Automated Scale-Down Development and Optimization of [68Ga]Ga-DOTA-EMP-100 for Non-Invasive PET Imaging and Targeted Radioligand Therapy of c-MET Overactivation in Cancer

The radioligand [18F]FPEB, used for PET imaging of the brain's metabotropic glutamate receptor subtype 5 (mGluR5), undergoes a thorough validation process to ensure its safety, efficacy, and quality for clinical use. The process starts by optimizing the synthesis of [18F]FPEB to achieve high radiochemical yield and purity. This study focuses on optimizing the radiolabeling process using an aryl-chloro precursor and validating the GMP production for clinical applications. Fully automated radiolabeling was achieved via one-step nucleophilic substitution reaction. [18F]FPEB was produced and isolated in high radioactivity and radiochemical purity. Throughout the validation process, thorough quality control measures are implemented. Radiopharmaceutical batch release criteria are established, including testing for physical appearance, filter integrity, pH, radiochemical purity, molar activity, radiochemical identity, chemical impurity, structural identity, stability, residual solvent, sterility, and endotoxin levels. In conclusion, the validation of [18F]FPEB involved a comprehensive process of synthesis optimization, quality control, which ensure the safety, efficacy, and quality of [18F]FPEB, enabling its reliable use in clinical PET. Here, we successfully radiolabeled and validated [18F]FPEB using aryl-chloro precursor according to GMP production for clinical application.

BackgroundA family of tropomyosin receptor kinases (TrkA/B/C) plays important roles in the regulation of neuronal differentiation, growth, and survival via their interactions with neurotrophins. A growing body of literature suggests the downregulation of Trk in many neurodegenerative conditions of the central nervous system (CNS), including Alzheimer’s disease (AD). We recently reported the development of [18F]TRACK, the PET tracers for in vivo imaging of TrkB and its first in‐human study. Here, we wish to report a fully automated GMP‐compliant radiosynthesis of [18F]TRACK at high radiochemical purity (RCP) and molar activity and its preliminary evaluation in wild‐type and a transgenic rat model of AD.MethodRadiosynthesis was performed using Scintomics GRP automated module via copper‐catalyzed 18F‐fluorination of the chiral boron pinacolate precursor. Brain imaging in wild‐type (n = 3) and TgF344‐AD rat models (n = 2) at 23 months was performed on microPET Concord R4 scanner.Result[18F]TRACK was synthesized with a 5.0±1.4% radiochemical yield not corrected for decay (activity range 95‐154 mCi) with >99% RCP and molar activities of 250 ± 75 GBq/µmol (n = 6). The synthesis was fully automated and all batches passed quality control procedures, including chemical purity, sterility and pyrogenicity. The tracer showed moderate brain uptake in wild‐type rats with the highest accumulation in the thalamus (SUVmax = 1.56 ± 0.28, 10 min post‐injection), consistent with the brain regional distribution in humans acquired in a parallel study. Preliminary data suggests lower tracer uptake in TgF344‐AD rat model of AD in thalamus, striatum and frontal cortex compared to wild‐type animals.ConclusionThis study demonstrated the feasibility of the GMP‐compliant production of [18F]TRACK in sufficient doses and molar activities for scanning multiple subjects per day or long range deliveries. Preliminary biodistribution studies showed moderate brain uptake of the tracer with preferential accumulation in the thalamus across species. These findings warrants further studies of Trk brain expression and its implication in neurodegenerative and psychiatric pathologies using [18F]TRACK.

BackgroundA family of tropomyosin receptor kinases (TrkA/B/C) plays important roles in the regulation of neuronal differentiation, growth, and survival via their interactions with neurotrophins. A growing body of literature suggests the downregulation of Trk in many neurodegenerative conditions of the central nervous system (CNS), including Alzheimer’s disease (AD). We recently reported the development of [18F]TRACK, the PET tracers for in vivo imaging of TrkB and its first in‐human study. Here, we wish to report a fully automated GMP‐compliant radiosynthesis of [18F]TRACK at high radiochemical purity (RCP) and molar activity and its preliminary evaluation in wild‐type and a transgenic rat model of AD.MethodRadiosynthesis was performed using Scintomics GRP automated module via copper‐catalyzed 18F‐fluorination of the chiral boron pinacolate precursor. Brain imaging in wild‐type (n = 3) and TgF344‐AD rat models (n = 2) at 23 months was performed on microPET Concord R4 scanner.Result[18F]TRACK was synthesized with a 5.0±1.4 % radiochemical yield not corrected for decay (activity range 95–154 mCi) with >99% RCP and molar activities of 250 ± 75 GBq/µmol (n = 6). The synthesis was fully automated and all batches passed quality control procedures, including chemical purity, sterility and pyrogenicity. The tracer showed moderate brain uptake in wild‐type rats with the highest accumulation in the thalamus (SUVmax = 1.56 ± 0.28, 10 min post‐injection), consistent with the brain regional distribution in humans acquired in a parallel study. Preliminary data suggests lower tracer uptake in TgF344‐AD rat model of AD in thalamus, striatum and frontal cortex compared to wild‐type animals.ConclusionThis study demonstrated the feasibility of the GMP‐compliant production of [18F]TRACK in sufficient doses and molar activities for scanning multiple subjects per day or long range deliveries. Preliminary biodistribution studies showed moderate brain uptake of the tracer with preferential accumulation in the thalamus across species. These findings warrants further studies of Trk brain expression and its implication in neurodegenerative and psychiatric pathologies using [18F]TRACK.

Background[211At]m-Astatobenzylguanidine ([211At]MABG) has demonstrated potent antitumor efficacy in preclinical models of malignant neuroendocrine tumours including neuroblastoma and pheochromocytoma/paraganglioma. The high linear energy transfer and short tissue penetration range of alpha particles enable highly localized cytotoxic effects, potentially overcoming therapeutic limitations associated with conventional beta-emitting radiopharmaceuticals. However, under clinical-scale (i.e., high radioactivity) conditions, the efficient and stable production of [211At]MABG has been hindered by radiolytic degradation during the manufacturing process limiting the availability of reliable methods offering high radiochemical yield and purity. In this study, we aimed to develop a scalable production methodology for [211At]MABG suitable for clinical translation.Results211At was produced via the 209Bi(α,2n)211At nuclear reaction using a cyclotron, with 210At formation minimised by precise control of the alpha particle energy. The resulting product was purified using an automated dry distillation system. [211At]MABG was synthesised using the COSMiC-Mini automated synthesiser in 28.2 ± 2.8 min from initial 211At activities of up to 586.1 MBq. The radiochemical yield and purity were 80.3 ± 4.4% (decay-corrected RCY: 84.0 ± 4.5%) and 99.0 ± 0.7%, respectively (n = 6). The addition of sodium ascorbate as a radical scavenger contributed to maintaining a high radiochemical yield and purity during large-scale production. The final product was obtained as a sterile solution.ConclusionsIn this study, we established a reliable and scalable production methodology for [211At]MABG, consistently achieving high radiochemical yield and purity across a wide range of radioactivity levels through optimization of the automated radiosynthesis process and the use of radiolytic stabilizers. This approach provides a solid technical foundation for the clinical application of [211At]MABG in targeted alpha therapy.Supplementary InformationThe online version contains supplementary material available at 10.1186/s41181-025-00376-1.

Introduction: Glioblastoma (GBM) is the most common and aggressive primary brain tumor. The 5-year survival rate is only 4% despite the current standard treatment approaches of surgery, chemotherapy, and radiation. Fibroblast Activation Protein (FAP)-targeted radioligand therapy (RLT) has emerged as a potential alternative to traditional radiation methods. FAP is a protein highly expressed in Cancer-Associated Fibroblasts (CAFs) and on GBM cells. It can be targeted by radiolabeled molecules for selective tumor irradiation, to enhance treatment precision and reduce damage to healthy tissue. Here we evaluated the relevance of FAP inhibitor 46 (FAPi-46) as a molecular probe for Radioligand Therapy (RLT) in GBM models. Methods: U87MG, a human GBM cell line shown to express human FAP and SB28, a murine GBM cell line engineered to express murine FAP were used as GBM models. NSG and C57BL6J mice were, respectively, inoculated with U87MG and SB28 cells subcutaneously. Tumor growth was evaluated by computed tomography (CT). FAP expression was assessed by 68Ga-FAPi-46 PET imaging when tumors reached around 100 mm3 prior to treatment. Mice were subsequently randomized into 4 groups: (1) vehicle, (2) 5 mg/kg temozolomide (TMZ), (3) 60 kBq 225Ac-FAPi-46, and (4) 5 mg/kg TMZ and 60 kBq 225Ac-FAPi-46. Dose of TMZ and 225Ac-FAPi-46 were increased for the SB28 study. Overall survival was tracked. Blood was collected 24h before, after, and 7 days after RLT treatment to assess blood toxicity. Tumor were resected 24h after RLT treatment to further evaluate DNA-damage. Results: Our results show that combining TMZ with 225Ac-FAPi-46 successfully delays tumor progression and extends survival in immunocompromised mice bearing subcutaneous human U87MG GBM tumors. In the SB28 GBM model neither TMZ nor a single dose of FAPi-RLT alone affected tumor growth or survival, confirming its in vivo resistance to both chemotherapy and radiation. However, by adapting the 225Ac-FAPi-46-RLT regimen, we observed a significant reduction in tumor volume and an increase in survival in immunocompetent mice. These results suggest that higher doses of 225Ac-FAPi-46-RLT can overcome resistance in this model. Conclusion: In conclusion, our study shows that 225Ac-FAPi-46-RLT could be an effective treatment for GBM, with positive results across different tumor models. To further investigate the efficacy of FAP-targeted RLT for GBM, we have initiated an evaluation of immune cell infiltration within subcutaneous SB28 tumors. Using immunohistochemistry, RNA sequencing, and flow cytometry, ongoing studies will characterize the immunogenic response induced by RLT in this GBM model. Citation Format: Pauline Jeanjean, Rachel Dove, Ines Camille Azrour, Samantha Kwock, Sarah Taylor, Sarina Smolev, Johannes Czernin, Giuseppe Carlucci, David Nathanson, Christine Mona, Elie Besserey-Offroy. Fibroblast Activation Protein (FAP)-targeted radioligand therapy as a promising treatment for glioblastoma. [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Translating Targeted Therapies in Combination with Radiotherapy; 2025 Jan 26-29; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(2_Suppl):Abstract nr P005

Fibroblast Activation Protein (FAP) is overexpressed in cancer-associated fibroblasts of many epithelial cancers. In nonmalignant conditions FAP is overexpressed in wounds healing, inflammatory and fibrotic tissues, whereas in healthy adult tissue FAP expression is low. Radiolabeled FAP Inhibitors (FAPIs) are used in clinic for imaging and/or radiotherapy. FAPIs are usually conjugated to a DOTA chelating site which allows the use of both diagnostic and therapeutic radionuclides. In this study we investigated the radiochemical properties, pharmacokinetics and dosimetry of FAPI-46 in after Lu-177 or Ga-68 labelling in preclinical mouse model of colorectal carcinoma. FAPI-46 (non-GMP grade) was radiolabeled with Ga-68 and Lu-177 using previous described synthesis with slight modifications (Loktev et al., J Nucl Med 2019). Radiochemical purity was determined with radio-HPLC (LabLogic). A colon cancer mouse model was created by inoculating 5x106 HCT116 cells in 100 µl 50% matrigel subcutaneously (s.c.) in the interscapular area of NMRI-Foxn1nu male mice. Approximately two weeks post inoculation, animals were randomized into groups based on tumor volume (n = 2-4 / timepoint). Animals were dosed with 177Lu-FAPI-46 or 68Ga-FAPI-46, scanned with SPECT (Mediso) or PET (Sedecal) up to 90 minutes. Simultaneously satellite animals were terminated and sampled for gamma counting (Perkin Elmer) at 30-, 60- and 90-minutes post injection. Image analysis was performed with PMOD software. Dosimetry calculations will be performed with OLINDA 2.0. 68Ga- and 177Lu-FAPI-46 were produced with high radiochemical yield and purity. Nuclear imaging of radiolabeled FAPI-46 with both radiolabels shows fast kinetics and excretion via kidney as shown in literature. The dosimetry calculations are still ongoing. FAPI is suitable for multipurpose imaging and there is a great interest towards this molecule in the fields of imaging and oncology. The same precursor structure can be labeled with more than one radionuclide with high radiochemical yield and purity. Citation Format: Johanna Rokka, Henrik Vaherto, Susanne Bäck, Jussi Rytkönen. Biodistribution and dosimetry of FAPI-46 in mouse model of colorectal carcinoma with PET and SPECT imaging [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2540.

A simple sodium chloride (NaCl) based (68)Ga eluate concentration and labeling method that enables rapid, high-efficiency labeling of DOTA conjugated peptides in high radiochemical purity is described. The method utilizes relatively few reagents and comprises minimal procedural steps. It is particularly well-suited for routine automated synthesis of clinical radiopharmaceuticals. For the (68)Ga generator eluate concentration step, commercially available cation-exchange cartridges and (68)Ga generators were used. The (68)Ga generator eluate was collected by use of a strong cation exchange cartridge. 98% of the total activity of (68)Ga was then eluted from the cation exchange cartridge with 0.5 mL of 5 M NaCl solution containing a small amount of 5.5 M HCl. After buffering with ammonium acetate, the eluate was used directly for radiolabeling of DOTATOC and DOTATATE. The (68)Ga-labeled peptides were obtained in higher radiochemical purity compared to other commonly used procedures, with radiochemical yields greater than 80%. The presence of (68)Ge could not be detected in the final product. The new method obviates the need for organic solvents, which eliminates the required quality control of the final product by gas chromatography, thereby reducing postsynthesis analytical effort significantly. The (68)Ga-labeled products were used directly, with no subsequent purification steps, such as solid-phase extraction. The NaCl method was further evaluated using an automated fluid handling system and it routinely facilitates radiochemical yields in excess of 65% in less than 15 min, with radiochemical purity consistently greater than 99% for the preparation of (68)Ga-DOTATOC.

595 Evaluation of [18F]PyKYNE-losartan in rats using pet imaging

<p indent="0mm">Boron neutron capture therapy (BNCT), as a duality radiotherapy method that combines neutron irradiation and boron-containing targeted drugs, has attracted much attention. The successful BNCT mainly depends on three aspects: (1) Ideal boron delivery agents, (2) reasonable neutron source, and (3) accurate dose measurement system. Therefore, it is very important to realize the rapid and accurate measurement of the boron concentration in the patient. There are a variety of methods that have been used to measure the boron concentration. The indirect measurement method often requires the blood/tissue sample, so it can only give an estimate of the boron concentration at a single time point and sampling point, but cannot accurately describe the biodistribution of ¹⁰B concentration and the boron concentration ratio between target and non-target tissues. The sensitivity of magnetic resonance imaging (MRI) is poor, while radionuclide imaging is a non-invasive method and can provide the distribution of boron delivery agents <italic>in vivo</italic>. This article briefly describes the existing methods of measuring the boron concentration in BNCT, and the progress of radionuclide (¹⁸F, ¹²⁵I/¹³¹I, and ^99mTc) labeling methods of boron delivery agents (such as 4-borono-<italic>L</italic>-phenylalanine (BPA) and disodium mercaptoundecahydrododecaborate (BSH)) for radionuclide imaging. The common methods for labeling boron delivery agents with ¹⁸F are [¹⁸F]F₂ electrophilic substitution with a carrier, [¹⁸F]F⁻ nucleophilic substitution without a carrier, and isotope exchange. ¹⁸F-labeled BPA ([¹⁸F]-FBPA) was first prepared by the electrophilic substitution method. Research has shown that BPA and [¹⁸F]-FBPA had similar pharmacokinetics and biodistribution results. Although electrophilic fluorination can yield [¹⁸F]-FBPA with high radiochemical purity, the overall yield of the reaction is low, and the [¹⁸F]F₂ used in this process is relatively active and highly corrosive. The effect of stable F₂ gas carrier on the reaction cannot be ignored, which makes the specific activity of the product lower and the imaging quality worse. [¹⁸F]-FBPA can also be obtained from the high-value iodine-ylide precursors by nucleophilic fluoridation reaction. This method has a short labeling time and high specific activity. Fluoroboronotyrosine (FBY), a metabolically stable boron-tyrosine derivative, can also be used as a boron delivery agent, and [¹⁸F]-FBY has been prepared easily and quickly with a high radiochemical yield and radiochemical purity by isotope exchange as a tumor-targeting PET imaging agent. [¹⁸F]-FBY was stable <italic>in vitro</italic>, and it had the highest uptake in tumor and low uptake in normal tissue in mice with cutaneous melanoma grafts. The boron delivery agents of nested and closed carboranes can be radioiodine-labeled using N-chlorosuccinimide (NCS) as oxidant by electrophile iodization reaction at room temperature for <sc>10−30 min,</sc> the radiochemical yield was basically above 70%. Radioiodine-labeled carborane derivatives can also be achieved using isotope exchange reactions under catalytic conditions, but they had a lower specific activity. Unfortunately, as for the radioiodine-labeled carborane compounds, most studies only described the labeling method without further <italic>in vivo</italic> experimental data. [^99mTc(CO)₃]⁺-labeled carboranes have been prepared in aqueous solution in the presence of potassium fluoride under mild conditions, but no further biological experiments were conducted. ^99mTc-labeled BPA (^99mTc-DMG-BPA) was also obtained. Biodistribution result showed that the complex was selectively enriched in the tumor and cleared faster in non-target tissues, but unfortunately, its uptake in liver and kidney was relatively high, which may affect tumor imaging. In conclusion, radionuclide-labeled boron delivery agents are still in their infancy, and there are many aspects that need to be considered, such as radionuclide (half-life and decay type), radionuclide labeling position (influence on the biological activity of the boron delivery agent), labeling method (nucleophilic substitution, electrophilic substitution, isotope exchange, and coordination chemistry), the stability of the labeled compound and its influencing factors, and the administration method and time, etc.

BackgroundFentanyl is a potent synthetic opioid widely used for pain management and anesthesia, but the high prevalence of its misuse and its key contribution to overdose fatalities in the United States have made it a major drug of concern. Although fentanyl’s onset, duration, and toxicity depend on its pharmacokinetics and specific tissue distribution, most studies have focused primarily on plasma concentrations, leaving its distribution in critical tissues largely unexplored (this knowledge gap limits our understanding of fentanyl’s clinical effects, tissue accumulation, and the factors influencing its efficacy and safety). Here, we report the radiosynthesis of [11C]fentanyl for PET imaging and present a preliminary whole-body pharmacokinetic study in rodents.Results[11C]Fentanyl was synthesized in 42 min in a high radiochemical yield (10.4 ± 5.7%, n = 5), radiochemical purity (> 99%), and molar activity (up to 2571.5 GBq/µmol at EOB). N,N-Diisopropylethylamine in chloroform was optimal for amidation. PET imaging in rats revealed rapid brain uptake (SUVmax 2.71 ± 1.04 g/mL) and fast washout (T1/2 = 5.06 min), both significantly increased by efflux transporter inhibition or knockout. Peripherally, high and prolonged uptake in adipose tissues was observed (SUVmax = 1.73 ± 0.313 g/mL, T1/2 = 177 min), with > 60% of C-11 remaining as unchanged [11C]fentanyl at 60 min.ConclusionsWe successfully developed and automated the radiosynthesis of [11C]fentanyl, enabling PET imaging that revealed rapid brain kinetics and a critical role of P-gp/BCRP efflux in fentanyl disposition in brain. Prolonged retention in adipose tissue may delay brain clearance, potentially increasing the risk of re-narcotization (as has been reported in clinical cases after naloxone reversal). These findings advance our ability to quantify fentanyl tissue distribution and pharmacokinetics in the brain and body and provide a valuable tool for further studies in preclinical and clinical settings.Supplementary InformationThe online version contains supplementary material available at 10.1186/s41181-025-00394-z.

BackgroundFentanyl is a potent synthetic opioid widely used for pain management and anesthesia, but the high prevalence of its misuse and its key contribution to overdose fatalities in the United States have made it a major drug of concern. Although fentanyl’s onset, duration, and toxicity depend on its pharmacokinetics and specific tissue distribution, most studies have focused primarily on plasma concentrations, leaving its distribution in critical tissues largely unexplored (this knowledge gap limits our understanding of fentanyl’s clinical effects, tissue accumulation, and the factors influencing its efficacy and safety). Here, we report the radiosynthesis of [11C]fentanyl for PET imaging and present a preliminary whole-body pharmacokinetic study in rodents.Results[11C]Fentanyl was synthesized in 42 mins in a high radiochemical yield (10.4 ± 5.7%, n = 5), radiochemical purity (> 99%), and molar activity (up to 2571.5 GBq/μmol at EOB). N,N-diisopropylethylamine in chloroform was optimal for amidation. PET imaging in rats revealed rapid brain uptake (SUVmax 2.71 ± 1.04 g/mL) and fast washout (T1/2 = 5.06 min), both significantly increased by efflux transporter inhibition or knockout. Peripherally, high and prolonged uptake in adipose tissues was observed (SUVmax = 1.73 ± 0.313 g/mL, T1/2 = 177 min), with > 60% of C-11 remaining as unchanged [11C]fentanyl at 60 min.ConclusionsWe successfully developed and automated the radiosynthesis of [11C]fentanyl, enabling PET imaging that revealed rapid brain kinetics and a critical role of P-gp/BCRP efflux in fentanyl disposition in brain. Prolonged retention in adipose tissue may delay brain clearance, potentially increasing the risk of renarcotization (as has been reported in clinical cases after naloxone reversal). These findings advance our ability to quantify fentanyl tissue distribution and pharmacokinetics in the brain and body and provide a valuable tool for further studies in preclinical and clinical settings.

In this practitioner protocol, the radiochemical synthesis of [11 C]CPPC is described in detail, and a quality control summary of three validation productions is presented. The results indicate that the radiotracer product can be produced in good radiochemical yield (> 60 mCi (2.22 GBq) at end-of-synthesis (EOS)), at high specific activity (molar activity > 11,435 mCi/μmole (423 GBq/μmole) at EOS) and high chemical and radiochemical purity. The entire production conforms to current Good Manufacturing Practice (cGMP) requirements. The final product is formulated as a sterile, pyrogen-free solution suitable for human injection.

This article describes a sequential Ir/Cu-mediated process for the meta-selective C-H radiofluorination of (hetero)arene substrates. In the first step, Ir-catalyzed C(sp2)-H borylation affords (hetero)aryl pinacolboronate (BPin) esters. The intermediate organoboronates are then directly subjected to copper-mediated radiofluorination with [18F]tetrabutylammonium fluoride to afford fluorine-18 labeled (hetero)arenes in high radiochemical yield and radiochemical purity. This entire process is performed on a benchtop without Schlenk or glovebox techniques and circumvents the need to isolate (hetero)aryl boronate esters. The reaction was automated on a TracerLab FXFN module with 1,3-dimethoxybenzene and a meta-tyrosine derivative. The products, [18F]1-fluoro-3,5-dimethoxybenzene and an 18F-labeled meta-tyrosine derivative, were obtained in 37 ± 5% isolated radiochemical yield and >99% radiochemical purity and 25% isolated radiochemical yield and 99% radiochemical purity, and 0.52 Ci/μmol (19.24 GBq/μmol) molar activity (Am), respectively.

64 Cu (T1/2 =12.7h) is an important radionuclide for diagnostic purposes and used for positron emission tomography (PET). A previous method utilized at Paul Scherrer Institute (PSI) proved to be unreliable and, while a method using anion exchange chromatography is a popular choice worldwide, it was felt a different approach was required to obtain a robust chemical separation method. Enriched 64 Ni targets were created by electroplating on gold foil. The targets were irradiated with protons degraded to approximately 11MeV at PSI's Injector 2 72 MeV research cyclotron and subsequently dissolved in HCl. The resultant solution was loaded onto AG MP-50 cation exchange resin and the 64 Cu separated from its target material and radiocobalt impurities, produced as part of the irradiation process, using various specific mixtures of HCl/acetone solution. The eluted product was evaporated and picked up in dilute HCl (0.05M). The chemical purity of 64 Cu was determined by radiolabeling experiments at the highest possible molar activities. Reproducible results were obtained, yielding 3.6 to 8.3 GBq 64 Cu of high radionuclidic and radiochemical purity. The product was labeled to NODAGA-RGD, achieved at up to 500MBq/nmol, indicating the high chemical purity. In a proof-of-concept in vivo study, 64 Cu-NODAGA-RGD was used for PET imaging of a tumor-bearing mouse. The chemical separation devised to produce high-quality 64 Cu proved to be robust and reproducible. The concept can be used at medical cyclotrons utilizing a solid target station, such that 64 Cu can be used at hospitals for PET imaging.

Prostate-specific membrane antigen (PSMA) radioligand therapy (PRLT) has become a promising option for treating metastatic castration-resistant prostate cancer (mCRPC). Radioligands labelled with the 68Ga/177Lu theranostic pair have been most widely used in the clinic for diagnosis and therapy, respectively. This study aims to develop a novel PSMA-targeted radioligand, LNC1011, radiolabeled with alpha-emitter 225Ac, to optimise pharmacokinetic properties and assess its potential for targeted alpha therapy (TAT) in prostate cancer treatment. LNC1011 (Dan-PSMA) was synthesised based on a PSMA-binding ligand with the addition of a dansylated amino acid. Systematic radiochemical analyses were conducted to confirm the successful synthesis and radiolabelling of [225Ac]Ac-LNC1011. Cell uptake and competition binding assays were performed in PSMA-positive PC3-PIP tumour cells to evaluate the binding affinity and PSMA targeting specificity. The pharmacokinetics properties and tumour uptake were characterised by biodistribution studies using healthy mice and a PC3-PIP xenograft mouse model injected with [225Ac]Ac-LNC1011. Radioligand therapy studies and maximum tolerated dose (MTD) assays were conducted to systematically evaluate the therapeutic efficacy and the safety of [225Ac]Ac-LNC1011. [225Ac]Ac-LNC1011 was successfully radiolabelled with high radiochemical purity (> 97%) and high stability within 96h (radiochemical purity > 96%). The high binding affinity of LNC1011 (IC50 = 16.28 nM) to PSMA was comparable to that of PSMA-617 (IC50 = 27.93 nM). Biodistribution studies confirmed that [225Ac]Ac-LNC1011 had moderate blood elimination half-life (T1/2z = 13.4 ± 0.57h), which was at an optimised level between [225Ac]Ac-PSMA-617 (T1/2z = 5.19 ± 0.12h) and [225Ac]Ac-PSMA-EB-01 (T1/2z = 25.18 ± 2.78h). In addition, high tumour uptake of [225Ac]Ac-LNC1011 was identified to be 38.28 ± 10.04%ID/g at 1h post-injection. The specific uptake gradually increased and peaked at 24h (80.57 ± 3.00%ID/g) and persisted at a high level up to 72h post-injection (50.58 ± 5.37%ID/g). Targeted alpha therapy results showed the complete inhibition of PC3-PIP tumour growth after administration of a single dose of 1 µCi and 0.5 µCi of [225Ac]Ac-LNC1011 similar to 0.5 µCi [225Ac]Ac-PSMA-617. At the 0.1 µCi dose level, partial remission was observed for [225Ac]Ac-LNC1011, as recurrence was found 20 days after administration. In contrast, mice treated with 0.1 µCi [225Ac]Ac-PSMA-617 showed incomplete tumour inhibition under the same conditions. [225Ac]Ac-LNC1011 was successfully radiolabelled with high radiochemical purity and stability. With significantly improved tumour uptake and retention over PSMA-617, [225Ac]Ac-LNC1011 showed significantly better therapeutic efficacy than [225Ac]Ac-PSMA-617 for targeted alpha therapy of prostate cancer.