An Fc-engineered IgG monoclonal antibody displays increased binding to the 158V and 158F variants of the CD16a gene (FCGR3A) on NK cells

BELEN C LOZADA MONTANARI; ADRIAN FRIEDRICH; MARIA VICTORIA REGGE; M NATALIA RUBINSZTAIN; MARÍA CECILIA SANTILLI; JESSICA MARIEL SIERRA; FLORENCIA SECCHIARI; MARIANA GANTOV; ALDANA TROTTA; JULIETA ERRAMOUSPE; MERCEDES BEATRIZ FUERTES; CAROLINA INES DOMAICA; NORBERTO WALTER ZWIRNER

Mar del Plata

Congreso; Reunión Conjunta SAIC. SAI. FAIC. SAFIS 2022; 2022

SAI/ SAIC/FAIC

NK cells play a crucial role during the treatment of cancer patients with monoclonal antibodies (mAb) against tumor cell surface molecules because they express CD16a, the type IIIA receptor for the Fc portion of IgG, which triggers antibody-dependent cellular cytotoxicity (ADCC). The CD16a gene (FCGR3A) exhibits a dimorphism in its extracellular domain (position 158 of the protein) due to a single nucleotide polymorphism (SNP), which generates the 158V and 158F variants. Variant 158V binds IgG with higher affinity than variant 158F. Thus, the genotype of an individual (V/V, V/F or F/F) may determine the ability of its NK cells to mediate ADCC in response to therapeutic mAb. Currently, it is possible to engineer mAb to promote increased binding to CD16a and enhanced ADCC. One possibility is to incorporate two mutations (S239D and I332E) in the heavy chain (H). Accordingly, our aim was to investigate the impact of the FCGR3A SNP on NK cell binding of a humanized mAb and its engineered S239D/I332E variant (DE variant) to establish whether Fc-enhanced engineered mAb can override the low binding ability of CD16a from individuals with the 158F allele. Healthy volunteers were genotyped for the FCGR3A SNP by PCR, and their NK cells were used for mAb binding assays. NK cells with V/V and V/F genotypes showed higher binding of the DE variant mAb than of the parental mAb (p< 0,0001 at 50 μg/ml). We did not detect F/F individuals so far. Also, the DE variant mAb exhibited significantly higher binding to NK cells with V/V genotype than to NK cells with V/F genotype in a dose-dependent manner (p< 0,0001 at 50 μg/ml), while there was a slight increased binding of the parental mAb to NK cells with V/V compared to NK cells with V/F genotypes (p< 0,001 at 50 μg/ml). Our results indicate that the DE variant mAb achieved adequate binding even to CD16a on NK cells from V/F individuals, which sustains the development of Fc-engineered mAb to trigger ADCC for immunotherapy.