2.277 OPTIMIZATION OF PHASE III STUDY DESIGN FOR PIMAVANSERIN IN THE TREATMENT OF PARKINSON'S DISEASE PSYCHOSIS (PDP)

Impact of Current Antipsychotic Medications on Comparative Mortality and Adverse Events in People With Parkinson Disease Psychosis

OBJECTIVES

To establish the mortality risk and adverse events associated with the use of atypical antipsychotic medications in people with Parkinson disease psychosis (PDP) in a clinically defined trial cohort.

DESIGN

Post hoc analysis of data from a multicenter, open-label extension study of pimavanserin comparing people taking and not taking current antipsychotics.

SETTING

Primary and secondary care medical centers in the United States, Canada, Europe, and India.

PARTICIPANTS

A total of 459 people with PDP enrolled in the extension study. Participants were between ages 30 and 80 years, and had an established diagnosis of idiopathic Parkinson disease and moderate to severe psychosis.

INTERVENTIONS

Participants were categorized into 2 groups: those receiving concomitant antipsychotic medications ("concurrent APD") and those who did not take antipsychotic medications at any time during the study ("no APD"). Participants were receiving 40 mg pimavanserin daily in addition to concurrent antipsychotics and Parkinson disease medications.

MAIN OUTCOME MEASURES

Safety assessments at 2 weeks; 1, 3, 6, 9, and 12 months; and every 6 months thereafter, including evaluation of adverse events (AEs), vital signs, weight, physical examinations, 12-lead electrocardiograms, clinical laboratory tests (serum chemistry, hematology, and urinalysis), and the Unified Parkinson's Disease Rating Scale Parts II and III (UPDRS-II+III, activities of daily living and motor impairment, respectively). Differences between participants taking and not taking current antipsychotics were evaluated using incidence rate ratios (IRRs) with 95% confidence intervals (CIs).

RESULTS

There was significant increase in the mortality rate for participants taking concurrent antipsychotics compared with the group not taking antipsychotic medications (IRR 4.20, 95% CI 2.13-7.96). Participants who received a concurrent antipsychotic were also significantly more likely to experience overall a serious AE (IRR 2.95, 95% CI 2.02-4.24), any antipsychotic-related event (IRR 1.66, 95% CI 1.18-2.29), cognition-related events (IRR 2.70, 95% CI 1.19-5.58), infections (IRR 1.97, 95% CI 1.17-3.16), and edema (IRR 2.61, 95% CI 1.09-5.59). The risk of falls, stroke, sedation, orthostatic hypotension, and thromboembolic events was also increased in these individuals but this was not significant.

CONCLUSIONS

This study highlights a significant risk of mortality, and severe AEs in patients with Parkinson disease receiving atypical antipsychotics. This is similar to or greater than the risks seen in people with Alzheimer disease, although with a less clear-cut risk of stroke and a longer delay to increased mortality.

On the discovery and development of pimavanserin: a novel drug candidate for Parkinson's psychosis

Parkinson’s disease psychosis (PDP) is a condition that may develop in up to 60 % of Parkinson’s patients, and is a major reason for nursing home placement for those affected. There are no FDA approved drugs for PDP but low doses of atypical anti-psychotic drugs (APDs) are commonly prescribed off-label. Only low-dose clozapine has shown efficacy in randomized controlled trials, but all APDs have black box warnings related to the increased mortality and morbidity when used in elderly demented patients. Using molecular pharmacological profiling of a large collection of marketed drugs, we discovered that potent inverse agonist activity against 5-HT_2A serotonin receptors was a common feature of atypical APDs, especially the atypical APDs used to treat PDP. Since low-dose clozapine therapy selectively blocks this receptor, it was hypothesized that a highly selective 5-HT_2A receptor inverse agonist might provide good symptom control in patients suffering from PDP, with a greatly improved safety and tolerability profile. A high throughput screening and subsequent chemical lead optimization campaign to develop potent, selective 5-HT_2A receptor inverse agonists was launched, eventually resulting in the discovery of pimavanserin. Pimavanserin displays nanomolar potency as a 5-HT_2A receptor inverse agonist, selectivity for 5-HT_2A over 5-HT_2C receptors, and no meaningful activity at any other G-protein coupled receptor. It demonstrated robust activity in preclinical models of schizophrenia and PDP, and did not worsen motoric symptoms, in contrast to the APDs tested. In a Phase III clinical trial, pimavanserin showed highly significant benefits in the primary endpoint, the scale for assessment of positive symptoms-PD, a scale adapted for use in PDP. In addition, improvements in all other efficacy endpoints, including physician’s clinical global impression, caregiver burden, night-time sleep quality and daytime wakefulness, were seen. Pimavanserin demonstrated good safety and tolerability and did not worsen motoric symptoms as assessed by the unified Parkinson’s disease rating scale parts II and III. An open-label extension study has further demonstrated that pimavanserin is safe and well-tolerated with long-term use. Pimavanserin may therefore offer a viable treatment option for patients suffering from PDP.