Overview of Prostaglandin E2 (PGE2)-Targeting Radiolabelled Imaging Probes from Preclinical Perspective: Lessons Learned and Road Ahead

As malignancies still represent one of the major health concerns worldwide, early tumor identification is among the priorities of today's science. Given the strong association between cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2), PGE2 receptors (EPs), and carcinogenesis, target-specific molecules directed towards the components of the COX2/PGE2/EP axis seem to be promising imaging probes in the diagnostics of PGE2pos. neoplasms and in the design of anti-cancer drugs. Featured with outstanding inclusion forming capability, β-cyclodextrins (CDs) including randomly methylated β-CD (RAMEB) were reported to complex with PGE2. Therefore, radiolabelled β-CDs could be valuable vectors in the molecular imaging of PGE2-related tumorigenesis. In vivo preclinical small animal model systems applying positron emission tomography (PET) ensure a well-suited scenario for the assessment of PGE2-affine labelled CD derivatives. Previous translational studies dealt with the evaluation of the tumor-homing capability of Gallium-68 (⁶⁸Ga) and Bismuth-205/206 (^205/206Bi)-appended β-CD compounds conjugated with chelator NODAGA or DOTAGA: [⁶⁸Ga]Ga-NODAGA-2-hydroxypropyl-β-cyclodextrin/HPBCD, [⁶⁸Ga]Ga-NODAGA-RAMEB, [⁶⁸Ga]Ga-DOTAGA-RAMEB, and [^205/206Bi]Bi-DOTAGA-RAMEB in experimental tumors with different PGE2 expression. These imaging probes project the establishment of tailor-made PET diagnostics of PGE2pos. malignancies. In the present review, we provide a detailed overview of the in vivo investigations of radiolabelled PGE2-directed CDs, highlighting the importance of the integration of translational discoveries into routine clinical usage.