Challenges in the Development of PET and SPECT Radiotracers: Innovative Ideas with Negative Outcomes

A special issue of Pharmaceuticals (ISSN 1424-8247). This special issue belongs to the section "Radiopharmaceutical Sciences".

Deadline for manuscript submissions: 25 September 2025 | Viewed by 978

Special Issue Editors


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Guest Editor
Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Research Site, Leipzig, Germany
Interests: brain tumours; PET/MRI; small animal imaging; radiotracer development

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Guest Editor
Department of Neuroradiopharmaceuticals, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Research Site, Leipzig, Germany
Interests: radiotracer development; brain PET imaging; radiochemistry; Fluorine-18; HPLC

Special Issue Information

Dear Colleagues,

We are pleased to announce a Special Issue dedicated to the challenges and innovative efforts in the development of PET and SPECT radiotracers. This collection aims to highlight the complexities and hurdles in this field and the importance of "unsuccessful" endeavors for the advancement of radiopharmaceutical research.

With this Special Issue, we will provide a space to present substantial research with negative results in the field of radiotracer development and seek to emphasize innovative ideas that, despite their potential, have resulted in supposedly unpublishable outcomes. We believe that knowing what fails is as important as knowing what succeeds to support a comprehensive understanding, encourage methodological improvements and finally strengthen the scientific community.

Radiotracer development for PET and SPECT imaging involves numerous challenges in medicinal chemistry, radiolabeling, purification, stability, target selectivity, and in vivo pharmacokinetics. These obstacles can lead to unexpected negative results, which are often underreported but crucial for scientific progress and innovation.

Publishing such results is essential for advancing our collective knowledge and guiding future research. Moreover, it prevents duplications of efforts and contributes to a more reliable scientific literature. We therefore look forward to receiving your contributions in the fields of medicinal chemistry, radiochemistry, and in vitro and/or in vivo preclinical evaluation of newly developed or known PET and SPECT radiopharmaceuticals.

This Special Issue is open to original research articles, brief reports, and reviews.

Dr. Magali Toussaint
Dr. Barbara Wenzel
Guest Editors

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Keywords

  • radiotracer development
  • positron emission tomography (PET)
  • single-photon emission computed tomography (SPECT)
  • negative results
  • diagnostic radiotracers
  • therapeutic radiopharmaceuticals
  • radiolabeling
  • automated synthesis and GMP
  • pre-clinical studies
  • medicinal chemistry

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Published Papers (1 paper)

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Research

14 pages, 3879 KiB  
Article
PET Imaging Expedites Detection of Aberration in the Humanization of an Annexin A1 Targeting Antibody
by Hailey A. Houson, Brian D. Wright, Solana R. Fernandez, Tim Buss, Sharon L. White, Brittany Cederstrom, James M. Omweri, Jonathan E. McConathy, Jan E. Schnitzer and Suzanne E. Lapi
Pharmaceuticals 2025, 18(3), 295; https://doi.org/10.3390/ph18030295 - 21 Feb 2025
Viewed by 483
Abstract
Objectives: Annexin-A1 is a 37 kDa phospholipid-binding protein which is concentrated in a truncated 34 kDa form (AnnA1) in caveolae on the tumor vascular endothelial cell surface with expression in many tumor types. PRISM developed the monoclonal mouse antibody mAnnA1 against AnnA1 [...] Read more.
Objectives: Annexin-A1 is a 37 kDa phospholipid-binding protein which is concentrated in a truncated 34 kDa form (AnnA1) in caveolae on the tumor vascular endothelial cell surface with expression in many tumor types. PRISM developed the monoclonal mouse antibody mAnnA1 against AnnA1 for evaluation of AnnA1 as a potential target for imaging and therapy in oncology. mAnnA1 was humanized to make hAnnA1 for translation to clinical studies. Both PRISM-produced mAnnA1 and cGMP contractor-produced hAnnA1 were investigated using noninvasive PET/CT imaging, and dosimetry was evaluated to enable clinical translation of this strategy and to investigate in vivo behavior of hAnnA1. Methods: Antibodies mAnnA1 and hAnnA1 (PRISM “hAnnA1-P” or contractor generated “hAnnA1-C”) were conjugated with the chelator deferoxamine and evaluated for immunoreactivity with ELISA. Conjugated antibodies were radiolabeled with zirconium-89. Naïve mice, rats, and non-human primates (NHP) were injected with [89Zr]mAnnA1 or [89Zr]hAnnA1 and imaged with PET/CT up to 10 days post injection. After imaging, mice and rats were euthanized and organs were collected, weighed, and radioactivity was quantified using a gamma counter. Dosimetry in mice and NHPs were calculated using OLINDA. Results: [89Zr]mAnnA1 showed similar biodistribution to other antibodies with slow clearance through the liver. Transition to [89Zr]hAnnA1-C during the dosimetry studies revealed substantial uptake in the spleen (130 ± 48% ID/g at day 5 post injection in female BALB/c), which was not observed with [89Zr]mAnnA1 (5.6 ± 1.7% ID/g at day 7 PI). Further studies in multiple strains of mice showed variable elevated splenic uptake of [89Zr]hAnnA1-C across mouse strains, with the highest uptake observed in female BALB/c mice (118.4 ± 23.1% ID/g) and the lowest uptake observed in male CD1 mice (34.7 ± 10.2% ID/g). Additionally, splenic uptake of hAnnA1-C was observed in Fischer rats (2.8 ± 0.6% ID/organ) and NHPs (1.6 ± 0.6% ID/organ), although at lower levels than what was observed in BALB/c mice (8.8 ± 1.8% ID/organ). Dosimetry results showed similar values between estimates based on mouse and NHP data, with the largest difference seen in the spleen (5.2 vs. 2.6 mSv/MBq in females respectively). Sequencing of hAnnA1-C revealed a frameshift mutation in the antibody sequence introduced during cGMP manufacture. Restoration of the antibody sequence by PRISM returned the antibody distribution into alignment with mAnnA1. Conclusions: An aberration introduced during cGMP production of hAnnA1-C resulted in increased splenic uptake and alteration of the biodistribution in mice. PET imaging enabled quantitative detection of the immunogenic behavior of hAnnA1, which led to detection of the sequence error. Restoration of the sequence resulted in an antibody which was non-immunogenic to mice. Full article
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