One of the six men hospitalized after participating in a clinical drug trial in north-western France died Sunday, the university hospital where he was being treated said in a statement.
The man was admitted to the University Hospital Center (CHU) of Rennes on January 10, three days after the launch of a clinical drug trial to test an oral medication developed by Portuguese firm Bial.
He was declared to be medically brain dead.
The five other men hospitalized, aged 28 to 49 years old, remain in stable condition, the hospital said.
Neuroscience chief Gilles Edan said Friday that one of the men had not yet shown symptoms but was being held for monitoring.
The hospital said it had already contacted the other 84 volunteers who had taken the drug during its Phase 1 trial stage. Ten of those volunteers have undergone medical examinations, and the hospital added that none of the conditions displayed by the hospitalized patients were found among the ten.