Development and evaluation of deuterated [F]JHU94620 isotopologues for the non-invasive assessment of the cannabinoid type 2 receptor in brain.

Background: The cannabinoid type 2 receptors (CB2R) represent a target of increasing importance in neuroimaging due to its upregulation under various neuropathological conditions. Previous evaluation of [F]JHU94620 for the non-invasive assessment of the CB2R availability by positron emission tomography (PET) revealed favourable binding properties and brain uptake, however rapid metabolism, and generation of brain-penetrating radiometabolites have been its main limitations. To reduce the bias of CB2R quantification by blood-brain barrier (BBB)-penetrating radiometabolites, we aimed to improve the metabolic stability by developing -d and -d deuterated isotopologues of [F]JHU94620.

Enhancing the radionuclide theranostic concept through the radiohybrid approach.

Radionuclide theranostics - a fast-growing emerging field in radiopharmaceutical sciences and nuclear medicine - offers a personalised and precised treatment approach by combining diagnosis with specific and selective targeted endoradiotherapy. This concept is based on the application of the same molecule, labelled with radionuclides possessing complementary imaging and therapeutic properties, respectively. In radionuclide theranostics, radionuclide pairs consisting of the same element, such as Cu/Cu, Pb/Pb or I/I are of significant interest due to their identical chemical and pharmacological characteristics.

Synthesis and Preclinical Evaluation of a Bispecific PSMA-617/RM2 Heterodimer Targeting Prostate Cancer.

Prostate-specific membrane antigen (PSMA) and gastrin-releasing peptide receptor (GRPR) have been used for diagnostic molecular imaging/therapy of prostate cancer (PCa). To address tumor heterogeneity, we synthesized and evaluated a bispecific PSMA/GRPR ligand () combining PSMA-617 () and the GRPR antagonist RM2 () with the radiometal chelator DOTA. was radiolabeled with Ga ([Ga]Ga-) and Lu ([Lu]Lu-).

Combined PET Radiotracer Approach Reveals Insights into Stromal Cell-Induced Metabolic Changes in Pancreatic Cancer In Vitro and In Vivo.

Pancreatic stellate cells (PSCs) in pancreatic adenocarcinoma (PDAC) are producing extracellular matrix, which promotes the formation of a dense fibrotic microenvironment. This makes PDAC a highly heterogeneous tumor-stroma-driven entity, associated with reduced perfusion, limited oxygen supply, high interstitial fluid pressure, and limited bioavailability of therapeutic agents. In this study, spheroid and tumor xenograft models of human PSCs and PanC-1 cells were characterized radiopharmacologically using a combined positron emission tomography (PET) radiotracer approach.

MicroRNA Inhibiting Atheroprotective Proteins in Patients with Unstable Angina Comparing to Chronic Coronary Syndrome.

Patients with unstable angina present clinical characteristics of atherosclerotic plaque vulnerability, contrary to chronic coronary syndrome patients. The process of athersclerotic plaque destabilization is also regulated by microRNA particles. In this study, the investigation on expression levels of microRNAs inhibiting the expression of proteins that protect from atherosclerotic plaque progression (miR-92a inhibiting KLF2, miR-10b inhibiting KLF4, miR-126 inhibiting MerTK, miR-98 inhibiting IL-10, miR-29b inhibiting TGFβ1) was undertaken.

The heterobivalent (SSTR2/albumin) radioligand [Cu]Cu-NODAGA-cLAB4-TATE enables efficient somatostatin receptor radionuclide theranostics.

Somatostatin type 2 receptor (SSTR2) radionuclide therapy using β particle-emitting radioligands has entered clinical practice for the treatment of neuroendocrine neoplasms (NENs). Despite the initial success of [Lu]Lu‑DOTA-TATE, theranostic SSTR2 radioligands require improved pharmacokinetics and enhanced compatibility with alternative radionuclides. Consequently, this study evaluates the pharmacokinetic effects of the albumin-binding domain cLAB4 on theranostic performance of copper‑67-labeled NODAGA-TATE variants in an SSTR2-positive mouse pheochromocytoma (MPC) model.

Highlight selection of radiochemistry and radiopharmacy developments by editorial board.

Background: The Editorial Board of EJNMMI Radiopharmacy and Chemistry releases a biannual highlight commentary to update the readership on trends in the field of radiopharmaceutical development.

Main Body: This selection of highlights provides commentary on 19 different topics selected by each coauthoring Editorial Board member addressing a variety of aspects ranging from novel radiochemistry to first-in-human application of novel radiopharmaceuticals.

Conclusion: Trends in radiochemistry and radiopharmacy are highlighted.

Cyclohexanediamine Triazole (CHDT) Functionalization Enables Labeling of Target Molecules with AlF/Ga/In.

The AlF-labeling approach offers a one-step access to radiofluorinated biomolecules by mimicking the labeling process for radiometals. Although these labeling conditions are considered to be mild compared to classic radiofluorinations, improvements of the chelating units have led to the discovery of , which allows AlF-labeling already at ambient temperature. While the suitability of for functionalization and radiofluorination of proteins is well established, its use for small molecules or peptides is less explored.

Scalability study on [La]LaCl production with a focus on potential clinical applications.

Background: In recent years, targeted alpha therapy has gained importance in the clinics, and in particular, the alpha-emitter Ac plays a fundamental role in this clinical development. Nevertheless, depending on the chelating system no real diagnostic alternative has been established which shares similar chemical properties with this alpha-emitting radionuclide. In fact, the race to launch a diagnostic radionuclide to form a matched pair with Ac is still open, and La features attractive radiation properties to claim this place.

Improved automated one-pot two-step radiosynthesis of (S)-[F]FETrp, a radiotracer for PET imaging of indoleamine 2,3-dioxygenase 1 (IDO1).

Background: (S)-[F]FETrp is a promising PET radiotracer for imaging IDO1 activity, one of the main enzymes involved in the tryptophan metabolism that plays a key role in several diseases including cancers. To date, the radiosynthesis of this tryptophan analogue remains highly challenging due to partial racemization occurring during the nucleophilic radiofluorination step. This work aims to develop a short, epimerization-free and efficient automated procedure of (S)-[F]FETrp from a corresponding enantiopure tosylate precursor.

Alpha-Emitting Radionuclides: Current Status and Future Perspectives.

The use of radionuclides for targeted endoradiotherapy is a rapidly growing field in oncology. In particular, the focus on the biological effects of different radiation qualities is an important factor in understanding and implementing new therapies. Together with the combined approach of imaging and therapy, therapeutic nuclear medicine has recently made great progress.

Combination of [F]FDG and [F]PSMA-1007 PET/CT predicts tumour aggressiveness at staging and biochemical failure postoperatively in patients with prostate cancer.

Purpose: [F]fluorodeoxyglucose ([F]FDG) positron emission tomography/computed tomography (PET/CT) has limitations in prostate cancer (PCa) detection owing to low glycolysis in the primary tumour. Recently, prostate-specific membrane antigen (PSMA) PET/CT has been useful for biochemical failure detection and radioligand therapy (RLT) guidance. However, few studies have evaluated its use in primary prostate tumours using PSMA and [F]FDG PET/CT.

Production of the PET radionuclide Cu via the Ni(p,2n)Cu nuclear reaction.

Background: There are only a handful of true theranostic matched pairs, and in particular the theranostic radiocopper trio Cu, Cu and Cu, for diagnosis and therapy respectively, is a very attractive candidate. In fact, the alternative of two imaging radionuclides with different half-lives is a clear advantage over other theranostic pairs, since it offers a better matching for the tracer biological and radionuclide physical half-lives. Due to the high availability of Cu, its translation into the clinic is being successfully carried out, giving the example of the FDA approved radiopharmaceutical Detectnet (copper Cu 64 dotatate injection).

Preclinical evaluation of an F-labeled N-acryloyllysine piperazide for covalent targeting of transglutaminase 2.

Background: Transglutaminase 2 (TGase 2) is a multifunctional protein and has a prominent role in various (patho)physiological processes. In particular, its transamidase activity, which is rather latent under physiological conditions, gains importance in malignant cells. Thus, there is a great need of theranostic probes for targeting tumor-associated TGase 2, and targeted covalent inhibitors appear to be particularly attractive as vector molecules.

Preparation of F-Labeled Tracers Targeting Fibroblast Activation Protein via Sulfur [F]Fluoride Exchange Reaction.

Early detection and treatment of cancers can significantly increase patient prognosis and enhance the quality of life of affected patients. The emerging significance of the tumor microenvironment (TME) as a new frontier for cancer diagnosis and therapy may be exploited by radiolabeled tracers for diagnostic imaging techniques such as positron emission tomography (PET). Cancer-associated fibroblasts (CAFs) within the TME are identified by biomarkers such as fibroblast activation protein alpha (FAPα), which are expressed on their surfaces.

Radiosynthesis and biological evaluation of [F]AG-120 for PET imaging of the mutant isocitrate dehydrogenase 1 in glioma.

Glioma are clinically challenging tumors due to their location and invasiveness nature, which often hinder complete surgical resection. The evaluation of the isocitrate dehydrogenase mutation status has become crucial for effective patient stratification. Through a transdisciplinary approach, we have developed an F-labeled ligand for non-invasive assessment of the IDH1R132H variant by using positron emission tomography (PET) imaging.

Synthesis, Structure-Activity Relationships, Radiofluorination, and Biological Evaluation of [F]RM365, a Novel Radioligand for Imaging the Human Cannabinoid Receptor Type 2 (CB2R) in the Brain with PET.

The development of cannabinoid receptor type 2 (CB2R) PET radioligands has been intensively explored due to the pronounced CB2R upregulation under various pathological conditions. Herein, we report on the synthesis of a series of CB2R affine fluorinated indole-2-carboxamide ligands. Compound RM365 was selected for PET radiotracer development due to its high CB2R affinity ( = 2.

Bispidine Chelators for Radiopharmaceutical Applications with Lanthanide, Actinide, and Main Group Metal Ions.

Octadentate and specifically nonadentate ligands with a bispidine scaffold (3,7-diazabicyclo[3.3.1]nonane) are known to be efficiently coordinated to a range of metal ions of interest in radiopharmaceutical chemistry and lead to exceedingly stable and inert complexes.

Equilibrium Thermodynamics of Macropa Complexes with Selected Metal Isotopes of Radiopharmaceutical Interest.

To pursue the design of stable chelating systems for radiometals, a concise and straightforward method toolbox was developed combining NMR, isothermal titration calorimetry (ITC), and europium time-resolved laser-induced fluorescence spectroscopy (Eu-TRLFS). For this purpose, the macropa chelator was chosen, and Lu, La, Pb, Ra, and Ba were chosen as radiopharmaceutically relevant metal ions. They differ in charge (2+ and 3+) and coordination properties (main group vs lanthanides).

Lysyl Oxidases as Targets for Cancer Therapy and Diagnostic Imaging.

The understanding of the contribution of the tumour microenvironment to cancer progression and metastasis, in particular the interplay between tumour cells, fibroblasts and the extracellular matrix has grown tremendously over the last years. Lysyl oxidases are increasingly recognised as key players in this context, in addition to their function as drivers of fibrotic diseases. These insights have considerably stimulated drug discovery efforts towards lysyl oxidases as targets over the last decade.

Radiofluorination of an Anionic, Azide-Functionalized Teroligomer by Copper-Catalyzed Azide-Alkyne Cycloaddition.

This study describes the synthesis, radiofluorination and purification of an anionic amphiphilic teroligomer developed as a stabilizer for siRNA-loaded calcium phosphate nanoparticles (CaP-NPs). As the stabilizing amphiphile accumulates on nanoparticle surfaces, the fluorine-18-labeled polymer should enable to track the distribution of the CaP-NPs in brain tumors by positron emission tomography after application by convection-enhanced delivery. At first, an unmodified teroligomer was synthesized with a number average molecular weight of 4550 ± 20 Da by free radical polymerization of a defined composition of methoxy-PEG-monomethacrylate, tetradecyl acrylate and maleic anhydride.

Cyclotron-Based Production of Cu for Radionuclide Theranostics via the Zn(p,α)Cu Reaction.

Theranostic matched pairs of radionuclides have aroused interest during the last couple of years, and in that sense, copper is one element that has a lot to offer, and although Cu and Cu are slowly being established as diagnostic radionuclides for PET, the availability of the therapeutic counterpart Cu plays a key role for further radiopharmaceutical development in the future. Until now, the Cu shortage has not been solved; however, different production routes are being explored. This project aims at the production of no-carrier-added Cu with high radionuclidic purity with a medical 30MeV compact cyclotron via the Zn(p,α)Cu reaction.