Positive Top-Line Results Announced from Phase 2 Study of Pimavanserin for Adjunctive Treatment of Major Depressive Disorder


Pimavanserin (Nuplazid; Acadia Pharmaceuticals, San Diego, CA), already approved for treatment of patients with Parkinson’s disease (PD) psychosis is also being studied as a potential adjunctive treatment for patients with major depressive disorder (MDD). In a phase 2 study, the primary end point of significant improvement in Hamilton Depression Rating Scale (HAMD-17) scores for those treated with pimavanserin compared to those treated with placebo was met (= .039). Secondary endpoints of significant improvement on the Sheehan Disability Scale (= .004) and other measures, including reduced daytime sleepiness, sexual function, and responder rate (50% reduction in HAMD-17 score) (= .0065), were also positive. 

In this study, patients with MDD who had not responded to existing first-line treatment with selective serotonin reuptake inhibitors (SSRIs) or selective norepinephrine reuptake inhibitors (SNRIs) received 34 mg of pimavanserin or a placebo in addition to preexisting first-line treatments for 5 weeks. If, after 5 weeks, patients treated with placebo did not respond, they were randomly reassigned to receive pimavanserin or placebo for another 5 weeks. Those who received pimavanserin in the first 5-week period had significant improvements in HAMD-17 scores (= .0003) that was seen in the first week of treatment (= .0365). The weighted average of patients’ HAMD scores for those who received pimavanserin were higher compared to placebo (= .039). Discontinuations due to adverse events were 1.2% for pimavanserin and 3.2% for placebo. 

“We are pleased with the robustness of the data from our phase 2 trial, which shows significant promise for patients with MDD, including early and sustained antidepressant response over placebo, decreased daytime sleepiness, no meaningful weight gain, and improved sexual function. This is important because most people with MDD do not respond to initial antidepressant therapies and experience significant unwanted side effects,” said Serge Stankovic, MD, MSPH, Acadia's Executive Vice President, Head of Research & Development. “Pimavanserin is a selective serotonin inverse agonist, or SSIA, that shows great potential as an antidepressant. We look forward to engaging with the FDA and initiating a phase 3 program in the first half of 2019.


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