18F-labeled anti-human CD20 cys-diabody for same-day immunoPET in a model of aggressive B cell lymphoma in human CD20 transgenic mice

Kirstin A Zettlitz; Richard Tavaré; Wen-Ting K Tsai; Reiko E Yamada; Noel S Ha; Jeffrey Collins; R Michael van Dam; John M Timmerman; Anna M Wu

doi:10.1007/s00259-018-4214-x

¹⁸F-labeled anti-human CD20 cys-diabody for same-day immunoPET in a model of aggressive B cell lymphoma in human CD20 transgenic mice

Eur J Nucl Med Mol Imaging. 2019 Feb;46(2):489-500. doi: 10.1007/s00259-018-4214-x. Epub 2018 Nov 19.

Authors

Kirstin A Zettlitz^{1

2}, Richard Tavaré^{3

4}, Wen-Ting K Tsai³, Reiko E Yamada⁵, Noel S Ha^{3

6}, Jeffrey Collins³, R Michael van Dam^{3

6}, John M Timmerman⁵, Anna M Wu^{3

7}

Affiliations

¹ Crump Institute for Molecular Imaging, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90095, USA. kzettlitz@coh.org.
² Department of Molecular Imaging and Therapy, Beckman Research Institute, City of Hope, 1500 E Duarte Rd, Duarte, CA, 91010, USA. kzettlitz@coh.org.
³ Crump Institute for Molecular Imaging, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 90095, USA.
⁴ Regeneron Pharmaceuticals, Inc, 777 Old Saw Mill River Road, Tarrytown, NY, 10591, USA.
⁵ Division of Hematology & Oncology, Department of Medicine, University of California, Los Angeles, Los Angeles, CA, 90095, USA.
⁶ Department of Bioengineering, Samueli School of Engineering, University of California, Los Angeles, Los Angeles, CA, 90095, USA.
⁷ Department of Molecular Imaging and Therapy, Beckman Research Institute, City of Hope, 1500 E Duarte Rd, Duarte, CA, 91010, USA.

Abstract

Purpose: Metabolic imaging using [¹⁸F]FDG is the current standard for clinical PET; however, some malignancies (e.g., indolent lymphomas) show low avidity for FDG. The majority of B cell lymphomas express CD20, making it a valuable target both for antibody-based therapy and imaging. We previously developed PET tracers based on the humanised anti-CD20 antibody obinutuzumab (GA101). Preclinical studies showed that the smallest bivalent fragment, the cys-diabody (GAcDb, 54.5 kDa) with a peak uptake at 1-2 h post-injection and a biological half-life of 2-5 h, is compatible with short-lived positron emitters such as fluorine-18 (¹⁸F, t_1/2 110 min), enabling same-day imaging.

Methods: GAcDb was radiolabeled using amine-reactive N-succinimidyl 4-[¹⁸F]-fluorobenzoate ([¹⁸F]SFB), or thiol-reactive N-[2-(4-[¹⁸F]-fluorobenzamido)ethyl]maleimide ([¹⁸F]FBEM) for site-specific conjugation to C-terminal cysteine residues. Both tracers were used for immunoPET imaging of the B cell compartment in human CD20 transgenic mice (hCD20TM). [¹⁸F]FB-GAcDb immunoPET was further evaluated in a disseminated lymphoma (A20-hCD20) syngeneic for hCD20TM and compared to [¹⁸F]FDG PET. Tracer uptake was confirmed by ex vivo biodistribution.

Results: The GAcDb was successfully ¹⁸F-radiolabeled using two different conjugation methods resulting in similar specific activities and without impairing immunoreactivity. Both tracers ([¹⁸F]FB-GAcDb and [¹⁸F]FBEM-GAcDb) specifically target human CD20-expressing B cells in transgenic mice. Fast blood clearance results in high contrast PET images as early as 1 h post injection enabling same-day imaging. [¹⁸F]FB-GAcDb immunoPET detects disseminated lymphoma disease in the context of normal tissue expression of hCD20, with comparable sensitivity as [¹⁸F]FDG PET but with added specificity for the therapeutic target.

Conclusions: [¹⁸F]FB-GAcDb and [¹⁸F]FBEM-GAcDb could monitor normal B cells and B cell malignancies non-invasively and quantitatively in vivo. In contrast to [¹⁸F]FDG PET, immunoPET provides not only information about the extent of disease but also about presence and localisation of the therapeutic target.

Keywords: 18F; Anti-CD20 cys-diabody; Antibody fragments; B cell lymphoma; ImmunoPET; Same-day imaging.

MeSH terms

Animals
Antibodies / immunology*
Antigens, CD20 / immunology*
Fluorine Radioisotopes*
Humans
Isotope Labeling
Lymphoma, B-Cell / diagnostic imaging*
Lymphoma, B-Cell / immunology
Lymphoma, B-Cell / pathology*
Mice
Mice, Transgenic
Positron-Emission Tomography / methods*
Radiochemistry
Time Factors
Tissue Distribution

Substances

Antibodies
Antigens, CD20
Fluorine Radioisotopes
Fluorine-18

Abstract

MeSH terms

Substances

Grants and funding