In two recent clinical trials that were presented at the annual meeting of the American Psychiatric Association in May 2012, the atypical antipsychotic lurasidone (Latuda), which is currently used to treat schizophrenia, was associated with significant improvement in bipolar depression compared to placebo. The studies, known as PREVAIL (or Program to Evaluate the Antidepressant Impact of Lurasidone), assessed lurasidone’s efficacy as an adjunctive treatment and as a monotherapy.
PREVAIL 1 assessed lurasidone’s efficacy and safety when the drug was added to treatment with lithium or valproate in bipolar patients who became depressed. In this 6-week study, scores on the Montgomery-Asberg Depression Rating Scale (MADRS) improved significantly more in patients taking lurasidone (20 – 120mg/day; N=183) in addition to their mood stabilizer compared to those who received placebo (N=165) in addition to their mood stabilizer.
In PREVAIL 2, patients received lurasidone at either 20-60mg/day (N=166) or 80-120mg/day (N=169) or placebo (N=170) as a monotherapy for bipolar depression. As measured by MADRS scores, lurasidone was significantly more effective in improving bipolar depression than placebo was by the end of the 6-week study period.
In both studies lurasidone showed significant effects on other measures and endpoints including: improvement in Clinical Global Impressions severity of depression (CGI-BP-S) scores, reductions in anxiety symptoms, and improvement in social or occupational functioning. Lurasidone also produced higher rates of response (50% improvement on the MADRS). The CGI-BP-S improved in patients on lurasidone significantly more than in those on placebo as early as week one.
Editor’s Note: These two trials in bipolar depression suggest new possibilities for treating the depressed phase of bipolar disorder.
In studies of patients with schizophrenia, lurasidone has had an excellent safety and tolerability profile; it is relatively weight neutral and does not increase metabolic indices such cholesterol, triglycerides, or blood sugar.
Lurasidone also has an unusual mechanism of action, blocking serotonin 5HT 7 receptors, that may be related to its antidepressant effects. Antagonism of 5HT 7 receptors has been closely linked to antidepressant effects in studies of animal models of depression by two different investigators, Stephen Stahl and Herb Meltzer. It remains to be seen whether this or some other mechanism of lurasidone accounts for its antidepressant effects.
As we have noted before, since all antipsychotic drugs used in the treatment of schizophrenia (which block dopamine D2 receptors) also show efficacy in mania, it is likely that lurasidone will show the same effects. Studies of the drug in mania have not yet been presented. Lurasidone is not yet FDA-approved for bipolar depression, but the PREVAIL studies may be sufficient for an application for FDA approval of lurasidone for this additional indication.
Currently quetiapine (Seroquel) is the only monotherapy approved for bipolar depression. Studies of two other atypical antipsychotics, ziprasidone (Geodon) and aripiprazole (Abilify), failed to show efficacy in bipolar depression when compared with placebo. Ziprasidone’s effects were similar to those of placebo, while aripiprazole showed evidence of significant improvement in the first weeks of treatment compared to placebo, but these failed to last, perhaps because of overly high doses that led to a high drop-out rate.
Antidepressants used for the treatment of unipolar depression are not FDA-approved for bipolar depression and did not appear to be beneficial compared to placebo in recent meta-analyses by Sidor and MacQueen. These antidepressants include the selective serotonin reuptake inhibitors (SSRIs), mixed serotonin and norepinephrine reuptake inhibitors (SNRIs), the dopamine active drug bupropion, and the older tricyclic antidepressants. Not only are these antidepressants not effective in bipolar depression, but some (especially the tricyclics and the SNRIs) appear to increase risk of switching into mania.
None of the mood stabilizers are FDA-approved for bipolar depression; these include lithium, valproate, carbamazepine, and lamotrigine. Thus, quetiapine has had the unique position of being FDA-approved to treat both phases of bipolar disorder—mania and depression—and for prevention of both mania and depression when used as an adjunct to lithium or valproate.
If the lurasidone data lead to FDA approval of this drug as a monotherapy, it will be only the second monotherapy (after quetiapine) approved for bipolar depression. (The combination of olanzapine and fluoxetine is also approved for this indication.) Since bipolar depression can take a serious toll on patients’ health, cognition, and life expectancy, the prospect of having another effective drug for this phase of the illness is especially promising.