2. Academic Validation
  3. Multiscale imaging of therapeutic anti-PD-L1 antibody localization using molecularly defined imaging agents

Multiscale imaging of therapeutic anti-PD-L1 antibody localization using molecularly defined imaging agents

  • J Nanobiotechnology. 2022 Feb 2;20(1):64. doi: 10.1186/s12951-022-01272-5.
Iris M Hagemans # 1 2,  Peter J Wierstra # 3,  Kas Steuten 1 2,  Janneke D M Molkenboer-Kuenen 3,  Duco van Dalen 1 2,  Martin Ter Beest 1,  Johan M S van der Schoot 1,  Olga Ilina 1 2,  Martin Gotthardt 3,  Carl G Figdor 1 2 4,  Ferenc A Scheeren 5,  Sandra Heskamp # 6,  Martijn Verdoes # 7 8
Affiliations

Affiliations

  • 1 Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands.
  • 2 Institute for Chemical Immunology, Nijmegen, The Netherlands.
  • 3 Department of Medical Imaging, Nuclear Medicine, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands.
  • 4 Division of Immunotherapy, Oncode Institute, Radboud University Medical Center, Nijmegen, The Netherlands.
  • 5 Department of Dermatology, Leiden University Medical Centre, Leiden, The Netherlands.
  • 6 Department of Medical Imaging, Nuclear Medicine, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands. [email protected].
  • 7 Department of Tumor Immunology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands. [email protected].
  • 8 Institute for Chemical Immunology, Nijmegen, The Netherlands. [email protected].
  • # Contributed equally.
PMID: 35109860 DOI: 10.1186/s12951-022-01272-5
Abstract

Background: While immune checkpoint inhibitors such as anti-PD-L1 antibodies have revolutionized Cancer treatment, only subgroups of patients show durable responses. Insight in the relation between clinical response, PD-L1 expression and intratumoral localization of PD-L1 therapeutics could improve patient stratification. Therefore, we present the modular synthesis of multimodal antibody-based imaging tools for multiscale imaging of PD-L1 to study intratumoral distribution of PD-L1 therapeutics.

Results: To introduce imaging modalities, a peptide containing a near-infrared dye (sulfo-Cy5), a chelator (DTPA), an azide, and a sortase-recognition motif was synthesized. This peptide and a non-fluorescent intermediate were used for site-specific functionalization of c-terminally sortaggable mouse IgG1 (mIgG1) and Fab anti-PD-L1. To increase the half-life of the Fab fragment, a 20 kDa PEG chain was attached via strain-promoted azide-alkyne cycloaddition (SPAAC). Biodistribution and imaging studies were performed with 111In-labeled constructs in 4T1 tumor-bearing mice. Comparing our site-specific antibody-conjugates with randomly conjugated antibodies, we found that antibody clone, isotype and method of DTPA conjugation did not change tumor uptake. Furthermore, addition of sulfo-Cy5 did not affect the biodistribution. PEGylated Fab fragment displayed a significantly longer half-life compared to unPEGylated Fab and demonstrated the highest overall tumor uptake of all constructs. PD-L1 in tumors was clearly visualized by SPECT/CT, as well as whole body fluorescence imaging. Immunohistochemistry staining of tumor sections demonstrated that PD-L1 co-localized with the fluorescent and autoradiographic signal. Intratumoral localization of the imaging agent could be determined with cellular resolution using fluorescent microscopy.

Conclusions: A set of molecularly defined multimodal antibody-based PD-L1 imaging agents were synthesized and validated for multiscale monitoring of PD-L1 expression and localization. Our modular approach for site-specific functionalization could easily be adapted to Other targets.

Keywords

Antibody; Cancer; Fluorescence imaging; Immune checkpoints; Nuclear imaging.

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