In its first human
clinical trials, it caused catastrophic systemic organ failures in the subjects, despite being administered at a supposed sub-clinical dose of 0.1 mg per kg, some 500 times lower than the dose found safe in animals. All six volunteers who were administered the drug were hospitalized between 12 and 16 hours later. At least four of them had
multiple organ dysfunction. Parexel is a company that carries out drug trials on behalf of pharmaceutical and biotechnology companies. Healthy volunteers were recruited to the study with a £2,000 fee. The trial resulted in hospitalization of all six volunteers administered the drug, at least four of whom had
multiple organ dysfunction. The trial was a double-blind, randomized,
placebo-controlled study, with two of the eight subjects receiving a
placebo, and six receiving 1/500th of the highest dose used in previous experiments with
cynomolgus macaques. All six of the trial subjects who received the drug were male, aged 19 to 34 (median 29.5); none had a notable medical history, and all were well in the 2 weeks before the trial. All of the men were reported to have experienced severe
cytokine release syndrome resulting in
angioedema, swelling of
skin and
mucous membranes, akin to the effects of the
complement cascade in
severe allergic reaction. The patients were treated with
corticosteroids to reduce inflammation, and
plasma-exchange to attempt to remove TGN1412 from their circulation. Paradoxically, some kinds of the men's
white blood cells (
lymphocytes and
monocytes, involved in immune responses) had vanished almost completely several hours after administration of TGN1412. TGN1412 had not previously been given to humans, however the trial was preceded by animal testing, including in
non-human primates. The company claims that these did not indicate any safety issues, and this was supported in subsequent MHRA reports. TeGenero apologised to the families involved soon after the events, insisting that the effects were completely unexpected, and that all protocols were followed. In an initial review of pre-clinical data and the protocol, the MHRA stated there was nothing to cause concern, and that the trial was correctly authorised. Participants who were harmed in the drug trial received some additional financial compensation later, which one participant used to hire a
personal trainer so he could regain physical fitness.
Investigations The Medicines and Healthcare products Regulatory Agency (MHRA) issued an interim report on the TGN1412 trial on 5 April 2006, followed by a final report on 25 May 2006. It found no deficiencies in TeGenero's pre-clinical work and no evidence of undisclosed studies. Parexel's records and processes appeared in order, including dose measurement and administration, and no deficiencies were found that may have led to contamination or overdose. The MHRA felt that their actions did not contribute to the serious adverse events. German regulatory authorities inspected the production of the material by
Boehringer Ingelheim, looking at the manufacture, testing, storage and distribution of the TGN1412, but no deficiencies were identified which could have contributed to the serious adverse effects. The MHRA concluded that the most likely cause of the reaction in trial subjects was an unpredicted biological action of the drug in humans. The UK
Secretary of State for Health agreed to establish a group of leading international experts to consider those issues and to provide a report on the future authorization of such trials with an interim report at three months, with
Gordon Duff, Professor of Molecular Medicine at
Sheffield University, as Chair of the group. Until the expert group reported, all further clinical trial applications involving first-in-humans trials of any monoclonal antibody or other novel molecules targeting the immune system were not to be authorised in the UK. In December 2006, the final report of the Expert Group on Phase One Clinical Trials was published. It found that the trial had not considered what constituted a safe dose in humans, and that then-current law had not required it. It made 22 recommendations, including the need for independent expert advice before a high-risk study was allowed, testing only one volunteer at a time (sequential inclusion of participants) in case there were rapid ill effects, and administering drugs slowly by infusion rather than as an injection.
Follow up publications The trial has become subject of several academic publications. In 2007, immunologists from the
Paul Ehrlich Institute, the German Federal Agency for Sera and Vaccines, reviewed Germany's regulatory requirements in the aftermath of the TGN1412 trial. They suggested that the predictive value of pre-clinical animal models required reevaluation, dose fixing needed refinement or redesign, and criteria for high-risk antibodies needed to be established. Additionally, they suggested that pre-Phase I studies were needed to calculate a dose with a pre-clinical "No effect" level, rather than a
No-observed-adverse-effect level. Scientists in early 2007 put forth the theory that the drug acted in a different fashion in humans as compared with the laboratory animals in which the drug was first tried. The severe reactions in humans could have only occurred, they believe, in those with
memory T lymphocytes. Animals raised in a sterile lab would presumably have no 'memory' of previous illnesses, thus would not exhibit the severe reactions that occurred in the human subjects. However this is a misunderstanding of the research: the research says that lab animals studied have fewer memory T cells than humans, and that stimulation through the CD28 receptor alone in memory T cells causes them to infiltrate organs and also activates them. Experimental
in-vitro research and modelling, published in 2008, suggested that the 0.1 mg per kg starting dose would bind to 86 to 91% of all CD28 receptors in the body, resulting in a possible higher than expected effect even at very low starting doses. In 2009, the UK
National Institute for Biological Standards and Control wrote that a near-maximum immuno-stimulatory dose had been given, because a safe starting dose in man had been calculated "based upon results from pre-clinical safety testing in a non-responsive species" (
Macaca fascicularis). It reported that the European guidelines for first-in-man phase-I clinical trials of biologics had been revised. In 2010, the failure to predict a severe
cytokine release syndrome in humans was explained. In vitro data revealed that the CD4+
effector memory T-cells of
Macaca fascicularis, the species of primate used for pre-clinical safety testing of TGN1412, lack CD28 expression. Since CD28 is the target of the TGN1412 antibody,
M. fascicularis effector T-cells could not be stimulated by the drug. In 2013, it was described that standard pro-inflammatory markers
TNFα and
IL-8 are not predictive of the unusual pro-inflammatory response to TGN1412, and gave a false negative result. IL-2 release and lymphoproliferation are more helpful predictors of the response. In 2016, a study carried out on
humanized mice evaluated TGN1412's effects on the immune system, and confirmed that it could cause
cytokine release syndrome, destruction of white blood cells, and other negative effects observed during the initial human trial. ==Controversies==