Two more men have been allowed home from hospital, two weeks after collapsing in pain during a clinical drugs trial in north-west London.
Two men are still being treated at Northwick Park hospital
Six men suffered agonising spasms shortly after being injected at a research unit on 13 March.
They had had an inflammatory response to the drug TGN1412.
Two men remain in hospital. One is still in intensive care but is conscious, the other is said to be making good progress.
The men collapsed at the research unit run by Paraxel, which has insisted it followed standard procedures during the trial.
Screaming and collapsing
Two other volunteers were given a placebo.
They said afterwards it felt like playing Russian roulette, as their fellow volunteers started screaming and collapsing one by one around them.
One man's face was puffed out "like the elephant man", according to his girlfriend.
The company which manufactures the drug, TeGenero, has said it caused the glands of two monkeys to swell during earlier tests.
But it said the symptoms differed from the human volunteers.
The first two men were allowed home on Tuesday, and the hospital announced on Friday that two more men were being released.
Dr Ganesh Suntharalingam, a director at Northwick Park Hospital, said he was pleased there had been "continued progress" among the patients.
He added: "Four of them have now improved sufficiently to be allowed home.
"A fifth patient is out of critical care and making a steady recovery under close observation.
"A sixth patient remains in critical care, but he is now fully conscious and we are encouraged by his progress."
The case is being investigated by the UK medicines watchdog, the Medicines and Healthcare products Regulatory Agency.