The efficacy of SYMBYAX in acute treatment resistant depression was demonstrated with data from 3 clinical studies (n=579) in adults (18 to 85 years). Doses evaluated in these studies ranged from 6 to 18 mg for olanzapine and 25 to 50 mg for fluoxetine. 

An 8-week randomized, double-blind controlled study was conducted to evaluate the efficacy of SYMBYAX in patients (n=300) who met DSM-IV criteria for Major Depressive Disorder and did not respond to 2 different antidepressants after at least 6 weeks at or above the minimally effective labeled dosage in their current episode. Patients who were not responding to an antidepressant in their current episode entered an 8-week open-label fluoxetine lead-in; non-responders were randomized (1:1:1) to receive SYMBYAX, olanzapine, or fluoxetine, and were treated for 8 weeks. SYMBYAX was flexibly dosed between 6/50 mg, 12/50 mg, and 18/50 mg. Results from this study yielded statistically significant greater reduction in mean total MADRS scores from baseline to endpoint for SYMBYAX versus fluoxetine and olanzapine. See Table 19 (Study 4). A second study with the same treatment-resistant patient population (n=28), when analyzed with change in MADRS as the outcome measure, demonstrated statistically significantly greater reduction in MADRS scores for SYMBYAX versus fluoxetine and olanzapine. See Table 19 (Study 5). A third study demonstrated statistically significantly greater reduction in total MADRS scores for SYMBYAX versus fluoxetine or olanzapine alone, when analyzed in a subpopulation of depressed patients (n=251) who met the definition of treatment resistance (patients who had not responded to 2 antidepressants of adequate dose and duration in the current episode). See Table 19 (Study 6). 

The efficacy of SYMBYAX in the maintenance therapy of treatment-resistant depression was demonstrated in a 47-week study (Study 7) in adults (18 to 65 years). SYMBYAX was dosed between 6/25 mg, 12/25 mg, 6/50 mg, 12/50 mg, and 18/50 mg. 

Patients (N=892) met DSM-IV criteria for Major Depressive Disorder and for treatment-resistant depression (a lack of response to 2 antidepressants after at least 6 weeks at or above the minimally effective labeled dose in their current episode of major depressive disorder). Patients were initially treated with open-label SYMBYAX; those who responded to and were stabilized on treatment over approximately 20 weeks were randomized to continue receiving treatment with SYMBYAX (n=221) or to receive treatment with fluoxetine (n=223) for another 27 weeks. Relapse was assessed using 3 criteria: a 50% increase in Montgomery-Åsberg Depression Rating Scale score from randomization with concomitant Clinical Global Impressions–Severity of Depression score increase to 4 or more; hospitalization due to depression or suicidality; or discontinuation due to lack of efficacy/worsening of depression/suicidality. A total of 15.8% of patients on SYMBYAX and 31.8% of patients on fluoxetine relapsed; this difference was statistically significant. Patients receiving continued SYMBYAX experienced statistically significantly longer time to relapse over the 27 weeks compared with those receiving fluoxetine (Figure 1).  
  


Figure 1 Kaplan-Meier Estimation of Cumulative Proportion of Patients with Relapse (Study 7)