Lawyers representing four of the six injured men are poised to begin immediate legal proceedings if last minute talks being held today with the US-owned contract research organisation (CRO) fail.
Parexel was at the centre of the drug trial disaster last year after six out of eight men it carried out Phase I trials on - under contract on behalf of small German biotech firm TeGenero - experienced a severe and systemic adverse reaction and were admitted to intensive care with hours of taking the experimental drug.
The drug behind the fury is called TGN1412, a monoclonal antibody (mAb) that was being developed by TeGenero to treat conditions including multiple sclerosis, rheumatoid arthritis and leukaemia.
TeGenero has since gone bust and Parexel has been left to weather the ensuing storm.
How it is weathering it though, remains questionable, according to Gene Matthews, a solicitor from Leigh Day & Co solicitors - the London law firm representing four of the victims.
"Their response to us to date, and to the media for that matter, has been total silence," Matthews told Outsourcing-Pharma.com.
"Our clients got sick of waiting for Parexel to acknowledge them and so have now instructed us to commence legal proceedings.
Only now after hearing this - one year after the event - have Parexel's lawyers agreed to sit down and talk with us to see if we can come up with some kind of compensation settlement."
According to Matthews, although Parexel was cleared of any blame in a subsequent UK Medicines and Healthcare products Regulatory Agency (MHRA) investigation, the CRO still has a case to answer for its role in the debacle.
"There are a number of issues surrounding the trial itself and the handling of the situation following the adverse reactions that we find questionable," he said.
Firstly there are questions over Parexel's involvement in the design of the trial.
"We don't know the extent of their involvement in the trial design yet
but it is very likely that TeGenero - being a small German firm - relied on Parexel - a large international firm - for getting the protocol approved by the regulatory bodies and ethics committees," said Matthews.
Secondly, the issue of drug dosing is being scrutinised by the victims' lawyers.
"According to documents we have, the subjects were administered the trial drug at five- to eight-minute intervals.
It is our understanding after speaking to a clinical immunologist and another industry expert that this was against good clinical practice (GCP) for this type of drug," said Matthews.
"They said that when testing a mAb for the first time, extra caution should be taken, including allowing sufficient time to wait for and deal with any sideeffects that may arise."
Thirdly, the lawyers believe that the way that Parexel staff dealt with the drug reactions was inadequate.
"It clearly states in the regulatory documents submitted by Parexel that cytokine release syndrome (which the six subjects suffered) was a possible consequence of the drug being tested," said Matthews.
The investigator's brochure also states that in the event of such a reaction, appropriate counter-measures - of which the application of high dose glucocorticoids or anti-histamines was suggested - must be taken, he said.
"However, the subjects did not receive high dose steroids until they were administered by the National Health Service (NHS) in intensive care 16-18 hours later," said Matthews.
"Our industry expert said that this delay in treatment worsened the health outcomes of our clients."
On the same subject, Matthews believes that Parexel should have informed the Northwick Park hospital of the type of drug it was testing before the trials started.
"The treating physicians at the hospital were in the dark - they had no idea what they were dealing with and this lad to delays in treatment."
"Our expert said testing on a drug of this type has a very high risk of a cytokine release syndrome reaction, and the hospital should have been forewarned so they could be prepared for a rapid response in the event of an emergency," said Matthews.
Parexel was asked by Outsourcing-Pharma.com to comment but failed to do so.