Research design considerations for chronic pain prevention clinical trials: IMMPACT recommendations.

Although certain risk factors can identify individuals who are most likely to develop chronic pain, few interventions to prevent chronic pain have been identified. To facilitate the identification of preventive interventions, an IMMPACT meeting was convened to discuss research design considerations for clinical trials investigating the prevention of chronic pain. We present general design considerations for prevention trials in populations that are at relatively high risk for developing chronic pain. Specific design considerations included subject identification, timing and duration of treatment, outcomes, timing of assessment, and adjusting for risk factors in the analyses. We provide a detailed examination of 4 models of chronic pain prevention (ie, chronic postsurgical pain, postherpetic neuralgia, chronic low back pain, and painful chemotherapy-induced peripheral neuropathy). The issues discussed can, in many instances, be extrapolated to other chronic pain conditions. These examples were selected because they are representative models of primary and secondary prevention, reflect persistent pain resulting from multiple insults (ie, surgery, viral infection, injury, and toxic or noxious element exposure), and are chronically painful conditions that are treated with a range of interventions. Improvements in the design of chronic pain prevention trials could improve assay sensitivity and thus accelerate the identification of efficacious interventions. Such interventions would have the potential to reduce the prevalence of chronic pain in the population. Additionally, standardization of outcomes in prevention clinical trials will facilitate meta-analyses and systematic reviews and improve detection of preventive strategies emerging from clinical trials.

Quantifying the probability of pharmacological success to inform compound progression decisions.

The Probability of Pharmacology Success, or PoPS, is a powerful metric to inform progression decisions by quantifying a compound's overall pharmacological strength based on its mechanism. It is defined as the probability that X level of pharmacology is achieved in Y proportion of patients at a safe dose. The importance of adequate drug exposure, target engagement and functional pharmacology for enabling a compound's efficacy is widely recognized. The PoPS estimates how well these conditions are met by integrating the compound's pharmacological properties and the target's modulation needs for the intended indication, in a pharmacometric model that includes the knowledge uncertainty. We use examples to illustrate how it can be used to compare drug candidates under specified benefit and risk conditions, support first-in-human decisions based on exposure limits, advise preclinical lead optimisation, and define clinical-trial populations.

Benefit-risk tradeoff preferences for chronic hand eczema treatments.

Hand eczema affects approximately 16% of the US population. The long-term prognosis is poor, and 5-7% experience severe chronic hand eczema (sCHE) that interferes with daily activities. Treatments for CHE may be ineffective or associated with adverse events (AEs) that may dissuade patients from pursuing or continuing treatment. For quantification of patient experiences and benefit-risk preferences for outcomes associated with CHE treatments, a web-based discrete choice experiment survey was administered to patients in the United States with a self-reported physician diagnosis of CHE and severe symptoms not resolved with topical agents. Respondents answered a series of treatment choice questions, each requiring evaluation of a pair of hypothetical profiles of medications for sCHE defined by efficacy and risk of several AEs. Improvement in CHE clearing of 25-50% was rated from 1.5 to 3.1 times as important as eliminating a 5% risk of permanent bone problems. The mean maximum acceptable risk of permanent vision problems in exchange for an improvement in CHE clearing of 25-50% ranged from 3.4% to 4.8%. This study demonstrated that patients with CHE rated efficacy improvements associated with treatment of sCHE as more important than eliminating the risks of specific AEs.

Safety of alitretinoin for severe refractory chronic hand eczema: Clinical studies and postmarketing surveillance.

BACKGROUND: Alitretinoin is approved for the treatment of adults with severe chronic hand eczema (CHE) refractory to potent topical steroids. In the 6 years since launch, approximately 250 000 patients have been treated with alitretinoin. OBJECTIVE: To compare the postmarketing safety surveillance experience of alitretinoin with data from clinical trials and key safety issues with other retinoids. METHODS: An integrated safety analysis of the pivotal studies of alitretinoin and postmarketing adverse event (AE) reports received since approval for alitretinoin were analyzed. RESULTS: In the pivotal trials, headache, erythema, nausea, increased blood triglycerides and increased blood creatinine phosphokinase were the most frequently reported AEs. Headache, hyperlipidemia and nausea were also frequently reported postmarketing AEs, but depression was relatively more frequently reported than in the pivotal trials. Inflammatory bowel disease and benign intracranial hypertension were rare, and very few cases have been reported in postmarketing surveillance. There have been no reports of teratogenicity in humans consequent to fetal exposure. CONCLUSIONS: Safety data collected in pivotal trials and postmarketing surveillance suggest that alitretinoin is well tolerated by patients with CHE with a relatively low incidence of serious reactions. The adverse reaction profile is congruent with reported effects of other marketed oral retinoids.

Research design considerations for chronic pain prevention clinical trials: IMMPACT recommendations.

Although certain risk factors can identify individuals who are most likely to develop chronic pain, few interventions to prevent chronic pain have been identified. To facilitate the identification of preventive interventions, an IMMPACT meeting was convened to discuss research design considerations for clinical trials investigating the prevention of chronic pain. We present general design considerations for prevention trials in populations that are at relatively high risk for developing chronic pain. Specific design considerations included subject identification, timing and duration of treatment, outcomes, timing of assessment, and adjusting for risk factors in the analyses. We provide a detailed examination of 4 models of chronic pain prevention (ie, chronic postsurgical pain, postherpetic neuralgia, chronic low back pain, and painful chemotherapy-induced peripheral neuropathy). The issues discussed can, in many instances, be extrapolated to other chronic pain conditions. These examples were selected because they are representative models of primary and secondary prevention, reflect persistent pain resulting from multiple insults (ie, surgery, viral infection, injury, and toxic or noxious element exposure), and are chronically painful conditions that are treated with a range of interventions. Improvements in the design of chronic pain prevention trials could improve assay sensitivity and thus accelerate the identification of efficacious interventions. Such interventions would have the potential to reduce the prevalence of chronic pain in the population. Additionally, standardization of outcomes in prevention clinical trials will facilitate meta-analyses and systematic reviews and improve detection of preventive strategies emerging from clinical trials.

A phase 3, randomized, double-blind, placebo-controlled study evaluating the efficacy and safety of alitretinoin (BAL4079) in the treatment of severe chronic hand eczema refractory to potent topical corticosteroid therapy.

Severe chronic hand eczema (sCHE) is a persistent, disfiguring disease that responds poorly to conventional treatment and causes substantial physical and psychological disability. The objective of this study was to evaluate efficacy and safety of oral alitretinoin in sCHE in a Phase 3, multicenter, randomized, double-blind, placebo-controlled, parallel-group study comparing alitretinoin with placebo. Efficacy was assessed every 4 weeks during treatment and 4 weeks after end of treatment (EOT, 24 weeks); responders were assessed every 4 weeks for a further 48 weeks after EOT. The study was conducted at academic and private dermatology centers. The participants were 596 patients with sCHE refractory to potent topical corticosteroids. Patients were treated with daily oral alitretinoin 30 mg or placebo for up to 24 weeks. Primary endpoint was proportion of responding patients based on Physician Global Assessment (PGA) of "clear" or "almost clear" at EOT. Key secondary endpoints: Patient Global Assessment (PaGA), change in modified Total Lesion Symptom Score (mTLSS), time to response (TTR), extent of disease at EOT, and duration of response (DOR). At EOT, 40% of alitretinoin-treated patients were responders vs 15% placebo-treated patients (odds ratio [OR] = 3.78; P < .001); a greater proportion of alitretinoin-treated patients achieved a PaGA of "cleared" or "almost cleared" (OR = 4.05; P< .001). A greater decrease in mTLSS occurred from baseline to EOT in alitretinoin- vs placebo-treated patients (treatment difference -24% P< .001). Median TTR for responders at EOT was shorter with alitretinoin vs placebo (65 vs 117 days; P< .001). Greater decreases in extent of disease at EOT were observed with alitretinoin vs placebo (treatment difference -22%; P< .001). The most common treatment-emergent adverse event was headache. Alitretinoin significantly improved signs/symptoms of sCHE, was well tolerated in patients refractory to potent topical corticosteroids, and may provide benefit to this population.

A phase 2a, randomized, crossover trial of gabapentin enacarbil for the treatment of postherpetic neuralgia in gabapentin inadequate responders.

OBJECTIVE: To compare the efficacy of high-dose (3,600 mg/day) vs low-dose (1,200 mg/day) oral gabapentin enacarbil (GEn) on pain intensity in adults with postherpetic neuralgia (PHN) and a history of inadequate response to ≥1,800 mg/day gabapentin. DESIGN: Multicenter, randomized, double-blind, crossover study (NCT00617461). SETTING: Thirty-five outpatient centers in Germany and the United States. SUBJECTS: Subjects aged ≥18 years with a diagnosis of PHN. METHODS: During a 2-week baseline period, subjects received open-label treatment with 1,800 mg/day gabapentin. Subjects who had a mean 24-hour average pain intensity score ≥4 during the last 7 days of the baseline period were randomized to receive GEn (1,200 or 3,600 mg/day) for treatment period 1 (28 days), followed by GEn 2,400 mg/day (4 days), and the alternate GEn dose for treatment period 2 (28 days). RESULTS: There was a modest but significant improvement in pain intensity scores with GEn 3,600 mg vs 1,200 mg (adjusted mean [90% confidence interval] treatment difference, -0.29 [-0.48 to -0.10]; P = 0.013). The difference in efficacy between doses was observed primarily in subjects who received the higher dose during treatment period 2; certain aspects of the study design may have contributed to this outcome. Plasma steady-state gabapentin exposure during GEn treatment was as expected and consistent between treatment periods. No new safety signals or adverse event trends relating to GEn exposure were identified. CONCLUSIONS: While the overall results demonstrated efficacy in a PHN population, the differences between treatment periods confound the interpretation. These findings could provide insight into future trial designs.

A randomized, double-blind, placebo-controlled trial to assess the efficacy and safety of gabapentin enacarbil in subjects with neuropathic pain associated with postherpetic neuralgia (PXN110748).

UNLABELLED: Gabapentin enacarbil (GEn) is an actively transported prodrug of gabapentin that provides sustained, dose-proportional exposure to gabapentin. This randomized, double-blind, parallel-group, placebo-controlled study evaluated the safety and efficacy of 3 different maintenance doses of oral GEn in subjects with postherpetic neuralgia. Adults with a 24-hour average pain intensity score of ≥4.0 received GEn 1,200 mg, 2,400 mg, 3,600 mg, or placebo for 14 weeks (including a 1-week up-titration, 12-week maintenance, and 1-week taper). The primary endpoint was change from baseline to end of maintenance treatment in mean 24-hour average pain intensity score. The intent-to-treat population consisted of 371 subjects (GEn 1,200 mg = 107, 2,400 mg = 82, 3,600 mg = 87, placebo = 95). With regard to the primary endpoint, all 3 GEn treatment groups demonstrated a statistically significant difference relative to placebo. The adjusted mean change from baseline for the treatment groups ranged from -2.36 to -2.72 versus -1.66 for the placebo group. Exposure-response modeling suggested an ED50 around 1,200 mg/day, which was consistent with historical findings reported for gabapentin. The most commonly reported adverse events were dizziness and somnolence. All studied doses of GEn significantly improved pain associated with postherpetic neuralgia as compared to placebo and were well tolerated. PERSPECTIVE: GEn provides clinically important pain relief with doses from 1,200 mg to 3,600 mg and is generally well tolerated and efficacious. As an actively transported prodrug of gabapentin, it provides dose-proportional and extended exposure to gabapentin.

A randomized, controlled trial of gabapentin enacarbil in subjects with neuropathic pain associated with diabetic peripheral neuropathy.

BACKGROUND: Gabapentin enacarbil (GEn), a transported prodrug of gabapentin, provides sustained, dose-proportional gabapentin exposure. The purpose of this study was to investigate the dose response of GEn to select the optimal dose(s) for clinical use in subsequent diabetic peripheral neuropathy (DPN) trials. METHODS: This was a multicenter, randomized, double-blind, double-dummy, parallel group, placebo-controlled trial with a study duration of approximately 20 weeks (Clinicaltrials.gov database, Identifier ! NCT00643760). Pregabalin (PGB) (Lyrica(®) ; Pfizer Inc.) was used as an active control to provide assay sensitivity of the trial. A total of 421 adult subjects with DPN were randomized in a ratio of 2:1:1:1:2 to receive oral GEn 3,600 mg/day, GEn 2,400 mg/day, GEn 1,200 mg/day, PGB 300 mg/day, or matching placebo, respectively. The primary efficacy endpoint was change from baseline to end of maintenance treatment with respect to the mean 24-hour average pain intensity score based on an 11-point Pain Intensity Numerical Rating Scale (PI-NRS). Safety and tolerability assessments included treatment-emergent adverse events (TEAEs), laboratory evaluations, vital signs, electrocardiograms (ECG), neurological examination, and pedal edema. RESULTS: The adjusted mean difference vs. placebo at the end of maintenance treatment with respect to the mean 24-hour average PI-NRS pain intensity score for GEn 1,200 mg (-0.35; [95% CI: -1.02, 0.31]; P = 0.295), GEn 2,400 mg (-0.02; [95% CI: -0.71, 0.66]; P = 0.946), and GEn 3,600 mg (-0.55; [95% CI: -1.10, 0.01]; P = 0.105) was not statistically significant. The active control, PGB (300 mg/day), did not differentiate from placebo. CONCLUSION: Overall, none of the GEn treatment groups differentiated from placebo. Analyses of the secondary endpoints showed comparable results across treatment groups. However, the majority of the endpoints, including all of the pain endpoints, showed the largest numerical treatment difference was between GEn 3,600 mg and placebo. The active control, PGB (300 mg/day), did not differentiate from placebo.

Firategrast for relapsing remitting multiple sclerosis: a phase 2, randomised, double-blind, placebo-controlled trial.

BACKGROUND: Monoclonal antibody therapy against α4ß-integrin is efficacious in patients with multiple sclerosis (MS) with some safety concerns. We assessed the safety and efficacy of firategrast, a small oral anti-α4ß-integrin molecule, in patients with relapsing remitting MS. METHODS: We did a multicentre, phase 2, randomised, double-blind, placebo-controlled, dose-ranging study in participants with clinically definite relapsing-remitting MS. A 24-week treatment period was followed by 12 weeks of core follow-up and 40 weeks of extended follow-up. Participants were randomly assigned, via computer-generated block randomisation in a 1:2:2:2 ratio, to receive one of four treatments twice a day: firategrast 150 mg, firategrast 600 mg, or firategrast 900 mg (women) or 1200 mg (men), or placebo. Brain scans were obtained at 4-week intervals to the end of core follow-up. The primary outcome was cumulative number of new gadolinium-enhancing brain lesions during the treatment phase and was analysed using a generalised linear model with an underlying negative binomial distribution, adjusted for sex, baseline number of new gadolinium-enhancing lesions, and country. This study is registered with ClinicalTrials.gov, NCT00395317. FINDINGS: Of 343 individuals enrolled, 49 received firategrast 150 mg, 95 received firategrast 600 mg, 100 received firategrast 900 mg or 1200 mg, and 99 received placebo. A 49% reduction (95% CI 21·2-67·6; p=0·0026) in the cumulative number of new gadolinium-enhancing lesions was seen for the 900 mg or 1200 mg firategrast group (n=92, mean number of lesions 2·69 [SE 1·18]) versus the placebo group (90, 5·31 [1·18]). In the 600 mg group (86, 4·12 [SE 1·19]), a non-significant 22% reduction (95% CI -21·3 to 49·7; p=0·2657) occurred in mean number of new gadolinium-enhanced lesions relative to placebo; for the 150 mg group (47, 9·51 [SE 1·24]), a 79% increase (95% CI 4·1-308·1; p=0·0353) occurred relative to placebo. Firategrast was generally well tolerated at all doses. The frequency of all adverse events was similar across all treatment groups except for an increased rate of urinary tract infections in the high-dose firategrast group. No cases of progressive multifocal leukoencephalopathy or evidence of reactivation of JC virus were identified. INTERPRETATION: This study showed efficacy on imaging endpoints for firategrast at the highest dose tested, and suggests that further investigation of oral short-acting α4ß integrin blockade therapies is warranted. FUNDING: GlaxoSmithKline.

Efficacy, safety, and tolerability of a triple reuptake inhibitor GSK372475 in the treatment of patients with major depressive disorder: two randomized, placebo- and active-controlled clinical trials.

GSK372475 is a triple reuptake inhibitor with approximately equipotent inhibition of serotonin, norepinephrine, and dopamine transporters. Two randomized, placebo- and active-controlled, double-blind studies examined the efficacy and safety of GSK372475 in outpatients (aged 18-64 years) with a diagnosis of major depressive episode associated with major depressive disorder (MDD). Patients were randomized 1:1:1 to placebo, GSK372475 (1-2 mg/d), or active control (Study 1: venlafaxine XR 150-225 mg/d; Study 2: paroxetine 20-30 mg/d). GSK372475 did not significantly differ from placebo on any of the key efficacy endpoints (six-item Bech scale, IDS-Clinician Rated, MADRS) in either study. Both active controls demonstrated significant antidepressant activity compared with placebo on both primary and secondary endpoints. The most common adverse effects (AEs) with GSK372475 were dry mouth, headache, insomnia, and nausea. AEs were more frequent for GSK372475 versus placebo for sleep, anxiety-related, gastrointestinal, and tachycardia events. Increases in mean change from baseline in heart rate and sitting blood pressure were greater for GSK372475 than observed for either placebo or active control groups. Completion rates were lower for GSK372475 (49%, 58%) compared with placebo (67%, 74%), venlafaxine XR (63%), or paroxetine (77%). GSK372475 was neither efficacious nor well tolerated in patients with MDD in two 10-week studies.

A randomized controlled trial of a novel mixed monoamine reuptake inhibitor in adults with ADHD.

BACKGROUND: NS2359 is a potent reuptake blocker of noradrenalin, dopamine, and serotonin. The aim of the study was to investigate the efficacy, safety and cognitive function of NS2359 in adults with a DSM IV diagnosis of ADHD. METHODS: The study was a multi-centre, double-blind, randomized placebo-controlled, parallel group design in outpatient adults (18-55 years) testing 0.5 mg NS2359 vs. placebo for 8 weeks. Multiple assessments including computerized neuropsychological evaluation were performed. RESULTS: There was no significant difference between NS2359 (n = 63) versus placebo (n = 63) on the primary outcome measure reduction in investigator rated ADHD-RS total score (7.8 versus 6.4; p < 0.45). However, in subjects with the inattentive subtype, there were significantly more responders in the NS2359 group compared to placebo (41% versus 7%; p < 0.01). For all secondary variables (ADHD-RS patient rated; The Conners Adult ADHD Scale; The Brown Adult Scale, and CGI-improvement scale) there were no significant differences between the two groups; however, in the inattentive subgroup, the response to treatment was significantly larger than to placebo. NS2359 improved composite factor scores of attention, episodic- and working memory. No serious adverse events were reported with insomnia, headaches and loss of appetite most commonly reported as side effects. CONCLUSION: No overall effect of NS2359 was found on overall symptoms of ADHD. There was also a modest signal of improvement in the inattentive adults with ADHD and cognition warranting further exploration using differing doses.