Search Results (931)

The growing use of experimental radiopharmaceuticals for targeted radionuclide therapy (TRT) highlights the need for robust “in house” radiolabeling protocols. Among these, PSMA-ALB-56 is a PSMA ligand incorporating an albumin-binding moiety to enhance pharmacokinetics, which showed promise for prostate cancer treatment. This study investigated manual radiolabeling conditions of this vector molecule with lutetium-177 and developed a corresponding automated synthesis protocol. Manual experiments on low activities explored buffer systems and antioxidants, identifying sodium acetate buffer and L-methionine as optimal, achieving radiochemical purities above 97% with excellent stability over 48 h. However, when these conditions were transposed directly to an automated process on a GAIA^® module with activities > 2 GBq, radiochemical purity dropped below 70% due to significant radiolysis. This result emphasized that conditions optimized at low activities are not directly transferable to high-activity automated production, and highlighted the crucial role of antioxidant concentration. An optimized automated method was subsequently developed, integrating a solid-phase extraction purification step, higher antioxidant levels during radiolabeling and formulation, and a larger final product volume. These changes led to radiochemical purities above 98.9% and excellent product stability over 120 h for 3 test batches. The presence of high concentrations of methionine and ascorbic acid was essential to protect against radiolysis. This work underscores the importance of adjusting radiolabeling strategies during process scale-up and confirmed that antioxidant concentration is essential for successful ¹⁷⁷Lu radiolabeling. The optimized automated method developed here for [¹⁷⁷Lu]Lu-PSMA-ALB-56 may also be adapted to other radiopharmaceuticals in development for TRT. Full article

Background/Objectives: Fibroblast activation protein (FAP) is highly expressed in tumor stroma and selected inflammatory conditions, offering a promising target for molecular imaging. [⁶⁸Ga]Ga-FAPI-46 is a DOTA-based FAP inhibitor with excellent tumor-to-background ratio and potential advantages over [¹⁸F]FDG in low-glycolytic tumors. This article aims to highlight the quality elements that are relevant to clinical practice and to describe the development of an investigational medicinal product dossier for a bicentric clinical trial involving [⁶⁸Ga]Ga-FAPI-46. Methods: The radiolabeling was performed by the two facilities using different automated synthesizers, but with the same specifications and acceptance criteria Results: Three validation batches per site were analyzed for radiochemical/radionuclidic purity, pH, endotoxin, sterility, and bioburden according to European Pharmacopoeia standards. Stability was as sessed up to 2 h post-synthesis. All batches met predefined acceptance criteria. Conclusions: Despite differences in radiosynthesizer modules, product quality and process reproducibility were maintained across both centers. [⁶⁸Ga]Ga-FAPI-46 can be reliably produced in academic settings under GMP-like conditions, enabling multicenter clinical research and facilitating IMPD submissions for broader adoption of FAP-targeted PET imaging. Full article

Background: B7-H3, an immunoregulatory protein of the B7 family, has been associated with both anti-cancer immunity and tumor promotion, with its expression commonly correlated with poor prognosis. Although it is frequently expressed across cancers, its heterogeneity may limit the effectiveness of B7-H3-targeted therapies. Consequently, a sensitive and non-invasive method is needed to assess B7-H3 expression for patient selection and stratification. Single-domain antibody fragments (sdAbs) offer a promising platform for developing such a diagnostic tool. Methods: To generate B7-H3 sdAbs, two Ilamas were immunized with the recombinant human B7-H3 protein. Positive clones were selected through Phage biopanning and characterized for thermal stability, binding specificity, and affinity to human and murine B7-H3 proteins. Selected sdAbs were radiolabeled with Technetium-99m (^99mTc) and evaluated for B7-H3 detection in two xenograft tumor models using micro-SPECT/CT imaging and dissection studies. Results: Sixteen purified sdAbs bound specifically to recombinant B7-H3 proteins and cells expressing native B7-H3 antigens, with nanomolar affinities. The four best-performing sdAbs bound promiscuously to tested mouse and human B7-H3 isoforms. Lead sdAb C51 labeled with ^99mTc displayed specific accumulation across two human B7-H3⁺ tumor models, achieving high contrast with a tumor-to-blood ratio of up to 10 ± 3.16, and a tumor uptake of up to 4.96 ± 1.4%IA/g at 1.5 h post injection. Conclusions: The lead sdAb enabled rapid, specific, and non-invasive imaging of human B7-H3⁺ tumors. Its isoform promiscuity supports broad applicability across cancers expressing different human B7-H3 isoforms. These results support further development for clinical translation to enable patient selection and improved B7-H3-targeted therapies. Full article

The development of positron emission tomography (PET) tracers targeting α-synuclein (α-syn) aggregates is critical for the early diagnosis, differential classification, and therapeutic monitoring of synucleinopathies such as Parkinson’s disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy. Despite recent advances, challenges including the low abundance of α-syn aggregates (10–50× lower than amyloid-beta (Aβ) or Tau), structural heterogeneity (e.g., flat fibrils in PD vs. cylindrical forms in DLB), co-pathology with Aβ/Tau, and poor metabolic stability have hindered PET tracer development for this target. To optimize our previously reported pyridothiophene-based radiotracer, [¹⁸F]asyn-44, we present the synthesis and evaluation of novel S,N-heterocyclic scaffold derivatives for α-syn. A library of 49 compounds was synthesized, with 8 potent derivatives (LMD-006, LMD-022, LMD-029, LMD-044, LMD-045, LMD-046, LMD-051, and LMD-052) demonstrating equilibrium inhibition constants (K_i) of 6–16 nM in PD brain homogenates, all of which are amenable for radiolabeling with fluorine-18. This work advances the molecular toolkit for synucleinopathies and provides a roadmap for overcoming barriers in PET tracer development, with lead compounds that can be considered for biomarker-guided clinical trials and targeted therapies. Full article

Background/Objectives: Homotypic targeting refers to the ability of cells to preferentially interact with other cells of the same type. An understanding of how cells use homotypic targeting (self-homing) characteristics for tumor-targeting purposes may aid in the effective delivery of radionuclides or other drugs for imaging or therapeutic applications. Additionally, studies investigating the targeting properties of cells from the same lineage may shed light on this interesting mechanism, allowing it to be harnessed for other applications. The objective of this study was to assess the tumor-self targeting potential of PC3 prostate cancer and 4T1 breast cancer cells using a direct cell labeling technique, with a focus on evaluation of cellular labeling efficiency, cell viability, cellular efflux, and in vivo tumor-self targeting capability using both identical and dissimilar tumor models. Methods: [⁸⁹Zr]Zr-oxine was prepared and utilized for the labeling of PC3 and 4T1 cells. Following the assessment of cell labeling efficacy, viability, and efflux, PET/CT imaging and biodistribution studies were conducted with [⁸⁹Zr]Zr-oxine labeled PC3 and 4T1 cells in PC3 and 4T1 tumor-bearing mice models. Results: Both PC3 cells and 4T1 cells were radiolabeled with [⁸⁹Zr]oxine, with PC3 cells illustrating a higher labeling efficiency (86.55 ± 0.38%) than 4T1 cells (46.95 ± 1.47%). Notably, radiolabeled PC3 cells illustrated significant uptake in PC3 tumors (7.54 ± 1.07%ID/gram at 24 h and 6.95 ± 3.56%ID/gram at 48 h) with lower tumor uptake in the 4T1 xenograft model (1.79 ± 0.29%ID/gram at 24 h and 1.42 ± 0.71%ID/gram at 48 h), illustrating the potential of self-targeting. Conclusions: Both PC3 and 4T1 cells followed a similar pattern of biodistribution, with labeled PC3 cells demonstrating lower blood retention and reduced uptake in non-target organs such as lungs and heart. Taken together, these results may indicate that PC3 cells illustrate homotypic targeting, warranting further investigation of this phenomenon. Full article

Alpha therapy (TAT) relies on combining alpha-emitting radionuclides with specific cell-targeting vectors to deliver a high payload of cytotoxic radiation capable of destroying tumor tissues. TAT efficacy comes from the tissue selectivity of the targeting vector, the high linear energy transfer (LET) of the radionuclide, and the short range of alpha particles in tissues. Recent research studies have been directed to evaluate TAT on a preclinical and clinical scale, including evaluating damage to tumor tissues with minimal toxic radiation effects on surrounding healthy tissues. This review highlights the use of Actinium-225/Bismuth-213 radionuclides as promising candidates for TAT. Herein, we begin with a discussion on the production and supply of [²²⁵Ac]Ac/[²¹³Bi]Bi followed by the formulation of [²²⁵Ac]Ac/[²¹³Bi]Bi-radiopharmaceuticals using different radiolabeling techniques. Finally, we have summarized the preclinical and clinical evaluation of these potential radiotheranostic agents. Full article

Objectives: Immunotherapy utilizing immune-stimulating cytokines such as IL12 holds great promise for the treatment of cancer. However, clinical use of IL12 is hampered due to severe toxicity following systemic administration. We here present a novel treatment strategy in which IL12 is chemically silenced by conjugation to PEG masks that sterically hinder the receptor binding. Subsequently, the masks can be released on demand using a bioorthogonal click reaction, cleaving the linker connecting the masks, thereby restoring the native cytokine. This “click-to-release” approach is based on the highly selective Inverse electron-demand Diels–Alder (IEDDA) pyridazine elimination reaction between a tetrazine (Tz) and a trans-cyclooctene (TCO), optimized for fast reaction kinetics and in vivo compatibility. Selective activation in the tumor microenvironment is achieved by pretargeting one component of this reaction to the tumor, triggering local activation of the masked IL12 once it is given in a secondary i.v. injection. Methods: IL12 masking and unmasking were evaluated in vitro with PAGE and HEK-Blue reporter cells and ex vivo with ELISA. Biodistribution in mice was evaluated with I-125 radiolabeling and biotin-click histochemistry. Results: Several designs were evaluated and optimized in vitro, resulting in an IL12-TCO-PEG construct that exhibited superior masking and subsequent reactivation upon reaction with a tetrazine bound to a TAG-72-targeted diabody. In tumor-bearing mice, we demonstrated that this diabody-tetrazine could efficiently pre-localize tetrazine in the tumor. Administration of IL12-TCO-PEG 24 h later afforded efficient and selective unmasking in tumors, but not in the blood. Conclusions: These results demonstrate proof of principle of the click-cleavable IL12 prodrug approach and showcase the versatility of the click-to-release reaction. Full article

With the rapid evolution of nanotechnology, magnetic iron oxide nanoparticles (MNPs)—primarily Fe₃O₄ and γ-Fe₂O₃—have gained prominence in biomedicine. Their extensive specific surface area, tunable surface functionalities, and intrinsic magnetic characteristics render them highly versatile for diverse clinical applications, including tumor visualization through Magnetic Resonance Imaging (MRI), radiolabeling, targeted radiotherapy, hyperthermia, gene transfer, drug delivery, Magnetic Particle Imaging (MPI), magnetic blood filtration and theranostic strategies. Nevertheless, ensuring the biocompatibility and non-toxicity of these nanostructures remains a fundamental prerequisite for their medical implementation. Hence, it is essential to continuously refine our understanding of MNP-related toxicity and pursue comprehensive research on this front. This article consolidates up-to-date insights into the evaluation of MNPs’ toxicological profiles, emphasizing the influence of physicochemical properties such as morphology, surface modifications, and electrostatic characteristics, along with operational factors like dosage and administration routes. Traditional toxicity testing strategies, including in vitro assays as first-line screening tools, together with standard ex vivo and in vivo models, are discussed. Special attention is given to the emerging role of New Approach Methodologies (NAMs), such as organoid formation, 3D bioprinting, in ovo chicken embryo assays, and image cytometry. These techniques offer ethical, human-relevant, and informative alternatives to animal testing, supporting more predictive and translationally relevant toxicity assessment of MNPs. Taken together, the integration of conventional assays with innovative NAMs, alongside careful consideration of physicochemical and operational factors, is essential to translate the laboratory promise of MNPs into safe and clinically effective nanomedicines. Full article

Neuroendocrine tumors (NETs) are a rare and heterogeneous class of neoplastic lesions, but their prevalence has increased significantly over the past three decades. These tumors are aggressive and difficult to treat. Improving diagnostic efficiency and treatment effectiveness is important for patients with neuroendocrine tumors. Radiopharmaceutical therapeutic diagnostics combines diagnosis and treatment technology and has broad prospects in precision medicine, especially for the early diagnosis and treatment of tumors. To compare the diagnostic advantages of radiolabeled somatostatin receptor agonists and antagonists for liver metastases from NETs and the disease control rate in NET patients. Systematic search of PubMed, Embase, Cochrane, Ovid, Scopus, and Web of Science databases up to 29 October 2024. Clinical trials of somatostatin receptor agonists and antagonists for NET diagnosis or treatment. Following PRISMA guidelines, data were independently extracted by two researchers. Pooled diagnostic or treatment effects and 95% CIs were reported using a random-effects meta-analysis model. Effect of somatostatin receptor agonists and antagonists in detecting liver metastases and disease control rate. Risk Ratio (RR) for liver metastasis detection and Effect Size (ES) for disease control rate were calculated. From 5291 articles, 52 were included in the meta-analysis. Radiolabeled somatostatin receptor antagonists were significantly more effective than agonists in detecting liver lesions (RR = 11.57, 95% CI: 4.10, 32.67). Disease control rates were higher with antagonists (ES = 0.90, 95% CI: 0.83, 0.96) compared to agonists (ES = 0.82, 95% CI: 0.78, 0.85, z = 2.12, p = 0.03). Radiolabeled somatostatin receptor antagonists outperform agonists in diagnosing hepatic lesions and controlling disease in NETs, highlighting their clinical superiority. This meta-analysis provides critical insights into the diagnostic and therapeutic efficacy of somatostatin receptor antagonists, and may offer a potential paradigm shift in the management of neuroendocrine tumors. Nevertheless, the smaller number of studies on antagonists may limit the generalizability of the findings and underscore the need for further clinical trials to validate these results. Full article

The utilization of antibodies to target radionuclides, known as radioimmunotherapy (RIT), has been actively researched for nearly five decades. Numerous significant preclinical and clinical studies in cancer therapy have been highlighted. Among them, RIT using alpha-emitting nuclides has shown high effectiveness and has attracted much interest in recent years. This review presents an overview of the basic elements of alpha-RIT, namely the target proteins (monoclonal antibodies and antibody-derived proteins), alpha-emitting radionuclides, and labeling methods, which are currently being adapted in cancer therapy. It also highlights efforts to expand the potential of alpha-RIT, including the control of radioactivity distribution in the body. Full article

Indolethylamine N-methyltransferase (INMT) is a Class 1 methyltransferase responsible for N-methylation of various endogenous and exogenous compounds, including tryptamine, serotonin, and dopamine. This review aims to provide a comprehensive overview of the biological and therapeutic relevance of INMT, emphasizing the human isoform (hINMT), highlighting its structural characteristics, disease association, and recent advances in analytical strategies. Dysregulation of INMT activity has been linked to a range of pathological conditions, including neuropsychiatric disorders, neurodegeneration, and several forms of cancer. These associations are addressed by integrating current findings across disease pathophysiology, enzyme inhibition, and analytical methodologies, including both radiolabeled and non-radiolabeled in vitro assays, for measuring INMT activity. We further explored the chemical diversity of INMT inhibitors, both natural and synthetic, and highlighted key compounds with therapeutic relevance. Additionally, recent commercial assays for quantifying INMT activity are emphasized. By integrating emerging evidence from structural biology and disease pathology with inhibitor profiling and analytical technologies, this review highlights the underexplored therapeutic potential of targeting INMT and underscores its value as a promising target for drug development and therapeutic applications. Full article

Background: [⁶⁸Ga]Ga-DOTATOC is widely used in PET imaging of neuroendocrine tumors (NETs) due to its high affinity for somatostatin receptors. Given the short physical half-life of gallium-68 (~68 min), rapid, reproducible, and GMP-compliant synthesis is essential for clinical application. Methods: An optimized cassette-based automated synthesis protocol was developed using a commercial cassette. Improvements included direct generator elution into the reactor without pre-purification, use of a SepPak^® C18 Plus Light cartridge for purification, replacement of HEPES with 0.3 M sodium acetate buffer (final pH ~3.8), and implementation of a non-vented sterile filter enabling automated pressure-hold integrity testing. Results: Across all batches, the synthesis yielded [⁶⁸Ga]Ga-DOTATOC with high radiochemical purity (> 97%) and reproducible decay-corrected radiochemical yields up to 88.3 ± 0.6%. Total synthesis time was approximately 13 min. The final product remained stable for at least 3 h post-synthesis. The use of acetate buffer eliminated the need for HEPES-specific testing, streamlining the workflow. Automated filter testing improved GMP-compliant documentation and reduced radiation exposure for personnel. Conclusions: This optimized, cassette-based synthesis protocol enables fast, high-yield, and GMP-compliant production of [⁶⁸Ga]Ga-DOTATOC. It supports clinical theranostic workflows by ensuring product quality, process standardization, and regulatory compliance. Full article

Hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2−) breast cancer is the most prevalent subtype. Positron emission tomography (PET) imaging with 16α-18F-fluoro-17β-fluoroestradiol (¹⁸F-FES), a radiolabeled form of estradiol, enables the assessment in vivo of ER expression, ER heterogeneity in metastatic sites and functionally active ER capable of ligand binding. This imaging modality has been recently approved as a diagnostic tool for detecting ER-positive lesions in patients with recurrent or metastatic breast cancer. Despite promising activity, the role of this powerful tool is still debated. Herein we critically analyzed current evidence supporting the use of 18F-FES PET in metastatic ER+/HER2− breast cancer, highlighting the potential challenges for clinical implementation. Full article

Gallium-68 is a widely used positron-emitting radionuclide in nuclear medicine, traditionally obtained from ⁶⁸Ge/⁶⁸Ga generators. However, increasing clinical demand has driven interest in alternative production methods, such as medical cyclotrons equipped with solid targets. This study evaluates the functional equivalence of gallium-68 chloride obtained from cyclotron solid target and formulated to be equivalent to the eluate from a germanium-gallium generator, aiming to determine whether this production method can serve as a reliable alternative for PET radiopharmaceutical applications. Preparations of [⁶⁸Ga]Ga-PSMA-11 and [⁶⁸Ga]Ga-DOTATOC, labeled with cyclotron-derived gallium-68 chloride, were subjected to quality control analysis using radio thin layer chromatography and radio high performance liquid chromatography. Subsequently, biodistribution studies were performed in mouse oncological models of expression of PSMA antigen and SSTR receptor to compare uptake of preparations produced with generator and cyclotron-derived isotopes. All tested formulations met the required radiochemical purity specifications. Moreover, tumor accumulation of the radiolabeled compounds was comparable regardless of the isotope source. The results support the conclusion that gallium-68 produced via cyclotron is functionally equivalent to that obtained from a generator, demonstrating its potential for interchangeable use in clinical and research radiopharmaceutical applications. Full article

Background/Objectives: Radiolabeled interleukin-2 (IL2) could allow for imaging activated T-lymphocytes in the tumor microenvironment (TME). The aims of this study were to assess the shelf life of a lyophilized kit containing THP-desIL2 to allow for the labeling of IL2 with ⁶⁸Ga at room temperature and to test the in vitro binding of ⁶⁸Ga-THP-desIL2 on different T-cell populations in order to determine which specific T-cell subset expresses the CD25 subunit of the IL2 receptor (IL2R). Methods: desIL2 was conjugated with THP and lyophilized. ⁶⁸Ga labeling was performed and several quality controls, including HPLC, iTLC and SDS-PAGE, were carried out at different storage times (1, 3 and 6 months) and temperatures (4 °C and −80 °C). Moreover, flow cytometric analysis on different T-cell populations and the in vitro and competitive binding of ⁶⁸Ga-THP-desIL2 were performed. Results: The lyophilized kit of THP-desIL2 was stable up to 6 months at −80 °C, preserving its sterility, integrity and acceptable values of labeling yield (51.80 ± 3.74%), radiochemical purity (>96%) and specific activity (5.59 ± 0.40 MBq/µg). Binding of ⁶⁸Ga-THP-desIL2 on activated lymphocytes was specific and exhibited a low dissociation constant from IL2R on stimulated Tregs (Kd: 10⁻⁹–10⁻¹⁰ mol/L). Conclusions: We assessed the shelf life of a lyophilized kit containing THP-desIL2 for the easy labeling of IL2 with ⁶⁸Ga at room temperature. The kit can be stored at −80 °C up to 6 months, thus facilitating the adoption of ⁶⁸Ga-THP-desIL2 into clinical practice. ⁶⁸Ga-THP-desIL2 showed high affinity and specificity for CD25 on activated T-lymphocytes, particularly Tregs, thus opening new opportunities for imaging immune cells trafficking in the TME. Full article