Ellis Wilson

Efficacy and tolerability of flexibly-dosed adjunct TC-5214 (dexmecamylamine) in patients with major depressive disorder and inadequate response to prior antidepressant

This paper reports the efficacy and tolerability of the nicotinic channel modulator TC-5214 (dexmecamylamine) as adjunct therapy for patients with major depressive disorder who have an inadequate response to initial antidepressant treatment in 2 Phase III studies. These double-blind, placebo-controlled studies (NCT01157078, D4130C00002 [Study 002] conducted in the US and India; NCT01180400, D4130C00003 [Study 003] conducted in Europe) comprised 8 weeks of open-label antidepressant treatment followed by 8 weeks of active treatment during which patients were randomized to flexibly-dosed TC-5214 1-4 mg twice daily (BID) or placebo as an adjunct to ongoing therapy with SSRI/SNRI. The primary efficacy endpoint in both studies was change in Montgomery Åsberg Depression Rating Scale (MADRS) total score from randomization (week 8) to treatment end (week 16). Secondary endpoints included change in Sheehan Disability Scale and Hamilton Depression Rating Scale 17-item scores. Study 002 randomized 319 patients and Study 003 randomized 295 patients to TC-5214 or placebo. At treatment end, no significant differences were seen for change in MADRS total score with TC-5214 versus placebo. Furthermore, there were no significant differences in any of the secondary endpoints. The most commonly reported (≥ 10%) adverse events with TC-5214 in these studies were constipation and headache. In these 2 flexibly-dosed studies, no specific therapeutic effects were observed for TC-5214 (1-4 mg BID) adjunct to antidepressant in the primary endpoint or any secondary endpoint; however, TC-5214 was generally well tolerated. In conclusion, no antidepressant effect of TC-5214 was observed in these studies.

Medication Nonadherence, "Professional Subjects," and Apparent Placebo Responders: Overlapping Challenges for Medications Development.

Abstract Nonadherence is a major problem in clinical trials of new medications. To evaluate the extent of nonadherence, this study evaluated pharmacokinetic sampling from 1765 subjects receiving active therapy across 8 psychiatric trials conducted between 2001 and 2011. With nonadherence defined as greater than 50% of plasma samples below the limit of quantification for study drug, the percentage of nonadherent subjects ranged from 12.8% to 39.2%. There was a trend toward increased nonadherence in studies with greater numbers of subjects, but an association with nonadherence was not apparent for other study design parameters or subject characteristics. For 2 trials with multiple recruitment sites in geographical proximity, several subjects attempted to simultaneously enroll at separate site locations. The construct of “professional subjects,” those who enroll in trials only for financial gain, is gaining attention, and we therefore modeled the impact of professional subjects on medication efficacy trials. The results indicate that enrollment of professional subjects who are destined to succeed (those who will appear to achieve treatment success regardless of study drug assignment) can substantially increase both the apparent placebo response rate and the sample size requirement for statistical power, while decreasing the observed effect size. The overlapping nature of nonadherence, professional subjects, and placebo response suggests that these issues should be considered and addressed together. Following this approach, we describe a novel clinical trial design to minimize the adverse effects of professional subjects on trial outcomes and discuss methods to monitor adherence.

Two Phase III randomised double-blind studies of fixed-dose TC-5214 (dexmecamylamine) adjunct to ongoing antidepressant therapy in patients with major depressive disorder and an inadequate response to prior antidepressant therapy

Objectives. To evaluate the neuronal nicotinic channel modulator TC-5214 (dexmecamylamine) as adjunct therapy in patients with major depressive disorder (MDD) and inadequate response to prior antidepressant treatment. Methods. Study 004 (D4130C00004) and Study 005 (D4130C00005) comprised an 8-week open-label antidepressant (SSRI/SNRI) treatment period followed by an 8-week randomised, active treatment with twice-daily TC-5214 (0.5, 2 or 4 mg in Study 004; 0.1, 1 or 4 mg in Study 005) or placebo, adjunct to ongoing SSRI/SNRI. Primary efficacy endpoint was change in MADRS total score from randomisation (Week 8) to treatment end (Week 16). Secondary endpoints included MADRS response and remission, and changes in SDS and HAM-D-17-item scores. Safety and tolerability were monitored throughout. Results. Studies 004 and 005 randomised 640 and 696 patients, respectively, to TC-5214 or placebo. No statistically significant improvements in MADRS total score or any secondary endpoints were seen with TC-5214 versus placebo in either study at treatment end. The most commonly reported adverse events (> 10%) with TC-5214 were constipation, dizziness and dry mouth. Conclusions. TC-5214 adjunct to antidepressant was generally well tolerated. However, the studies were not supportive of an antidepressant effect for TC-5214 in patients with MDD and inadequate response to prior antidepressant therapy.

Safety and tolerability of dexmecamylamine (TC-5214) adjunct to ongoing antidepressant therapy in patients with major depressive disorder and an inadequate response to antidepressant therapy: results of a long-term study.

Abstract Safety and tolerability are important considerations when selecting patients’ treatment for major depressive disorder. We report the long-term safety and tolerability of the nicotinic channel modulator dexmecamylamine (TC-5214), adjunct to selective serotonin reuptake inhibitors (SSRIs)/serotonin-norepinephrine reuptake inhibitors (SNRIs) in patients with major depressive disorder and who had an inadequate response to antidepressants. This 52-week, double-blind, placebo-controlled study explored the long-term safety and tolerability of dexmecamylamine. Patients were randomized 3:1 to receive flexibly dosed dexmecamylamine 1 to 4 mg adjunct to SSRI/SNRI or placebo plus SSRI/SNRI. The patient population comprised inadequate responders from 2 Phase III acute dexmecamylamine studies (NCT01157078 [study 002], NCT01153347 [study 004]) and de novo patients who responded inadequately during a 6-week open-label antidepressant treatment period preceding randomization. Safety and tolerability were assessed by monitoring adverse events, vital signs, and physical and laboratory parameters. Descriptive statistical analyses were performed on most efficacy-related end points. Sustained efficacy was analyzed using logistic regression. Overall, 813 patients were randomized (610 received dexmecamylamine, 203 received placebo). In total, 82.4% and 84.6% of patients, respectively, experienced an adverse event. Adverse events occurring more frequently with dexmecamylamine vs placebo were constipation (19.6% vs 6.0%), dizziness (12.0% vs 7.0%), and dry mouth (9.7% vs 5.0%). Back pain (2.8% vs 8.5%), weight increase (4.4% vs 7.0%), and fatigue (5.6 % vs 7.5%) occurred more frequently in placebo-treated patients. No notable differences were observed between dexmecamylamine and placebo for any secondary end point. In this long-term study, safety and tolerability of dexmecamylamine were consistent with that reported in acute Phase III studies of dexmecamylamine.