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

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.

A randomized trial of a low-trapping nonselective N-methyl-D-aspartate channel blocker in major depression.

BACKGROUND: The high-affinity N-methyl-D-aspartate (NMDA) antagonist ketamine exerts rapid antidepressant effects but has psychotomimetic properties. AZD6765 is a low-trapping NMDA channel blocker with low rates of associated psychotomimetic effects. This study investigated whether AZD6765 could produce rapid antidepressant effects in subjects with treatment-resistant major depressive disorder (MDD). METHODS: In this double-blind, randomized, crossover, placebo-controlled study, 22 subjects with DSM-IV treatment-resistant MDD received a single infusion of either AZD6765 (150 mg) or placebo on 2 test days 1 week apart. The primary outcome measure was the Montgomery-Åsberg Depression Rating Scale, which was used to rate overall depressive symptoms at baseline and 60, 80, 110, and 230 min postinfusion and on Days 1, 2, 3, and 7 postinfusion. Several secondary outcome measures were also used, including the Hamilton Depression Rating Scale. RESULTS: Within 80 min, Montgomery-Åsberg Depression Rating Scale scores significantly improved in subjects receiving AZD6765 compared with placebo; this improvement remained significant only through 110 min (d = .40). On the Hamilton Depression Rating Scale, a drug difference was found at 80 and 110 min and at Day 2 (d = .49). Overall, 32% of subjects responded to AZD6765, and 15% responded to placebo at some point during the trial. No difference was observed between the groups with regard to psychotomimetic or dissociative adverse effects. CONCLUSIONS: In patients with treatment-resistant MDD, a single intravenous dose of the low-trapping NMDA channel blocker AZD6765 was associated with rapid but short-lived antidepressant effects; no psychotomimetic effects were observed.

Efficacy of a protein kinase C inhibitor (tamoxifen) in the treatment of acute mania: a pilot study.

OBJECTIVES: Considerable preclinical biochemical and behavioral data suggest that protein kinase C inhibition would bring about antimanic effects. Notably, the structurally highly dissimilar antimanic agents lithium and valproate, when administered in therapeutically relevant paradigms, attenuate protein kinase C [corrected] function. There is currently only one relatively selective protein kinase C inhibitor that crosses the blood-brain barrier available for human use--tamoxifen. Our group recently conducted a single-blind study with tamoxifen in acute mania and found that it significantly decreased manic symptoms within a short period of time (3-7 days). In this study, we investigated whether antimanic effects can be achieved with a protein kinase C inhibitor in subjects with mania. METHODS: In a double-blind, placebo-controlled study, 16 subjects with bipolar disorder, manic or mixed, with or without psychotic features, were randomly assigned to receive tamoxifen (20-140 mg/day; n = 8) or placebo (n = 8) for three weeks. Primary efficacy was assessed by the Young Mania Rating Scale. RESULTS: Subjects on tamoxifen showed significant improvement in mania compared to placebo as early as five days, an effect that remained significant throughout the three-week trial. The effect size for the drug difference was very large (d = 1.08, 95% confidence interval 0.45-1.71) after three weeks (p = 0.001). At study endpoint, response rates were 63% for tamoxifen and 13% for placebo (p = 0.12). CONCLUSIONS: Antimanic effects resulted from a protein kinase C inhibitor; onset occurred within five days. Large, controlled studies with selective protein kinase C inhibitors in acute mania are warranted.