Zalospirone is a 5-HT1A receptor agonist that can be used to study anxiety disorders and major depressive disorder.

We report here the results of an antidepressant trial with zalospirone, a novel cyclic imide with 5-HT1A partial agonist activity. Two hundred eighty-seven outpatients (mean age 44 years, 55% men, 45% nonfertile women) who met the criteria for unipolar major depression with a minimum 21-item Hamilton Rating Scale for Depression (HAM-D) score of 20 were randomly assigned to receive 6 weeks of double-blind treatment with either placebo or one of three fixed doses of zalospirone (6, 15, or 45 mg/day), administered three times daily. The high dose (45 mg) of zalospirone produced a significant antidepressant effect compared with the placebo from week 2 with mean improvement (change from baseline) in HAM-D total score of 12.8 versus 8.4 (p < 0.05) at week 6. Clinical improvement with the high dose of zalospirone was consistent across all outcome measures, however, only in the observed cases and not the last-observation-carried-forward analyses. Improvement with the 6-mg or 15-mg doses was greater than that with placebo, but not significantly so, suggesting a dose-response effect. Although the 45-mg dose of zalospirone seemed to have significant antidepressant efficacy, it was not well tolerated.[1]