CSTI-300 (SMP-100); a Novel 5-HT3 Receptor Partial Agonist with Potential to Treat Patients with Irritable Bowel Syndrome or Carcinoid Syndrome.

The 5-hydroxytryptamine (5-HT) (serotonin) 5-HT3 receptor represents a clinical target for antagonists to deliver symptomatic relief to patients with diarrhea-predominant irritable bowel syndrome (IBS-d) or carcinoid syndrome. Unfortunately, this pharmacological strategy can present side effects (e.g., severe constipation). The present study investigates the potential of a novel 5-HT3 receptor partial agonist, CSTI-300, to treat patients with IBS-d and other conditions associated with discomfort from colonic distension, with a predicted reduced side-effect profile. The in vitro and in vivo preclinical pharmacology of the drug CSTI-300 was investigated to explore the potential to treat patients with IBS-d. CSTI-300 displayed selective high affinity for the human and rat 5-HT3 receptor (Ki approximately 2.0 nM) and acted as a partial agonist (approximately 30%-50% intrinsic efficacy) in vitro. In an in vivo model of IBS-d, the rat colon distension model, CSTI-300 displayed dose-dependent efficacy. In addition, oral administration of CSTI-300 to dogs that achieved plasma levels of the drug exceeding the Ki value for the 5-HT3 receptor failed to either evoke emesis or alter the state of feces. Pharmacokinetics for CSTI-300 in rat and dog identified high levels of oral availability with t 1/2 range of 1.6-4.4 hours. The preclinical pharmacology of the lead candidate drug, CSTI-300, supports the potential of this novel drug to offer symptomatic relief to patients with irritable bowel syndrome and carcinoid syndrome with a rationale for a reduced "on-target" side-effect profile relative to 5-HT3 receptor antagonists, such as alosetron. SIGNIFICANCE STATEMENT: There is a lack of effective current treatment for diarrhea-predominant irritable bowel syndrome and carcinoid syndrome, and in both conditions, overactivity of the 5-hydroxytryptamine (5-HT) 5-HT3 receptor is thought to be implicated in the pathophysiology. Because 5-HT3 receptor blockade with antagonists results in significant side effects, we present evidence that treatment with a suitable 5-HT3 receptor partial agonist will alleviate some symptoms associated with these conditions yet, without fully inhibiting the receptor, predict a less pronounced side-effect profile associated with this therapeutic strategy.

Systematic Approximations to Susceptible-Infectious-Susceptible Dynamics on Networks.

Network-based infectious disease models have been highly effective in elucidating the role of contact structure in the spread of infection. As such, pair- and neighbourhood-based approximation models have played a key role in linking findings from network simulations to standard (random-mixing) results. Recently, for SIR-type infections (that produce one epidemic in a closed population) on locally tree-like networks, these approximations have been shown to be exact. However, network models are ideally suited for Sexually Transmitted Infections (STIs) due to the greater level of detail available for sexual contact networks, and these diseases often possess SIS-type dynamics. Here, we consider the accuracy of three systematic approximations that can be applied to arbitrary disease dynamics, including SIS behaviour. We focus in particular on low degree networks, in which the small number of neighbours causes build-up of local correlations between the state of adjacent nodes that are challenging to capture. By examining how and when these approximation models converge to simulation results, we generate insights into the role of network structure in the infection dynamics of SIS-type infections.

Ex vivo modelling of PD-1/PD-L1 immune checkpoint blockade under acute, chronic, and exhaustion-like conditions of T-cell stimulation.

Blockade of PD-1/PD-L1 interactions is proving an exciting, durable therapeutic modality in a range of cancers whereby T cells are released from checkpoint inhibition to revive their inherent anti-tumour activity. Here we have studied various ways to model ex vivo T cell function in order to compare the impact of the clinically utilised anti-PD-1 antibody, pembrolizumab (Keytruda) on the activation of human T cells: focussing on the release of pro-inflammatory IFNγ and anti-inflammatory IL-10 to assess functionality. Firstly, we investigated the actions of pembrolizumab in an acute model of T-cell activation with either immature or mature allogeneic dendritic cells (DCs); pembrolizumab enhanced IFNγ and IL-10 release from purified CD4+ T-cells in the majority of donors with a bias towards pro-inflammatory cytokine release. Next, we modelled the impact of pembrolizumab in settings of more chronic T-cell activation. In a 7-day antigen-specific response to EBV peptides, the presence of pembrolizumab resulted in a relatively modest increase in both IFNγ and IL-10 release. Where pembrolizumab was assessed against long-term stimulated CD4+ cells that had up-regulated the exhaustion markers TIM-3 and PD-1, there was a highly effective enhancement of the otherwise exhausted response to allogeneic DCs with respect to IFNγ production. By contrast, the restoration of IL-10 production was considerably more limited. Finally, to assess a direct clinical relevance we investigated the consequence of PD-1/PD-L1 blockade in the disease setting of dissociated cells from lung and colon carcinomas responding to allogeneic DCs: here, pembrolizumab once more enhanced IFNγ production from the majority of tumour preparations whereas, again, the increase in IL-10 release was modest at best. In conclusion, we have shown that the contribution of PD-1-revealed by using a canonical blocking antibody to interrupt its interaction with PD-L1-to the production of an exemplar pro- and anti-inflammatory cytokine, respectively, depends in magnitude and ratio on the particular stimulation setting and activation status of the target T cell. We have identified a number of in vitro assays with response profiles that mimic features of dissociated cell populations from primary tumours thereby indicating these represent disease-relevant functional assays for the screening of immune checkpoint inhibitors in current and future development. Such in vitro assays may also support patient stratification of those likely to respond to immuno-oncology therapies in the wider population.

Recent research on the relative efficiency of speaker and listener instruction for children with autism spectrum disorder.

The traditional recommendation for sequencing speaker and listener instruction has been to teach listener skills prior to teaching speaker skills. In a review of the research literature prior to 2011, Petursdottir and Carr (2011) concluded that research did not support this recommendation. We reviewed the most recent research on the efficiency of skill acquisition during speaker and listener instruction and found similar results to Petursdottir and Carr. Recommendations for future research and practice are provided.

N-glycosylation and expression in human tissues of the orphan GPR61 receptor.

A number of members of the G protein-coupled receptor class of cell surface receptors are 'orphans' with no known endogenous ligand. One of these orphan receptors is GPR61; there are little data about its expression in human cells and tissues. In this study, we investigated the post-translational modification of GPR61 by N-glycosylation at an identified consensus N-glycosylation site (N12) and the impact of this modification upon the subcellular expression of the protein. The N-glycosylation inhibitor tunicamycin reduced the apparent molecular weight of immunoreactivity associated with myc-tagged GPR61 by 1-2 kDa, which was comparable to the evident molecular weight of the myc-tagged N12S GPR61 mutant with disrupted consensus N-glycosylation site. Analysis of GPR61 expression demonstrated that tunicamycin treatment reduced considerably heterologous expression of GPR61 in the cell membrane despite the N12S GPR61 mutant being readily expressed at the cell surface. These results demonstrate that GPR61 is subject to N-glycosylation but suggest this is not a prerequisite for cell surface expression, although N-glycosylation of other proteins may be important for cell membrane expression of GPR61. Expression of GPR61 protein was demonstrated at the cellular level in human hippocampus and human peripheral blood mononuclear cells. In the latter, there was a significantly higher expression of GPR61 in the Th17 cell subset in comparison with resting CD4+ cells, which may point toward a potential role for the GPR61 receptor in autoimmune diseases. This is the first report that GPR61 protein is subject to post-translational modification and is expressed in immune cell subsets and the hippocampus. These findings will help guide studies to investigate the function of GPR61.

The 5-HT2C receptor agonist, lorcaserin, and the 5-HT6 receptor antagonist, SB-742457, promote satiety; a microstructural analysis of feeding behaviour.

RATIONALE: Whilst the FDA-approved anorectic, lorcaserin and various 5-hydroxytryptamine (5-HT)6 receptor antagonists reduce feeding, a direct assessment of their impact upon feeding behaviour is less clear. We therefore examined the action of lorcaserin and the clinical-stage developmental candidate 5-HT6 receptor antagonist, SB-742457, upon microstructural analysis of licking behaviour. Such analysis provides a rich source of information about the mechanisms controlling food intake. OBJECTIVES: The objective of the present study was to gain insight into the influence upon feeding behaviour of the 5-HT2C receptor agonist, lorcaserin and the developmental 5-HT6 receptor antagonist, SB-742457. METHODS: The impact of lorcaserin and SB-742457 upon licking behaviour of non-deprived rats for a glucose solution was assessed using microstructural analysis. RESULTS: Lorcaserin (0.1-3.0 mg/kg) displayed a dose-dependent ability to reduce glucose consumption via reduction in the number of bouts of licking. A similar action was evident with SB-742457, but only at the lowest dose tested (3.0 mg/kg). CONCLUSIONS: The behavioural actions of both lorcaserin and SB-742457 demonstrate they directly promote satiety.

Novel mechanism of modulation at a ligand-gated ion channel; action of 5-Cl-indole at the 5-HT3 A receptor.

BACKGROUND AND PURPOSE: The 5-HT3 receptor is a prototypical member of the Cys-loop ligand-gated ion channel (LGIC) superfamily and an established therapeutic target. In addition to activation via the orthosteric site, receptor function can be modulated by allosteric ligands. We have investigated the pharmacological action of Cl-indole upon the 5-HT3 A receptor and identified that this positive allosteric modulator possesses a novel mechanism of action for LGICs. EXPERIMENTAL APPROACH: The impact of Cl-indole upon the 5-HT3 receptor was assessed using single cell electrophysiological recordings and [3 H]-granisetron binding in HEK293 cells stably expressing the 5-HT3 receptor. KEY RESULTS: Cl-indole failed to evoke 5-HT3 A receptor-mediated responses (up to 30 µM) or display affinity for the [3 H]-granisetron binding site. However, in the presence of Cl-indole, termination of 5-HT application revealed tail currents mediated via the 5-HT3 A receptor that were independent of the preceding 5-HT concentration but were antagonized by the 5-HT3 receptor antagonist, ondansetron. These tail currents were absent in the 5-HT3 AB receptor. Furthermore, the presence of 5-HT revealed a concentration-dependent increase in the affinity of Cl-indole for the orthosteric binding site of the human 5-HT3 A receptor. CONCLUSIONS AND IMPLICATIONS: Cl-indole acts as both an orthosteric agonist and an allosteric modulator, but the presence of an orthosteric agonist (e.g. 5-HT) is a prerequisite to reveal both actions. Precedent for ago-allosteric action is available, yet the essential additional presence of an orthosteric agonist is now reported for the first time. This widening of the pharmacological mechanisms to modulate LGICs may offer further therapeutic opportunities.

Reversal of sibutramine-induced anorexia with a selective 5-HT(2C) receptor antagonist.

RATIONALE: The monoamine reuptake inhibitor sibutramine reduces food intake but the receptor subtypes mediating the effects of sibutramine on feeding remain to be clearly identified. OBJECTIVES: The involvement of the 5-HT(2C) receptor subtype in the satiety-enhancing effects of sibutramine was investigated by examining the effects of co-administration of sibutramine with the selective 5-HT(2C) receptor antagonist SB 242084 METHODS: Microstructural analyses of licking for a glucose solution by non-deprived, male rats were performed over a range of doses of sibutramine to identify a selective satiety-enhancing dose (experiment 1). Similar analyses were performed after administration of a vehicle control, two doses of SB 242084 alone or two doses of SB 242084 in combination with sibutramine (experiment 2). RESULTS: Sibutramine at doses of 1-3 mg/kg selectively reduced glucose consumption via a reduction in the number of bouts of licking. Non-selective effects to increase latency to lick were only observed at the higher dose of 6 mg/kg. Co-administration of sibutramine (3 mg/kg) with SB 242084 (1 or 3 mg/kg) reversed the effect of sibutramine on bout number whereas either dose of SB 242084 alone had no significant effect. CONCLUSIONS: We confirm behaviourally selective effects of sibutramine on feeding and provide further support for the satiety-enhancing effects of sibutramine. Our data also provide evidence for the involvement of the 5-HT(2C) receptor in the satiety-enhancing effects of sibutramine although additional targets may have an impact, and further investigation of the molecular mechanisms underlying the efficacy of sibutramine as an anorectic is warranted.