The combination of AstraZeneca’s schizophrenia drug Seroquel and antidepressants seems to be an effective treatment regimen for patients with major depression, according to the results of two new clinical trials.

Seroquel (quetiapine fumarate) is already approved for schizophrenia and bipolar disorder (also known as manic depression), and AstraZeneca has filed for approval to market the drug to treat depressive episodes in the latter indication. But the new data also suggest that the drug could be used as a single-agent therapy in patients with major depressive disorder, adding another potentially lucrative revenue stream for the product, which had sales of $2.8 billion last year.

One study evaluated the use of Seroquel in combination with selective serotonin reuptake inhibitor (SSRI) or serotonin norepinephrine reuptake inhibitor (SNRI) antidepressants to improve residual depressive and anxiety symptoms in patients with major depressive disorder, while the second examined the benefit of adding the drug to antidepressants in patients with treatment-resistant depression. Both were presented at the annual meeting of the American Psychiatric Association yesterday.

"There is growing evidence that augmentation of antidepressant therapy with atypical antipsychotics may help improve symptoms of depression," commented Greg Mattingly of Washington University School of Medicine.

The first study of 58 subjects showed significant reduction in symptoms compared to placebo as early as week one and continuing throughout the eight-week trial, the company said. In the second, 39-patient study, significantly more patients on Seroquel (67%) demonstrated a response to treatment than those on placebo (27%).

"These studies are encouraging and warrant further investigation of the potential of Seroquel both as a monotherapeutic agent as well as in the augmentation of SSRI/SNRI therapy, in patients with major depressive disorder," said Mattingly.