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

LOZADA MONTANARI, BELÉN CANDELA; FRIEDRICH, ADRIÁN DAVID; REGGE, MARÍA VICTORIA; RUBINSZTAIN, NATALIA; SANTILLI, MARÍA CECILIA; SIERRA, JESSICA MARIEL; SECCHIARI, FLORENCIA; GANTOV, MARIANA; TROTTA, ALDANA; ERRAMOUSPE, JULIETA; FUERTES, MERCEDES BEATRIZ; DOMAICA, CAROLINA INÉS; ZWIRNER, NORBERTO WALTER

Mar del Plata

Congreso; 70ª Reunión Anual de la Sociedad Argentina de Inmunología y 3rd French-Argentine Immunology Congress (FAIC); 2022

Sociedad Argentina de Inmunología

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.