Variation of Diagnostic Approaches and Treatment Practices for Hemophagocytic Lymphohistiocytosis/Macrophage Activation Syndrome Among Pediatric Subspecialists.

OBJECTIVE: To assess the diagnostic and treatment practices among a variety of subspecialists at pediatric institutions in the US. STUDY DESIGN: Using a web-based survey, we assessed the consultation, diagnostic, and treatment preferences of providers from the different pediatric subspecialties who care for pediatric patients with hemophagocytic lymphohistiocytosis (HLH)/macrophage activating syndrome (MAS). Domains included demographics, provider training level and specialty, experience and comfort level with the diagnosis and treatment of HLH/MAS, and institutional approaches toward the diagnosis and management of HLH/MAS. Participants also were given 2 case scenarios: one describing Epstein-Barr virus-associated HLH and another describing an underlying rheumatologic condition with MAS. RESULTS: Of 263 respondents, 23%, 29%, 39%, and 7% identified as hematology/oncology, rheumatology, general pediatrics/critical care/hospitalist, and allergy/immunology, respectively. For Epstein-Barr virus/HLH, hematology/oncology was the preferred first consultant by most respondents other than rheumatologists, of whom only 47% agreed. For MAS, 92% of respondents from all specialties favored a rheumatology consultation. Preferred diagnostic tests varied by subspecialty, with hematology/oncology more likely than rheumatology to order an infectious workup, natural killer cell function, soluble interleukin-2 receptor, bone marrow biopsy, and genetic testing. First-line therapy also varied, with hematology/oncology preferring dexamethasone and etoposide and rheumatology more often preferring methylprednisolone and anakinra. One-half of respondents were unaware of institutional algorithms for diagnosis and treatment of HLH/MAS. Most (85.6%) favored the development of treatment algorithms for HLH/MAS, and 90% supported a multidisciplinary approach. CONCLUSIONS: Current consulting patterns, diagnostic workup, and treatment approaches of HLH/MAS vary by specialty, highlighting the need for standardized management algorithms and institutional multidisciplinary HLH/MAS teams.

Parathyroid hormone (PTH) and PTH-related peptide domains contributing to activation of different PTH receptor-mediated signaling pathways.

Parathyroid hormone (PTH) and parathyroid hormone-related peptide (PTHrP), acting through the osteoblast PTH1 receptor (PTH1R), play important roles in bone remodeling. Intermittent administration of PTH(1-34) (teriparatide) leads to bone formation, whereas continuous administration paradoxically leads to bone resorption. Activation of PTH1R promotes regulation of multiple signaling pathways, including G(s)/cAMP/protein kinase A, G(q)/calcium/protein kinase C, ß-arrestin recruitment, and extracellular signal-related kinase (ERK)1/2 phosphorylation, as well as receptor internalization, but their role in promoting anabolic and catabolic actions of PTH(1-34) are unclear. In the present investigation, a collection of PTH(1-34) and PTHrP(1-34) peptide analogs were evaluated in orthogonal human PTH1R (hPTH1R) functional assays capturing G(s)- and G(q)-signaling, ß-arrestin recruitment, ERK1/2 phosphorylation, and receptor internalization to further define the patterns of PTH1R signaling that they stimulate and further establish peptide domains contributing to agonist activity. Results indicate that both N- and C-terminal domains of PTH and PTHrP are critical for activation of signaling pathways. However, modifications of both regions lead to more substantial decreases in agonist potency and efficacy to stimulate G(q)-signaling, ß-arrestin recruitment, ERK1/2 phosphorylation, and receptor internalization than to stimulate G(s)-signaling. The substantial contribution of the peptide C-terminal domain in activation of hPTH1R signaling suggests a role in positioning of the peptide N-terminal region into the receptor J-domain. Several PTH and PTHrP peptides evaluated in this study promote different patterns of biased agonist signaling and may serve as useful tools to further elucidate therapeutically relevant PTH1R signaling in osteoblasts. With a better understanding of therapeutically relevant signaling, novel biased peptides with desired signaling could be designed for safer and more effective treatment of osteoporosis.

Nelotanserin, a novel selective human 5-hydroxytryptamine2A inverse agonist for the treatment of insomnia.

5-Hydroxytryptamine (5-HT)(2A) receptor inverse agonists are promising therapeutic agents for the treatment of sleep maintenance insomnias. Among these agents is nelotanserin, a potent, selective 5-HT(2A) inverse agonist. Both radioligand binding and functional inositol phosphate accumulation assays suggest that nelotanserin has low nanomolar potency on the 5-HT(2A) receptor with at least 30- and 5000-fold selectivity compared with 5-HT(2C) and 5-HT(2B) receptors, respectively. Nelotanserin dosed orally prevented (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI; 5-HT(2A) agonist)-induced hypolocomotion, increased sleep consolidation, and increased total nonrapid eye movement sleep time and deep sleep, the latter marked by increases in electroencephalogram (EEG) delta power. These effects on rat sleep were maintained after repeated subchronic dosing. In healthy human volunteers, nelotanserin was rapidly absorbed after oral administration and achieved maximum concentrations 1 h later. EEG effects occurred within 2 to 4 h after dosing, and were consistent with vigilance-lowering. A dose response of nelotanserin was assessed in a postnap insomnia model in healthy subjects. All doses (up to 40 mg) of nelotanserin significantly improved measures of sleep consolidation, including decreases in the number of stage shifts, number of awakenings after sleep onset, microarousal index, and number of sleep bouts, concomitant with increases in sleep bout duration. Nelotanserin did not affect total sleep time, or sleep onset latency. Furthermore, subjective pharmacodynamic effects observed the morning after dosing were minimal and had no functional consequences on psychomotor skills or memory. These studies point to an efficacy and safety profile for nelotanserin that might be ideally suited for the treatment of sleep maintenance insomnias.

APD791, 3-methoxy-n-(3-(1-methyl-1h-pyrazol-5-yl)-4-(2-morpholinoethoxy)phenyl)benzamide, a novel 5-hydroxytryptamine 2A receptor antagonist: pharmacological profile, pharmacokinetics, platelet activity and vascular biology.

We have evaluated the receptor pharmacology, antiplatelet activity, and vascular pharmacology of APD791 [3-methoxy-N-(3-(1-methyl-1H-pyrazol-5-yl)-4-(2-morpholinoethoxy)phenyl)benzamide] a novel 5-hydroxytryptamine 2A (5-HT(2A)) receptor antagonist. APD791 displayed high-affinity binding to membranes (K(i) = 4.9 nM) and functional inverse agonism of inositol phosphate accumulation (IC(50) = 5.2 nM) in human embryonic kidney cells stably expressing the human 5-HT(2A) receptor. In competition binding assays, APD791 was greater than 2000-fold selective for the 5-HT(2A) receptor versus 5-HT(2C) and 5-HT(2B) receptors, and was inactive when tested against a wide panel of other G-protein-coupled receptors. APD791 inhibited 5-HT-mediated amplification of ADP-stimulated human and dog platelet aggregation (IC(50) = 8.7 and 23.1 nM, respectively). Similar potency was observed for inhibition of 5-HT-stimulated DNA synthesis in rabbit aortic smooth muscle cells (IC(50) = 13 nM) and 5-HT-mediated vasoconstriction in rabbit aortic rings. Oral administration of APD791 to dogs resulted in acute (1-h) and subchronic (10-day) inhibition of 5-HT-mediated amplification of collagen-stimulated platelet aggregation in whole blood. Two active metabolites, APD791-M1 and APD791-M2, were generated upon incubation of APD791 with human liver microsomes and were also indentified in dogs after oral administration of APD791. The affinity and selectivity profiles of both metabolites were similar to APD791. These results demonstrate that APD791 is an orally available, high-affinity 5-HT(2A) receptor antagonist with potent activity on platelets and vascular smooth muscle.

Solubilized phenyl-pyrazole ureas as potent, selective 5-HT(2A) inverse-agonists and their application as antiplatelet agents.

Potent 5-HT(2A) inverse-agonists containing phenyl-pyrazole ureas with an amino side chain were identified. Optimization of this series resulted in selective compounds that proved effective in modulating 5HT-induced amplification of ADP-stimulated human platelet aggregation.

Pyrimidine-based antagonists of h-MCH-R1 derived from ATC0175: in vitro profiling and in vivo evaluation.

A series of pyrimidine analogues derived from ATC0175 were potent antagonists of human MCH-R1 in vitro. Significantly improved receptor selectivity was achieved with several analogues from this series, but no improvement in brain partitioning was noted. One example from this series was shown to inhibit food intake and decrease body weight in a chronic study. However no clear correlation between the pharmacodynamic effect and the pharmacokinetic data with respect to brain concentration was discernible leading us to conclude that the observed effect was most likely not due to interaction with the MCH-R1.

Lorcaserin, a novel selective human 5-hydroxytryptamine2C agonist: in vitro and in vivo pharmacological characterization.

5-Hydroxytryptamine (5-HT)(2C) receptor agonists hold promise for the treatment of obesity. In this study, we describe the in vitro and in vivo characteristics of lorcaserin [(1R)-8-chloro-2,3,4,5-tetrahydro-1-methyl-1H-3 benzazepine], a selective, high affinity 5-HT(2C) full agonist. Lorcaserin bound to human and rat 5-HT(2C) receptors with high affinity (K(i) = 15 +/- 1 nM, 29 +/- 7 nM, respectively), and it was a full agonist for the human 5-HT(2C) receptor in a functional inositol phosphate accumulation assay, with 18- and 104-fold selectivity over 5-HT(2A) and 5-HT(2B) receptors, respectively. Lorcaserin was also highly selective for human 5-HT(2C) over other human 5-HT receptors (5-HT(1A), 5-HT(3), 5-HT(4C), 5-HT5(5A), 5-HT(6), and 5-HT(7)), in addition to a panel of 67 other G protein-coupled receptors and ion channels. Lorcaserin did not compete for binding of ligands to serotonin, dopamine, and norepinephrine transporters, and it did not alter their function in vitro. Behavioral observations indicated that unlike the 5-HT(2A) agonist (+/-)-1-(2,5-dimethoxy-4-phenyl)-2-aminopropane, lorcaserin did not induce behavioral changes indicative of functional 5-HT(2A) agonist activity. Acutely, lorcaserin reduced food intake in rats, an effect that was reversed by pretreatment with the 5-HT(2C)-selective antagonist 6-chloro-5-methyl-1-[6-(2-methylpyridin-3-yloxy)pyridin-3-yl-carbamoyl]indoline (SB242,084) but not the 5-HT(2A) antagonist (R)-(+)-alpha-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenylethyl)]-4-piperidine-methanol (MDL 100,907), demonstrating mediation by the 5-HT(2C) receptor. Chronic daily treatment with lorcaserin to rats maintained on a high fat diet produced dose-dependent reductions in food intake and body weight gain that were maintained during the 4-week study. Upon discontinuation, body weight returned to control levels. These data demonstrate lorcaserin to be a potent, selective, and efficacious agonist of the 5-HT(2C) receptor, with potential for the treatment of obesity.

Discovery and structure-activity relationship of (1R)-8-chloro-2,3,4,5-tetrahydro-1-methyl-1H-3-benzazepine (Lorcaserin), a selective serotonin 5-HT2C receptor agonist for the treatment of obesity.

The synthesis and SAR of a novel 3-benzazepine series of 5-HT2C agonists is described. Compound 7d (lorcaserin, APD356) was identified as one of the more potent and selective compounds in vitro (pEC50 values in functional assays measuring [(3)H]phosphoinositol turnover: 5-HT2C = 8.1; 5-HT2A = 6.8; 5-HT2B = 6.1) and was potent in an acute in vivo rat food intake model upon oral administration (ED50 at 6 h = 18 mg/kg). Lorcaserin was further characterized in a single-dose pharmacokinetic study in rat (t1/2 = 3.7 h; F = 86%) and a 28-day model of weight gain in growing Sprague-Dawley rat (8.5% decrease in weight gain observed at 36 mg/kg b.i.d.). Lorcaserin was selected for further evaluation in clinical trials for the treatment of obesity.

Anti-thrombotic and vascular effects of AR246686, a novel 5-HT2A receptor antagonist.

We have evaluated the anti-platelet and vascular pharmacology of AR246686, a novel 5-hydroxytryptamine2A (5-HT2A) receptor antagonist. AR246686 displayed high affinity binding to membranes of HEK cells stably expressing recombinant human and rat 5-HT2A receptors (Ki=0.2 nM and 0.4 nM, respectively). Functional antagonism (IC50=1.9 nM) with AR246686 was determined by inhibition of ligand-independent inositol phosphate accumulation in the 5-HT2A stable cell line. We observed 8.7-fold and 1360-fold higher affinity of AR246686 for the 5-HT2A receptor vs. 5-HT2C and 5-HT2B receptors, respectively. AR246686 inhibited 5-HT-induced amplification of ADP-stimulated human platelet aggregation (IC50=21 nM). Similar potency was observed for inhibition of 5-HT stimulated DNA synthesis in rat aortic smooth muscle cells (IC(50)=10 nM) and 5-HT-mediated contraction in rat aortic rings. Effects of AR246686 on arterial thrombosis and bleeding time were studied in a rat model of femoral artery occlusion. Oral dosing of AR246686 to rats resulted in prolongation of time to occlusion at 1 mg/kg, whereas increased bleeding time was observed at a dose of 20 mg/kg. In contrast, both bleeding time and time to occlusion were increased at the same dose (10 mg/kg) of clopidogrel. These results demonstrate that AR246686 is a high affinity 5-HT2A receptor antagonist with potent activity on platelets and vascular smooth muscle. Further, oral administration results in anti-thrombotic effects at doses that are free of significant effects on traumatic bleeding time.

A new family of H3 receptor antagonists based on the natural product Conessine.

A new family of Histamine H(3) receptor antagonists (5a-t) has been prepared based on the structure of the natural product Conessine, a known H(3) antagonist. Several members of the new series are highly potent and selective binders of rat and human H(3) receptors and display inverse agonism at the human H(3) receptor. Compound 5n exhibited promising rat pharmacokinetic properties and demonstrated functional antagonism of the H(3) receptor in an in-vivo pharmacological model.

Novel H3 receptor antagonists with improved pharmacokinetic profiles.

A new series of H(3) antagonists derived from the natural product Conessine are presented. Several compounds from these new series retain the potency and selectivity of earlier diamine based analogs while exhibiting improved PK characteristics. One compound (3u) demonstrated functional antagonism of the H(3) receptor in an in vivo pharmacological model.

A Novel Presentation of Littoral Cell Angioma and Lymphatic Malformations in a Neonate.

This case report describes a novel presentation of littoral cell angioma (LCA) and lymphatic malformations involving the omentum and mesentery. To our knowledge, these 2 entities have not been reported in the same patient. A 1-month term infant male presented with chylous ascites. During his workup, imaging detected splenic nodules. Biopsies revealed that the nodules were LCA and the chylous ascites was secondary to microscopic mesenteric and omental lymphatic malformations. Evaluation for a secondary malignancy, an underlying immunologic defect, and genetic causes were unrevealing. The presence of LCA and lymphatic malformations in the same patient suggests a genetic link between these 2 rare vascular disorders and may help elucidate the etiopathogenesis of these 2 poorly understood anomalies.

Functional assays for screening GPCR targets.

G-protein-coupled receptors (GPCRs) are valuable molecular targets for drug discovery. An important aspect of the early drug discovery process is the design and implementation of high-throughput GPCR functional assays that allow the cost-effective screening of large compound libraries to identify novel drug candidates. Several functional assay kits based on fluorescence and/or chemiluminescence detection are commercially available for convenient screen development, each having advantages and disadvantages. In addition, new GPCR biosensors and high-content imaging technologies have recently been developed that hold promise for the development of functional GPCR screens in living cells.

G protein-coupled receptors as therapeutic targets for obesity and type 2 diabetes.

The prevalence of obesity and type 2 diabetes, two strongly correlated disorders, is increasing worldwide. Weight loss can reduce the risk of developing type 2 diabetes and the pharmacological treatments normally required to manage this disorder. Even though dietary and lifestyle changes may eventually reduce obesity for some individuals, new safe and more efficacious drugs are required for successful weight reduction and treatment of type 2 diabetes in a large proportion of obese individuals. In addition to targeting known G protein-coupled receptors (GPCRs), several orphan GPCRs expressed in central nervous system areas known to regulate feeding may provide new targets for the treatment of obesity. Similarly, the pancreas contains numerous islet GPCRs as well as an abundance of orphan GPCRs that potentially could emerge as targets for future antidiabetic compounds. One of the major challenges facing the pharmaceutical industry is how to rapidly establish the function and therapeutic relevance of orphan GPCRs, some of which may represent novel targets for the discovery of the next generation of drugs to effectively treat obesity and type 2 diabetes. This review will focus on the significant potential of known and orphan GPCRs as targets for the discovery of new drugs to successfully treat these serious disorders.

Orphan GPCR target validation.

Nearly half of the identified non-olfactory G protein-coupled receptors (GPCRs) have no identified cognate ligand. These 'orphan' receptors are likely to have important physiological roles that could potentially be exploited therapeutically. However, by definition, such receptors are not immediately open for pharmacological investigation of their function. Here we summarize several strategic approaches to facilitate the discovery of orphan GPCR biology.

Activation of the insulin-like growth factor-1 receptor induces resistance to epidermal growth factor receptor antagonism in head and neck squamous carcinoma cells.

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) have poor efficacy in head and neck squamous carcinoma cells (HNSCC). Because the IGF-1 receptor (IGF1R) generates potent prosurvival signals and has been implicated in therapeutic resistance, its ability to induce resistance to EGFR-TKIs was studied in vitro. Five HNSCC cell lines showed reduced sensitivity to the EGFR-TKI gefitinib when the IGF1R was activated. In SCC-25 and Cal27 cells, gefitinib inhibited basal and EGF-stimulated EGFR, extracellular signal-regulated kinase (Erk), and Akt phosphorylation and reduced cell number. This correlated with initiation of apoptosis based on a 4-fold increase in PARP cleavage and a 2.5-fold increase in Annexin V positivity. The apoptotic response and reduction in cell number were blocked by IGF1R activation, which resulted in phosphorylation of both Erk and Akt. In both the cell lines, IGF1R-induced Erk, but not Akt, activation was eliminated by gefitinib. IGF1R-induced gefitinib resistance was unaffected by MAP/Erk kinase inhibition with U0126 but was partially impaired by inhibition of phosphoinositide-3-kinase with LY294002. The IGF1R-TKI PQ401 inhibited growth of SCC-25 and Cal27 cells alone and also acted synergistically with gefitinib. Thus, the IGF1R can make HNSCC cells resistant to EGFR-TKI treatment via a prosurvival mechanism. Of the 8 HNSCC tumor samples studied, all samples expressed the IGF1R and 5 showed detectable IGF1R phosphorylation, suggesting that this receptor may be relevant in vivo, and thus, combined EGFR/IGF1R inhibition may be necessary in some patients for effective targeted molecular therapy.

Discovery of 1-[3-(4-bromo-2-methyl-2h-pyrazol-3-yl)-4-methoxyphenyl]-3-(2,4-difluorophenyl)urea (nelotanserin) and related 5-hydroxytryptamine2A inverse agonists for the treatment of insomnia.

Insomnia affects a growing portion of the adult population in the U.S. Most current therapeutic approaches to insomnia primarily address sleep onset latency. Through the 5-hydroxytryptamine(2A) (5-HT(2A)) receptor, serotonin (5-HT) plays a role in the regulation of sleep architecture, and antagonists/inverse-agonists of 5-HT(2A) have been shown to enhance slow wave sleep (SWS). We describe here a series of 5-HT(2A) inverse-agonists that when dosed in rats, both consolidate the stages of NREM sleep, resulting in fewer awakenings, and increase a physiological measure of sleep intensity. These studies resulted in the discovery of 1-[3-(4-bromo-2-methyl-2H-pyrazol-3-yl)-4-methoxyphenyl]-3-(2,4-difluorophenyl)urea (Nelotanserin), a potent inverse-agonist of 5-HT(2A) that was advanced into clinical trials for the treatment of insomnia.

Discovery of the first potent and orally efficacious agonist of the orphan G-protein coupled receptor 119.

GPR119 is a rhodopsin-like GPCR expressed in pancreatic beta-cells and incretin releasing cells in the GI tract. As with incretins, GPR119 increases cAMP levels in these cell types, thus making it a highly attractive potential target for the treatment of diabetes. The discovery of the first reported potent agonist of GPR119, 2-fluoro-4-methanesulfonyl-phenyl)-{6-[4-(3-isopropyl-[1,2,4]oxadiazol-5-yl)-piperidin-1-yl]-5-nitro-pyrimidin-4-yl}-amine (8g, AR231453), is described starting from an initial inverse agonist screening hit. Compound 8g showed in vivo activity in rodents and was active in an oral glucose tolerance test in mice following oral administration.