W. Joseph Herring

Orexin receptor antagonism for treatment of insomnia A randomized clinical trial of suvorexant

ABSTRACT Objective: To assess the utility of orexin receptor antagonism as a novel approach to treating insomnia. Methods: We evaluated suvorexant, an orexin receptor antagonist, for treating patients with primary insomnia in a randomized, double-blind, placebo-controlled, 2-period (4 weeks per period) crossover polysomnography study. Patients received suvorexant (10 mg [n = 62], 20 mg [n = 61], 40 mg [n = 59], or 80 mg [n = 61]) in one period and placebo (n = 249) in the other. Polysomnography was performed on night 1 and at the end of week 4 of each period. The coprimary efficacy end points were sleep efficiency on night 1 and end of week 4. Secondary end points were wake after sleep onset and latency to persistent sleep. Results: Suvorexant showed significant (p values <0.01) dose-related improvements vs placebo on the coprimary end points of sleep efficiency at night 1 and end of week 4. Dose-related effects were also observed for sleep induction (latency to persistent sleep) and maintenance (wake after sleep onset). Suvorexant was generally well tolerated. Conclusions: The data suggest that orexin receptor antagonism offers a novel approach to treating insomnia. Classification of evidence: This study provides Class I evidence that suvorexant improves sleep efficiency over 4 weeks in nonelderly adult patients with primary insomnia.

A Randomized, placebo-controlled, crossover pilot trial of the oral selective NR2B antagonist MK-0657 in patients with treatment-resistant major depressive disorder.

Abstract Converging lines of evidence suggest that the glutamatergic system may play an increasingly important role in the development of novel therapeutics for major depressive disorder (MDD), particularly agents associated with rapid antidepressant effects. Diverse glutamatergic modulators targeting N-methyl-D-aspartate receptors have shown efficacy in MDD, but their associated psychotomimetic effects presently preclude their use in larger samples. This small, randomized, double-blind, placebo-controlled, crossover pilot study evaluated the potential antidepressant efficacy and tolerability of an oral formulation of the selective N-methyl-D-aspartate NR2B antagonist MK-0657 in patients with treatment-resistant MDD (TRD). The TRD subjects underwent a 1-week drug-free period and were subsequently randomized to receive either MK-0657 monotherapy (4–8 mg/d) or placebo for 12 days. Because of recruitment challenges and the discontinuation of the compound’s development by the manufacturer, only 5 of the planned 21 patients completed both periods of the crossover administration of MK-0657 and placebo. Significant antidepressant effects were observed as early as day 5 in patients receiving MK-0657 compared with those receiving placebo, as assessed by the Hamilton Depression Rating Scale and Beck Depression Inventory; however, no improvement was noted when symptoms were assessed with the Montgomery-Asberg Depression Rating Scale, the primary efficacy measure. No serious or dissociative adverse effects were observed in patients receiving this oral formulation of MK-0657. Despite the small sample size, this pilot study suggests that an oral formulation of the NR2B antagonist MK-0657 may have antidepressant properties in TRD patients. Further studies with larger sample sizes are necessary to confirm these preliminary findings.

Suvorexant in Patients With Insomnia: Results From Two 3-Month Randomized Controlled Clinical Trials

BACKGROUND Suvorexant is an orexin receptor antagonist for treatment of insomnia. We report results from two pivotal phase 3 trials. METHODS Two randomized, double-blind, placebo-controlled, parallel-group, 3-month trials in nonelderly (18-64 years) and elderly (≥65 years) patients with insomnia. Suvorexant doses of 40/30 mg (nonelderly/elderly) and 20/15 mg (nonelderly/elderly) were evaluated. The primary focus was 40/30 mg, with fewer patients randomized to 20/15 mg. There was an optional 3-month double-blind extension in trial 1. Each trial included a 1-week, randomized, double-blind run-out after double-blind treatment to assess withdrawal/rebound. Efficacy was assessed at week 1, month 1, and month 3 by patient-reported subjective total sleep time and time to sleep onset and in a subset of patients at night 1, month 1, and month 3 by polysomnography end points of wakefulness after persistent sleep onset and latency to onset of persistent sleep (LPS). One thousand twenty-one patients were randomized in trial 1 and 1019 patients in trial 2. RESULTS Suvorexant 40/30 mg was superior to placebo on all subjective and polysomnography end points at night 1/week 1, month 1, and month 3 in both trials, except for LPS at month 3 in trial 2. Suvorexant 20/15 mg was superior to placebo on subjective total sleep time and wakefulness after persistent sleep onset at night 1/week 1, month 1, and month 3 in both trials and at most individual time points for subjective time to sleep onset and LPS in each trial. Both doses of suvorexant were generally well tolerated, with <5% of patients discontinuing due to adverse events over 3 months. The results did not suggest the emergence of marked rebound or withdrawal signs or symptoms when suvorexant was discontinued. CONCLUSIONS Suvorexant improved sleep onset and maintenance over 3 months of nightly treatment and was generally safe and well tolerated.

Randomized controlled trial of the orexin receptor antagonist filorexant for migraine prophylaxis

Background This study explored whether antagonism of orexin receptors might be an effective mechanism for migraine prevention. Methods We conducted a randomized, double-blind, placebo-controlled, pilot trial. Patients experiencing four to 14 days with migraine during a one-month baseline period were randomized to the orexin receptor antagonist filorexant 10 mg nightly or placebo for three months. Efficacy was assessed by mean monthly migraine days (headache plus at least one associated migraine symptom) and headache days. Safety and tolerability were assessed by adverse event reports and laboratory tests. Results Of 120 patients treated with filorexant and 115 treated with placebo, 97 (81%) and 101 (88%), respectively, completed the trial. There was no statistically significant difference between treatments for change from baseline in mean monthly migraine days (filorexant = −1.7, placebo = −1.3, difference = −0.4 (95% CI: −1.3, 0.4)) or headache days (filorexant = −1.7, placebo = −1.2, difference = −0.5 (95% CI: −1.4, 0.4)). Filorexant was generally well tolerated but was associated with a higher proportion of patients who reported adverse events than placebo (47% vs 37%), particularly somnolence (13% vs 4%). Conclusions These data fail to provide evidence that antagonism of orexin receptors with filorexant, when administered at night, is effective for migraine prophylaxis.

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 Parkinsons 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 Parkinsons disease. A randomized, double‐blind, double‐dummy, placebo‐controlled, 3‐period crossover study was conducted in patients with moderate Parkinsons disease to evaluate the pharmacologic activity of MK‐0657, an NR2B‐selctive 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 Parkinsons 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 Parkinsons disease.

Randomized controlled study of the histamine H3 inverse agonist MK-0249 in adult attention-deficit/hyperactivity disorder.

BACKGROUND It has been suggested that the histamine subtype 3 receptor inverse agonists such as MK-0249 might be effective in treating attention-deficit/hyperactivity disorder (ADHD). We evaluated the effects of MK-0249 in adults with ADHD. METHOD A randomized, double-blind, placebo-controlled, incomplete block, 2-period crossover study of MK-0249 5-10 mg/d and osmotic-release oral system (OROS) methylphenidate 54-72 mg/d (active comparator) was performed in 72 men and women aged ≥ 18 to ≤ 55 years who met DSM-IV criteria for ADHD of either inattentive or combined subtype and who had a chronic course of behavior disorder. The study was conducted from August 2007 through April 2008 at 6 US sites. Primary efficacy was assessed by the mean change from baseline in the Adult ADHD Investigator Symptom Rating Scale (AISRS) total score after 4 weeks of treatment. RESULTS Change from baseline in AISRS at week 4 for MK-0249 was not different from placebo (P = .341), whereas a significant benefit was seen for OROS methylphenidate versus placebo (P < .001). Analysis of secondary end points, including the Conners Adult ADHD Rating Scales, showed results consistent with the AISRS. A similar percentage of patients reported adverse events for MK-0249 compared with placebo (73% versus 69%, respectively). However, a greater percentage of patients reported insomnia as an adverse event with MK-0249 treatment compared with placebo (32% versus 11%, respectively). CONCLUSIONS MK-0249 10 mg/d is not effective for the treatment of adult ADHD. TRIAL REGISTRATION ClinicalTrials.gov identifier: NCT00475735.

Orexin 2 Receptor Antagonism is Sufficient to Promote NREM and REM Sleep from Mouse to Man

Orexin neuropeptides regulate sleep/wake through orexin receptors (OX1R, OX2R); OX2R is the predominant mediator of arousal promotion. The potential for single OX2R antagonism to effectively promote sleep has yet to be demonstrated in humans. MK-1064 is an OX2R-single antagonist. Preclinically, MK-1064 promotes sleep and increases both rapid eye movement (REM) and non-REM (NREM) sleep in rats at OX2R occupancies higher than the range observed for dual orexin receptor antagonists. Similar to dual antagonists, MK-1064 increases NREM and REM sleep in dogs without inducing cataplexy. Two Phase I studies in healthy human subjects evaluated safety, tolerability, pharmacokinetics and sleep-promoting effects of MK-1064, and demonstrated dose-dependent increases in subjective somnolence (via Karolinska Sleepiness Scale and Visual Analogue Scale measures) and sleep (via polysomnography), including increased REM and NREM sleep. Thus, selective OX2R antagonism is sufficient to promote REM and NREM sleep across species, similarly to that seen with dual orexin receptor antagonism.

The Discovery of Suvorexant, the First Orexin Receptor Drug for Insomnia

Historically, pharmacological therapies have used mechanisms such as γ-aminobutyric acid A (GABAA) receptor potentiation to drive sleep through broad suppression of central nervous system activity. With the discovery of orexin signaling loss as the etiology underlying narcolepsy, a disorder associated with hypersomnolence, orexin antagonism emerged as an alternative approach to attenuate orexin-induced wakefulness more selectively. Dual orexin receptor antagonists (DORAs) block the activity of orexin 1 and 2 receptors to both reduce the threshold to transition into sleep and attenuate orexin-mediated arousal. Among DORAs evaluated clinically, suvorexant has pharmacokinetic properties engineered for a plasma half-life appropriate for rapid sleep onset and maintenance at low to moderate doses. Unlike GABAA receptor modulators, DORAs promote both non-rapid eye movement (NREM) and REM sleep, do not disrupt sleep stage-specific quantitative electroencephalogram spectral profiles, and allow somnolence indistinct from normal sleep. The preservation of cognitive performance and the ability to arouse to salient stimuli after DORA administration suggest further advantages over historical therapies.

Electroencephalographic power spectral density profile of the orexin receptor antagonist suvorexant in patients with primary insomnia and healthy subjects

STUDY OBJECTIVES Suvorexant, an orexin receptor antagonist, improves sleep in healthy subjects (HS) and patients with insomnia. We compared the electroencephalographic (EEG) power spectral density (PSD) profile of suvorexant with placebo using data from a phase 2 trial in patients with insomnia. We also compared suvorexants PSD profile with the profiles of other insomnia treatments using data from 3 HS studies. DESIGN Phase 2 trial--randomized, double-blind, two-period (4 w per period) crossover. HS studies--randomized, double-blind, crossover. SETTING Sleep laboratories. PARTICIPANTS Insomnia patients (n = 229) or HS (n = 124). INTERVENTIONS Phase 2 trial--suvorexant 10 mg, 20 mg, 40 mg, 80 mg, placebo; HS study 1--suvorexant 10 mg, 50 mg, placebo; HS study 2--gaboxadol 15 mg, zolpidem 10 mg, placebo; HS study 3--trazodone 150 mg, placebo. MEASUREMENTS AND RESULTS The PSD of the EEG signal at 1-32 Hz of each PSG recording during nonrapid eye movement (NREM) and rapid eye movement (REM) sleep were calculated. The day 1 and day 28 PSD profiles of suvorexant at all four doses during NREM and REM sleep in patients with insomnia were generally flat and close to 1.0 (placebo) at all frequencies. The day 1 PSD profile of suvorexant in HS was similar to that in insomnia patients. In contrast, the other three drugs had distinct PSD profiles in HS that differed from each other. CONCLUSIONS Suvorexant at clinically effective doses had limited effects on power spectral density compared with placebo in healthy subjects and in patients with insomnia, in contrast to the three comparison insomnia treatments. These findings suggest the possibility that antagonism of the orexin pathway might lead to improvements in sleep without major changes in the patients neurophysiology as assessed by electroencephalographic.

Effects of suvorexant on sleep architecture and power spectral profile in patients with insomnia: analysis of pooled phase 3 data

BACKGROUND The orexin receptor antagonist, suvorexant, is approved for treating insomnia at a maximum dose of 20 mg. We evaluated its effects on sleep architecture. METHODS The analyses included pooled polysomnography data from two similar randomized, double-blind, placebo-controlled, 3-month trials evaluating two age-adjusted (non-elderly/elderly) dose regimes of 20/15 mg and 40/30 mg in 1482 patients with insomnia. Polysomnography was recorded at baseline and on three nights during the treatment: Night-1, Month-1, and Month-3. Effects on non-REM sleep stages 1 (N1), 2 (N2), 3 (N3)/slow wave sleep (SWS), and REM sleep were evaluated. A power spectral analysis of non-REM sleep was also performed. RESULTS Suvorexant increased the time (in minutes) spent in all sleep stages compared with placebo. When suvorexant and placebo were compared in terms of changes in percentage of total sleep time spent in each stage, there were small decreases of ≤1%, ≤2.2%, and ≤0.8% for N1, N2, and N3/SWS on average, respectively, and an average increase of ≤3.9% in REM. The largest differences from placebo were observed at Night-1 and generally diminished over time. Suvorexant reduced REM latency (number of non-REM 30-s epochs from lights-off to the first REM epoch) compared with placebo; the reduction was greater at Night-1 (~40-50 non-REM epochs) in comparison to later time points (~12-25 non-REM epochs at Month-3). The spectral analysis of non-REM showed a small decrease in power of 3-6% in the gamma and beta bands, and a small increase of 4-8% in the delta band, at Night-1 for suvorexant relative to placebo; these effects were not apparent at the later Month-1 and Month-3 time points. CONCLUSION Overall sleep architecture appears to be preserved in insomnia patients taking suvorexant. The power spectral profile of suvorexant is generally similar to placebo.