A preliminary report is out, from France's General Inspectorate of Social Affairs. Here's the worst of it, from Science:
Biotrial was testing a compound called BIA 10-2474, developed by Portuguese pharma company Bial as a candidate drug for a range of diseases. The study started in July 2015, and initial administrations of the drug produced no severe side effects; things went wrong in a group of eight people who entered the study on 6 January and received multiple, high doses. Six of them were scheduled to receive 10 daily doses of BIA 10-2474, two others a daily placebo. On 10 January, a subject identified as "volunteer 2508" complained of headaches and blurry vision; he was taken to the hospital in the early evening and stayed there overnight.
The next morning at 8 a.m., Biotrial staff proceeded to give the seven remaining volunteers their daily dose of BIA 10-2474 or placebo without first finding out how volunteer 2508 was doing. Biotrial apparently assumed his condition wasn't serious and that he was recovering. "We expected to see him come back," one staffer told the investigators. "The hospital didn't call us," said another. But at 9 a.m., a Biotrial doctor was told by the hospital that the patient's condition had worsened and that he had been sent to get an MRI. The patient was declared brain-dead later that day, and the study was halted. Four others who had received their doses that day fell ill and subsequently needed hospitalization.