Having passed all pre-clinical safety testing, the superagonistic anti -CD28 therapeutic monoclonal antibody (mAb ) TGN 1412, intended for the treatment of rheumatoid arthritis and B-cell chronic lymphocytic leukaemia, was approved by German and UK regulatory authorities for first-in-man Phase One clinical trial. Shortly after infusion, all six healthy trial volunteers suffered unexpected and profound systemic pro-inflammatory cytokine release, later termed a 'cytokine storm,' causing multi-organ failure. This unexpected and near fatal cytokine release syndrome (CRS) publically highlighted the failure of current pre-clinical safety testing procedures, emphasising an urgent need for novel cytokine release assays (CRAs) capable of predicting adverse properties of therapeutic mAbs. A wet coat mAb immobilisation approach, developed here, has proven predictive of clinical outcome and would have anticipated TGN1412 immunotoxicity in man. This approach IS now being widely applied by the pharmaceutical industry and contract research organisations (CROs). Comparative studies, testing TGN 1412 against a panel , of therapeutic mAbs, identified a unique mechanism of TGNl412-driven cytokine release. Substantial concentrations of the cytokine lL-2 were subsequently found to be a hallmark for the cytokine storm observed in-vivo, signifYing IL-2 as a TGN1412-like response biomarker. Multiple pro-inflammatory cytokine release was also shown to be principally effector memory T cell (T EM) derived in man. Human and macaque comparative immunophenotyping crucially identified macaque T EM cells as lacking CD28 expression, explaining pre-clinical animal model testing failures. A more physiologically relevant aqueous phase co-culture assay using monocyte-derived dendritic cells is also shown capable of eliciting a TGN1412-like cytokine release profile equivalent to that detected in-vivo and in-vitro using wet coat immobilisation; implying presentation in-vivo likely involved dendritic cells. This thesis describes the most likely mechanisms of action responsible for TGN1412 immunotoxicology in man and provides a plausible explanation for the pre-clinical safety testing failures, findings vital to the fields of immunomodulatory therapeutic mAb development and immunotoxicology.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:676898 |
| Date | January 2015 |
| Creators | Eastwood, David Geoffrey Douglas |
| Publisher | St George's, University of London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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