A man who fell ill following drug trials at Northwick Park Hospital says he now has the early signs of cancer.
Northwick Park Hospital in London was the scene of the drug trials
Six men were left seriously ill after volunteering to take part in the trials in north-west London earlier this year.
David Oakley told the Mail on Sunday that he is now seeking compensation from Parexel, which arranged for the drug trials to take place.
There is no evidence to show Mr Oakley's cancer was caused by the experimental treatments.
Mr Oakley said he was first made aware of a potential problem about two months ago when blood tests revealed "cells that shouldn't be there", which he says indicate he has early stages of the disease.
He said: "It's an early sign of cancer. The best I could actually get was that if we catch it early enough it is treatable.
"At the moment I haven't felt any physical effects but the paperwork, the blood work, that's all there and apparently there are early indications [of cancer].
"I'm going to try and be as positive as I can and if mind over matter has anything to do with it, well, I'll give it a good try.
"I can't dwell on it because if I dwell on it I'm just going to go down in a heap."
Mr Oakley said he was particularly concerned about potential damage to his auto-immune system that could lead to illnesses such as rheumatoid arthritis and multiple sclerosis.
"If anything they worry me more because I don't want to be left in a situation where I'm stuck in intense pain and can't do anything about it.
"That's probably my worst fear."
He said that "someone has to be accountable and Parexel should be accountable. They made a mistake.
"Really I'm just trying to do my bit and pointing out their mistake. If someone doesn't point it out it could happen again and there's no way I would like to see someone else go through what we're going through right now."
Mr Oakley is now seeking compensation and said he hoped the company would "do the right thing" in respect to his claim.
BBC News attempted to contact Parexel on Saturday evening but was unsuccessful.
Parexel is a clinical research organisation which carried out the trial on behalf of TeGenero, a German pharmaceutical company.
The Medicines and Healthcare products Regulatory Authority (MHRA) has previously said Parexel failed to follow proper procedures.
It found there was no contract in place between TeGenero and Parexel at the beginning of the trial.
TeGenero has maintained that the men's reactions were "completely unexpected" and did not reflect the results obtained from the earlier laboratory studies.
Parexel has previously said all guidelines were followed during the drug trials.