Nanobody Engineering: Toward Next Generation Immunotherapies and Immunoimaging of Cancer

Abstract

In the last decade, cancer immunotherapies have produced impressive therapeutic results. However, the potency of immunotherapy is tightly linked to immune cell infiltration within the tumor and varies from patient to patient. Thus, it is becoming increasingly important to monitor and modulate the tumor immune infiltrate for an efficient diagnosis and therapy. Various bispecific approaches are being developed to favor immune cell infiltration through specific tumor targeting. The discovery of antibodies devoid of light chains in camelids has spurred the development of single domain antibodies (also called VHH or nanobody), allowing for an increased diversity of multispecific and/or multivalent formats of relatively small sizes endowed with high tissue penetration. The small size of nanobodies is also an asset leading to high contrasts for non-invasive imaging. The approval of the first therapeutic nanobody directed against the von Willebrand factor for the treatment of acquired thrombotic thrombocypenic purpura (Caplacizumab, Ablynx), is expected to bolster the rise of these innovative molecules. In this review, we discuss the latest advances in the development of nanobodies and nanobody-derived molecules for use in cancer immunotherapy and immunoimaging.

Keywords: Cancer; Imaging; Immunotherapy; Nanobody; Single Domain Antibody.

Figure 1

Nanobody-based formats in development for tumor immunotherapy and imaging. (A) Camelids specificity domains derived of conventional IgG1 or HcAbs (IgG2 and IgG3). The nanobody crystal structure shown is pdb entry 6GZP. (B) Formats of nanobody engineered molecules discussed in this review. Nb: nanobody; ARD: antigen recognition domain; TAA: tumor associated antigen.

Figure 2

Nanobody-based strategies targeting the immune stroma of tumors. Nanobody-derived immunomodulatory molecules are under investigation to increase anti-tumor immunity (orange arrows) and prevent tumor-driven immune suppression (blue arrows). TAA: Tumor associated antigen; IC: Immune checkpoint; ARD: Antibody recruiting domain.

Figure 3

Nanobodies as potent tools for tumor immunoimaging. (A) Nanobody labelling strategies allow for site-specific and oriented conjugation. (B) Penetration of an anti-GFP nanobody (left) or full-size IgG (right) within an YFP-expressing brain tissue in vitro. Adapted from Fang T. et al. [120]. (C) SPECT/CT imaging of PD-L1 positive mouse lung epithelial cell line TC-1 in C57/BL6 mice with radiolabeled ^99mTc nanobodies 1 h after injection. The arrows indicate the tumor site. Adapted from Broos K. et al. [124].