Nanobodies: Next Generation of Cancer Diagnostics and Therapeutics

Abstract

The development of targeted medicine has greatly expanded treatment options and spurred new research avenues in cancer therapeutics, with monoclonal antibodies (mAbs) emerging as a prevalent treatment in recent years. With mixed clinical success, mAbs still hold significant shortcomings, as they possess limited tumor penetration, high manufacturing costs, and the potential to develop therapeutic resistance. However, the recent discovery of "nanobodies," the smallest-known functional antibody fragment, has demonstrated significant translational potential in preclinical and clinical studies. This review highlights their various applications in cancer and analyzes their trajectory toward their translation into the clinic.

Keywords: cancer; imaging; immunetherapy; nanobodies; therapeutics.

Figure 1

General nanobody structure and types of nanobodies. (A) Comparison of the monoclonal antibody (mAb) vs. heavy chain antibody (HcAb) to highlight the structural differences of their respective antigen binding regions. The VHH/Nanobody has a much longer CDR3 loop compared to that of the VH-VL domains in mAbs, providing antigen affinity and access to hidden epitopes. (B) A generalized overview of the types of engineered nanobodies to demonstrate how their high modularity enables various modifications. For enhanced antigen avidity, bivalent nanobodies can be created by connecting two identical nanobodies with a linker peptide. Biparatopic nanobodies are a fusion of two nanobodies targeting unique epitopes for the same antigen, with decreased dissociation from the target antigen. Bispecific nanobodies are composed of two nanobodies targeting different antigens and are often utilized as T cell engagers. Nanobodies can also be conjugated to other cancer therapies, nanoparticles, viral vectors, or to imaging agents for targeted tumor visualization. CDR3, complementarity-determining region 3; scFv, short-chain variable fragment; IL-2, Interleukin-2.

Figure 2

Nanobodies: targeting the tumor microenvironment. The synergistic potential of utilizing nanobodies to enhance tumor therapies targeting the tumor microenvironment. TAA, tumor associated antigen; DC, dendritic cell; MMR, mannose macrophage receptor; MHC-II, major histocompatibility complex-II; VEGF, vascular endothelial growth factor; VEGFR2, vascular endothelial growth factor receptor-2; IFN-γ, interferon- γ; IL-2, Interleukin-2; TNFα, tumor necrosis factor- α; IL-23, Interleukin-23; GCSFR, granulocyte colony-stimulating factor receptor; BiTE, bispecific T cell engager; CD16, cluster of differentiation-16; NK, natural killer; TRAIL, tumor necrosis factor- related apoptosis-inducing ligand; TCR, T-cell receptor; Treg, regulatory T cells; CAR, chimeric antigen receptor; UniCAR, universal CAR; TM, targeting module.