This file photo taken Jan. 16, 2016 shows the logo of the Biotrial laboratory on its building in Rennes, western France, where a clinical trial of an oral medication left one person brain-dead and five hospitalized. The man who had been left brain-dead in a French drug trial has died, the Rennes hospital said Jan. 17, 2016.LOIC VENANCE/AFP / Getty Images
A man died in a French hospital Sunday after taking part in a drug trial for a painkiller based on a compound similar to cannabis, and five other participants remain hospitalized after one of France's most troubling medical incidents.
French prosecutors have launched a manslaughter investigation into the unusual case, which shined a spotlight on the practice of testing drugs on paid, healthy human volunteers. Scores of others were also given the drug.
The Portuguese pharmaceutical company testing the drug, Bial, said in a statement that it's working with health authorities to determine what caused "this tragic and unfortunate situation."
The drug is aimed at easing pain and mood and anxiety troubles, as well as motor problems linked to neurodegenerative illnesses.
The Rennes University Hospital in western France announced the death in a statement, but didn't identify the patient, who had already been in a state of brain death.
He was among six male volunteers between 28 and 49 hospitalized last week after volunteering to take the drug. French health authorities have said three of the hospitalized volunteers face possible brain damage.
The Paris prosecutor's office said the investigation was expanded after the death to include potential manslaughter charges.
The trial, which began Jan. 7, involved 90 healthy volunteers who were given the experimental drug in varying doses at different times.
The hospital said it has contacted the 84 other volunteers exposed to the new painkiller. Ten of those volunteers underwent medical exams Saturday, but the hospital found no anomalies, the statement says. It said another five will have medical exams closer to their homes, but didn't say whether the others are being monitored or tested.
The drug, based on a natural brain compound similar to the active ingredient in marijuana, was given orally to healthy volunteers as part of a Phase 1 trial by Biotrial, a drug evaluation company based in Rennes, on behalf of Bial.
Bial said clinical trials started last June following toxicology tests and that 108 healthy people had already taken part in trials with no moderate or serious reactions.
It's rare for volunteers to fall seriously ill during Phase 1 trials, which study safe usage, side effects and other measures on healthy volunteers, rather than drug effectiveness.
But cases of early-stage clinical trials going badly wrong are not unheard of. In 2006, six healthy volunteers given an experimental drug in London ended up in intensive care.
Associated Press with a report from Reuters