A randomized, double-blind, placebo-controlled phase 2 study of the augmentation of a nicotinic acetylcholine receptor partial agonist in depression: is there a relationship to leptin levels?

This randomized, double-blind, placebo-controlled trial evaluated the efficacy of CP-601,927, an α4β2 nicotinic acetylcholine receptor partial agonist and an augmenting agent of antidepressants in major depressive disorder patients with insufficient response to selective serotonin reuptake inhibitors (SSRIs). After open-label treatment with an SSRI for 8 weeks, subjects with a Hamilton Depression Scale 17 score greater than or equal to 16 were entered into a double-blind phase and randomized to CP-601,927 2 mg twice daily or placebo for 6 weeks. The primary end point was the change in Montgomery-Åsberg Depression Rating Scale (MADRS) score from double-blind baseline to week 14. There was no significant difference in change from baseline to week 14 in the MADRS score for CP-610,927 versus placebo (least square mean difference [80% confidence interval], -1.30 [-3.32-0.71]). Post hoc analyses revealed that the drug-placebo difference in change from baseline (SE) to week 14 in MADRS score was greater in subjects with body mass index (BMI) less than or equal to 35 kg/m (-3.43 [1.87], P = 0.069) than those with BMI greater than 35 kg/m (3.37 [2.8], P = 0.230). Analysis of biomarkers associated with increased BMI suggests that baseline leptin had a significant effect on treatment outcome. P values for the effect of treatment on mean change in MADRS score for subjects with baseline leptin levels below and above the median were 0.055 and 0.0055, respectively. CP-601,927 was equivalent to placebo as an augmenting agent of antidepressants in major depressive disorder patients with insufficient response to SSRIs. However, post hoc analyses suggest that BMI, particularly elevated leptin levels, may have affected the response to CP-601,927; however, further study may be needed to confirm these results.