Production of (177)Lu for Targeted Radionuclide Therapy: Available Options

Simulation and analysis of the medical radioisotope 177Lu production based on a high-intensity DT neutron generator

177Lu is one of the medical radioisotopes with wide application prospects. To explore the 177Lu production besides using reactors, a concept of utilizing high-enriched cylindrical 176Lu based on a high-intensity DT neutron generator via the direct neutron capture reaction has been proposed. The production of 177Lu in a176Lu2O3 solid shell target has been simulated considering layers of neutron multiplier, moderator, and reflector around itself. Materials used as multipliers, moderators, and reflectors have been investigated and analyzed for neutronics optimization. The combinations and thicknesses of different layers have been calculated using the response surface methodology (RSM), and the three layers were found almost independently for the 177Lu production. Both the activity and the specific activity of produced 177Lu were improved significantly using the RSM. According to the calculations, about 13.5 Ci 177Lu can be produced after 40 days of irradiation with a stable neutron yield of 5 × 1011 n/s.

[natY/90Y]Yttrium and [natLu/177Lu]Lutetium Complexation by Rigid H4OCTAPA Derivatives. Effect of Ligand Topology

We present a detailed investigation on the coordination chemistry of [nat/90Y]Y3+ and [nat/177Lu]Lu3+ with the new acyclic chelator H4CHXOITAPA. This octadentate chelator forms nine-coordinated Y3+ and Lu3+ complexes thanks to the coordination of a water molecule, as demonstrated by the X-ray structure of [Y(HCHXOITAPA)(H2O)] and 1H, 13C, and 89Y NMR studies in solution. These complexes display slightly higher thermodynamic stabilities compared with those of the known H4CHXOCTAPA and H4OCTAPA chelators, reaching log KYL and log KLuL values of 21.24(5) and 21.96(1), respectively. Kinetic studies indicate that these complexes dissociate mainly through the spontaneous and proton-assisted pathways at pH 7.4. The chelator can be readily radiolabeled with [90Y]Y3+ and [177Lu]Lu3+ at room temperature in 10 min. The radio-complexes are stable in human serum at 37 °C, in contrast with the analogues of the known H4CHXOCTAPA and H4OCTAPA chelators, which experience significant dissociation under these conditions. Thus, the H4CHXOITAPA chelator represents the most promising candidate among the H4OCTAPA family for the development of 90Y- and 177Lu-based radiopharmaceuticals.

Unlocking the power of affibody conjugated radioactive metallopharmaceuticals for targeted cancer diagnosis and therapy

Cancer is the second-largest death-causing disease after cardiovascular diseases. Effective research on cancer diagnosis and subsequent elimination plays a vital role in reducing the cancer-related death toll. Radiotherapy is one of the best strategies that could kill masses of solid tumour tissues; however, the efficacy is limited due to the bystander effect. This issue could be solved by the emergence of targeted delivery of radiometallic complexes, enabling clinicians to monitor the tumour regions and effectively destroy the tumour. Affibody® molecules are a class of synthetic peptides known as antibody mimics having the binding sites of an antibody. The specificity of affibodies is found to be greater than that of antibodies due to their small size. This review intends to highlight the recent developments in the field of affibody-targeted radiometallopharmaceuticals. These approaches could be essential for early cancer detection, tumour staging, and monitoring the response to therapy and could produce better therapeutic outcomes. In an attempt to provide ideas and inspiration for the researchers to design affibody-conjugated radiopharmaceuticals that are clinically applicable, we have provided an in-depth exploration of the various types of affibody-conjugated radiopharmaceuticals that are currently in clinical trials and various other pre-clinically tested conjugates in this article. Only a few review reports on affibody-conjugated radiometallopharmaceuticals, typically focusing on a specific molecular target or radionuclides reported. In this review, we provide a comprehensive overview of most radiometals, such as 111In, 68Ga, 64Cu, 55Co, 57Co, 44Sc, 99mTc, 89Zr, 90Y, 211At, 188Re, and 177Lu, choice of chelators, and potential cancer-associated molecular targets such HER2, EGFR or HER1, HER3, IGF-1R, PDGFRβ, VEGFR2, PD-L1, CAIX, PD-L1, neonatal Fc receptor (FcRn) and B7-H3. This approach highlights the advancements made over the past twenty years in affibody conjugates for radio imaging and therapy in oncology.

Pr3+ Visible to Ultraviolet Upconversion for Antimicrobial Applications

This paper addresses the upconversion of blue light to ultraviolet-C (UVC) with Pr3+-activated materials for antibacterial applications of UVC. It discusses the processes through which UV radiation provides biocidal effects on microorganisms, along with the most popular UVC sources employed in these processes. We describe the electronic and optical properties of the Pr3+ ion, emphasizing the conditions the host material must meet to obtain broad and intense emission in the UVC from parity-allowed transitions from the 4f5d levels and provide a list of materials that fulfill these conditions. This paper also delineates lanthanide-based upconversion, focusing on Pr3+ blue to UVC upconversion via the 3P0 and 1D2 intermediate states, and suggests routes for improving the quantum efficiency of the process. We review literature related to the use of upconversion materials in antimicrobial photodynamic treatments and for the blue to UVC upconversion germicidal effects. Further, we propose the spectral overlap between the UVC emission of Pr3+ materials and the germicidal effectiveness curve as a criterion for assessing the potential of these materials in antimicrobial applications. Finally, this paper briefly assesses the toxicity of materials commonly used in the preparation of upconversion materials.

Quality and Safety Considerations for Radiopharmaceutical Therapy in the Radiation Oncology Environment: An ASTRO Safety White Paper

PURPOSE

Radiopharmaceutical therapy (RPT) is the latest topic in a series of white papers published by ASTRO addressing quality processes and patient safety. The availability of radiopharmaceutical agents for therapeutic use has broadened patient treatment options; although generally administered systemically, their effects are targeted to cellular receptors or the tumor microenvironment. Radiation oncology is well suited to delivering RPT because clinicians are already experienced in radiation safety, treatment delivery, and ongoing patient care. This paper focuses on the logistics of initiating and/or maintaining an RPT program in radiation oncology and includes collaborating with other medical specialties. The white paper addresses the safety processes and workflow considerations for alpha- and beta-emitting radionuclides used for RPT.

METHODS

ASTRO convened a multidisciplinary task force, composed of experts from radiation oncology, nuclear medicine, medical and health physics, to provide consensus on key workflows and processes for RPT. Recommendations were created using a consensus-building methodology and task force members indicated their level of agreement based on a 5-point Likert scale, from "strongly agree" to "strongly disagree." A prespecified threshold of ≥75% of raters who select "strongly agree" or "agree" indicated consensus. Content not meeting this threshold was removed or revised.

SUMMARY

Establishing an RPT program in radiation oncology requires specific infrastructure for receiving, storing, preparing, and administering radiopharmaceuticals by staff with expertise in specific infusion methods. RPT cases benefit from a multidisciplinary approach led by a radiation medicine physician and authorized user with support from additional personnel trained in RPT. A comprehensive quality management program must be developed to comply with applicable regulations and standards, including the handling of radioactive materials. Participation in incident reporting and external audits of a practice's overall quality assurance processes is encouraged. Using the guidance provided, authorized users can assess the viability of starting an RPT program, develop the necessary infrastructure, and sustain a safe, high-quality RPT program that includes radiation oncology.

Production and Supply of Raw Materials for Radiometals used in Radionuclide Imaging and Therapy in Korea

Radiometals, with their favorable decay properties and rich coordination chemistry, have found widespread applications in both diagnostic and therapeutic nuclear medicine. To ensure effective utilization, radiometal-based radiopharmaceuticals are designed to target specific organs or cells. Radiometals are primarily produced in cyclotrons or reactors using stable isotopes as raw materials. Many countries, including Korea, are pursuing self-sufficiency in radiometal production at the government level. This review examines the current production and supply status of raw materials for key radiometals that are either actively used or expected to see a significant demand growth in the future in Korea.

Graphical Abstract

Flow of radiometal production.

Preliminary experiments to produce lutetium-177 in the TRR-1/M1 Thai research reactor

Lutetium-177 has emerged as a highly efficient radionuclide for medical applications, particularly in the field of targeted radionuclide therapy. Its production has been increasingly optimized through neutron activation techniques, which offer distinct advantages over alternative methods. Utilizing the TRR-1/M1 research reactor, which has been in operation for nearly six decades, provides a strategic opportunity for advancing domestic radioisotope production, thereby supporting the medical sector in Thailand. The TRR-1/M1 reactor, despite its operational age, continues to exhibit considerable potential for contributing to medical research and radioisotope development in Thailand. Preliminary experimental results, conducted at a flux of 1.42 × 1012 n/cm2/s demonstrated promising outcomes, even under operational constraints such as fuel management limitations. Notably, the direct neutron activation of natural lutetium oxide notably yielded a specific activity of 177Lu at 10.92 GBq/g (295.06 mCi/g) with a production yield of 44.8%, with projections reaching 222 GBq/g (6 Ci/g) after 40 days of neutron irradiation. In comparison, the indirect method, using natural ytterbium oxide as a precursor, achieved a maximum specific activity of 177Lu at 6.6 MBq/g (180.3 μCi/g) with a yield of 37.8% of a theoretical maximum of 17.6 MBq/g (476 μCi/g) after only 10 h of neutron activation. These results highlight the feasibility and promise of 177Lu radioisotope production in Thailand.

Recent advances in transition metal-mediated/ catalyzed radiofluorination of arenes and heteroarenes for positron emission tomography

Positron emission tomography (PET) imaging endows the possibility of precise diagnosis and effective treatment of diseases. Aromatic (hetero)cycle is one of the most fundamental groups in pharmaceuticals as well as in the development of PET tracers. In particular, incorporation of 18F to aromatic (hetero)cycles has accelerated the progress of nuclear medicine tracers. Current trend indicates a rapid progress in 18F-labeling of aromatic (hetero)cycles for PET imaging. Transition metal-catalyzed 18F-labeling method speeds up the reaction by lowering the activation energy of the substrate by the metal complex. The reaction conditions are mild, and a wide range of substrates can be used. In this article we systematically reviewed the methods of radioactive 18F-labeling of aromatic (hetero)cycles with different precursors mediated by transition metals‑copper, ruthenium, nickel, palladium, silver, and titanium. The precursors, radiolabeling conditions, catalytic efficiency, catalytic mechanism, optimization of transition metal-catalyzed 18F-labeling methods, and corresponding frontier applications of 18F-labeled molecular probes were discussed.

Laser isotope enrichment of 168Er

This present study investigates a three-step laser isotope separation method for the enrichment of 168Er isotope using 631.052 nm - 586.912 nm - 566.003 nm three-step photoionization scheme. The lineshape contours observed in three-step photoionization process have been investigated in detail. This study shows that enrichment of 168Er isotope can be achieved with a relatively simple experimental configuration. With the derived system configuration, it has been shown that it is possible to produce 18 g/day of 90% enriched 168Er. Using the enriched 168Er isotope obtained from the laser isotope separation process, irradiation in low, medium, and high flux reactors can produce 180, 1800, and 18,000 doses per day (each with an activity of 7.4 GBq) respectively. After 24 h of irradiation and chemical separation, the radioisotopic purity of the medical isotope reaches to > 99% making it suitable for the medical applications. This is the first ever study on the laser isotope separation of 168Er isotope.

Novel 177Lu-Labeled [Thz14]Bombesin(6-14) Derivatives with Low Pancreas Accumulation for Targeting Gastrin-Releasing Peptide Receptor-Expressing Cancer

Background/Objectives: Gastrin-releasing peptide receptor is a promising target for cancer diagnosis and therapy. However, the high pancreas uptake of reported GRPR-targeted radioligands limits their clinical applications. Our group previously reported one 68Ga-labeled GRPR antagonist, [68Ga]Ga-TacsBOMB5 (68Ga-DOTA-Pip-[D-Phe6,NMe-Gly11,Leu13ψThz14]Bombesin(6-14)), and two agonists, [68Ga]Ga-LW01110 (68Ga-DOTA-Pip-[D-Phe6,Tle10,NMe-His12,Thz14]Bombesin(6-14)) and [68Ga]Ga-LW01142 (68Ga-DOTA-Pip-[D-Phe6,His7,Tle10,NMe-His12,Thz14]Bombesin(6-14)) showing minimal pancreas uptake. Thus, in this study, we prepared their 177Lu-labeled analogs, evaluated their therapeutic potentials, and compared them with the clinically evaluated [177Lu]Lu-AMBA. Methods: GRPR binding affinities were determined by in vitro competition binding assay using PC-3 prostate cancer cells. Longitudinal SPECT/CT imaging and ex vivo biodistribution studies were conducted in PC-3 tumor-bearing mice. Dosimetry data were calculated from the biodistribution results. Results: The Ki(GRPR) values of Lu-TacsBOMB5, Lu-LW01110, Lu-LW01142, and Lu-AMBA were 12.6 ± 1.02, 3.07 ± 0.15, 2.37 ± 0.28, and 0.33 ± 0.16 nM, respectively. SPECT/CT images and biodistribution results demonstrated good tumor accumulation of [177Lu]Lu-TacsBOMB5, [177Lu]Lu-LW01110, and [177Lu]Lu-LW01142 at early time points with rapid clearance over time. The pancreas uptake of all three [Thz14]Bombesin(6-14)-derived ligands was significantly lower than that of [177Lu]Lu-AMBA at all time points. The calculated absorbed doses of [177Lu]Lu-TacsBOMB5, [177Lu]Lu-LW01110, and [177Lu]Lu-LW01142 in PC-3 tumor xenografts were 87.1, 312, and 312 mGy/MBq, respectively, higher than that of [177Lu]Lu-AMBA (79.1 mGy/MBq), but lower than that of the previously reported [177Lu]Lu-RM2 (429 mGy/MBq). Conclusions: Our data suggest that [177Lu]Lu-TacsBOMB5 and [177Lu]Lu-LW01142 reduce radiation exposure to the pancreas. However, further optimizations are needed for both radioligands to prolong their tumor retention and enhance treatment efficacy.

A Comparative Analysis of Alpha and Beta Therapy in Prostate Cancer Using a 3D Image-Based Spatiotemporal Model

PURPOSE

In treating prostate cancer, distinguishing alpha and beta therapies is vital for efficient radiopharmaceutical delivery. Our study introduces a 3D image-based spatiotemporal computational model that utilizes MRI-derived images to evaluate the efficacy of 225Ac-PSMA and 177Lu-PSMA therapies. We examine the impact of tumor size, diffusion, interstitial fluid pressure (IFP), and interstitial fluid velocity (IFV) on the absorbed doses.

METHODS

An MRI-based geometric model of the tumor and its surrounding environment is initially developed. Subsequently, COMSOL Multiphysics software is utilized to solve convection-diffusion-reaction equations and conduct numerical analyses of blood pressure distribution. This computational methodology provides valuable insights into interstitial fluid patterns and the spatiotemporal distribution of extracellular and intracellular concentrations of 225Ac-PSMA and 177Lu-PSMA. In addition, our study investigates the impacts of increasing tumor size on absorbed doses and mechanisms involved in radiopharmaceutical transport and delivery.

RESULTS

Larger tumors have diminished absorbed doses, highlighting the need for customized treatments according to tumor size. Diffusion significantly influences the transport and delivery of radiopharmaceuticals. Additionally, alpha therapy was observed to consistently yield higher absorbed doses within the tumor than beta therapy.

CONCLUSIONS

This study reveals the complex interplay between radiopharmaceutical properties, the tumor microenvironment, and treatment outcomes. It highlights the potential of 225Ac-PSMA in prostate cancer treatment, advocating for personalized treatment strategies tailored to the specific characteristics of each patient and their tumor.

Navigating Radiation Safety After Radiopharmaceutical Therapies: Proposed Workflow and Essential Guidelines for Nonspecialists

With the increasing use of radiopharmaceutical therapies, there is a critical need to appropriately inform health care professionals (HCPs) who are unfamiliar with these therapies about the radiation safety precautions required when managing recently treated patients. Clear and easily accessible instructions are essential for minimizing radiation exposure to medical staff and simultaneously reducing fear of interacting with a radioactive patient, as these factors can impact the delivery of adequate and timely medical care. In this paper, we present a workflow designed to provide clear guidelines and safety protocols for HCPs who may encounter postradiopharmaceutical therapy patients during urgent medical visits or hospital admissions. This workflow consists of 2 key strategies: an electronic medical record flag system and a physical wristband that alerts the HCP that the patient may be radioactive and includes a link to a website with detailed information. These tools ensure that HCPs who encounter these patients will have immediate access to essential radiation safety information, thereby safeguarding staff and maintaining the continuity of patient care.

Comparison of radiobiological effects induced by radiolabeled antibodies in human cancer cells and fungal cells

PURPOSE

Acute myeloid leukemia (AML) is a deadly form of leukemia, and its treatment often leaves patients immunocompromised, making them vulnerable to fungal infections. Radioimmunotherapy (RIT) is explored for both AML and fungal infections. This study compares the radiobiological effects of alpha emitter Actinium-225 (225Ac) and beta emitter Lutetium-177 (177Lu)-labeled antibodies on AML and Cryptococcus neoformans cells.

MATERIALS AND METHODS

AML OCI-AML3 and C. neoformans Cap-67 cells were treated with anti-(1-3)-beta-glucan antibody 400-2 and anti-CD33 antibody HuM-195, conjugated to DOTA and radiolabeled with 225Ac or 177Lu. Clonogenic survival, γH2A/X staining, and micronuclei assays were conducted. Antibody internalization was assessed by flow cytometry.

RESULTS

Both 225Ac- and 177Lu-enabled RIT resulted in decreased clonogenic survival in Cap-67 and OCI-AML3 cells, with Cap-67 recovering more rapidly. DNA double-strand breaks and micronuclei formation revealed DNA damage, with fewer micronuclei in OCI-AML3 cells due to radiation destruction. HuM-195 antibody internalized into OCI-AML3 cells, whereas 400-2 did not internalize into Cap-67 cells.

CONCLUSIONS

While both cell lines showed similar responses to 225Ac- and 177Lu-enabled RIT, variations were observed based on cellular structure, doubling times and DNA repair mechanisms. This study offers insights for future in vivo research on fungal infections in cancer setting.

Terbium-161 in nuclear medicine: Preclinical and clinical progress in comparison with lutetium-177

The use of new radiopharmaceuticals labeled with lutetium-177 represents a successful translation of experimental results into clinical practice. Recent experimental data suggests that terbium-161 might well follow the example of lutetium-177 regarding applicability in nuclear medicine. Similarly to lutetium-177, the terbium-161 emits beta particles and gamma-radiation, although terbium-161 emits short-ranged conversion and Auger electrons, creating an effect that may eliminate smaller tumor metastases more effectively than lutetium-177. Terbium-161 may exert a higher radiobiological effect in the target tissues in comparison with lutetium-177, a difference which makes possible a reduction in the doses of radioactivity administered. Further, due to the similar chemical properties of lutetium-177 and terbium-161, similar radiolabeling techniques can be used. The differences found in preclinical experiments on radiotoxicity of the counterparts seem to be minor. Despite intensive progress, the number of preclinical studies on 161Tb-labeled agents is still not comparable to studies on lutetium-177. Clinical trials with 161Tb-labeled radiopharmaceuticals focused on the treatment of prostate cancer and selected neuroendocrine tumors have already begun, although none of them have been completed yet.

Chlorambucil Conjugation Enhances the Potency of Rituximab: Synthesis and Evaluation of the Novel [177Lu]Lu-Labeled Rituximab-Chlorambucil Conjugate toward Therapy of Non-Hodgkin's Lymphoma

In this study, a novel antibody-drug conjugate (ADC) consisting of Rituximab and Chlorambucil (Rituximab-CMB) was synthesized. The average number of drug molecules attached per Rituximab molecule was determined using MALDI-TOF mass spectrometry, revealing a range of 4-6 drug molecules per antibody. To further improve the therapeutic potential of the ADC, it was radiolabeled with the therapeutic radionuclide 177Lu via a DOTA chelator, achieving a final radiochemical purity of over 95%. In vitro assays demonstrated that the Rituximab-CMB conjugate had greater cytotoxicity compared to that of both unconjugated Rituximab and Chlorambucil alone. Moreover, [177Lu]Lu-labeled-Rituximab-CMB (15.67 MBq/mg) exhibited higher radiotoxicity (37.08 ± 1.40% cell death) compared to [177Lu]Lu-labeled-Rituximab (83.99 MBq/mg) (25.25 ± 0.8% cell death) when administered at similar radioactivity doses. Ex vivo experiments indicated that coinjecting cold Rituximab with the radiolabeled formulations significantly improved tumor accumulation and reduced nontarget organ uptake. SPECT-CT imaging results supported these findings, further confirming the enhanced tumor-targeting and biodistribution of the radiolabeled ADC.

Trop2-Targeted Molecular Imaging in Solid Tumors: Current Advances and Future Outlook

Trophoblast cell surface antigen 2 (Trop2), a transmembrane glycoprotein, plays a dual role in physiological and pathological processes. In healthy tissues, Trop2 facilitates development and orchestrates intracellular calcium signaling. However, its overexpression in numerous solid tumors shifts its function toward driving cell proliferation and metastasis, thus leading to a poor prognosis. The clinical relevance of Trop2 is underscored by its utility as both a biomarker for diagnostic imaging and a target for therapy. Notably, the U.S. Food and Drug Administration (FDA) has approved sacituzumab govitecan (SG), a novel Trop2-targeted agent, for treating triple-negative breast cancer (TNBC) and refractory urothelial cancer, highlighting the significance of Trop2 in clinical oncology. Molecular imaging, a powerful tool for visualizing and quantifying biological phenomena at the molecular and cellular levels, has emerged as a critical technique for studying Trop2. This approach encompasses various modalities, including optical imaging, positron emission tomography (PET), single photon emission computed tomography (SPECT), and targeted antibodies labeled with radioactive isotopes. Incorporating Trop2-targeted molecular imaging into clinical practice is vital for the early detection, prognostic assessment, and treatment planning of a broad spectrum of solid tumors. Our review captures the latest progress in Trop2-targeted molecular imaging, focusing on both diagnostic and therapeutic applications across diverse tumor types, including lung, breast, gastric, pancreatic, prostate, and cervical cancers, as well as salivary gland carcinomas. We critically evaluate the current state by examining the relevant applications, diagnostic accuracy, therapeutic efficacy, and inherent limitations. Finally, we analyze the challenges impeding widespread clinical application and offer insights into strategies for advancing the field, thereby guiding future research endeavors.

SeHCAT retention measurements may be compromised by traces of 177 Lu/ 177m Lu more than 90 days after 177 Lu-DOTATATE was administered

[ 75 Se]tauroselcholic acid (SeHCAT) retention measurement provides a noninvasive test for bile acid diarrhea (BAD); however, it is sensitive to the presence of other radionuclides. Two SeHCAT patients at the Royal Free Hospital (RFH) had significant discrepancies between the lower photopeak (111-159 keV) and central photopeak (242-296 keV) windows, indicating contamination with a radionuclide other than 75 Selenium. These patients had received lutetium-177 oxodotreotide ( 177 Lu-DOTATATE) therapy 98 and 151 days before their SeHCAT tests. Traces of 177 Lu may be retained longer than typically modeled, along with the contaminant 177m Lu. This work includes a retrospective audit to examine the prevalence of SeHCAT tests being affected by 177 Lu and phantom measurements to investigate the potential impact. Of 579 patients who received 177 Lu-DOTATATE therapy at our center, 11 subsequently attended for a SeHCAT test. The two previously identified patients may have had compromised SeHCAT results; however, the other patients had longer intervals between their therapy and test, and their tests are believed to be valid. Spectra were acquired from a phantom containing either a SeHCAT capsule or a mixture of 177 Lu/ 177m Lu representative of a patient >90 days after their treatment. The SeHCAT spectrum was scaled to produce simulated day-7 spectra, and the SeHCAT retention that would have been calculated if 177 Lu/ 177m Lu were present was determined. All SeHCAT measurement windows are affected by the 177 Lu/ 177m Lu, producing clinically significant errors. Patients requiring SeHCAT testing should be asked whether they have ever received 177 Lu-DOTATATE. Patient-specific background measurements may be useful for checking for significant levels of other radionuclides.

Preliminary Study on Lutetium-177 and Gold Nanoparticles: Apoptosis and Radiation Enhancement in Hepatic Cancer Cell Line

This study investigates a novel approach toward enhancing the efficacy of Lutetium-177 (Lu-177) radiopharmaceutical therapy by combining it with gold nanoparticles (AuNPs) in the HepG2 hepatic cancer cell line. Lu-177, known for its effective β radiation, also emits gamma rays at energies (113 keV and 208 keV) near the photoelectric absorption range, suggesting potential for targeted and localized radiation enhancement when used in conjunction with AuNPs. Thus, HepG2 cells were treated at two different activity levels (74 MBq and 148 MBq), with Lu-177 alone, with a combination of Lu-177 and AuNPs in two sizes (10 nm and 50 nm), while some received no treatment. Treatment efficacy was assessed by quantifying the radiation enhancement ratio (RER) and the apoptosis levels. The results reveal that combining Lu-177 with AuNPs significantly increases cell death and apoptosis compared to Lu-177 alone, with 10 nm AuNPs demonstrating superior effectiveness. Additionally, varying Lu-177 activity levels influenced the treatment outcomes, with higher activity levels further augmenting the therapeutic impact of combined therapy. These findings underscore the potential of utilizing Lu-177's beta, but also gamma, emissions, traditionally considered non-therapeutic, for localized radiation enhancement when combined with AuNPs. This novel strategy leverages Lu-177 as an internal irradiator to exploit gamma radiation for a targeted therapeutic advantage without requiring nanoparticle functionalization. The study provides a promising approach to improving radionuclide therapy and sets the stage for future research aimed at optimizing cancer treatments through the combined use of Lu-177 and AuNPs.

Radiomics Analysis for Clinical Decision Support in 177Lu-DOTATATE Therapy of Metastatic Neuroendocrine Tumors using CT Images

Background

Radiomics is the computation of quantitative image features extracted from medical imaging modalities to help clinical decision support systems, which could ultimately meliorate personalized management based on individual characteristics.

Objective

This study aimed to create a predictive model of response to peptide receptor radionuclide therapy (PRRT) using radiomics computed tomography (CT) images to decrease the dose for patients if they are not a candidate for treatment.

Material and Methods

In the current retrospective study, 34 patients with neuroendocrine tumors whose disease is clinically confirmed participated. Effective factors in the treatment were selected by eXtreme gradient boosting (XGBoost) and minimum redundancy maximum relevance (mRMR). Classifiers of decision trees (DT), random forest (RF), and K-nearest neighbors (KNN) with selected quantitative and clinical features were used for modeling. A confusion matrix was used to evaluate the performance of the model.

Results

Out of 866 quantitative and clinical features, nine features with the XGBoost method and ten features with the mRMR pattern were selected that had the most relevance in predicting response to treatment. Selected features of the XGBoost method in integration with the RF classifier provided the highest accuracy (accuracy: 89%), and features selected by the mRMR method in combination with the RF classifier showed satisfactory performance (accuracy: 74%).

Conclusion

This exploratory analysis shows that radiomic features with high accuracy can effectively predict response to personalize treatment.

Dosimetry of [177Lu]Lu-PSMA-Targeted Radiopharmaceutical Therapies in Patients with Prostate Cancer: A Comparative Systematic Review and Metaanalysis

Novel theranostic approaches using radiopharmaceuticals targeting prostate-specific membrane antigen (PSMA) have emerged for treating metastatic castration-resistant prostate cancer. The physical properties and commercial availability of 177Lu make it one of the most used radionuclides for radiopharmaceutical therapy (RPT). In this literature review, we aimed at comparing the dosimetry of the most used [177Lu]Lu-PSMA RPT compounds. Methods: This was a systematic review and metaanalysis of [177Lu]Lu-PSMA RPT (617, I&T, and J591) dosimetry in patients with prostate cancer. Absorbed doses in Gy/GBq for each organ at risk (kidney, parotid and submandibular glands, bone marrow, liver, and lacrimal glands) and for tumor lesions (bone and nonbone lesions) were extracted from included articles. These were used to estimate the pooled average absorbed dose of each agent in Gy/GBq and in Gy/cycle, normalized to the injected activity (per cycle) used in the VISION (7.4 GBq), SPLASH (6.8 GBq), and PROSTACT trials (5.8 GBq). Results: Twenty-nine published articles comprising 535 patients were included in the metaanalysis. The pooled doses (weighted average across studies) of [177Lu]Lu-PSMA-617 and [177Lu]Lu-PSMA-I&T were 4.04 Gy/GBq (17 studies, 297 patients) and 4.70 Gy/GBq (10 studies, 153 patients) for the kidney (P = 0.10), 5.85 Gy/GBq (14 studies, 216 patients) and 2.62 Gy/GBq (5 studies, 86 patients) for the parotids (P < 0.01), 5.15 Gy/GBq (5 studies, 81 patients) and 4.35 Gy/GBq (1 study, 18 patients) for the submandibular glands (P = 0.56), 11.03 Gy/GBq (6 studies, 121 patients) and 19.23 Gy/GBq (3 studies, 53 patients) for the lacrimal glands (P = 0.20), 0.24 Gy/GBq (12 studies, 183 patients) and 0.19 Gy/GBq (4 studies, 68 patients) for the bone marrow (P = 0.31), and 1.11 Gy/GBq (9 studies, 154 patients) and 0.56 Gy/GBq (4 studies, 56 patients) for the liver (P = 0.05), respectively. Average tumor doses tended to be higher for [177Lu]Lu-PSMA-617 than for [177Lu]Lu-PSMA-I&T in soft tissue tumor lesions (4.19 vs. 2.94 Gy/GBq; P = 0.26). Dosimetry data of [177Lu]Lu-J591 were limited to one published study of 35 patients with reported absorbed doses of 1.41, 0.32, and 2.10 Gy/GBq to the kidney, bone marrow, and liver, respectively. Conclusion: In this metaanalysis, there was no significant difference in absorbed dose between [177Lu]Lu-PSMA-I&T and [177Lu]Lu-PSMA-617. There was a possible trend toward a higher kidney dose with [177Lu]Lu-PSMA-I&T and a higher tumor lesion dose with [177Lu]Lu-PSMA-617. It remains unknown whether this finding has any clinical impact. The dosimetry methodologies were strikingly heterogeneous among studies, emphasizing the need for standardization.

Numerical studies on lutetium isotopic selective photoionization based on a three-step ionization scheme

Numerical studies of lutetium selective photoionization have been carried out based on a three-step photoionization scheme, 5d6s2 2D3/2 → 5d6s6p4Fo5/2 → 5d6s7s4D3/2 → (53,375 cm-1)1/2 → Lu+, by the density matrix theory. Atomic hyperfine structures and magnetic sublevels are considered in our photoionization dynamics model. To examine the effectiveness of this model, the simulated 176Lu ion strengths are compared with the experimental results, and the simulated excitation cross sections of 176Lu excitation channels are compared with the analytical and experimental results. Semi-quantitative agreements are acquired for these two cases. On this basis, selective photoionization processes of two lutetium isotopes are simulated and discussed. Considering the ionization probability and abundance of target isotope, the 8.5-9.5-8.5 two-step excitation channel is optimal for 176Lu enrichment from natural lutetium. The influences of laser parameters and atomic Doppler broadening are presented numerically and optimization excitation conditions are identified. For the co-propagating excitation lasers, extra-narrow laser bandwidth (at the magnitude of 0.1 GHz) and atomic Doppler broadening (smaller than 0.3 GHz) is required. A new time-delayed configuration is proposed to implement multiple counter-propagating laser exposures for high target isotope abundance at the larger atomic Doppler broadening.

A phase 2, single-arm trial evaluating 131 I-PSMA-1095 targeted radioligand therapy for metastatic castration-resistant prostate cancer

BACKGROUND

Metastatic castration-resistant prostate cancer (mCRPC) remains uniformly lethal. Prostate specific membrane antigen (PSMA) is a transmembrane glycoprotein overexpressed in prostate cancer. 131 I-PSMA-1095 (also known as 131 I-MIP-1095) is a PSMA-targeted radioligand which selectively delivers therapeutic radiation to cancer cells and the tumor microenvironment.

METHODS

We conducted a single-arm, phase 2 trial to assess efficacy and tolerability of 131 I-PSMA-1095 in mCRPC patients who had exhausted all lines of approved therapy. All patients underwent 18 F-DCFPyL PET and 18 F-FDG PET to determine PSMA-positive tumor volume, and patients with >50% PSMA-positive tumor volume were treated with up to four doses of 131 I-PSMA-1095. The primary endpoint was the response rate of prostate specific antigen (PSA). Secondary endpoints included rates of radiographic response and adverse events. Overall and radiographic progression-free survival were also analyzed.

RESULTS

Eleven patients were screened for inclusion and nine patients received 131 I-PSMA-1095. The median baseline PSA was 162 µg/l, and six patients demonstrated a >50% PSA decrease. One patient demonstrated a confirmed radiographic response. Median overall survival was 10.3 months, and median progression-free survival was 5.4 months. Four patients experienced adverse events of grade 3 or higher, the most frequent being thrombocytopenia and anemia.

CONCLUSION

131 I-PSMA-1095 is highly active against heavily-pretreated PSMA-positive mCRPC, significantly decreasing tumor burden as measured by PSA. Adverse events, mainly hematologic toxicity, were not infrequent, likely related to off-target irradiation. This hematologic toxicity, as well as a higher logistical burden associated with use, could represent relative disadvantages of 131 I-PSMA-1095 compared to 177 Lu-PSMA-617.

Role of Lutetium Radioligand Therapy in Prostate Cancer

Theranostics utilize ligands that chelate radionuclides and selectively bind with cancer-specific membrane antigens. In the case of prostate cancer (PCa), the state-of-the-art lutetium-177-PSMA combines the radioactive β-emitter 177Lu with Vipivotide Tetraxetan, a prostate-specific membrane antigen (PSMA)-binding ligand. Several studies have been conducted, and the therapy is not without adverse effects (e.g., xerostomia, nausea, and fatigue); however, few events are reported as severe. The available evidence supports the use of 177Lu-PSMA in selected metastatic castration-resistant prostate cancer patients, and the treatment is considered a standard of care in several clinical scenarios. Emerging research shows promising results in the setting of hormone-sensitive prostate cancer; however, evidence from high-quality controlled trials is still missing. In this review, we discuss the available evidence for the application of 177Lu-PSMA in the management of PCa patients.

Radiation Safety Assessment of 177Lu-DOTATATE Intra-arterial Peptide Receptor Therapy (PRRT)

Objective

177Lu-DOTATATE peptide receptor therapy (PRRT) is an established treatment for patients suffering from neuroendocrine tumors. In the last few years, intra-arterial PRRT is being considered for patients having liver metastatic disease predominantly. The aim of our study is to measure the radiation doses received by the treating intervention radiologists involved in intra-arterial PRRT treatment using 177Lu-DOTATATE.

Materials and Methods

Radiation safety-related data of 31 patients who underwent 177Lu-DOTATATE intra-arterial PRRT treatment were used for this study. The exposure rate was measured at the hand and eye and chest level of treating intervention radiologists continuously from the beginning to the end of the administration. Exposure from the patient at the body surface (at the level of liver, thigh, and extremities) and 1 m from the body surface was measured just after the administration. The mean radiation exposure from the patient at the body surface and 1 m from the body was also calculated.

Results

The mean administered activity was found to be 194 (±17) mCi. The mean radiation exposure at the surface at the level of the liver, thigh, and feet and at 1 m from the surface was found to be 100 (±25.11), 9 (±1.27), 5.6 (±0.52), and 5.3± (0.50) μSv/hr, respectively. The mean administration time was found to be 23 ± 5.6 min. The mean radiation dose to the hands, and eyes, of the treating intervention radiologist per procedure, was found to be 6.425 ± 2.75 μSv, 5.43 ± 1.76 μSv and 1-m exposure from the patient was found to be 5.3 ± 0.246 μSv, respectively.

Conclusion

Our result shows that the radiation exposure from the patient postadministration is below the permissible limit of discharge. The radiation exposure to the intervention radiologist is also suggestive of a safe procedure to be performed by maintaining the radiation dose well within the permissible limit for radiation professionals.

Recent advances and impending challenges for the radiopharmaceutical sciences in oncology

This paper is the first of a Series on theranostics that summarises the current landscape of the radiopharmaceutical sciences as they pertain to oncology. In this Series paper, we describe exciting developments in radiochemistry and the production of radionuclides, the development and translation of theranostics, and the application of artificial intelligence to our field. These developments are catalysing growth in the use of radiopharmaceuticals to the benefit of patients worldwide. We also highlight some of the key issues to be addressed in the coming years to realise the full potential of radiopharmaceuticals to treat cancer.

Production study of Fr, Ra and Ac radioactive ion beams at ISOLDE, CERN

The presented paper discusses the production of radioactive ion beams of francium, radium, and actinium from thick uranium carbide (UCx ) targets at ISOLDE, CERN. This study focuses on the release curves and extractable yields of francium, radium and actinium isotopes. The ion source temperature was varied in order to study the relative contributions of surface and laser ionization to the production of the actinium ion beams. The experimental results are presented in the form of release parameters. Representative extractable yields per μ C are presented for222 - 231 Ac, several Ra and Fr isotopes in the mass ranges 214 ≤ A ≤ 233 and 205 ≤ A ≤ 231 respectively. The release efficiency for several isotopes of each of the studied elements was calculated by comparing their yields to the estimated in-target production rates modeled by CERN-FLUKA. The maximal extraction efficiency of actinium was calculated to be 2.1(6)% for a combination of surface ionization using a Ta ion source and resonant laser ionization using the two-step 438.58 nm, and 424.69 nm scheme.

Nuclear Localization Signal Enhances the Targeting and Therapeutic Efficacy of a Porphyrin-Based Molecular Cargo: A Systemic In Vitro and Ex Vivo Evaluation

The objective of the present work was to evaluate the potential of a nuclear localization signal (NLS) toward facilitating intracellular delivery and enhancement in the therapeutic efficacy of the molecular cargo. Toward this, an in-house synthesized porphyrin derivative, namely, 5-carboxymethyelene-oxyphenyl-10,15,20-tris(4-methoxyphenyl) porphyrin (UTriMA), was utilized for conjugation with the NLS sequence [PKKKRKV]. The three compounds synthesized during the course of the present work, namely DOTA-Lys-NLS, DOTA-UTriMA-Lys-NLS, and DOTA-Lys-UTriMA, were evaluated for cellular toxicity in cancer cell lines (HT1080), wherein all exhibited minimal dark toxicity. However, during photocytotoxicity studies with DOTA-Lys-UTriMA and DOTA-UTriMA-Lys-NLS conjugates in the same cell line, the latter exhibited significantly higher light-dependent toxicity compared to the former. Furthermore, the photocytotoxicity for DOTA-UTriMA-Lys-NLS in a healthy cell line (WI26VA4) was found to be significantly lower than that observed in the cancer cells. Fluorescence cell imaging studies carried out in HT1080 cancer cells revealed intracellular accumulation for the NLS-conjugated porphyrin (DOTA-UTriMA-Lys-NLS), whereas unconjugated porphyrin (DOTA-Lys-UTriMA) failed to do so. To evaluate the radiotherapeutic effects of the synthesized conjugates, all three compounds were radiolabeled with 177Lu, a well-known therapeutic radionuclide with high radiochemical purity (>95%). During in vitro studies, the [177Lu]Lu-DOTA-UTriMA-Lys-NLS complex exhibited the highest cell binding as well as internalization among the three radiolabeled complexes. Biological distribution studies for the radiolabeled compounds were performed in a fibrosarcoma-bearing small animal model, wherein significantly higher accumulation and prolonged retention of [177Lu]Lu-DOTA-UTriMA-Lys-NLS (9.32 ± 1.27% IA/g at 24 h p.i.) in the tumorous lesion compared to [177Lu]Lu-UTriMA-Lys-DOTA (2.3 ± 0.13% IA/g at 24 h p.i.) and [177Lu]Lu-DOTA-Lys-NLS complexes (0.26 ± 0.17% IA/g at 24 h p.i.) were observed. The results of the biodistribution studies were further corroborated by recording serial SPECT-CT images of fibrosarcoma-bearing Swiss mice administered with [177Lu]Lu-DOTA-UTriMA-Lys-NLS at different time points. Tumor regression studies performed with [177Lu]Lu-DOTA-UTriMA-Lys-NLS in the same animal model with two different doses [250 μCi (9.25 MBq) and 500 μCi (18.5 MBq)] resulted in a significant reduction in tumor mass in the treated group of animals. The above results revealed a definite enhancement in the targeting ability of molecular cargo upon conjugation with NLS and hence indicated that this strategy may be helpful for the preparation of drug-NLS conjugates as multimodal agents.

Current clinical application of lutetium‑177 in solid tumors (Review)

Radionuclide-based therapy represents a novel treatment regimen for tumors. Among these therapies, lutetium-177 (177Lu) has gained significant attention due to its stability and safety, as well as its ability to emit both γ and β rays, allowing for both imaging with single photon emission computed tomography and tumor treatment. As a result, 177Lu can be used for both diagnosis and treatment for diseases such as prostatic and gastric cancer. Therefore, based on the available data, the present review provides a brief overview of the clinical applications of 177Lu-targeted radionuclide therapy in metastatic prostate cancer, neuroendocrine tumors and other types of solid tumors, and highlights the current therapeutic effect, reduction in damage to normal tissues and future research directions, including the development of new nuclides and the application of more nuclides in different tumors. In the future, such treatments could be used in more tumors.

177Lu-PSMA therapy in metastatic prostate cancer: An updated review of prognostic and predictive biomarkers

177Lu-PSMA has been approved for the treatment of PSMA-positive metastatic castration-resistant (mCRPC) patients who progressed to androgen receptor pathway inhibitors (ARPIs) and taxane-based chemotherapy. However, a higher proportion of patients do not respond to this type of radioligand therapy (RLT). To date, there is a lack of validated prognostic and predictive biomarkers for 177Lu-PSMA therapy in prostate cancer. Several studies have investigated the prognostic and predictive role of clinical and molecular factors and also the metabolic features of PET imaging. In this review, we aim to take stock of the current scenario, focusing on new emerging data from retrospective/prospective series and clinical trials. Given the high costs and the possibility of primary resistance, it seems essential to identify clinical and molecular characteristics that could allow clinicians to choose the right patient to treat with 177Lu-PSMA. Biomarker-based clinical trials are urgently needed in this field.

Interrogating the Theranostic Capacity of a MUC16-Targeted Antibody for Ovarian Cancer

Aberrantly expressed glycans on mucins such as mucin-16 (MUC16) are implicated in the biology that promotes ovarian cancer (OC) malignancy. Here, we investigated the theranostic potential of a humanized antibody, huAR9.6, targeting fully glycosylated and hypoglycosylated MUC16 isoforms. Methods: In vitro and in vivo targeting of the diagnostic radiotracer [89Zr]Zr-DFO-huAR9.6 was investigated via binding experiments, immuno-PET imaging, and biodistribution studies on OC mouse models. Ovarian xenografts were used to determine the safety and efficacy of the therapeutic version, [177Lu]Lu-CHX-A″-DTPA-huAR9.6. Results: In vivo uptake of [89Zr]Zr-DFO-huAR9.6 supported in vitro-determined expression levels: high uptake in OVCAR3 and OVCAR4 tumors, low uptake in OVCAR5 tumors, and no uptake in OVCAR8 tumors. Accordingly, [177Lu]Lu-CHX-A″-DTPA-huAR9.6 displayed strong antitumor effects in the OVCAR3 model and improved overall survival in the OVCAR3 and OVCAR5 models in comparison to the saline control. Hematologic toxicity was transient in both models. Conclusion: PET imaging of OC xenografts showed that [89Zr]Zr-DFO-huAR9.6 delineated MUC16 expression levels, which correlated with in vitro results. Additionally, we showed that [177Lu]Lu-CHX-A″-DTPA-huAR9.6 displayed strong antitumor effects in highly MUC16-expressing tumors. These findings demonstrate great potential for 89Zr- and 177Lu-labeled huAR9.6 as theranostic tools for the diagnosis and treatment of OC.

Activity quantification and dosimetry in radiopharmaceutical therapy with reference to 177Lutetium

Radiopharmaceutical therapy has been widely adopted owing primarily to the development of novel radiopharmaceuticals. To fully utilize the potential of these RPTs in the era of precision medicine, therapy must be optimized to the patient's tumor characteristics. The vastly disparate dosimetry methodologies need to be harmonized as the first step towards this. Multiple factors play a crucial role in the shift from empirical activity administration to patient-specific dosimetry-based administrations from RPT. Factors such as variable responses seen in patients with presumably similar clinical characteristics underscore the need to standardize and validate dosimetry calculations. These efforts combined with ongoing initiatives to streamline the dosimetry process facilitate the implementation of radiomolecular precision oncology. However, various challenges hinder the widespread adoption of personalized dosimetry-based activity administration, particularly when compared to the more convenient and resource-efficient approach of empiric activity administration. This review outlines the fundamental principles, procedures, and methodologies related to image activity quantification and dosimetry with a specific focus on 177Lutetium-based radiopharmaceuticals.

Exploring Aqueous Coordination Chemistry of Highly Lewis Acidic Metals with Emerging Isotopes for Nuclear Medicine

Nuclear medicine harnesses radioisotopes for the diagnosis and treatment of disease. While the isotopes 99mTc and 111In have enabled the clinical diagnosis of millions of patients over the past 3 decades, more recent clinical translation of numerous 68Ga/177Lu-based radiopharmaceuticals for diagnostic imaging and therapy underscores the clinical utility of metal-based radiopharmaceuticals in mainstream cancer treatment. In addition to such established radionuclides, advancements in radioisotope production have enabled the production of radionuclides with a broad range of half-lives and emission properties of interest for nuclear medicine. Chemical means to form kinetically inert, in vivo-compatible species that can be modified with disease-targeting vectors is imperative. This presents a challenge for radiosiotopes of elements where the aqueous chemistry is still underdeveloped and poorly understood. Here, we discuss our efforts to date in exploring the aqueous, radioactive coordination chemistry of highly Lewis acidic metal ions and how our discoveries apply to the diagnosis and treatment of cancer in preclinical models of disease. The scope of this Account includes approaches to aqueous coordination of to-date understudied highly Lewis acidic metal ions with radioisotopes of emerging interest and the modulation of well-understood coordination environments of radio-coordination complexes to induce metal-catalyzed reactivity for separation and pro-drug applications.First, we discuss the development of seven-coordinate, small-cavity macrocyclic chelator platform mpatcn/picaga as an exemplary case study, which forms robust complexes with 44Sc/47Sc isotopes. Due to the high chemical hardness and pronounced Lewis acidity of the Sc3+ ion, the displacement of ternary ligand H2O by 18/natF- can be achieved to form an inert Sc-18/natF bond. Corresponding coordination complex natSc-18F is in vivo compatible and forms a theranostic tetrad with corresponding 44Sc/47Sc, 177Lu complexes all exhibiting homologous biodistribution profiles. Another exceptionally hard, highly Lewis acidic ion with underdeveloped aqueous chemistry and emerging interest in nuclear medicine is 45Ti4+. To develop de novo approaches to the mononuclear chelation of this ion under aqueous conditions, we employed a fragment-based bidentate ligand screening approach which identified two leads. The screen successfully predicted the formation of [45Ti][Ti(TREN-CAM)], a Ti-triscatechol complex that exhibits remarkable in vivo stability. Furthermore, the fragment-based screen also identified approaches that enabled solid-phase separation of Ti4+ and Sc3+ of interest in streamlining the isotope production of 45Ti and accessing new ways to separate 44Ti/44Sc for the development of a long-lived generator system. In addition to establishing the inert chelation of Ti4+ and Sc3+, we introduce controlled, metal-induced reactivity of corresponding coordination complexes on macroscopic and radiotracer scales. Metal-mediated autolytic amide bond cleavage (MMAAC) enables the temperature-dependent release of high-molar-activity, ready-to-inject radiopharmaceuticals; cleavage is selectively triggered by coordinated trivalent Lewis acid nat/68Ga3+ or Sc3+. Following the scope of reactivity and mechanistic studies, we validated MMAAC for the synthesis of high-molar-activity radiopharmaceuticals to image molecular targets with low expression and metal-mediated prodrug hydrolysis in vivo.This Account summarizes how developing the aqueous coordination chemistry and tuning the chemical reactivity of metal ions with high Lewis acidity at the macroscopic and tracer scales directly apply to the radiopharmaceutical synthesis with clinical potential.

Enhanced Lutetium Ion Sorption from Aqueous Solutions Using Activated Ion Exchangers

The growing demand for rare earth elements (REE) requires the search for economically viable materials to efficiently recover REE from various solutions. Our research aims to investigate the potential of using a combination of the ion exchangers Lewatit CNP LF (in H+ form) and AV-17-8 (in OH- form) as an interpolymer system, "Lewatit CNP LF@AV-17-8" (X:Y), with varying mass ratios of X:Y to enhance the sorption efficiency of lutetium ions from nitrate solution. During the study, we used a range of analytical methodologies, including gravimetry, ultraviolet-visible (UV-VIS) spectroscopy, and inductively coupled plasma optical emission spectroscopy (ICP-OES). Our findings demonstrate that the interpolymer system "Lewatit CNP LF@AV-17-8" (X:Y), with a mass ratio of 4:2, exhibited a significantly enhanced sorption rate of Lu3+ ions (42%) compared to the individual Lewatit CNP LF (6:0) (25%) and the individual AV-17-8 (0:6) (21%) over a 48 h period. Moreover, this interpolymer system has demonstrated notable conformity to the Freundlich adsorption model, highlighting its performance as an effective sorbent for lutetium (III) ions. Notably, our study presents a novel utilization of the interpolymer system "Lewatit CNP LF@AV-17-8" (4:2), with an adsorption capacity of 221.05 mg/g, to enhance the recovery of lutetium ions. The research findings demonstrate its potential for enhancing the recovery of REE.

Need for enrichment of lutetium isotope and design of a laser based separator module

Lutetium-177 radio-pharmaceutical has become an important theranostic candidate in cancer treatment. Its availability from bench-to-bed requires strategic implementation of isotope-enrichment, neutron-irradiation and radio-chemical techniques. In this paper, the need for enrichment of lutetium-176 is emphasized by estimating specific activity of lutetium-177 as a function of enrichment percentage for typical neutron flux available at Dhruva reactor, India. A novel Atomic Vapour Laser Isotope Separation (AVLIS) module for lutetium-176 enrichment is designed to meet the above requirement. The paper documents its characteristics and production estimates. The design is carried out after critical assessment and evaluation of available AVLIS-infrastructure in the country. Outline of lutetium-177 enrichment, capable of producing non-carrier-added lutetium is also provided. This work concludes that India has taken a step forward towards self-reliance (Atmanirbhar Bharat) in securing the supply chain of lutetium-177.

Radiation exposure assessment of nuclear medicine staff administering [177Lu]Lu-DOTA-TATE with active and passive dosimetry

BACKGROUND

The use of lutetium-177 (177Lu)-based radiopharmaceuticals in peptide receptor nuclear therapy is increasing, but so is the number of nuclear medicine workers exposed to higher levels of radiation. In recent years, [177Lu]Lu-DOTA-TATE has begun to be widely used for the treatment of neuroendocrine tumours. However, there are few studies evaluating the occupational radiation exposure during its administration, and there are still some challenges that can result in higher doses to the staff, such as a lack of trained personnel or fully standardised procedures. In response, this study aims to provide a comprehensive analysis of occupational doses to the staff involved in the administration of [177Lu]Lu-DOTA-TATE.

RESULTS

A total of 32 administrations of [177Lu]Lu-DOTA-TATE (7.4 GBq/session) carried out by a physician and a nurse, were studied. In total, two physicians and four nurses were independently monitored with cumulative (passive) and/or real-time (active) dosemeters. Extremity, eye lens and whole-body doses were evaluated in terms of the dosimetric quantities Hp(0.07), Hp(3) and Hp(10), respectively. It was obtained that lead aprons reduced dose rates and whole-body doses by 71% and 69% for the physicians, respectively, and by 56% and 68% for the nurses. On average, normalised Hp(10) values of 0.65 ± 0.18 µSv/GBq were obtained with active dosimetry, which is generally consistent with passive dosemeters. For physicians, the median of the maximum normalised Hp(0.07) values was 41.5 µSv/GBq on the non-dominant hand and 45.2 µSv/GBq on the dominant hand. For nurses 15.4 µSv/GBq on the non-dominant and 13.9 µSv/GBq on the dominant hand. The ratio or correction factor between the maximum dose measured on the hand and the dose measured on the base of the middle/ring finger of the non-dominant hand resulted in a factor of 5/6 for the physicians and 3/4 for the nurses. Finally, maximum normalised Hp(3) doses resulted in 2.02 µSv/GBq for physicians and 1.76 µSv/GBq for nurses.

CONCLUSIONS

If appropriate safety measures are taken, the administration of [177Lu]Lu-DOTA-TATE is a safe procedure for workers. However, regular monitoring is recommended to ensure that the annual dose limits are not exceeded.

Lutetium-177-Labeled Prostate-Specific Membrane Antigen-617 for Molecular Imaging and Targeted Radioligand Therapy of Prostate Cancer

Prostate-specific membrane antigen (PSMA) represents a promising target for PSMA-overexpressing diseases, especially prostate cancer-a common type of cancer among men worldwide. In response to the challenges in tackling prostate cancers, several promising PSMA inhibitors from a variety of molecular scaffolds (e.g., phosphorous-, thiol-, and urea-based molecules) have been developed. In addition, PSMA inhibitors bearing macrocyclic chelators have attracted interest due to their favorable pharmacokinetic properties. Recently, conjugating a small PSMA molecule inhibitor-bearing 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelator, as exemplified by [177Lu]Lu-PSMA-617 could serve as a molecular imaging probe and targeted radioligand therapy (TRT) of metastatic castration resistant prostate cancer (mCRPC). Hence, studies related to mCRPC have drawn global attention. In this review, the recent development of PSMA ligand-617-labeled with 177Lu for the management of mCRPC is presented. Its molecular mechanism of action, safety, efficacy, and future direction are also described.

Theranostic Nuclear Medicine with Gallium-68, Lutetium-177, Copper-64/67, Actinium-225, and Lead-212/203 Radionuclides

Molecular changes in malignant tissue can lead to an increase in the expression levels of various proteins or receptors that can be used to target the disease. In oncology, diagnostic imaging and radiotherapy of tumors is possible by attaching an appropriate radionuclide to molecules that selectively bind to these target proteins. The term "theranostics" describes the use of a diagnostic tool to predict the efficacy of a therapeutic option. Molecules radiolabeled with γ-emitting or β+-emitting radionuclides can be used for diagnostic imaging using single photon emission computed tomography or positron emission tomography. Radionuclide therapy of disease sites is possible with either α-, β-, or Auger-emitting radionuclides that induce irreversible damage to DNA. This Focus Review centers on the chemistry of theranostic approaches using metal radionuclides for imaging and therapy. The use of tracers that contain β+-emitting gallium-68 and β-emitting lutetium-177 will be discussed in the context of agents in clinical use for the diagnostic imaging and therapy of neuroendocrine tumors and prostate cancer. A particular emphasis is then placed on the chemistry involved in the development of theranostic approaches that use copper-64 for imaging and copper-67 for therapy with functionalized sarcophagine cage amine ligands. Targeted therapy with radionuclides that emit α particles has potential to be of particular use in late-stage disease where there are limited options, and the role of actinium-225 and lead-212 in this area is also discussed. Finally, we highlight the challenges that impede further adoption of radiotheranostic concepts while highlighting exciting opportunities and prospects.

Radiometals in Imaging and Therapy: Highlighting Two Decades of Research

The present article highlights the important progress made in the last two decades in the fields of molecular imaging and radionuclide therapy. Advancements in radiometal-based positron emission tomography, single photon emission computerized tomography, and radionuclide therapy are illustrated in terms of their production routes and ease of radiolabeling. Applications in clinical diagnostic and radionuclide therapy are considered, including human studies under clinical trials; their current stages of clinical translations and findings are summarized. Because the metalloid astatine is used for imaging and radionuclide therapy, it is included in this review. In regard to radionuclide therapy, both beta-minus (β-) and alpha (α)-emitting radionuclides are discussed by highlighting their production routes, targeted radiopharmaceuticals, and current clinical translation stage.

Neutron-activated, plasmonically excitable Fe-Pt-Yb2O3 nanoparticles delivering anti-cancer radiation against human glioblastoma cells

Magnetic nanoparticles can be functionalized in many ways for biomedical applications. Here, we combine four advantageous features in a novel Fe-Pt-Yb2O3 core-shell nanoparticle. (a) The nanoparticles have a size of 10 nm allowing them to diffuse through neuronal tissue. (b) The particles are superparamagnetic after synthesis and ferromagnetic after annealing, enabling directional control by magnetic fields, enhance NMRI contrast, and hyperthermia treatment. (c) After neutron-activation of the shell, they carry low-energetic, short half-life β-radiation from 175Yb, 177Yb, and 177Lu. (d) Additionally, the particles can be optically visualized by plasmonic excitation and luminescence. To demonstrate the potential of the particles for cancer treatment, we exposed cultured human glioblastoma cells (LN-18) to non-activated and activated particles to confirm that the particles are internalized, and that the β-radiation of the radioisotopes incorporated in the neutron-activated shell of the nanoparticles kills more than 98% of the LN-18 cancer cells, promising for future anti-cancer applications.

Optimization of Deuteron Irradiation of 176Yb for Producing 177Lu of High Specific Activity Exceeding 3000 GBq/mg

The irradiation of 176Yb with deuterons offers a promising pathway for the production of the theranostic radionuclide 177Lu. To optimize this process, calculations integrating deuteron transport, isotope production, and decay have been performed. In pure 176Yb, the undesired production of 174g+mLu occurs at higher deuteron energies, corresponding to a distribution slightly shallower than that of 177Lu. Hence, 174g+mLu can be effectively filtered out by employing either a low-energy deuteron beam or stacked foils. The utilization of stacked foils enables the production of 177Lu using a high-energy linear accelerator. Another unwanted isotope, 176mLu, is produced roughly at the same depth as 177Lu, but its concentration can be significantly reduced by selecting an appropriate post-irradiation processing time, owing to its relatively short half-life. The modeling approach extended to the mapping of yields as a function of irradiation time and post-irradiation processing time. An optimized processing time window was identified. The study demonstrates that a high-energy deuteron beam can be employed to produce 177Lu with high specific activity exceeding 3000 GBq/mg. The effect of different purity levels (ranging from 98% to 100%) was also discussed. The impurity levels have a slight impact. The modeling demonstrates the feasibility of obtaining 177Lu with a specific activity > 3000 GBq/mg and radionuclidic purity > 99.5% when using a commercially available 176Yb target of 99.6% purity.

Nuclear Imaging of CAR T Immunotherapy to Solid Tumors: In Terms of Biodistribution, Viability, and Cytotoxic Effect

Immunotherapy has become a mainstay of cancer therapy. Since chimeric antigen receptor (CAR) T immunotherapy achieves unprecedented success in curing hematological malignancies, the possibility of it revolutionizing the paradigm of solid tumors has aroused increasing attention. However, the restricted accessibility to tumor parenchyma, the immunosuppressive tumor microenvironment, and antigen heterogeneity of solid tumors make it difficult to replicate its success. Therefore, dynamic evaluation of CAR T cells' tumor accessibility, intratumoral viability, and anti-tumor cytotoxicity is necessary to facilitate its translation to solid tumors. Besides, real-timely imaging above events in vivo can help evaluate therapeutic responses and optimize CAR T immunotherapy for solid tumors. Nuclear imaging, including positron emission tomography (PET) and single-photon emission computed tomography (SPECT) imaging, is frequently applied for evaluating adoptive cell therapies owing to its excellent sensitivity, high tissue penetration, and great translation potential. In addition, quantitative analysis can be performed in dynamic and noninvasive patterns. This review focuses on recent advances in PET/SPECT technologies and imaging probes in monitoring CAR T cells' migration, viability, and cytotoxicity to solid tumors post-administration. Prospects of what should be done in the next stage to promote CAR T therapy's application in solid tumors are also discussed.

Introduction of a Polyethylene Glycol Linker Improves Uptake of 67Cu-NOTA-Conjugated Lactam-Cyclized Alpha-Melanocyte-Stimulating Hormone Peptide in Melanoma

The aim of this study was to evaluate the effect of linker on tumor targeting and biodistribution of ⁶⁷Cu-NOTA-PEG₂Nle-CycMSH_hex {⁶⁷Cu-1,4,7-triazacyclononane-1,4,7-triyl-triacetic acid-polyethylene glycol-Nle-c[Asp-His-DPhe-Arg-Trp-Lys]-CONH₂} and ⁶⁷Cu-NOTA-GGNle-CycMSH_hex {⁶⁷Cu-NOTA-GlyGlyNle-CycMSH_hex} on melanoma-bearing mice. NOTA-PEG₂Nle-CycMSH_hex and NOTA-GGNle-CycMSH_hex were synthesized and purified by HPLC. The biodistribution of ⁶⁷Cu-NOTA-PEG₂Nle-CycMSH_hex and ⁶⁷Cu-NOTA-GGNle-CycMSH_hex was determined in B16/F10 melanoma-bearing C57 mice. The melanoma imaging property of ⁶⁷Cu-NOTA-PEG₂Nle-CycMSH_hex was further examined in B16/F10 melanoma-bearing C57 mice. ⁶⁷Cu-NOTA-PEG₂Nle-CycMSH_hex exhibited higher tumor uptake than ⁶⁷Cu-NOTA-GGNle-CycMSH_hex at 2, 4, and 24 h post-injection. The tumor uptake of ⁶⁷Cu-NOTA-PEG₂Nle-CycMSH_hex was 27.97 ± 1.98, 24.10 ± 1.83, and 9.13 ± 1.66% ID/g at 2, 4, and 24 h post-injection, respectively. Normal organ uptake of ⁶⁷Cu-NOTA-PEG₂Nle-CycMSH_hex was lower than 2.6% ID/g at 4 h post-injection, except for kidney uptake. The renal uptake of ⁶⁷Cu-NOTA-PEG₂Nle-CycMSH_hex was 6.43 ± 1.31, 2.60 ± 0.79, and 0.90 ± 0.18% ID/g at 2, 4, and 24 h post-injection, respectively. ⁶⁷Cu-NOTA-PEG₂Nle-CycMSH_hex showed high tumor to normal organ uptake ratios after 2 h post-injection. The B16/F10 melanoma lesions could be clearly visualized by single photon emission computed tomography (SPECT) using ⁶⁷Cu-NOTA-PEG₂Nle-CycMSH_hex as an imaging probe at 4 h post-injection. The favorable tumor targeting and biodistribution properties of ⁶⁷Cu-NOTA-PEG₂Nle-CycMSH_hex underscored its potential as an MC1R-targeted therapeutic peptide for melanoma treatment.

Neutronic simulation of medical radioisotope 99Mo and 177Lu production in IPR 14 MeV neutron generator facility

An accelerator based 14 MeV neutron generator is commissioned at Institute for Plasma Research India. The generator is based on the linear accelerator concept where the deuterium ion beam impinged to the tritium target to produce neutrons. The generator is designed to produce 1 × 10¹² neutrons per sec. The 14 MeV neutron source facilities are an emerging tool for the lab scale experiments and research. In order to utilize the generator for the welfare of humanity, the assessment is made for the production of medical radioisotopes using the neutron facility. The usage of radioisotopes in the treatment and diagnosis of a disease is an important factor in the healthcare sector. A series of calculations are conducted to generate radioisotopes, especially ⁹⁹Mo and ¹⁷⁷Lu those are having huge applications in the medical and pharmaceutical industries. ⁹⁹Mo can be also generated through neutron reactions ⁹⁸Mo(n, g)⁹⁹Mo and ¹⁰⁰Mo(n, 2n)⁹⁹Mo apart from fission reaction. The cross section of ⁹⁸Mo(n, g)⁹⁹Mo is high in the thermal energy range whereas ¹⁰⁰Mo(n,2n)⁹⁹Mo occurs at a high energy range. ¹⁷⁷Lu can be produced using the reactions ¹⁷⁶Lu (n, g)¹⁷⁷Lu and ¹⁷⁶Yb (n, g)¹⁷⁷Yb. The cross section of both ¹⁷⁷Lu production routes is higher at thermal energy range. The neutron flux level near the target is around 10¹⁰ cm^-2s^-1. In order to enhance production capabilities, the neutron energy spectrum moderators are used to thermalize the neutrons. The materials used as a moderator are beryllium, HDPE, graphite, etc. Moderators enhance the capabilities of medical isotope production in neutron generators.

Effective half-life, excretion and radiation exposure of 177Lu-PSMA

The study aims to evaluate the radiation safety conditions by detecting the patient's urine excretion rate, calculating the effective half-life, and determining the retention of 177Lu-PSMA in the body. Urine samples of patients were collected for 24 hours (6, 12, 18, and 24 hours) following the infusion, excretion rate and retention of 177Lu-PSMA in the body of patients were calculated. The measurements of dose rate were performed. Effective half-life calculated from dose rate measurements was found as 18.5 ± 11 h within the first 24 h and 48.1 ± 22.8 h between 24 and 72 h. Excreted activity in urine was found as 33.8 ± 20.7, 40.4 ± 20.3, 46.1 ± 22.4, and 53.3 ± 21.5% of total doses at 6, 12, 18, and 24 h after administration, respectively. External dose rates for 4 h and 24 h were 24.51 μSv/h, 16.14 μSv/h, respectively. Our results showed that 177Lu-PSMA treatment was suitable for outpatient treatment in terms of radiation safety.

Safety and Therapeutic Optimization of Lutetium-177 Based Radiopharmaceuticals

Peptide receptor radionuclide therapy (PRRT) using Lutetium-177 (¹⁷⁷Lu) based radiopharmaceuticals has emerged as a therapeutic area in the field of nuclear medicine and oncology, allowing for personalized medicine. Since the first market authorization in 2018 of [¹⁷⁷Lu]Lu-DOTATATE (Lutathera®) targeting somatostatin receptor type 2 in the treatment of gastroenteropancreatic neuroendocrine tumors, intensive research has led to transfer innovative ¹⁷⁷Lu containing pharmaceuticals to the clinic. Recently, a second market authorization in the field was obtained for [¹⁷⁷Lu]Lu-PSMA-617 (Pluvicto®) in the treatment of prostate cancer. The efficacy of ¹⁷⁷Lu radiopharmaceuticals are now quite well-reported and data on the safety and management of patients are needed. This review will focus on several clinically tested and reported tailored approaches to enhance the risk-benefit trade-off of radioligand therapy. The aim is to help clinicians and nuclear medicine staff set up safe and optimized procedures using the approved ¹⁷⁷Lu based radiopharmaceuticals.

Logistical, technical, and radiation safety aspects of establishing a radiopharmaceutical therapy program: A case in Lutetium-177 prostate-specific membrane antigen (PSMA) therapy

Prostate-specific membrane antigen (PSMA) is a cell surface protein highly expressed in nearly all prostate cancers, with restricted expression in some normal tissues. The differential expression of PSMA from tumor to non-tumor tissue has resulted in the investigation of numerous targeting strategies for therapy of patients with metastatic prostate cancer. In March of 2022, the FDA granted approval for the use of lutetium-177 PSMA-617 (Lu-177-PSMA-617) for patients with PSMA-positive metastatic castration-resistant prostate cancer (mCRPC) who have been treated with androgen receptor pathway inhibition and taxane-based chemotherapy. Therefore, the use of Lu-177-PSMA-617 is expected to increase and become more widespread. Herein, we describe logistical, technical, and radiation safety considerations for implementing a radiopharmaceutical therapy program, with particular focus on the development of operating procedures for therapeutic administrations. Major steps for a center in the U.S. to implement a new radiopharmaceutical therapy (RPT) program are listed below, and then demonstrated in greater detail via examples for Lu-177-PSMA-617 therapy.

Radiolabeled nanomaterial for cancer diagnostics and therapeutics: principles and concepts

In the last three decades, radiopharmaceuticals have proven their effectiveness for cancer diagnosis and therapy. In parallel, the advances in nanotechnology have fueled a plethora of applications in biology and medicine. A convergence of these disciplines has emerged more recently with the advent of nanotechnology-aided radiopharmaceuticals. Capitalizing on the unique physical and functional properties of nanoparticles, radiolabeled nanomaterials or nano-radiopharmaceuticals have the potential to enhance imaging and therapy of human diseases. This article provides an overview of various radionuclides used in diagnostic, therapeutic, and theranostic applications, radionuclide production through different techniques, conventional radionuclide delivery systems, and advancements in the delivery systems for nanomaterials. The review also provides insights into fundamental concepts necessary to improve currently available radionuclide agents and formulate new nano-radiopharmaceuticals.

Clinical Best Practices for Radiation Safety During Lutetium-177 Therapy

IMPORTANCE

177 Lu therapy as part of theranostic treatment for cancer is expanding but it can be a challenge for sites with limited radiation protection staff to implement the radiation safety program required for therapeutic nuclear medicine.

OBJECTIVE

To increase the adoption of 177 Lu therapy, especially in smaller centers and clinics, by providing a collection of radiation safety best practices and operational experience. To provide a resource for radiation safety officers supporting the implementation of a 177 Lu therapy program.

METHODS

A panel of 11 radiation safety professionals representing sites across Canada and the United States with experience delivering 177 Lu therapy was assembled and discussed their responses to a list of questions focused on the following radiation safety topics: facility layout and design; radiation safety program; and drug management and patient care.

RESULTS

A comprehensive set of best practice guidelines for clinical radiation safety during 177 Lu therapy has been developed based on the collective operational experience of a group of radiation safety professionals. Significant findings included that 177 Lu therapy is often safely administered in unshielded rooms, that staff radiation exposure associated with 177 Lu therapy is minimal relative to other nuclear medicine programs, and that some relatively simple preparation in advance including papering of common surfaces and planning for incontinence can effectively control contamination during therapy.

CONCLUSION

The guidance contained in this paper will assist radiation safety professionals in the implementation of safe, effective 177 Lu therapy programs, even at smaller sites with limited to no experience in therapeutic nuclear medicine.

Dealing with dry waste disposal issues associated with 177mLu impurities: a long-term challenge for nuclear medicine departments

PURPOSE

A strategy for management of radioactive waste associated with ¹⁷⁷Lu-dotatate (Lutathera®) treatments was established in our institution, based on predicted storage times of 3-5 years extrapolated from the results of a 2-year measurement study. The aim of this work was to validate this strategy by identifying contaminants and confirming disposal based on the clearance level twice-the-background was within expected time frames.

METHODS

We conducted a prospective series of measurements of radioactive waste associated with the first 65 treatments administered. Sequential measurements of the first 45 vials used were performed on a dose calibrator to identify contaminants. Exposure rates in contact were monitored with a dose ratemeter on a 6-monthly basis for all waste stored: 46 empty vials, 19 vials partially used and 61 biohazard containers.

RESULTS

Initial median activity of the first vials used was 118 MBq [4-4188 MBq]. For each vial, the decay curve of activity obtained was adjusted to a bi-exponential model. The major component, representing 99.7% of the activity, has a median half-life of 6.6 days [5.7-7.2 days] corresponding to ¹⁷⁷Lu. The second, representing only 0.3% of the activity and having a median half-life of 152 days [104-205 days] corresponding to ^177mLu, determines necessary storage times. Partially used vials can be disposed of after 5 years, other waste after 3 years. Compliance with the regulatory clearance level is achieved within expected time frames.

CONCLUSION

Although only present as traces, ^177mLu associated with the direct production route results in major radioactive waste disposal issues for hospitals. Availability of radiopharmaceuticals without impurities appears to be crucial for an expanding use of targeted radionuclide therapy.