One of six men who fell seriously ill after a drug trial said he and the others are "furious" about the ordeal.
The men were all treated at Northwick Park Hospital
Mohamed Abdelhady, 28, told the Daily Mail and Daily Mirror that his head swelled so much his fiancée said he looked like the Elephant Man.
The restaurant manager said the men fell ill "straightaway", adding: "That's why we're so furious".
Mr Abdelhady and the other volunteers had an inflammatory response after being hired to test the drug TGN1412.
The trial participants had been given the drug, created by German pharmaceutical company TeGenero, by medical research company Parexel.
The previously healthy men had volunteered to test the medication, which was designed to treat rheumatoid arthritis, leukaemia and multiple sclerosis.
Mr Abdelhady said he could tell things were not going to plan before his turn came to be injected with the drug, because of immediate adverse effects on others.
"If everybody started feeling ill why did they keep on?" he said.
Mr Abdelhady, who remained unconscious in intensive care at Northwick Park Hospital, London, for eight days, said he thought the drugs companies should have carried out more investigations before conducting the first human trials.
He thought the volunteers had been let down by TeGenero.
"I'm very happy-go-lucky, but this whole awful experience has fundamentally changed me," he said.
"It seemed like a straightforward thing, but that injection changed me forever."
Describing his ordeal, he said: "I felt like there were rocks shooting through my head.
"The last thing I remember was my body turning lifeless and crumbling to the floor."
Mr Abdelhady was given steroids for five days to allow his organs to recover following his adverse reaction to the drug.
His skin began to peel off and doctors have warned him that he may have suffered long-term damage to his immune system.
Meanwhile, student Nav Modi, 24, who also took part in the trial, told the Sun he felt like his brain was "on fire".
Speaking for the first time, he said the experience had been a "terrible nightmare".
Mr Abdelhady, who was paid £2,000 for participating in the trial, remains in hospital and hopes to return home in two weeks.
Dr Ganesh Suntharalingam, clinical director of intensive care at Northwick Park Hospital, said four of the patients have now been allowed to go home.
The worst-affected patient is still in intensive care but is now fully conscious.
Doctors are understood to be encouraged by his progress.