title: Monoclonal antibody TGN1412 trial failure explained by species differences in CD28 expression on CD4+ effector memory T-cells.
abstract: OBJECTIVE
  In 2006, a life-threatening 'cytokine storm', not predicted by pre-clinical safety testing, rapidly occurred in all six healthy volunteers during the phase I clinical trial of the CD28 superagonist monoclonal antibody (mAb) TGN1412. To date, no unequivocal explanation for the failure of TGN1412 to stimulate profound cytokine release in vitro or in vivo in species used for pre-clinical safety testing has been established. Here, we have identified a species difference almost certainly responsible for this disparate immunopharmacology.
  
  
  METHODS
  Polychromatic flow cytometry and intracellular cytokine staining were employed to dissect the in vitro immunopharmacology of TGN1412 and other therapeutic mAbs at the cellular level to identify differences between humans and species used for pre-clinical safety testing.
  
  
  RESULTS
  In vitro IL-2 and IFN-γ release from CD4+ effector memory T-cells were key indicators of a TGN1412-type response. This mechanism of cytokine release differed from that of other therapeutic mAbs, which can cause adverse reactions, because these other mAbs stimulate cytokine release primarily from natural killer cells. In contrast to humans, CD28 is not expressed on the CD4+ effector memory T-cells of all species used for pre-clinical safety testing, so cannot be stimulated by TGN1412.
  
  
  CONCLUSIONS
  It is likely that activation of CD4+ effector memory T-cells by TGN1412 was responsible for the cytokine storm. Lack of CD28 expression on the CD4+ effector memory T-cells of species used for pre-clinical safety testing of TGN1412 offers an explanation for the failure to predict a 'cytokine storm' in humans.
authors.affiliation: Biotherapeutics Group, NIBSC, Potters Bar, Hertfordshire, UK.
authors.forename: D
authors.initials: D
authors.lastname: Eastwood
authors.forename: L
authors.initials: L
authors.lastname: Findlay
authors.forename: S
authors.initials: S
authors.lastname: Poole
authors.forename: C
authors.initials: C
authors.lastname: Bird
authors.forename: M
authors.initials: M
authors.lastname: Wadhwa
authors.forename: M
authors.initials: M
authors.lastname: Moore
authors.forename: C
authors.initials: C
authors.lastname: Burns
authors.forename: R
authors.initials: R
authors.lastname: Thorpe
authors.forename: R
authors.initials: R
authors.lastname: Stebbings
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000009:adverse effects*; D061067:Antibodies, Monoclonal, Humanized; D018106:CD28 Antigens / Q000187:drug effects* / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D002478:Cells, Cultured; D017321:Clinical Trials, Phase I as Topic / Q000379:methods*; D016207:Cytokines / Q000009:adverse effects / Q000378:metabolism; D006801:Humans; D007156:Immunologic Memory; D007371:Interferon-gamma / Q000378:metabolism; D007376:Interleukin-2 / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects*; D008251:Macaca; D008252:Macaca fascicularis; D013045:Species Specificity; D013601:T-Lymphocytes / Q000187:drug effects; D018675:Toxicity Tests / Q000379:methods
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D018106:CD28 Antigens; D016207:Cytokines; D007376:Interleukin-2; D007371:Interferon-gamma; C509303:TGN-1412