title: After TGN1412: recent developments in cytokine release assays.
abstract: The failure of regulatory science to keep pace with and support the development of new biological medicines was very publically highlighted in March 2006 when the first-in-man Phase I clinical trial of the immunomodulatory CD28-specific monoclonal antibody (mAb) TGN1412 ended in disaster when all six volunteers suffered a life-threatening adverse reaction termed a 'Cytokine Storm'. The poor predictive value of standard pre-clinical safety tests and animal models applied to TGN1412 demonstrated the need for a new generation of immunotoxicity assays and animal models that are both sensitive and predictive of clinical outcome in man. The non-predictive result obtained from pre-clinical safety testing in cynomolgus macaques has now been attributed to a lack of CD28 expression on CD4+ effector memory T-cells that therefore cannot be stimulated by TGN1412. In contrast, high levels of CD28 are expressed on human CD4+ effector memory T-cells, the source of most TGN1412-stimulated pro-inflammatory cytokines. Standard in vitro safety tests with human cells were also non-predictive as they did not replicate in vivo presentation of TGN1412. It was subsequently shown that, if an immobilized therapeutic mAb-based assay or endothelial cell co-culture assay was used to evaluate TGN1412, then these would have predicted a pro-inflammatory response in man. New in vitro assays based on these approaches are now being applied to emerging therapeutics to hopefully prevent a repeat of the TGN1412 incident. It has emerged that the mechanism of pro-inflammatory cytokine release stimulated by TGN1412 is different to that of other therapeutic mAbs, such that standard pro-inflammatory markers such as TNFα and IL-8 are not discriminatory. Rather, IL-2 release and lymphoproliferation are optimal readouts of a TGN1412-like pro-inflammatory response.
authors.affiliation: Biotherapeutics Group, NIBSC, Potters Bar, Hertfordshire EN6 3QG, UK. richard.stebbings@nibsc.hpa.org.uk
authors.forename: R
authors.initials: R
authors.lastname: Stebbings
authors.forename: D
authors.initials: D
authors.lastname: Eastwood
authors.forename: S
authors.initials: S
authors.lastname: Poole
authors.forename: R
authors.initials: R
authors.lastname: Thorpe
mesh_terms: D000818:Animals; D055910:Antibodies, Immobilized; D061067:Antibodies, Monoclonal, Humanized / Q000009:adverse effects*; D018106:CD28 Antigens / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects* / Q000276:immunology; D017321:Clinical Trials, Phase I as Topic; D018920:Coculture Techniques; D016207:Cytokines / Q000276:immunology; D003601:Cytotoxicity Tests, Immunologic; D004195:Disease Models, Animal; D004353:Drug Evaluation, Preclinical; D042783:Endothelial Cells; D006801:Humans; D007156:Immunologic Memory / Q000187:drug effects; D007249:Inflammation / Q000209:etiology; D007376:Interleukin-2 / Q000276:immunology*; D008252:Macaca fascicularis; D011237:Predictive Value of Tests; D017211:Treatment Failure
chemical_list: D055910:Antibodies, Immobilized; D061067:Antibodies, Monoclonal, Humanized; D018106:CD28 Antigens; D016207:Cytokines; D007376:Interleukin-2; C509303:TGN-1412