Dihydroxyphenylglycol as a Biomarker of Norepinephrine Transporter Inhibition by Atomoxetine: Human Model to Assess Central and Peripheral Effects of Dosing.

To assess the primary metabolite of norepinephrine, 3,4-dihydroxyphenylglycol (DHPG), as a sensitive biomarker for norepinephrine transporter (NET) function and the relationship of DHPG measured peripherally and centrally, NET was antagonized with 80 mg/d atomoxetine for 18 days. Twelve healthy subjects were treated with atomoxetine in an open-label, multiple-dose exploratory study. Plasma atomoxetine reached steady state by day 6, and the pharmacokinetic results demonstrated availability of atomoxetine to the central nervous system. The cerebrospinal fluid (CSF)/plasma ratios of atomoxetine based on area under concentration-time curve from 0 to 12 hours postdose (AUC0-12), maximum concentration (Cmax), and predose were 0.3%, 0.2%, and 11%, respectively. Plasma from atomoxetine-treated subjects (ex vivo) significantly inhibited radioligand binding to human NET (P < 0.001) only 1 hour after dosing. Plasma DHPG and DHPG/norepinephrine (ratio) during repeated posture tests were reduced significantly (P < 0.001) on day 5 and stayed significantly reduced up to 1 day after treatment. In CSF, both DHPG and the ratio were significantly reduced (P < 0.001) on day 18. Urine results showed significant decreases for both DHPG and the ratio (P = 0.010 to P < 0.001). Brain-derived neurotrophic factor in CSF was lesser than the limits of detection. The findings suggest that NET blockade can be assessed with DHPG concentration or with the ratio in plasma, CSF, and urine. The data suggest that DHPG is a useful biomarker to proactively assess the pharmacological activity of compounds intended to inhibit NET activity within the brain. The study shows that CSF is a medium for early identification and quantification of biomarkers useful in assessing novel neuroscience targets.

A single-dose, 3-way crossover pharmacokinetic comparison between immediate-release oxycodone hydrochloride with aversion technology (IRO-A, Oxecta), IRO-a with Niacin, and Oxycodone Hydrochloride (Roxicodone) in healthy adults under fasting conditions.

Snorting and intravenous use are common routes of administration for advanced opioid abusers. A tablet form of immediate-release oxycodone (IRO) developed using Aversion Technology combines immediate release (IR) oxycodone HCl with inactive functional excipients that are intended to discourage tampering associated with intranasal and intravenous abuse (IRO-A; Oxecta, Pfizer). The purpose of this single-dose, open-label, randomized, 3-period, 3-treatment crossover study was to evaluate the bioequivalence of IRO-A to the marketed immediate-release oxycodone HCl (IRO; Roxicodone, Xanodyne Pharmaceuticals Inc., Newport, KY). IRO-A was also compared with IRO-A with niacin, a product previously developed containing the same functional excipients plus niacin as an aversive agent to discourage oral overconsumption. Healthy adults (N = 40) aged 18-55 years received single 15-mg doses of IRO-A, IRO-A with niacin (60 mg), or IRO after fasting overnight. Naltrexone was administered to diminish opioid effects. Doses were separated by a ≥7-day washout. Plasma samples taken at designated time points were analyzed using liquid chromatography with tandem mass spectrometry. Geometric mean ratios for ln-transformed parameters for IRO-A and IRO were 92%, 104%, and 104% for Cmax, AUClast (AUC is area under the concentration-time curve), and AUCinf; 90% confidence intervals were within the accepted 80%-125% range. IRO-A was also bioequivalent to IRO-A with niacin. Adverse events were mild to moderate in intensity and typical of opioid therapy (nausea, headache, vomiting). Flushing only occurred when the subjects received the IRO-A with niacin treatment (9/37 subjects). The results demonstrated that IRO-A is bioequivalent to IRO and IRO-A with niacin. With features designed to discourage tampering associated with common forms of abuse, IRO-A may provide an alternative to conventional immediate-release oxycodone formulations.

Aldafermin in patients with non-alcoholic steatohepatitis (ALPINE 2/3): a randomised, double-blind, placebo-controlled, phase 2b trial.

BACKGROUND: Non-alcoholic steatohepatitis (NASH) is characterised by hepatic steatosis, inflammation, and injury, and is associated with an increased risk of liver transplantation and death. NASH affects more than 16 million people in the USA, and there is no approved therapy. The aim of this study was to evaluate the safety and efficacy of aldafermin, an engineered analogue of the gut hormone fibroblast growth factor 19 (FGF19). METHODS: In this randomised, double-blind, placebo-controlled, phase 2b study (ALPINE 2/3) in patients with biopsy-confirmed NASH and stage 2 or 3 fibrosis, we randomly assigned patients stratified by fibrosis stage in a 1:1:1:1 ratio to receive placebo, aldafermin 0·3 mg, 1·0 mg, or 3·0 mg once daily for 24 weeks at 30 study sites in the USA. Patients, investigators, the funder, and all other staff, were masked to treatment assignment throughout the study. The primary endpoint was an improvement in liver fibrosis of at least one stage with no worsening of NASH at week 24. Analyses were done by intention-to-treat. This trial is registered with ClinicalTrials.gov, number NCT03912532, and has been completed. FINDINGS: Between May 16, 2019, and Sept 4, 2020, 786 patients were screened, of whom 171 were randomly assigned to a treatment group and included in the intention-to-treat population: 43 in the 0·3 mg aldafermin group, 42 in the 1·0 mg group, 43 in the 3·0 mg group, and 43 in the placebo group. In total, 145 (85%) of patients completed treatment. At week 24, among patients with biopsies at both baseline and week 24, was seven (19%) of 36 patients in the placebo group, 11 (31%) of 36 in the 0·3 mg aldafermin group (difference 90% CI 12% [-9 to 33]; p=0·11), five (15%) of 34 patients in the 1·0 mg group (difference -5% [-24 to 13]; p=0·80), and 11 (30%) of 37 patients in the 3·0 mg group (difference 10% [-9 to 30]; p=0·12) had an improvement in liver fibrosis of at least one stage with no worsening of NASH, without meeting the prespecified significance for dose response (p=0·55). Adverse events were mostly mild or moderate in severity. Diarrhoea occurred in six (14%) of 43 patients in the placebo group, three (7%) of 43 patients in the 0·3 mg aldafermin group, five (12%) of 41 patients in the 1·0 mg group, and ten (23%) of 43 patients in the 3·0 mg group. Incidences of serious adverse events and discontinuations owing to adverse events were similar between groups. INTERPRETATION: Aldafermin was generally well tolerated but did not produce a significant dose response on fibrosis improvement of at least one stage with no worsening of NASH, despite positive effects on a number of secondary endpoints. The findings of this trial may have implications for the design of future NASH trials. FUNDING: NGM Biopharmaceuticals.

Pharmacological manipulation of the RAR/RXR signaling pathway maintains the repopulating capacity of hematopoietic stem cells in culture.

The retinoid X receptor (RXR) contributes to the regulation of diverse biological pathways via its role as a heterodimeric partner of several nuclear receptors. However, RXR has no established role in the regulation of hematopoietic stem cell (HSC) fate. In this study, we sought to determine whether direct modulation of RXR signaling could impact human HSC self-renewal or differentiation. Treatment of human CD34(+)CD38(-)lin(-) cells with LG1506, a selective RXR modulator, inhibited the differentiation of HSCs in culture and maintained long-term repopulating HSCs in culture that were otherwise lost in response to cytokine treatment. Further studies revealed that LG1506 had a distinct mechanism of action in that it facilitated the recruitment of corepressors to the retinoic acid receptor (RAR)/RXR complex at target gene promoters, suggesting that this molecule was functioning as an inverse agonist in the context of this heterodimer. Interestingly, using combinatorial peptide phage display, we identified unique surfaces presented on RXR when occupied by LG1506 and demonstrated that other modulators that exhibited these properties functioned similarly at both a mechanistic and biological level. These data indicate that the RAR/RXR heterodimer is a critical regulator of human HSC differentiation, and pharmacological modulation of RXR signaling prevents the loss of human HSCs that otherwise occurs in short-term culture.

Single-dose administration of MK-0657, an NR2B-selective NMDA antagonist, does not result in clinically meaningful improvement in motor function in patients with moderate Parkinson's disease.

The glutamatergic system is thought to contribute to the motor disturbances observed in Parkinson's disease. Blockade of glutamatergic activity by a selective antagonist of the NR2B subunit of the N-methyl-D-aspartate (NMDA) receptor is associated with improvement in motor symptoms in a preclinical model of Parkinson's disease. A randomized, double-blind, double-dummy, placebo-controlled, 3-period crossover study was conducted in patients with moderate Parkinson's disease to evaluate the pharmacologic activity of MK-0657, an NR2B-selective NMDA receptor antagonist. Patients (n=16) received single oral doses of MK-0657 7 mg, carbidopa/levodopa 25/250 mg (LD) as a positive control, and placebo, after which motor function was serially evaluated by means of the Unified Parkinson's Disease Rating Scale-Motor Examination (UPDRS-ME). LD administration resulted in significant improvement in the UPDRS-ME relative to placebo (P=.025), confirming the sensitivity of the test paradigm; however, the UPDRS-ME change following MK-0657 administration showed no improvement compared with placebo (P=.110) despite exceeding the target MK-0657 plasma concentration of 400 nM. Although the administration of MK-0657 was generally well tolerated, it was associated with increases in systolic and diastolic blood pressure relative to placebo. The results of this study do not support ongoing clinical development of MK-0657 as a novel monotherapy for Parkinson's disease.

LGD-5552, an antiinflammatory glucocorticoid receptor ligand with reduced side effects, in vivo.

Treatment of inflammation is often accomplished through the use of glucocorticoids. However, their use is limited by side effects. We have examined the activity of a novel glucocorticoid receptor ligand that binds the receptor efficiently and strongly represses inflammatory gene expression. This compound has potent antiinflammatory activity in vivo and represses the transcription of the inflammatory cytokine monocyte chemoattractant protein-1 and induces the antiinflammatory cytokine IL-10. The compound demonstrates differential gene regulation, compared with commonly prescribed glucocorticoids, effectively inducing some genes and repressing others in a manner different from the glucocorticoid prednisolone. The separation between the antiinflammatory effects of LGD-5552 and the side effects commonly associated with glucocorticoid treatment suggest that this molecule differs significantly from prednisolone and other steroids and may provide a safer therapeutic window for inflammatory conditions now commonly treated with steroidal glucocorticoids.

Biological characterization of a heterodimer-selective retinoid X receptor modulator: potential benefits for the treatment of type 2 diabetes.

Specific retinoid X receptor (RXR) agonists, such as LG100268 (LG268), and the thiazolidinedione (TZD) PPARgamma agonists, such as rosiglitazone, produce insulin sensitization in rodent models of insulin resistance and type 2 diabetes. In sharp contrast to the TZDs that produce significant increases in body weight gain, RXR agonists reduce body weight gain and food consumption. Unfortunately, RXR agonists also suppress the thyroid hormone axis and generally produce hypertriglyceridemia. Heterodimer-selective RXR modulators have been identified that, in rodents, retain the metabolic benefits of RXR agonists with reduced side effects. These modulators bind specifically to RXR with high affinity and are RXR homodimer partial agonists. Although RXR agonists activate many heterodimer partners, these modulators selectively activate RXR:PPARalpha and RXR:PPARgamma, but not RXR:RARalpha, RXR:LXRalpha, RXR:LXRbeta, or RXR:FXRalpha. We report the in vivo characterization of one RXR modulator, LG101506 (LG1506). In Zucker fatty (fa/fa) rats, LG1506 is a potent insulin sensitizer that also enhances the insulin-sensitizing activities of rosiglitazone. Administration of LG1506 reduces both body weight gain and food consumption and blocks the TZD-induced weight gain when coadministered with rosiglitazone. LG1506 does not significantly suppress the thyroid hormone axis in rats, nor does it elevate triglycerides in Sprague Dawley rats. However, LG1506 produces a unique pattern of triglycerides elevation in Zucker rats. LG1506 elevates high-density lipoprotein cholesterol in humanized apolipoprotein A-1-transgenic mice. Therefore, selective RXR modulators are a promising approach for developing improved therapies for type 2 diabetes, although additional studies are needed to understand the strain-specific effects on triglycerides.

Mechanism of selective retinoid X receptor agonist-induced hypothyroidism in the rat.

The retinoid X receptor (RXR) agonist bexarotene can cause clinically significant hypothyroidism in cutaneous T cell lymphoma patients. The mechanism by which the RXR agonist produces this effect is unclear. We have studied the impact of a selective RXR agonist (rexinoid), LG100268, on rat thyroid axis hormones and show that the acute phase of hypothyroidism is associated with reduced pituitary TSH secretion. A single oral administration of LG100268 to naive Sprague Dawley rats causes a rapid and statistically significant decline in TSH levels (apparent in 0.5-1 h). Total T(4) and T(3) levels decline more gradually, reaching statistical significance 24 h after treatment. Increasing doses of LG100268 produce greater suppression of thyroid axis hormones. To investigate the mechanism(s) mediating this suppression, we determined pituitary TSHbeta mRNA, TSH protein levels, and TRH-stimulated TSH secretion. Two hours after treatment, neither TSHbeta mRNA nor TSH protein levels were altered by LG100268. However, LG100268 treatment reduced the area under the curve for TRH-stimulated TSH secretion by 54%. We have identified an unexpected mechanism by which rexinoids induce hypothyroidism by acutely reducing TSH secretion from the anterior pituitary. This mechanism is independent of the rexinoid's previously demonstrated inhibition of TSHbeta gene transcription.

Activation of the retinoid X receptor suppresses appetite in the rat.

The retinoid X receptor (RXR), a ubiquitously expressed intracellular receptor, regulates pathways controlling glucose, triglycerides, cholesterol, and bile acid metabolism. In addition to its role in those metabolic pathways, we reported that RXR activation with a pan agonist [e.g. LG100268 (LG268)] decreases both body weight gain (BWG) and food consumption (FC) in obese, insulin-resistant rodents. In parallel with those changes in energy balance, we show here that activation of RXR pathways results in adipose tissue remodeling, particularly within sc fat where the rate of apoptosis is increased 5-fold. This change may underlie the selective decrease in fat mass observed in Zucker fatty rats treated with LG268 for 6 wk. Because FC is strongly correlated with BWG in treated animals, we hypothesized that regulation of FC might be the primary mechanism underlying reduced BWG during RXR agonist administration. Importantly, decreased FC is due to decreased meal size, suggestive of induced satiety rather than malaise and/or aversion to food. Furthermore, administration of LG268 directly into the brain via intracerebroventricular injection also reduces FC, BWG, and insulin, whereas the elevation in triglycerides observed after oral administration is absent. The latter observation suggests that RXR actions on energy balance and lipid homeostasis are separable. Therefore, ligand-mediated activation of either an RXR homodimer or an unidentified heterodimeric complex regulates pathways controlling energy balance at least in part via a central nervous system-mediated mechanism.

Design, synthesis, and structure-activity relationship studies of novel 6,7-locked-[7-(2-alkoxy-3,5-dialkylbenzene)-3-methylocta]-2,4,6-trienoic acids.

Retinoid X receptor:peroxisome proliferative-activated receptor (RXR:PPAR) heterodimers play a critical role in the regulation of glucose (RXR/PPARgamma) and lipid metabolism (RXR/PPARalpha). Previously, we described a concise structure-activity relationship study of selective RXR modulators possessing a (2E,4E,6Z)-3-methyl-7-(3,5-dialkyl-6-alkoxyphenyl)-octa-2,4,6-trienoic acid scaffold. These studies were focused on the 2-position alkoxy side chain. We describe here the design and synthesis of a novel series of RXR selective modulators possessing the same aromatic core structure with the addition of a ring locked 6-7-Z-olefin on the trienoic acid moiety. The synthesis and structure-activity relationship studies of these 6,7-locked cyclopentenyl, phenyl, thienyl, furan, and pyridine-trienoic acid derivatives is presented herein.

Similarity of insulin detemir pharmacokinetics, safety, and tolerability profiles in healthy caucasian and Japanese american subjects.

The objective of this study was to compare the pharmacokinetics of insulin detemir in three ascending doses in healthy Japanese and Caucasian subjects. This was an open-label, single-center, parallel-group design evaluating 30 subjects (15 Japanese and 15 Caucasians). Subjects received a total of three subcutaneous injections (one injection per visit) of insulin detemir (0.19, 0.38, 0.75 U/kg [1 U = 24 nmol]) in ascending order. Following drug administration, subjects received intravenous glucose in 0.5-mg/kg/min increments every 30 minutes, followed by a constant rate of 2.0 mg/kg/min for up to 12 hours. For pharmacokinetic evaluations, serial blood sampling was performed over a period of 30 hours after dosing. Of the subjects, 36 were enrolled, and 30 completed the study. There was a linear dose-response relationship between the three ascending insulin detemir doses and serum insulin detemir AUC values for both the Japanese and Caucasian subjects. The two dose-response regression lines had equivalent slopes but slightly different intercepts (although not statistically significant). This difference may be due to variation in AUC, body weight differences, or chance. Six subjects discontinued the study, 2 as a result of adverse events (blood draw-related ecchymosis and hypoglycemia). The most frequent treatment-emergent adverse events (TEAE) were headache, dizziness, and reactions related to blood draws/infusion sites. All TEAEs were mild to moderate in severity. The results show that an increase in insulin detemir dose will result in a similar increase in insulin detemir concentration in the two ethnic groups. Therefore, therapeutic dosing of insulin detemir is expected to be similar in both ethnic groups, with no special dose adjustment or algorithm based on race. Insulin detemir at 0.19, 0.38, and 0.75 U/kg was generally well tolerated in both Japanese and Caucasian subjects.

A randomized, double-blind, placebo-controlled, multicenter, 28-day, polysomnographic study of gabapentin in transient insomnia induced by sleep phase advance.

STUDY OBJECTIVE: To evaluate multiple doses of gabapentin 250 mg on polysomnography (PSG) and participant-reported sleep assessments in a 5-h phase advance insomnia model. METHODS: Adults reporting occasional disturbed sleep received gabapentin 250 mg (n = 128) or placebo (n = 128). On Days 1 and 28, participants received medication 30 min before bedtime and were in bed from 17:00 to 01:00, ∼5 h before their habitual bedtime. Sleep was assessed by PSG, a post sleep questionnaire, and the Karolinska Sleep Diary. Next-day residual effects and tolerability were evaluated. On Days 2-27, participants took medication at home 30 min before their habitual bedtime. RESULTS: Treatment-group demographics were comparable. Gabapentin resulted in significantly less PSG wake after sleep onset (WASO) compared with placebo on Day 1 (primary endpoint, mean: 107.0 versus 149.1 min, p ≤ 0.001) and Day 28 (113.6 versus 152.3 min, p = 0.002), and significantly greater total sleep time (TST; Day 1: 347.6 versus 283.9 min; Day 28: 335.3 versus 289.1 min) (p ≤ 0.001). Participant-reported WASO and TST also showed significant treatment effects on both days. Gabapentin was associated with less %stage1 on Day 1, and greater %REM on Day 28, versus placebo. During home use, gabapentin resulted in significantly less participant-reported WASO and higher ratings of sleep quality. Gabapentin was well tolerated (most common adverse events: headache, somnolence) with no evidence of next-day impairment. CONCLUSION: Gabapentin 250 mg resulted in greater PSG and participant-reported sleep duration following a 5-h phase advance on Day 1 and Day 28 of use without evidence of next-day impairment, and greater sleep duration during at-home use.

Dose proportionality and the effects of food on bioavailability of an immediate-release oxycodone hydrochloride tablet designed to discourage tampering and its relative bioavailability compared with a marketed oxycodone tablet under fed conditions: a single-dose, randomized, open-label, 5-way crossover study in healthy volunteers.

BACKGROUND: An immediate-release oxycodone hydrochloride formulation (IRO-A) indicated for moderate to severe pain was designed (by adding functional excipients) to discourage tampering associated with intranasal and intravenous abuse of prescription opioids. OBJECTIVES: The primary objective of this study was to determine the dose proportionality of oxycodone in IRO-A tablets under fasted conditions. Secondary objectives were to assess food effects on the pharmacokinetics of IRO-A tablets, to compare the relative bioavailability of oxycodone in IRO-A tablets versus marketed oxycodone hydrochloride (IRO) tablets under fed conditions and to evaluate the single-dose safety profile of the IRO-A tablets in healthy volunteers pretreated with naltrexone. METHODS: This open-label, single-dose, randomized, 5-way crossover study was conducted in healthy adults who received each of the following treatments, separated by a washout period of ≥7 days: IRO-A 1 × 5 mg, 2 × 5 mg, and 2 × 7.5 mg under fasted conditions, and IRO-A 2 × 7.5 mg and IRO 1 × 15 mg after a high-fat, high-calorie breakfast. Naltrexone was administered to minimize untoward pharmacologic effects of oxycodone. Dose proportionality (IRO-A), food effects (IRO-A), and relative bioavailability in a fed state (IRO-A and IRO) were assessed by using bioequivalence criteria (90% CIs between 80% and 125% for C(max) and AUC). RESULTS: Of the 35 adults enrolled in the study, 33 completed at least 1 dosing period. Most participants were male (54%) and white (69%), with a mean (SD) age of 32.6 (11.1) years and mean weight of 75.5 (12.3) kg. Plasma levels of oxycodone in IRO-A suggested dose-proportional pharmacokinetics; 90% CIs for dose-normalized C(max), AUC(0-last), and AUC(0-∞) fell within the 80% to 125% range. Concomitant food intake with IRO-A resulted in an ~14% reduction in oxycodone C(max) and an ~21% increase in AUC(0-last). The bioavailability of oxycodone from IRO-A tablets in the fed state was comparable with IRO tablets based on AUC parameters, although C(max) was ~16.5% lower. Reported or observed treatment-emergent adverse events were monitored throughout the study and were similar for IRO-A and IRO tablets. Nausea, headache, abdominal pain, and dizziness were the most common and are consistent with known effects of oxycodone after naltrexone blockade. CONCLUSIONS: Plasma levels of oxycodone in IRO-A tablets were compatible with proportional single-dose pharmacokinetics from 5 to 15 mg under fasted conditions. Administration of IRO-A with food suggested increased overall bioavailability relative to fasting conditions and a reduction in peak systemic exposure of oxycodone that is not expected to be clinically significant. When comparing IRO-A tablets with IRO tablets in the fed state, the overall systemic exposure of oxycodone was comparable, and peak systemic exposure was lower.

RAR and RXR modulation in cancer and metabolic disease.

Retinoic acid receptors (RARs) are ligand-controlled transcription factors that function as heterodimers with retinoid X receptors (RXRs) to regulate cell growth and survival. The success of RAR modulation in the treatment of acute promyelocytic leukaemia (APL) has stimulated considerable interest in the development of RAR and RXR modulators. This has been aided by recent advances in the understanding of the biological role of RARs and RXRs and in the design of selective receptor modulators that might overcome the limitations of current drugs. Here, we discuss the challenges and opportunities for therapeutic strategies based on RXR and RAR modulators, with a focus on cancer and metabolic diseases such as diabetes and obesity.

The effects of supratherapeutic doses of duloxetine on blood pressure and pulse rate.

The effects of supratherapeutic dosages of duloxetine, a serotonin and norepinephrine reuptake inhibitor, on blood pressure and pulse rate were assessed in a multicenter, double-blind, randomized, placebo-controlled, crossover study in 117 healthy women aged 19 to 74 years. Dosages were escalated from 60 mg twice daily (BID) to 200 mg BID over 16 days. Vital signs were monitored at baseline, before morning dosing, and sequentially at steady state. Duloxetine produced increases in supine systolic and diastolic blood pressures, which reached maximums of approximately 12 mm Hg and approximately 7 mm Hg above baseline, respectively, during dosing at 120 mg BID and then stabilized. Supine pulse rate increased gradually with dose, reaching 10 to 12 bpm above baseline after 4 days of dosing at 200 mg BID. Duloxetine caused changes in orthostatic blood pressures and pulse rate that reached plateau values after 3 to 4 days of dosing at 160 mg BID and were generally not associated with subjectively reported orthostatic-related adverse events. All vital signs normalized by 1 to 2 days after study drug discontinuation. Prehypertensive subjects may become hypertensive upon initial duloxetine dosing, but this can be predicted from predose blood pressure. Short-term supratherapeutic duloxetine dosages up to 200 mg BID are not well tolerated but are generally not associated with severe, clinically important adverse events. Overall, the types of adverse events reported in this study were similar to those in other studies of duloxetine in healthy subjects.

QT effects of duloxetine at supratherapeutic doses: a placebo and positive controlled study.

BACKGROUND: The electrophysiological effects of duloxetine at supratherapeutic exposures were evaluated to ensure compliance with regulatory criteria and to assess the QT prolongation potential. METHODS: Electrocardiograms were collected in a multicenter, double-blind, randomized, placebo-controlled, crossover study that enrolled 117 healthy female subjects aged 19 to 74 years. Duloxetine dosages escalated from 60 mg twice daily to 200 mg twice daily; a single moxifloxacin 400 mg dose was used as a positive control. Data were analyzed using 3 QT interval correction methods: mixed-effect analysis of covariance model with RR interval change from baseline as the covariate, the QT Fridericia's correction method, and the individual QT correction method. Concentrations of duloxetine and its 2 major metabolites were measured. RESULTS: Compared with placebo, the mean change from baseline in QTc decreased with duloxetine 200 mg twice daily. The upper limits of the 2-sided 90% confidence intervals for duloxetine vs. placebo were <0 msec at each time point by any correction method. No subject had absolute QT Fridericia's correction values >445 msec with duloxetine, and the change in QT Fridericia's correction from baseline with duloxetine did not exceed 36 msec. No relationship was detected between QTc change and plasma concentrations of duloxetine or its metabolites even though average duloxetine concentrations ranged to more than 5 times those achieved at therapeutic doses. Moxifloxacin significantly prolonged QTc at all time points, regardless of correction method. CONCLUSIONS: Duloxetine does not affect ventricular repolarization as assessed by both mean changes and outliers in QT corrected by any method.

Effects of rexinoids on glucose transport and insulin-mediated signaling in skeletal muscles of diabetic (db/db) mice.

Rexinoids and thiazolidinediones (TZDs) are two classes of nuclear receptor ligands that induce insulin sensitization in diabetic rodents. TZDs are peroxisome proliferator-activated receptor gamma (PPARgamma) activators, whereas rexinoids are selective ligands for the retinoid X receptors (RXRs). Activation of both the insulin receptor substrates (IRSs)/Akt and the c-Cbl-associated protein (CAP)/c-Cbl pathways are important in regulating insulin-stimulated glucose transport. We have compared the effects of a rexinoid (LG268) and a TZD (rosiglitazone) on these two signal pathways in skeletal muscle of diabetic (db/db) mice. The results we have obtained show that treatment of db/db mice with either LG268 or rosiglitazone for 2 weeks results in a significant increase in insulin-stimulated glucose transport activity in skeletal muscle. Treatment with LG268 increases insulin-stimulated IRS-1 tyrosine phosphorylation and Akt phosphorylation in skeletal muscle without affecting the activity of the CAP/c-Cbl pathway. In contrast, rosiglitazone increases the levels of CAP expression and insulin-stimulated c-Cbl phosphorylation without affecting the IRS-1/Akt pathway. The effects of LG268 on the IRS-1/Akt pathway were associated with a decrease in the level of IRS-1 Ser(307) phosphorylation. Taken together, these data suggest that rexinoids improve insulin sensitivity via changes in skeletal muscle metabolism that are distinct from those induced by TZDs. Rexinoids represent a novel class of insulin sensitizers with potential applications in the treatment of insulin resistance.

Rosiglitazone induction of Insig-1 in white adipose tissue reveals a novel interplay of peroxisome proliferator-activated receptor gamma and sterol regulatory element-binding protein in the regulation of adipogenesis.

Insulin-induced gene 1 (INSIG-1) is a key regulator in the processing of the sterol regulatory element-binding proteins (SREBPs). We demonstrated that Insig-1 is regulated by peroxisome proliferator-activated receptor gamma (PPARgamma) providing a link between insulin sensitization/glucose homeostasis and lipid homeostasis. Insig-1 was identified as a PPARgamma target gene using microarray analysis of mRNA from the white adipose tissue of diabetic (db/db) animals treated with PPARgamma agonists. Insig-1 was induced in subcutaneous (9-fold) and epididymal (4-fold) fat pads from db/db mice treated for 8 days with the PPARgamma agonist rosiglitazone (30 mg/kg/day). This in vivo response was confirmed in differentiated C3H10T1/2 adipocytes treated with rosiglitazone. To elucidate the molecular mechanisms regulating INSIG-1 expression, we cloned and characterized the human INSIG-1 promoter. Co-expression of PPARgamma and RXRalpha transactivated the INSIG-1 promoter in the presence of PPARgamma agonists. This induction was attenuated when a dominant negative PPARgamma construct was transfected into cells. Furthermore, a PPARgamma antagonist repressed the transactivation of the INSIG-1 promoter-reporter construct. Truncations of the promoter resulted in the identification of a PPAR response element that mediated the regulation of the promoter. We demonstrated with recombinant proteins that the PPARgamma/RXRalpha heterodimer binds directly to this PPAR response element. In addition to regulation by PPARgamma/RXRalpha, we demonstrated that the INSIG-1 promoter is regulated by transcriptionally active SREBP. The sterol response element was identified 380 base pairs upstream of the transcriptional start site. These findings suggest that the regulation of Insig-1 by PPARgamma agonists could in turn regulate SREBP processing and thus couple insulin sensitizers with the regulation of lipid homeostasis.

Design, synthesis and structure-activity relationship of novel RXR-selective modulators.

The synthesis and in vitro characterization of novel RXR-selective ligands possessing various substituted 1-benzofuran or 1-benzothiophene moieties are described.