RT Journal Article SR Electronic T1 Pre-existing antitherapeutic antibodies against the Fc region of the hu14.18K322A mAb are associated with outcome in patients with relapsed neuroblastoma JF Journal for ImmunoTherapy of Cancer JO J Immunother Cancer FD BMJ Publishing Group Ltd SP e000590 DO 10.1136/jitc-2020-000590 VO 8 IS 1 A1 Jacob L Goldberg A1 Fariba Navid A1 Jacquelyn A Hank A1 Amy K Erbe A1 Victor Santana A1 Jacek Gan A1 Fenna de Bie A1 Amal M Javaid A1 Anna Hoefges A1 Michael Merdler A1 Lakeesha Carmichael A1 KyungMann Kim A1 Michael W Bishop A1 Michael M Meager A1 Stephen D Gillies A1 Janardan P Pandey A1 Paul M Sondel YR 2020 UL http://jitc.bmj.com/content/8/1/e000590.abstract AB Purpose Patients with cancer receiving tumor-reactive humanized monoclonal antibody (mAb) therapy can develop a human antihuman antibody (HAHA) response against the therapeutic mAb. We evaluated for HAHA in patients with neuroblastoma treated in a phase I study of humanized anti-GD2 mAb (immunoglobulin (Ig)G1 isotype), hu14.18K322A (NCT00743496). The pretreatment sera (collected prior to mAb treatment) from 9 of 38 patients contained antitherapeutic antibodies, even though they had no prior mAb exposure. We sought to characterize these pre-existing antitherapeutic antibodies (PATA).Experimental design The PATA+ pretreatment samples were characterized via ELISA; clinical associations with PATA status were evaluated.Results Pretreatment sera from eight of nine PATA+ patients also bound rituximab and demonstrated preferential ELISA reactivity against the Fc portions of hu14.18K322A and rituximab as compared with the Fab portions of these mAbs. These PATA+ sera also recognized dinutuximab (human IgG1 isotype) and mouse IgG2a isotype mAbs, but not a mouse IgG1 isotype or the fully human panitumumab (IgG2 isotype) mAb. Of the 38 treated patients, only 4 patients (all in the PATA+ cohort) demonstrated no disease progression for >2.5 years without receiving further therapy (p=0.002).Conclusions This study demonstrates an association between clinical outcome and the presence of PATA against determinant(s) on the Fc component of the therapeutic mAb, suggesting that the PATA may be playing a role in augmenting mAb-based antitumor effects. Further analyses for the presence of PATA in a larger cohort of patients with relapsed neuroblastoma, analyses of their clinical correlates, identification of their immunological targets, and potential antitumor mechanisms are warranted.