Depression
Clinical depression is one of the most common mental illnesses. Between 14 and 21 million US adults suffer from unipolar depression, and as many as two million Americans suffer from bipolar affective disorder. While unipolar depression is treatable, only one-third to one-half of US and European adults with depression seek or receive any form of treatment. Though both psychotherapy and pharmacotherapy are important components of a comprehensive treatment plan, medications are the cornerstone of treatment. Electroconvulsive therapy is considered the most effective therapy for severe depression but is not commonly utilized. Nearly all patients with depression who are diagnosed and treated with pharmacotherapy are initially treated with SSRIs, though tricyclic antidepressants also retain significant use.
Antidepressant sales in the United States exceeded $10 billion in 2001, driven primarily by sales of SSRIs such as Paxil®, Zoloft®, and others. All of the agents currently used to treat depression require several weeks to achieve onset of clinical activity, and have a range of bothersome side effects that limit their tolerability (eg, stimulatory, sexual dysfunction, and antimuscarinic effects). In addition, a variable but significant percentage of patients treated with SSRIs have an inadequate response to therapy.
Agents that provide enhanced efficacy, a rapid onset of clinical antidepressant activity, and/or an improved side effect profile would be viewed as a major medical and commercial opportunity.