Adnectin-Based Design of Chimeric Antigen Receptor for T Cell Engineering

Abstract

Although chimeric antigen receptor (CAR)-engineered Tcell therapy has achieved encouraging clinical trial results for treating hematological cancers, further optimization can likely expand this therapeutic success to more patients and other cancer types. Most CAR constructs used in clinical trials incorporate single chain variable fragment (scFv) as the extracellular antigen recognition domain. The immunogenicity ofnonhuman scFv could cause host rejection against CAR Tcells and compromise their persistence and efficacy. The limited availability of scFvs and slow discovery of new monoclonal antibodies also limit the development of novel CAR constructs. Adnectin, a class of affinity molecules derived from the tenth type III domain of human fibronectin, can be an alternative to scFv as an antigen-binding moiety in the design of CAR molecules. We constructed adnectin-based CARs targeting epithelial growth factor receptor (EGFR) and found that compared to scFv-based CAR, Tcells engineered with adnectin-based CARs exhibited equivalent cell-killing activity against target H292 lung cancer cells invitro and had comparable antitumor efficacy in xenograft tumor-bearing mice invivo. In addition, with optimal affinity tuning, adnectin-based CAR showed higher selectivity on target cells with high EGFR expression than on those with low expression. This new design of adnectin CARs can potentially facilitate the development of Tcell immunotherapy for cancer and other diseases.