Nanobody-enhanced chimeric antigen receptor T-cell therapy: overcoming barriers in solid tumors with VHH and VNAR-based constructs

Abstract

CAR-T cells are genetically modified T lymphocytes that express chimeric antigen receptors (CAR) on their surfaces. These receptors enable T lymphocytes to recognize specific antigens on target cells, triggering a response that leads to targeted cytotoxicity. While CAR-T therapy has effectively treated various blood cancers, it faces significant challenges in addressing solid tumors. These challenges include identifying precise tumor antigens, overcoming antigen evasion, and enhancing the function of CAR-T cells within the tumor microenvironment. Single domain antibody, versatile tools with low immunogenicity, high stability, and strong affinity, show promise for improving the efficacy of CAR-T cells against solid tumors. By addressing these challenges, single domain antibody has the potential to overcome the limitations associated with ScFv antibody-based CAR-T therapies. This review highlights the benefits of utilizing single domain antibody in CAR-T therapy, particularly in targeting tumor antigens, and explores development strategies that could advance the field.

Keywords: CAR-T; Single domain antibody; Solid tumor; VHH; VNAR.

Fig. 1

Timeline of the development of CAR-T cell therapy

Fig. 2

Limitations of CAR-T for the treatment of solid tumors.The picture summarizes the limiting factors of CAR-T cells in the treatment of solid tumors

Fig. 3

Structures of ScFv, VHH and VNAR with structural sequences derived from PDB: 7AQL, 1I3V and 8HT3. In ScFv and VHH, purple represents CDR1, yellow represents CDR2, and red represents CDR3. In VNAR, purple represents CDR1, gold represents HV2, yellow represents HV4, and red represents CDR3

Fig. 4

Advantages of single domain antibody for CAR-T therapy. VHH and VNAR have the characteristics of small molecular weight, strong tissue permeability, high affinity, good water solubility and difficulty in aggregation, low immunogenicity, and easy genetic modification, which are helpful for the further development of CAR-T

Fig. 5

Selection of tumor types and targets treated with single domain antibody-based CAR-T therapy. (A). The therapeutic targets that have been used in the development of single domain antibody CAR-T therapy. The colored parts are targets related to solid tumors, and the brunet are targets related to blood tumors. (B). Statistics on the treatment proportion of single domain antibody CAR-T therapy in solid tumors and hematological tumors

Fig. 6

Single domain antibody-based CAR-T cell structure. (A). CAR-T cell structure of traditional ScFv. (B). CAR-T cell structure of monovalent VHH antibodies. (C). CAR-T cell structure of bivalent VHH antibodies. (D). CAR-T cell structure secreting VHH antibodies. E. Shark VNAR-based CAR-T cell structure