Six men left seriously ill by a drugs trial are all showing some signs of improvement, doctors said.
The six are being treated at Northwick Park hospital
Two of the volunteers have been taken off organ support while another two are receiving less organ support. All four are fully conscious, the hospital said.
Another two men remain in a critical condition in the high dependency unit but are also continuing to progress.
An inquiry into the trial, carried out by Paraxel, at Northwick Park Hospital in north-west London, is ongoing.
Police and regulators are probing whether problems were caused by errors or were an unpredictable side-effect.
Staff from Parexel insist the right procedures were followed.
A statement issued on Saturday said all the patients were continuing to receive anti-inflammatory treatment.
Doctors said due to the complexity of the condition of the two men in a critical condition it was too early to give a prognosis.
Four of the men suffered multiple organ failure within hours of taking the drug TGN1412 on Monday.
The case is being investigated by the Medicines and Healthcare products Regulatory Agency (MHRA), which has seized documents and sealed off offices.
Scotland Yard said officers were talking to the MHRA and doctors.
Herman Scholtz, head of Parexel, praised staff's swift response when volunteers suffered a reaction during tests of an anti-inflammatory drug.
In a statement posted on the website of US-based Parexel Dr Scholtz said: "An initial review at the site has shown that best practices were followed.
"We remain in close and constant contact with the Northwick Park Hospital concerning the medical status of the six volunteers."
On Friday, local Labour MP Barry Gardiner met the North West London Hospital Trust chief executive Mary Wells, and said there was no better place for the patients to be treated.
Mr Gardiner said: "The MHRA has sealed the offices of Parexel, bagged and taken away all the relevant information, is conducting interviews with Parexel and with their staff."
He added it was unclear how long the inquiry by the UK medicines watchdog would take.
TeGenero, which manufactures the drug, apologised to the sick men's families and said the medicine had shown no signs of problems in earlier tests.
The company's chief scientific officer, Thomas Hanke, said he and his colleagues were "devastated" by what had happened.
He said TGN1412 had been tested extensively in laboratories and on rabbits and monkeys with no adverse effects and no drug-related deaths.
It was the first time the drug, designed to treat conditions such as rheumatoid arthritis, leukaemia and multiple sclerosis, had been tested on humans.
Dr Ganesh Suntharalingam, head of intensive care at Northwick Park, said the two men worst affected by the trial were showing signs of recovery but they remained under sedation.
He added: "Some of them have made noticeable progress in response to our treatment and we have been able to reduce the amount of organ support that is required.
"However, it is early days and they will clearly still continue to need specialist observation for some considerable time.
"There are also some very early signs of response to treatment in the most critically ill patients but I must stress that their condition remains very serious and complex and it wouldn't be sensible to comment on prognosis."