Asymmetrical Fc engineering greatly enhances antibody-dependent cellular cytotoxicity (ADCC) effector function and stability of the modified antibodies.

ABSTRACT: Antibody-dependent cellular cytotoxicity (ADCC) is mediated through the engagement of the Fc segment of antibodies with Fc? receptors (Fc?Rs) on immune cells upon binding of tumor or viral antigen. The co-crystal structure of Fc?RIII in complex with Fc revealed that Fc binds to Fc?RIII asymmetrically with two Fc chains contacting separate regions of the Fc?RIII by utilizing different residues. To fully explore this asymmetrical nature of the Fc-Fc?R interaction, we screened more than 9,000 individual clones in Fc heterodimer format in which different mutations were introduced at the same position of two Fc chains using a high throughput competition AlphaLISA® assay. To this end, we have identified a panel of novel Fc variants with significant binding improvement to Fc?RIIIA (both Phe-158 and Val-158 allotypes), increased ADCC activity in vitro, and strong tumor growth inhibition in mice xenograft human tumor models. Compared with previously identified Fc variants in conventional IgG format, Fc heterodimers with asymmetrical mutations can achieve similar or superior potency in ADCC-mediated tumor cell killing and demonstrate improved stability in the CH2 domain. Fc heterodimers also allow more selectivity toward activating Fc?RIIA than inhibitory Fc?RIIB. Afucosylation of Fc variants further increases the affinity of Fc to Fc?RIIIA, leading to much higher ADCC activity. The discovery of these Fc variants will potentially open up new opportunities of building the next generation of therapeutic antibodies with enhanced ADCC effector function for the treatment of cancers and infectious diseases.

SUBMITTER: Liu Z 

PROVIDER: S-EPMC3916558 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature