Safety and Efficacy of Oral Cannabidiol in Treating Parkinson’s Psychosis Focus of Phase 2 Study in UK

A planned Phase 2 clinical trial will assess the safety and effectiveness of pharmaceutical-grade cannabidiol (CBD) in treating Parkinson’s-related psychosis.

The trial was announced by Parkinson’s UK, which is investing £1.2 million (roughly $1.5 million) to support the study, due to begin enrolling patients in 2020.

Psychosis is estimated to affect more than half of people with Parkinson’s disease. It is characterized by hallucinations (seeing, hearing, or feeling things that are not really there) and delusions (fixed beliefs that are demonstrably untrue).

These symptoms are typically managed by reducing or stopping the use of medications used to treat Parkinson’s, but such choices have the obvious drawback of arresting any benefits those treatments provide. Antipsychotics are sometimes also used, but they can carry side effects or worsen motor symptoms.

Nuplazid (pimavanserin, by Acadia Pharmaceuticals) is the only medicine currently approved to treat Parkinson’s-related psychosis in the United States; no approved therapies for this condition are available in the United Kingdom.

“Current treatments prescribed by clinicians for psychosis typically work by blocking dopamine receptors, which can increase the problems people with Parkinson’s experience with movement and other symptoms of the condition,” Sagnik Bhattacharya, a professor at King’s College London who will help lead the trial, said in the press release.

This trial will “will determine, for the first time, whether CBD can correct the abnormal functioning of the brain that is causing symptoms such as hallucinations and delusions,” Bhattacharya added.

Cannabidiol is a non-psychoactive component of the cannabis plant, meaning it is found in cannabis, but unlike tetrahydrocannabinol or THC does not induce a feeling of being “high.” CBD is currently undergoing a renaissance of interest for its potential medical uses.

“We know from a recent survey we carried out, that people with Parkinson’s would continue to use, or start using, cannabis-derived products if robust evidence became available that they are safe and effective in treating Parkinson’s symptoms,” said Arthur Roach, PhD, the director of research at Parkinson’s UK. “One of the key questions this clinical trial will address is if CBD is safe to use for Parkinson’s-related psychosis, which has never been done before.”

The two-part study will begin with a six-week pilot phase to evaluate the safety, tolerability and effectiveness of CBD in people with Parkinson’s-related psychosis. Participants will be given daily oral CBD capsules at doses up to 1 gram per day to find the optimum dose. Then, 120 patients will be randomized to treatment with either CBD or a placebo for 12 weeks.

In addition to safety, trial goals (endpoints) will include a detailed assessment of psychotic, motor and non-motor symptoms, as well as brain imaging.

“We will be assessing how safe CBD is for people with Parkinson’s, what the correct dosage is and how it is tolerated alongside the different medications someone with the condition may already be on,” Bhattacharya said. “The study will also look at the effect of CBD on other symptoms which will pave the way for scientists to investigate the potential of the compound in treating these in future studies.

“We hope that this will progress to large-scale clinical trials — the final step towards becoming a new treatment that will improve the lives of people with Parkinson’s,” Bhattacharya added.

If successful, this study “could result in a regulated cannabinoid-based medicine being prescribed and used in the clinic, as opposed to self-administration of expensive supplements that have not been monitored for their composition or effects,” Roach said.