Evaluation of affinity matured Affibody molecules for imaging of the immune checkpoint protein B7-H3

• Published in: Nuclear medicine and biology Vol. 124-125; p. 108384
• Main Authors: Oroujeni, Maryam, Bezverkhniaia, Ekaterina A., Xu, Tianqi, Liu, Yongsheng, Plotnikov, Evgenii V., Klint, Susanne, Ryer, Eva, Karlberg, Ida, Orlova, Anna, Frejd, Fredrik Y., Tolmachev, Vladimir
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.09.2023
• Subjects: AC12-GGGC; Affibody molecule; Affinity maturation; Animals; B7 Antigens - metabolism; B7-H3; Cell Line, Tumor; GGGC; Humans; Immune Checkpoint Proteins - metabolism; Mice; Neoplasms - metabolism; Peptide-based cysteine-containing chelator; Radionuclide Imaging; SKOV-3 xenograft; SPECT/CT imaging; Technetium - chemistry; Technetium-99m ( 99m Tc); Technetium-99m (99mTc); Tissue Distribution; SPECT/CT imaging; Peptide-based cysteine-containing chelator; Affibody molecule; B7-H3; AC12-GGGC; SKOV-3 xenograft; Technetium-99m (99mTc); Affinity maturation; GGGC; Technetium-99m ((99m)Tc)
• ISSN: 0969-8051; 1872-9614; 1872-9614
• DOI: 10.1016/j.nucmedbio.2023.108384

B7-H3 (CD276), an immune checkpoint protein, is a promising molecular target for immune therapy of malignant tumours. Sufficient B7-H3 expression level is a precondition for successful therapy. Radionuclide molecular imaging is a powerful technique for visualization of expression levels of molecular targets in vivo. Use of small radiolabelled targeting proteins would enable high-contrast radionuclide imaging of molecular targets if adequate binding affinity and specificity of an imaging probe could be provided. Affibody molecules, small engineered affinity proteins based on a non-immunoglobulin scaffold, have demonstrated an appreciable potential in radionuclide imaging. Proof-of principle of radionuclide visualization of expression levels of B7-H3 in vivo was demonstrated using the [99mTc]Tc-AC12-GGGC Affibody molecule. We performed an affinity maturation of AC12, enabling selection of clones with higher affinity. Three most promising clones were expressed with a –GGGC (triglycine-cysteine) chelating sequence at the C-terminus and labelled with technetium-99m (99mTc). 99mTc-labelled conjugates bound to B7-H3-expressing cells specifically in vitro and in vivo. Biodistribution in mice bearing B7-H3-expressing SKOV-3 xenografts demonstrated improved imaging properties of the new conjugates compared with the parental variant [99mTc]Tc-AC12-GGGC. [99mTc]Tc-SYNT-179 provided the strongest improvement of tumour-to-organ ratios. Thus, affinity maturation of B7-H3 Affibody molecules could improve biodistribution and targeting properties for imaging of B7-H3-expressing tumours. [Display omitted]