The risk of participating in clinical trials:

The drug is being developed for a German company to treat chronic inflammatory conditions and leukemia, a British medicines watchdog said.

The Sun newspaper said the head and neck of one of the men had swollen to three times normal size.

It quoted a friend as saying the 21-year-old man was a student and had taken part in the trial to make money after seeing an advert on the Internet.

The girlfriend of another volunteer told the BBC her partner looked like the “Elephant Man” — a freak show figure in Victorian Britain whose head ballooned outwards until his skull was wider than his waist. She said all his internal organs had failed.