Pretargeted PET Imaging with a TCO-Conjugated Anti-CD44v6 Chimeric mAb U36 and [89Zr]Zr-DFO-PEG5‑Tz

• Published in: Bioconjugate chemistry Vol. 33; no. 5; pp. 956 - 968
• Main Authors: Lumen, Dave, Vugts, Danielle, Chomet, Marion, Imlimthan, Surachet, Sarparanta, Mirkka, Vos, Ricardo, Schreurs, Maxime, Verlaan, Mariska, Lang, Pauline A., Hippeläinen, Eero, Beaino, Wissam, Windhorst, Albert D., Airaksinen, Anu J.
• Format: Journal Article
• Language: English
• Published: Washington American Chemical Society 18-05-2022
• Subjects: Antibodies; Drug development; Head & neck cancer; Head and neck carcinoma; Imaging; In vivo methods and tests; Monoclonal antibodies; Pharmacokinetics; Positron emission; Positron emission tomography; Radioisotopes; Squamous cell carcinoma; Tomography; Tumors; Xenografts; Xenotransplantation; Zirconium; Zirconium isotopes
• ISSN: 1043-1802; 1520-4812
• DOI: 10.1021/acs.bioconjchem.2c00164

The recent advances in the production of engineered antibodies have facilitated the development and application of tailored, target-specific antibodies. Positron emission tomography (PET) of these antibody-based drug candidates can help to better understand their in vivo behavior. In this study, we report an in vivo proof-of-concept pretargeted immuno-PET study where we compare a pretargeting vs targeted approach using a new 89Zr-labeled tetrazine as a bio-orthogonal ligand in an inverse electron demand Diels–Alder (IEDDA) in vivo click reaction. A CD44v6-selective chimeric monoclonal U36 was selected as the targeting antibody because it has potential in immuno-PET imaging of head-and-neck squamous cell carcinoma (HNSCC). Zirconium-89 (t 1/2 = 78.41 h) was selected as the radionuclide of choice to be able to make a head-to-head comparison of the pretargeted and targeted approaches. [89Zr]­Zr-DFO-PEG5-Tz ([89Zr]­Zr-3) was synthesized and used in pretargeted PET imaging of HNSCC xenografts (VU-SCC-OE) at 24 and 48 h after administration of a trans-cyclooctene (TCO)-functionalized U36. The pretargeted approach resulted in lower absolute tumor uptake than the targeted approach (1.5 ± 0.2 vs 17.1 ± 3.0% ID/g at 72 h p.i. U36) but with comparable tumor-to-non-target tissue ratios and significantly lower absorbed doses. In conclusion, anti-CD44v6 monoclonal antibody U36 was successfully used for 89Zr-immuno-PET imaging of HNSCC xenograft tumors using both a targeted and pretargeted approach. The results not only support the utility of the pretargeted approach in immuno-PET imaging but also demonstrate the challenges in achieving optimal in vivo IEDDA reaction efficiencies in relation to antibody pharmacokinetics.