Acadia Pharmaceuticals saw its shares more than double to close at $5.43 yesterday after it reported phase III data on lead drug pimavanserin, which would seem to confirm its blockbuster potential.
A first look at data from the trial in patients with Parkinson’s disease-associated psychosis (PDP) showed that pimavanserin met its target of reducing psychotic symptoms compared to placebo after six weeks’ treatment, without worsening patients’ motor function.
Psychosis is a common side effect of dopamine-based therapy for Parkinson’s, and clinicians often have to walk a tightrope between alleviating the motor problems of the disease and introducing schizophrenia-like symptoms.
Pimavanserin has been designed to work independently of dopamine, exerting its antipsychotic effects via blockade of serotonin 5-HT2A receptors.
“Among Parkinson’s patients, psychosis is the leading cause of institutionalisation and dramatically increases the risk of mortality,” said Jeffrey Cummings of the Cleveland Clinic in the US, one of the key investigators in the trial.
“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,” he added.
In the phase III trial, treatment with pimavanserin resulted in a 5.79-point reduction in psychotic behaviour measured by the 9-point SAPS scale, compared to a 2.73-point reduction with placebo.
The drug was also better than placebo on a physician assessment of efficacy, with improvements in nighttime sleep, daytime wakefulness and caregiver burden.
An earlier trial in PDP failed to meet is endpoint in 2009, which has been attributed to greater-than-expected improvements in placebo patients.
Analysts have suggested that the scale of the problem of psychosis associated with Parkinson’s could make pimavanserin a $1bn-plus product worldwide, provided the findings are reinforced in a confirmatory phase III trial expected to start in the coming weeks.
They also suggest that Acadia may now move quickly ahead with trying to find a marketing partner for pimavanserin outside the US.