A Review of the Therapeutic Targeting of SCN9A and Nav1.7 for Pain Relief in Current Human Clinical Trials.

Introduction: There is a great need to find alternative treatments for chronic pain which have become a healthcare problem. We discuss current therapeutic targeting Nav1.7. Areas Covered: Nav1.7 is a sodium ion channel protein that is associated with several human pain genetic syndromes. It has been found that mutations associated with Nav1.7 lead to the loss of the ability to perceive pain in individuals that are otherwise normal. Several therapeutic interventions are presently undergoing preclinical and research using the methodology of damping Nav1.7 expressions as a methodology to decrease the sensation of pain leading to analgesia. Expert Opinion: It is our strong belief that there is a viable future in the targeting of protein of Nav1.7 for the relief of chronic pain in humans. The review will look at the genomics associated with SCN1A and proteomic of Nav1.7 as a foundation to explain the mechanism of the therapeutic interventions targeting Nav1.7, the human disease that are associated with Nav1.7, and the current development of treatment for chronic pain whether in preclinical or clinical trials targeting Nav1.7 expressions. The development of therapeutic antagonists targeting Nav1.7 could be a viable alternative to the current treatments which have led to the opioid crisis. Therefore, Nav1.7 targeted treatment has a major clinical significance that will have positive consequences as it relates to chronic pain interventions.

Effect of LX4211 on glucose homeostasis and body composition in preclinical models.

Treatments that lower blood glucose levels and body weight should benefit patients with type 2 diabetes mellitus (T2DM). We developed LX4211 [(2S,3R,4R,5S,6R)-2-(4-chloro-3-(4-ethoxybenzyl)phenyl)-6-(methylthio)tetrahydro-2H-pyran-3,4,5-triol], an orally available small molecule that decreases postprandial glucose excursions by inhibiting intestinal sodium/glucose cotransporter 1 (SGLT1) and increases urinary glucose excretion (UGE) by inhibiting renal SGLT2. In clinical studies of patients with T2DM, LX4211 appears to act through dual SGLT1/SGLT2 inhibition to improve glycemic control and promote weight loss. Here, we present preclinical studies that explored the ability of LX4211 to improve glycemic control and promote weight loss. We found that 1) LX4211 inhibited in vitro glucose transport mediated by mouse, rat, and dog SGLT1 and SGLT2; 2) a single daily LX4211 dose markedly increased UGE for >24 hours in mice, rats, and dogs; and 3) in the KK.Cg-Ay/J heterozygous (KKA(y)) mouse model of T2DM, LX4211 lowered A1C and postprandial glucose concentrations while increasing postprandial glucagon-like peptide 1 concentrations. Also, long-term LX4211 treatment 1) decreased oral glucose tolerance test (OGTT) glucose excursions, increased OGTT 30-minute insulin concentrations and increased pancreatic insulin content in KKA(y) mice; and 2) decreased weight gain in dogs and rats but not in KKA(y) mice while increasing food consumption in dogs, rats, and KKA(y) mice; in these KKA(y) mice, calories lost through UGE were completely offset by calories gained through hyperphagia. These findings suggest that LX4211 improves glycemic control by dual SGLT1/SGLT2 inhibition in mice as in humans, and that the LX4211-mediated weight loss observed in patients with T2DM may be attenuated by LX4211-mediated hyperphagia in some of these individuals.

Inhibition of sphingosine 1-phosphate lyase for the treatment of rheumatoid arthritis: discovery of (E)-1-(4-((1R,2S,3R)-1,2,3,4-tetrahydroxybutyl)-1H-imidazol-2-yl)ethanone oxime (LX2931) and (1R,2S,3R)-1-(2-(isoxazol-3-yl)-1H-imidazol-4-yl)butane-1,2,3,4-tetraol (LX2932).

Sphingosine 1-phosphate lyase (S1PL) has been characterized as a novel target for the treatment of autoimmune disorders using genetic and pharmacological methods. Medicinal chemistry efforts targeting S1PL by direct in vivo evaluation of synthetic analogues of 2-acetyl-4(5)-(1(R),2(S),3(R),4-tetrahydroxybutyl)-imidazole (THI, 1) led to the discovery of 2 (LX2931) and 4 (LX2932). The immunological phenotypes observed in S1PL deficient mice were recapitulated by oral administration of 2 or 4. Oral dosing of 2 or 4 yielded a dose-dependent decrease in circulating lymphocyte numbers in multiple species and showed a therapeutic effect in rodent models of rheumatoid arthritis (RA). Phase I clinical trials indicated that 2, the first clinically studied inhibitor of S1PL, produced a dose-dependent and reversible reduction of circulating lymphocytes and was well tolerated at dose levels of up to 180 mg daily. Phase II evaluation of 2 in patients with active rheumatoid arthritis is currently underway.

Early toxicology signal generation in the mouse.

The rat has been the preferred rodent toxicology species since before regulatory requirements have been in place, and there exists in the pharmaceutical industry and the regulatory agencies a significant amount of historical data for the rat. The resulting experience base with the rat makes the possibility of replacing it with the mouse for regulated toxicology studies untenable for all but the most extreme circumstances. However, toxicologists are very familiar with the mouse as a model for chronic carcinogenicity studies, and there exist multiple preclinical mouse models of disease. The authors evaluated the use of the mouse for early in vivo toxicology signal generation and prioritization of small molecule lead compounds prior to nomination of a development candidate. In five-day oral gavage studies with three test agents in the mouse, the authors were able to identify the same dose-limiting toxicities as those identified in the rat, including examples of compound-mediated hemolysis as well as microscopic lesions in the alimentary canal, kidney, and pancreas. Performing early signal generation studies in the mouse allows for earlier assessment of the safety liabilities of small molecules, requires significantly less compound, and allows evaluation of more compounds earlier in the project's life cycle.

Discovery and characterization of novel tryptophan hydroxylase inhibitors that selectively inhibit serotonin synthesis in the gastrointestinal tract.

5-Hydroxytryptamine (serotonin) (5-HT) is a neurotransmitter with both central and peripheral functions, including the modulation of mood, appetite, hemodynamics, gastrointestinal (GI) sensation, secretion, and motility. Its synthesis is initiated by the enzyme tryptophan hydroxylase (TPH). Two isoforms of TPH have been discovered: TPH1, primarily expressed in the enterochromaffin cells of the gastrointestinal tract, and TPH2, expressed exclusively in neuronal cells. Mice lacking Tph1 contain little to no 5-HT in the blood and GI tract while maintaining normal levels in the brain. Because GI 5-HT is known to play important roles in normal and pathophysiology, we set out to discover and characterize novel compounds that selectively inhibit biosynthesis of GI 5-HT. Here, we describe two of a series of these inhibitors that are potent for TPH activity both in biochemical and cell-based assays. This class of compounds has unique properties with respect to pharmacokinetic and pharmacodynamic effects on GI serotonin production. Similar to the Tph1 knockout results, these TPH inhibitors have the ability to selectively reduce 5-HT levels in the murine GI tract without affecting brain 5-HT levels. In addition, administration of these compounds in a ferret model of chemotherapy-induced emesis caused modest reductions of intestinal serotonin levels and a decreased emetic response. These findings suggest that GI-specific TPH inhibitors may provide novel treatments for various gastrointestinal disorders associated with dysregulation of the GI serotonergic system, such as chemotherapy-induced emesis and irritable bowel syndrome.

A randomized, placebo-controlled trial of citalopram for the treatment of major depression in children and adolescents.

OBJECTIVE: Open-label trials with the selective serotonin reuptake inhibitor citalopram suggest that this agent is effective and safe for the treatment of depressive symptoms in children and adolescents. The current study investigated the efficacy and safety of citalopram compared with placebo in the treatment of pediatric patients with major depression. METHOD: An 8-week, randomized, double-blind, placebo-controlled study compared the safety and efficacy of citalopram with placebo in the treatment of children (ages 7-11) and adolescents (ages 12-17) with major depressive disorder. Diagnosis was established with the Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version. Patients (N=174) were treated initially with placebo or 20 mg/day of citalopram, with an option to increase the dose to 40 mg/day at week 4 if clinically indicated. The primary outcome measure was score on the Children's Depression Rating Scale-Revised; the response criterion was defined as a score of < or =28. RESULTS: The overall mean citalopram dose was approximately 24 mg/day. Mean Children's Depression Rating Scale-Revised scores decreased significantly more from baseline in the citalopram treatment group than in the placebo treatment group, beginning at week 1 and continuing at every observation point to the end of the study (effect size=2.9). The difference in response rate at week 8 between placebo (24%) and citalopram (36%) also was statistically significant. Citalopram treatment was well tolerated. Rates of discontinuation due to adverse events were comparable in the placebo and citalopram groups (5.9% versus 5.6%, respectively). Rhinitis, nausea, and abdominal pain were the only adverse events to occur with a frequency exceeding 10% in either treatment group. CONCLUSIONS: In this population of children and adolescents, treatment with citalopram reduced depressive symptoms to a significantly greater extent than placebo treatment and was well tolerated.

Naturalistic study of the early psychiatric use of citalopram in the United States.

We obtained information on the efficacy and safety of citalopram in settings that resemble actual clinical practice. A total of 1,783 patients participated in this open, uncontrolled, naturalistic Phase IV evaluation of citalopram at 447 U.S. investigative sites. Participants were selected by guidelines in the citalopram package insert using minimal exclusion criteria. Citalopram dosing began at 20 mg/day and could be titrated to 60 mg/day. Outcomes included the Clinical Global Impressions-Improvement scale (CGI-I) and a Patient Global Evaluation. Separate analyses were performed on patients with a primary diagnosis of major depressive disorder (MDD) (76%) who reported intolerance or nonresponse to previous selective serotonin reuptake inhibitors (SSRIs). Patients included tended to have treatment-resistant or intolerant, chronic or recurrent, comorbid depression with a mean duration of illness of 10 years. At study completion, more than 68% of treatment completers were classified as responders (CGI-I score of 1 or 2). Endpoint analyses showed response rates of 54% in all patients, 56% in patients with MDD, 49% in SSRI nonresponsive patients, and 53% in patients with a history of SSRI intolerance. Nausea (9.8%) and headache (7.3%) were the most often reported adverse events. Patients with a history of SSRI intolerance had a discontinuation rate of 21.8%, whereas those without such a history had a discontinuation rate of 13.3%. Citalopram administered at an average dose of 23.6 mg/day was associated with favorable outcomes and was generally well tolerated.