A preliminary investigation into the UK drug trial which made six healthy young volunteers critically ill has blamed the drug, not the trial design or the manufacturer. The Medicines and Healthcare Products Regulatory Agency (MHRA) says that the trial of the monoclonal antibody TGN1412 was run according to approved protocols, that the correct dose was used, and that no manufacturing problems or contamination were involved.

The MHRA report suggests that it was just a case of extremely bad luck for the participants. However, critics still insist that the drug should have been tested on one volunteer at a time, rather than giving it to the whole group at once. The response of the MHRA is that dosing all patients within two hours seemed to be reasonable at the time. Given that the human dose was a tiny fraction of what had been given to animals, there seemed to be a wide margin of safety.

The Academy of Medical Sciences, a group of medical scientists from hospitals, universities, industry and the public service, points out that the specificity of antibody action and the novelty of the drug means there is a small body of knowledge to draw on when attempting to predict unwanted effects."