Anti-human PD-L1 Nanobody for Immuno-PET Imaging: Validation of a Conjugation Strategy for Clinical Translation.

Abstract

Immune checkpoints, such as programmed death-ligand 1 (PD-L1), limit T-cell function and tumor cells use this ligand to escape the anti-tumor immune response. Treatments with monoclonal antibodies blocking these checkpoints have shown long-lasting responses, but only in a subset of patients. This study aims to develop a Nanobody (Nb)-based probe in order to assess human PD-L1 (hPD-L1) expression using positron emission tomography imaging, and to compare the influence of two different radiolabeling strategies, since the Nb has a lysine in its complementarity determining region (CDR), which may impact its affinity upon functionalization. The Nb has been conjugated with the NOTA chelator site-specifically via the Sortase-A enzyme or randomly on its lysines. [68Ga]Ga-NOTA-(hPD-L1) Nbs were obtained in >95% radiochemical purity. In vivo tumor targeting studies at 1 h 20 post-injection revealed specific tumor uptake of 1.89 ± 0.40%IA/g for the site-specific conjugate, 1.77 ± 0.29%IA/g for the random conjugate, no nonspecific organ targeting, and excretion via the kidneys and bladder. Both strategies allowed for easily obtaining 68Ga-labeled hPD-L1 Nbs in high yields. The two conjugates were stable and showed excellent in vivo targeting. Moreover, we proved that the random lysine-conjugation is a valid strategy for clinical translation of the hPD-L1 Nb, despite the lysine present in the CDR.

• Authors: Jessica Bridoux, Katrijn Broos, Quentin Lecocq, Pieterjan Debie, Charlotte Martin, Steven Ballet, Geert Raes, Sara Neyt, Christian Vanhove, Karine Breckpot, Nick Devoogdt, Vicky Caveliers, Marleen Keyaerts, Catarina Xavier
• Journal: Biomolecules (Biomolecules) Vol. 10 Issue 10 (09 29 2020) ISSN: 2218-273X [Electronic] Switzerland
• PMID: 33003481 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antibodies, Anti-Idiotypic
• Antibodies, Monoclonal
• B7-H1 Antigen
• CD274 protein, human
• Radiopharmaceuticals

Topics

• Antibodies, Anti-Idiotypic (immunology)
• Antibodies, Monoclonal (pharmacology)
• B7-H1 Antigen (immunology, pharmacology)
• Cell Line, Tumor
• Humans
• Isotope Labeling
• Neoplasms (diagnostic imaging, immunology, pathology)
• Positron-Emission Tomography
• Radiopharmaceuticals (pharmacology)
• Tissue Distribution (drug effects)