Addition of an NK1 receptor antagonist to an SSRI did not enhance the antidepressant effects of SSRI monotherapy: results from a randomized clinical trial in patients with major depressive disorder.

OBJECTIVE: Aprepitant is a neurokinin 1 receptor antagonist approved for prevention of chemotherapy-induced and post-operative nausea and vomiting. Early studies demonstrated promising antidepressant activity as monotherapy, although this was unsupported by subsequent phase 3 trials. This phase 2 study evaluated whether aprepitant potentiated the antidepressant effects of paroxetine. METHODS: Outpatients with major depressive disorder were randomized to aprepitant 200 mg + paroxetine 20 mg, paroxetine + placebo, or aprepitant + placebo for 6 weeks. The primary endpoint was change in HAMD-17 total score. Secondary/exploratory endpoints included changes in HAMA, CGI-S, CGI-I, and HAMD Item-1 scores at week 6. RESULTS: A total of 79, 78, and 79 patients received aprepitant + paroxetine, paroxetine + placebo, and aprepitant + placebo, respectively. At week 6, mean changes in HAMD-17 were -11.0 (95% confidence interval [CI]: -12.7, -9.4), -11.7 (95% CI: -13.3, -10.0), and -9.5 (95% CI: -10.9, -8.1), respectively. Pairwise comparisons of HAMD-17 change with combination therapy versus paroxetine alone demonstrated no significant difference (p = 0.567). Changes in CGI-S, CGI-I, and HAMD Item-1 scores were also comparable, although there was a greater reduction in anxiety (HAMA) with paroxetine alone than aprepitant + paroxetine (p = 0.045). Adverse events were generally more common with the combination than either monotherapy. CONCLUSION: Concomitant use of aprepitant + paroxetine for 6 weeks did not provide greater antidepressant benefit compared with paroxetine + placebo in patients with major depression.

Is bigger better for depression trials?

OBJECTIVE: A key assumption underlying the principle that power increases with sample size is that the standardized effect size is fixed over time. In therapeutic areas where it may be difficult to continually recruit from a homogeneous population, this assumption may not be valid; patients randomized toward the end of enrollment may derive from a more heterogeneous population and negatively impact the power of a study. Post hoc analyses were performed on clinical data from four phase III depression trials with paroxetine to evaluate this possibility. METHODS: Each study used a randomized, double-blind, placebo-controlled design and enrolled approximately 150 patients per treatment arm. Plots of observed p-values for the treatment difference between paroxetine and placebo (on the HAM-D17 change from baseline score at week 8) by cumulative enrollment were made for each study. RESULTS: As previously reported, three of the four studies showed an overall significant treatment effect and one did not. In each study, a significant treatment effect was observed before approximately 100 patients had been enrolled per treatment arm. Continuing to enroll additional patients did not maintain the achieved level of significance in most instances, and in one case appeared to alter a potentially positive study into a failed study. Plots of p-values versus cumulative enrollment by patient quarters using combined data from all four studies suggested that late-enrolling patients were more likely to be placebo responders than early-enrolling patients. Hypothesized explanations for this finding include a depleted pool of depressed patients and the rush for patient recruitment at the end of a study in order to meet completion timelines. However, no corroborative evidence could be found to support either possibility. CONCLUSIONS: This analysis demonstrates that bigger is not necessarily better for depression trials.

Demonstration of the efficacy and safety of a novel substance P (NK1) receptor antagonist in major depression.

The efficacy and safety of a selective NK(1) antagonist, L-759274, was investigated in outpatients with diagnosis of major depressive disorder with melancholic features, following evidence obtained with the novel compound aprepitant that Substance P (NK(1)) antagonists may provide a unique mechanism of antidepressant activity. A randomized, double-blind placebo-controlled study was carried out. Patients, male or female, aged 18-60, scoring >/=25 points on total of first 17 items of 21-item Hamilton Depression Scale (HAMD), and scoring >/=4 (moderately ill) on Clinical Global Impressions-Severity Scale were randomized to oral L-759274 40 mg daily (n=66) or placebo (n=62) for 6 weeks. For patients receiving L-759274, improvement (mean decrease from baseline) in HAMD-17 total score was 10.7 points, compared with a mean 7.8 point improvement in patients receiving placebo (p<0.009). Mean scores for item 1 of HAMD-17 (depressed mood) also improved to a greater extent in the active group compared with the placebo group (0.3 points, p<0.058). Compared with placebo, mean scores on Clinical Global Impressions-Improvement Scale improved significantly by the end of the trial (p=0.009). L-759274 was generally safe and well-tolerated. The incidence of sexual side effects was on par with that observed in patients receiving placebo, and the incidences of gastrointestinal effects were low. Antidepressant actions have now been observed with two different highly selective NK(1) antagonists (aprepitant and L-759274). NK(1) antagonism is a replicated and generally well-tolerated antidepressant mechanism.