Purpose: Anti-GD2 murine IgG3 antibody 3F8 kills neuroblastoma cells by antibody-dependent cell-mediated cytotoxicity (ADCC). Granulocyte macrophage colony-stimulating factor (GM-CSF) enhances phagocyte-mediated ADCC. The differential affinity of the human FCGR polymorphic alleles for 3F8 may influence the effectiveness of antibody immunotherapy.
Patients and methods: The entire cohort of high risk neuroblastoma patients (N = 136) treated on protocol using 3F8 and GM-CSF were the subjects of this analysis. Tumor response was measured by standard clinical tools plus sensitive molecular monitoring using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Polymorphic alleles of FCGR2A and FCGR3A were determined by PCR plus direct sequencing using genomic DNA samples obtained from marrow or blood of patients.
Results: FCGR2A (R/R) genotype correlated with progression-free survival for the entire cohort (P = .049) and for the subset of patients with no history of prior relapse (P = .023). FCGR2A (R/R) also correlated with marrow remission 2.5 months after treatment initiation: by histology (P = .021 and P = .036, for the entire cohort and the subset, respectively) and by qRT-PCR (P = .052 and P = .033, respectively).
Conclusion: The favorable outcome associated with FCGR2A (R/R) genotype is consistent with the proposed role of FCGR2A and phagocyte-mediated ADCC in 3F8 plus GM-CSF immunotherapy.