Shares in Acadia Pharmaceuticals have rocketed following positive late-stage data on pimavanserin in patients with Parkinson’s disease psychosis.

The San Diego-based firm announced successful top-line results from its Phase III trial which showed that pimavanserin met the primary endpoint in by demonstrating highly significant antipsychotic efficacy compared to placebo. All secondary efficacy measures, including significant improvements in night-time sleep, daytime wakefulness and caregiver burden, were met and the drug was safe and well-tolerated.

Specifically, patients in the pimavanserin arm of 199-patient trial demonstrated a 5.79 point improvement in psychosis at day 43 compared to 2.73 for placebo. Acadia quoted Jeffrey Cummings, director of the Cleveland Clinic Lou Ruvo Center for Brain Health, who said that among Parkinson’s patients, psychosis is the leading cause of institutionalisation "and dramatically increases the risk of mortality".

He added that "neurologists have limited options to treat this serious disorder, and off-label use of current antipsychotics is linked to increased risk of death and serious adverse events, as well as loss of motor control". Pimavanserin, a non-dopaminergic once-a-day oral drug that selectively blocks serotonin 5-HT2A receptors, did not worsen motor function in the trial.

Acadia chief executive Uli Hacksell said that "we remain committed to advancing pimavanserin to registration as a first-in-class treatment for this large unmet medical need". He went on to say the results also suggest that the drug "may have the ideal clinical profile to address a broader range of neuropsychiatric disorders that are underserved by currently marketed antipsychotics".

Investors were hugely impressed and Acacia shares ended the day up 136% at $5.43. The data comes some three years after pimavanserin failed in a Phase III study for PDP and in October 2010, then-partner Biovail, which had just merged with Valeant, returned the rights to Acadia.

One million people in the USA (and four to six million people worldwide) suffer from Parkinson’s and PDP develops in up to 60% of patients. Currently, there is no approved therapy to treat the debilitating disorder.