Photopharmacological Applications for Cherenkov Radiation Generated by Clinically Used Radionuclides

Translational photopharmacological applications are limited through irradiation by light showing wavelengths within the bio-optical window. To achieve sufficient tissue penetration, using wavelengths >500 nm is mandatory. Nevertheless, the majority of photopharmacological compounds respond to irradiation with more energetic UV light, which shows only a minor depth of tissue penetration in the µm range. Thus, we became interested in UV light containing Cherenkov radiation (CR) induced as a by-product by clinically employed radionuclides labeling specific tissues. Therefore, CR may be applicable in novel photopharmacological approaches. To provide evidence for the hypothesis, we verified the clinically established radionuclides 68Ga and 90Y but not 18F in clinically used activities to be capable of generating CR in aqueous solutions. We then investigated whether the generated CR was able to photoactivate the caged kinase inhibitor cagedAZD5438 as a photoresponsive model system. Herein, 21% uncaging of the model system cagedAZD5438 occurred by incubation with 90Y, along with a non-specific compound decomposition for 68Ga and partly for 90Y. The findings suggest that the combination of a clinically employed radionuclide with an optimized photoresponsive agent could be beneficial for highly focused photopharmacological therapies

Automated synthesis of [68Ga]Ga-FAPI-46 without pre-purification of the generator eluate on three common synthesis modules and two generator types

Background The recent development of quinoline-based radiotracers, which act as fibroblast activation protein inhibitors (FAPIs), has shown promising preclinical and clinical advantages. [68Ga]Ga-FAPI-46 is a new radiotracer for in vivo detection of the fibroblast activation protein by positron emission tomography (PET). Recently, the automated synthesis of [68Ga]Ga-FAPI-46 was reported based on pre-concentration and purification of the generator eluate by using a cation exchange-cartridge. Our aim was to simplify the synthesis and shorten the automated synthesis of [68Ga]Ga-FAPI-46 to make it accessible and thus even more attractive to a broader clinical and scientific community. Results We developed and evaluated the GMP compliant automatic synthesis of [68Ga]Ga-FAPI-46 using two different 68Ge/68Ga generators (an Eckert & Ziegler, GalliaPharm generator, 1.85 GBq/50 mCi and an iThemba generator, 1.85 GBq/50 mCi) Somerset West, South Africa) and three different commercial and customized systems: the EasyOne module from Trasis; the GaSy module from Synthra with a customized synthesis template and a customized single use cassette. Additionally, the automatic synthesis of [68Ga]Ga-FAPI-46 was established on a GallElut synthesis module from Scintomics with fixed tubing. Conclusions Independent of the synthesis modules or the generators employed we were able to complete the synthesis of [68Ga]Ga-FAPI-46 in 12 min including the process of purification and formulation. In all cases, the final products showed more than 99.5% chemical purity and the radiochemical yield reached around 92.5% (decay corrected). All quality control parameters (e.g. sterility, stability and radiochemical purity) were conform to the European Pharmacopoeia

Pre- and intratherapeutic predictors of overall survival in patients with advanced metastasized castration-resistant prostate cancer receiving Lu-177-PSMA-617 radioligand therapy

Background Systemic Lutetium-177 prostate-specific membrane antigen-617 radioligand therapy (Lu-177-PSMA-617-RLT) is a novel treatment approach in patients suffering from metastasized castration-resistant prostate cancer. Nonetheless, a therapeutic response may fail to appear in a proportion of patients. This study aims to identify routinely obtainable pre- and intratherapeutic parameters to allow a prediction of overall survival in patients receiving Lu-177-PSMA-617 radioligand therapy. Methods Between January 2015 and December 2020 52 patients treated with a total of 146 cycles Lu-177-PSMA-617-RLT were retrospectively analysed in a single-center trial. The median overall survival time (OS) was compared to pre-therapeutic serological parameters, the extend of metastatic spread and previously performed therapies using Kaplan-Meier estimators and multivariate Cox-regression. Bonferroni-Holm correction was performed on all statistical tests. Results The median OS of all patients was 55.6 weeks. Multivariate Cox-regression revealed significant lower survival for decreased pretherapeutic hemoglobin levels (HR 0.698 per g/dl; 95%-CI 0.560-0.872; p = 0.001), increased lactate dehydrogenase (LDH) levels (HR 1.073 per 25 U/l; 95%-CI 1.024-1.125; p = 0.003) and the presence of hepatic metastasis (HR 6.981; 95%-CI 2.583-18.863; p < 0.001). Increased pretherapeutic c-reactive protein (CRP), alkaline phosphatase (ALP) and gamma-glutamyltransferase (GGT) levels were also associated with a shorter survival. Conclusion Pre-therapeutic hemoglobin and LDH levels, as well as the presence of hepatic metastasis are independent predictors of overall survival in patients receiving Lu-177-PSMA-617-RLT. CRP, ALP and GGT levels cloud be utilized as additional decision aids when a Lu-177-PSMA-617-RLT is intended. Trial Registration Not applicable (retrospective observational study)

New Approach for Analysing the Discrepancy of Pretherapeutic Tc-99m and Intra-therapeutic I-131 uptake in Scintigraphies of Thyroid Autonomies using a Parametric 3D Analysis Programs

<div> <p><small><b>Introduction:</b> Radioiodine therapy is a standard procedure in thyroid autonomy treatment. Discrepancies in the visual comparisons of the scintigraphies prepared for this purpose using Tc-99m-O4- and I-131 have been known for years. In this study a new method is used to calculate and perform a quantitative comparison of both uptakes using subtraction analysis and 3D imaging. The results and their causes are discussed together with practice-relevant conclusions for better clinical results.</small></p> <p><small><b>Material and Methods:</b> The new method was used in 38 patients with thyroid autonomies for the subtraction analysis of standardized pretherapeutic and intratherapeutic scintigraphies. The parametric distribution of activity was calculated absolutely and as a percentage and displayed three-dimensionally. These results were compared with the visual assessment of the different scintigraphies by the experts. Inclusion criteria were pretherapeutic and intratherapeutic hyperthyroidism without medication affecting the thyroid. The time difference between acquiring the scintigraphies was 28 days maximum.</small></p> <p><small><b>Results:</b> Activity distribution was visually discrepant in 39.5% of cases. 60.5% displayed comparable uptake. The calculated values showed reversed results after applying the new method. The results using our method show a higher rate of calculated discrepancies compared with visual analysis.</small></p> <p><small><b>Conclusion:</b> Accurate functional imaging of the thyroid is next to further aspects very important in establishing the diagnosis and deciding about the therapy activity for thyroid treatment. In combination with clinical symptoms and laboratory values, Tc-99m-O4 - scintigram can be used for an orientated, preliminary assessment of functional disorders of the thyroid. But because of the higher rate of found discrepancies, the solely use of Tc-99m-O4 - scintigram is not always capable for exact and reliable diagnosis. The known reason for this is most probably due to the different biokinetics of both radiopharmaceuticals, which can be imaged more sensitively with this method. Consequently, a scintigram should be performed in the pretherapeutic radioiodine uptake test. Despite higher costs and radiation exposure, alternatively, pretherapeutic use of other diagnostic iodine isotopes like I-123 or -124 should be discussed, because they could overcome the limitation of the different biokinetics. Following this approach the preliminary assessment using Tc-99m-O4 - scintigraphy can be precised and double checked to improve diagnostic confi dence and treatment results for a better outcome of the patients.</small></p> </div

New Approach for Analysing the Discrepancy of Pretherapeutic Tc-99m and Intra-therapeutic I-131 uptake in Scintigraphies of Thyroid Autonomies using a Parametric 3D Analysis Program

Introduction: Radioiodine therapy is a standard procedure in thyroid autonomy treatment. Discrepancies in the visual comparisons of the scintigraphies prepared for this purpose using Tc-99m-O4- and I-131 have been known for years. In this study a new method is used to calculate and perform a quantitative comparison of both uptakes using subtraction analysis and 3D imaging. The results and their causes are discussed together with practice-relevant conclusions for better clinical results. Material and Methods: The new method was used in 38 patients with thyroid autonomies for the subtraction analysis of standardized pretherapeutic and intratherapeutic scintigraphies. The parametric distribution of activity was calculated absolutely and as a percentage and displayed three-dimensionally. These results were compared with the visual assessment of the different scintigraphies by the experts. Inclusion criteria were pretherapeutic and intratherapeutic hyperthyroidism without medication affecting the thyroid. The time difference between acquiring the scintigraphies was 28 days maximum. Results: Activity distribution was visually discrepant in 39.5% of cases. 60.5% displayed comparable uptake. The calculated values showed reversed results after applying the new method. The results using our method show a higher rate of calculated discrepancies compared with visual analysis. Conclusion: Accurate functional imaging of the thyroid is next to further aspects very important in establishing the diagnosis and deciding about the therapy activity for thyroid treatment. In combination with clinical symptoms and laboratory values, Tc-99m-O4 - scintigram can be used for an orientated, preliminary assessment of functional disorders of the thyroid. But because of the higher rate of found discrepancies, the solely use of Tc-99m-O4 - scintigram is not always capable for exact and reliable diagnosis. The known reason for this is most probably due to the different biokinetics of both radiopharmaceuticals, which can be imaged more sensitively with this method. Consequently, a scintigram should be performed in the pretherapeutic radioiodine uptake test. Despite higher costs and radiation exposure, alternatively, pretherapeutic use of other diagnostic iodine isotopes like I-123 or -124 should be discussed, because they could overcome the limitation of the different biokinetics. Following this approach the preliminary assessment using Tc-99m-O4 - scintigraphy can be precised and double checked to improve diagnostic confi dence and treatment results for a better outcome of the patients. &nbsp

Activation of intracellular angiotensin AT 2 receptors induces rapid cell death in human uterine leiomyosarcoma cells

Abstract The presence of angiotensin type 2 (AT 2 ) receptors in mitochondria and their role in NO generation and cell aging were recently demonstrated in various human and mouse non-tumour cells. We investigated the intracellular distribution of AT 2 receptors including their presence in mitochondria and their role in the induction of apoptosis and cell death in cultured human uterine leiomyosarcoma (SK-UT-1) cells and control human uterine smooth muscle cells (HutSMC). The intracellular levels of the AT 2 receptor are low in proliferating SK-UT-1 cells but the receptor is substantially up-regulated in quiescent SK-UT-1 cells with high densities in mitochondria. Activation of the cell membrane AT 2 receptors by a concomitant treatment with angiotensin II and the AT 1 receptor antagonist, losartan, induces apoptosis but does not affect the rate of cell death. We demonstrate for the first time that the high-affinity, non-peptide AT 2 receptor agonist, Compound 21 (C21), penetrates the cell membrane of quiescent SK-UT-1 cells, activates intracellular AT 2 receptors and induces rapid cell death; approximately 70 % of cells died within 24 h. The cells, which escaped cell death, displayed activation of the mitochondrial apoptotic pathway, i.e. down-regulation of the Bcl-2 protein, induction of the Bax protein and activation of caspase-3. All quiescent SK-UT-1 cells died within 5 days after treatment with a single dose of C21. C21 was devoid of cytotoxic effects in proliferating SK-UT-1 cells and in quiescent HutSMC. Our results point to a new, unique approach enabling the elimination non-cycling uterine leiomyosarcoma cells providing that they over-express the AT 2 receptor

Activation of intracellular angiotensin AT2 receptors induces rapid cell death in human uterine leiomyosarcoma cells

Abstract The presence of angiotensin type 2 (AT 2 ) receptors in mitochondria and their role in NO generation and cell aging were recently demonstrated in various human and mouse non-tumour cells. We investigated the intracellular distribution of AT 2 receptors including their presence in mitochondria and their role in the induction of apoptosis and cell death in cultured human uterine leiomyosarcoma (SK-UT-1) cells and control human uterine smooth muscle cells (HutSMC). The intracellular levels of the AT 2 receptor are low in proliferating SK-UT-1 cells but the receptor is substantially up-regulated in quiescent SK-UT-1 cells with high densities in mitochondria. Activation of the cell membrane AT 2 receptors by a concomitant treatment with angiotensin II and the AT 1 receptor antagonist, losartan, induces apoptosis but does not affect the rate of cell death. We demonstrate for the first time that the high-affinity, non-peptide AT 2 receptor agonist, Compound 21 (C21), penetrates the cell membrane of quiescent SK-UT-1 cells, activates intracellular AT 2 receptors and induces rapid cell death; approximately 70 % of cells died within 24 h. The cells, which escaped cell death, displayed activation of the mitochondrial apoptotic pathway, i.e. down-regulation of the Bcl-2 protein, induction of the Bax protein and activation of caspase-3. All quiescent SK-UT-1 cells died within 5 days after treatment with a single dose of C21. C21 was devoid of cytotoxic effects in proliferating SK-UT-1 cells and in quiescent HutSMC. Our results point to a new, unique approach enabling the elimination non-cycling uterine leiomyosarcoma cells providing that they over-express the AT 2 receptor