships of novel benzofuran derivatives as MT(2) melatonin receptor selective ligands.

A series of N-(2-phenylbenzofuran-3-yl) ethyl amide and N-(2-arylalkylbenzofuran-3-yl) ethyl amide derivatives were synthesized and evaluated as melatonin receptor ligands. The affinity of each compound for the two MT(1) and MT(2) melatonin receptor subtypes was determined by binding studies using 2-[(125)I]iodomelatonin on human embryonic kidney cell line HEK293 membrane homogenates. The intrinsic activity of the most interesting compounds was evaluated on the [(35)S]GTPgammaS binding assay. Introduction of a 2-phenyl substituent in the C-2 benzofuran position leads to an agonist compound, 10q, which binds more strongly than melatonin itself to both MT(1) and MT(2) subtypes. On the other hand, a 2-benzyl group in the same position allows MT(2) antagonist selective ligands to be obtained. The MT(2) selectivity and antagonist potency can be modulated with suitable modifications on the N-acyl and benzyl substituents, and the most selective compounds 10c and 19 show affinity ratios of 123 and 192, respectively, and bind to the MT(2) subtype similarly to melatonin itself (0.1 nM). Nevertheless, 10c acts as an MT(1) and MT(2) antagonist, whereas 19 is a partial agonist.