By Pat Anson, Editor

Six men have been hospitalized in France after being sickened during a clinical trial of an experimental painkiller. One victim has been declared brain-dead and four others are in critical condition.

(Update: The man who was brain-dead has died, according to local media reports.)

The Phase I trial of the drug has been suspended and all 90 participants have been urged to contact a hospital.

According to reports, the experimental drug being developed by the Portuguese company Bial inhibits a brain enzyme that degrades endogenous cannabinoidsthat are produced naturally by the brain to relieve pain.

By degrading the enzyme called FAAH, Bial hopes to develop compounds that increase brain levels of cannabinoids for use as anti-depressants or pain relievers.

French health officials say the unidentified drug “does not contain cannabis or any derivative of cannabis.”

"We were informed that five participants showed severe symptoms. Following the best international medical practices, they were immediately transferred by the company responsible for conducting the clinical trial to observation at the University Hospital of Rennes, being currently under permanent medical supervision," Bial said in a statement.

Phase I trials are usually conducted to prove the safety of a drug, while the effectiveness of a drug is tested in Phase II and III clinical studies.

The men who were hospitalized were all given multiple doses of the drug, starting January 7. Three days later they started developing neurological symptoms. Two people who were given a harmless placebo developed no symptoms.

“It is definitely the product that is responsible,” said Gilles Edan, head of neuroscience at Pontchaillou Hospital in Rennes, where the men are being treated. She said there is no anti-dote to the drug and its effects could be “irreversible.”

The trial in Rennes was being conducted by Biotrial, a firm that conducts early clinical trials in France and Newark, New Jersey. In France, volunteers can earn nearly $5,000 for participating.  

According to the Daily Mail, Biotrial is able to fast-track early patient studies by “combining the favourable regulatory environment in Western Europe with fast and efficient patient recruitment in Eastern Europe.” 

 “Our thoughts go out to the volunteers and their families. We are working hand in hand with the Health Authorities to understand the cause of this accident,” the company said in a statement.

“The trial has been conducted in full compliance with the international regulations and Biotrial’s procedures were followed at every stage throughout the trial, in particular the emergency procedures for the transfer of subjects to the hospital.”