Immunogenicity assessment for Affibody-Fc fusion therapeutics

SOBI is developing novel biopharmaceutical drugs based on the antibody-like Affibody scaffold. The molecules are fusion proteins composed of target specific Affibody domains of non-human origin, fused to the human IgG1-Fc for half-life extension. The E. coli produced non-glycosylated Fc fusions are devoid of Fc-gamma receptor and C1q mediated effector functions but still retain FcRn-mediated recycling with associated decreased clearance. In the screening process to select the most promising drug candidates, a multi-tiered approach was used to evaluate immunogenicity of Affibody-Fc fusion proteins. Several in silico platforms were used for a broad primary screening. Next we investigated which peptides were presented on MHC-II after protein uptake and processing by dendritic cells (DCs). Predicted or presented peptides, protein domains or full-length proteins were next used to stimulate CD4+ T-cells using PBMCs or DC:T assays. The selected candidates had a DC:T assay response-index similar to therapeutic grade human antibodies or human Fc indicating low immunogenicity