Pimavanserin – Major Depressive Disorder


Pimavanserin is a proprietary small molecule that we are advancing to Phase 3 development for major depressive disorder (MDD). Pimavanserin is a selective serotonin inverse agonist (SSIA) preferentially targeting 5-HT2A receptors. Its distinct mechanism of action targets serotonergic 5-HT2A receptors that may play a role in depression.

About Major Depressive Disorder (MDD)

According to the National Institute of Mental Health, MDD affects approximately 16 million adults in the U.S., with approximately 2.5 million adults treated with adjunctive therapy. MDD is a condition characterized by depressive symptoms, such as a depressed mood or a loss of interest or pleasure in daily activities for more than two weeks, as well as impaired social, occupational or other important functioning. The majority of people who suffer from MDD do not respond adequately to initial antidepressant therapy.


In April 2019, we initiated the Phase 3 CLARITY program to evaluate the efficacy and safety of pimavanserin as adjunctive treatment in patients with MDD who have an inadequate response to standard antidepressant therapy with either a selective serotonin reuptake inhibitor (SSRI) or a serotonin norepinephrine reuptake inhibitor (SNRI).

The Phase 3 CLARITY program consists of two studies, CLARITY-2 and CLARITY-3 are both 6-week, parallel-designed, randomized, double-blind, placebo-controlled, multi-center studies. CLARITY-2 will enroll approximately 280 patients in the U.S. and CLARITY-3 will enroll approximately 280 patients internationally who have had an inadequate response to SSRI/SNRI antidepressant treatment. Patients in both studies will be randomized to receive six weeks of oral treatment with either 34 mg of pimavanserin or placebo, once daily, in addition to their ongoing antidepressant. The primary endpoint in both studies is the change from baseline on the 17-item Hamilton Depression Rating Scale (HAMD-17) total score.

Patients who complete the CLARITY-2 or CLARITY-3 studies will be eligible to participate in a 52-week open-label extension study to evaluate the long-term safety and tolerability of pimavanserin.