Study to Evaluate the Efficacy and Safety of Adjunctive Pimavanserin in Major Depressive Disorder (CLARITY)

Inclusion Criteria:

1. Adult patients, aged 18 years and above

2. A clinical diagnosis of major depressive disorder (MDD)

3. Is being treated with one of the following SSRI or SNRI antidepressants as
monotherapy:

- Citalopram

- Escitalopram

- Paroxetine

- Fluoxetine

- Sertraline

- Duloxetine

- Venlafaxine

- Desvenlafaxine

- Venlafaxine XR

4. Has a history of inadequate response to antidepressant treatments

Exclusion Criteria:

1. Patient has a psychotic disorder other than MDD

2. Patient has current evidence of a serious and/or unstable neurologic, cardiovascular,
respiratory, gastrointestinal, renal, hepatic, hematologic, or other medical disorder,
including cancer or malignancies, which would affect the patient's ability to
participate in the program

3. Patient has a history or symptoms of long QT syndrome

Patients will be evaluated at screening to ensure that all criteria for study participation
are met. Patients may be excluded from the study based on these assessments (and
specifically if it is determined that their baseline health and psychiatric condition do
not meet all pre-specified entry criteria).