[5] Parexel was founded in 1982 by Josef von Rickenbach[6] and organic chemist Anne B. Sayigh[7] initially to advise Japanese and German firms on how to navigate the FDA approval process.

Josef von Rickenbach is credited with establishing Parexel's culture and practices based on the principles he experienced as a researcher at Schering-Plough in Lucerne, Switzerland, before leaving the company upon retiring in 2018.

When the liable company[48] subsequently declared bankruptcy,[49] lawyers for the volunteers initiated legal proceeding against Parexel and the two parties later entered into talks;[50] the results of this meeting have not been made public.

[51] A documentary shown in the UK on 28 September 2006 featuring journalist Brian Deer as part of Channel 4's Dispatches series exposed uncertainty about the existence of data that should mandatorily have been submitted by TeGenero to the Medicines and Healthcare products Regulatory Agency (MHRA) prior to the trial indicating whether TGN1412 had been adequately tested on human blood in vitro.

The MHRA however concluded that none of the companies involved could be held responsible for the outcome of the test and that the adverse events that occurred were most likely caused by an unpredicted biological action of the drug in humans.