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

LOZADA MONTANARI, BELEN; FRIEDRICH ADRIAN; REGGE, MARÍA VICTORIA; RUBINZSTEIN, NATALIA; SANTILLI, MARÍA CECILIA; SIERRA, JESSICA MARIEL; SECCHIARI, FLORENCIA; GANTOV, MARIANA; TROTTA, ALDANA; ERRAMOUSPE, JULIETA; FUERTES, MERCEDES BEATRIZ; DOMAICA, CAROLINA INÉS; ZWIRNER, NORBERTO WALTER

Congreso; Reunion anual de Biociencias; 2022

SAI

NK cells play a crucial role during the treatment of cancer patients with monoclonalantibodies (mAb) against tumor cell surface molecules because they express CD16a,the type IIIA receptor for the Fc portion of IgG, which triggers antibody-dependentcellular cytotoxicity (ADCC). The CD16a gene (FCGR3A) exhibits a dimorphism in itsextracellular domain (position 158 of the protein) due to a single nucleotidepolymorphism (SNP), which generates the 158V and 158F variants. Variant 158V bindsIgG with higher affinity than variant 158F. Thus, the genotype of an individual (V/V, V/For F/F) may determine the ability of its NK cells to mediate ADCC in response totherapeutic mAb. Currently, it is possible to engineer mAb to promote increasedbinding 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 theimpact of the FCGR3A SNP on NK cell binding of a humanized mAb and itsengineered S239D/I332E variant (DE variant) to establish whether Fc-enhancedengineered mAb can override the low binding ability of CD16a from individuals with the158F allele. Healthy volunteers were genotyped for the FCGR3A SNP by PCR, andtheir NK cells were used for mAb binding assays. NK cells with V/V and V/F genotypesshowed higher binding of the DE variant mAb than of the parental mAb (p< 0,0001 at50 µg/ml). We did not detect F/F individuals so far. Also, the DE variant mAb exhibitedsignificantly higher binding to NK cells with V/V genotype than to NK cells with V/Fgenotype in a dose-dependent manner (p< 0,0001 at 50 µg/ml), while there was aslight increased binding of the parental mAb to NK cells with V/V compared to NK cellswith V/F genotypes (p< 0,001 at 50 µg/ml). Our results indicate that the DE variantmAb achieved adequate binding even to CD16a on NK cells from V/F individuals,which sustains the development of Fc-engineered mAb to trigger ADCC forimmunotherapy.