ImmunoPET studies of 64Cu-labeled CD30 monoclonal antibody 64Cu-NOTA-CD30 in lymphoma models / 中华核医学与分子影像杂志

Objective:To develop the anti-CD30 monoclonal antibody 64Cu-1, 4, 7-trizacyclononane-1, 4, 7-triacetic acid (NOTA)-CD30 and visualize CD30 expression in lymphoma non-invasively. Methods:The CD30 expression levels of 5 cell lines (Karpas299, Raji, Daudi, Ramos, and U266) were assessed by Western blot. Cell lines with high and low CD30 expression were selected for flow cytometry to evaluate the specific binding affinity of anti-CD30 monoclonal antibody. Thirteen NSG mice were used to established CD30 positive and negative subcutaneous xenograft models. 64Cu-NOTA-CD30 was obtained and 64Cu-NOTA-immunoglobulin (Ig)G was used as the control. ImmunoPET imaging was performed 2, 24, and 48 h after the injection of 64Cu-NOTA-CD30 or 64Cu-NOTA-IgG. Finally, the biodistribution studies were conducted. Repeated-measures analysis of variance and Bonferroni test were conducted for comparison. Results:Karpas299 showed the highest CD30 expression, while Raji showed the lowest. Flow cytometry showed specific binding affinity of the anti-CD30 monoclonal antibody to the Karpas299 cell line. The radiochemical purities of the probes were both higher than 95%. In microPET, the 64Cu-NOTA-CD30 uptake of Karpas299 xenograft tumors increased over time, with (11.46±0.58), (17.60±1.16) and (19.46±0.99) percentage activity of injection dose per gram of tissue (%ID/g) at 2, 24 and 48 h respectively. The contrast to normal tissue was good at 48 h, with the tumor/heart (blood) ratio of 2.20±0.22. The uptake of 64Cu-NOTA-CD30 in Karpas299 tumor at 48 h after injection was significantly higher than that in Raji tumor ((6.10±1.03) %ID/g) and 64Cu-NOTA-IgG in Karpas299 tumor ((5.12±0.89) %ID/g; F=290.99, t values: 19.65 and 22.25, all P<0.001). The uptake of 64Cu-NOTA-CD30 and the control probe in the heart and liver decreased over time in all groups. Ex vivo biodistribution at 48 h was mainly consistent with the results of microPET in vivo. Conclusions:64Cu-NOTA-CD30 is able to visualize the expression level and distribution of CD30 non-invasively. It is promising to be applied for screening the beneficial groups and evaluating efficacy for CD30-targeted immunotherapy.

An Albumin-Binding PSMA Ligand with Higher Tumor Accumulation for PET Imaging of Prostate Cancer.

Prostate-specific membrane antigen (PSMA) is an ideal target for the diagnosis and treatment of prostate cancer. Due to the short half-life in blood, small molecules/peptides are rapidly cleared by the circulatory system. Prolonging the half-life of PSMA probes has been considered as an effective strategy to improve the tumor detection. Herein, we reported a 64Cu-labeled PSMA tracer conjugating with maleimidopropionic acid (MPA), 64Cu-PSMA-CM, which showed an excellent ability to detect PSMA-overexpressing tumors in delayed time. Cell experiments in PSMA-positive 22Rv1 cells, human serum albumin binding affinity, and micro-PET imaging studies in 22Rv1 model were performed to investigate the albumin binding capacity and PSMA specificity. Comparisons with 64Cu-PSMA-BCH were performed to explore the influence of MPA on the biological properties. 64Cu-PSMA-CM could be quickly prepared within 30 min. The uptake of 64Cu-PSMA-CM in 22Rv1 cells increased over time and it could bind to HSA with a high protein binding ratio (67.8 ± 1.5%). When compared to 64Cu-PSMA-BCH, 64Cu-PSMA-CM demonstrated higher and prolonged accumulation in 22Rv1 tumors, contributing to high tumor-to-organ ratios. These results showed that 64Cu-PSMA-CM was PSMA specific with a higher tumor uptake, which demonstrated that MPA is an optional strategy for improving the radioactivity concentration in PSMA-expressing tumors and for developing the ligands for PSMA radioligand therapy.

A feasibility study of the therapeutic application of a mixture of 67/64 Cu radioisotopes produced by cyclotrons with proton irradiation.

PURPOSE: 64 Cu and 67 Cu radioisotopes have nuclear characteristics suitable for nuclear medicine applications. The production of 64 Cu is already well established. However, the production of 67 Cu in quantities suitable to conduct clinical trials is more challenging as it leads to the coproduction of other Cu isotopes, in particular 64 Cu. The aim of this study is to investigate the possibility of using a CuCl2 solution with a mixture of 67/64 Cu radioisotopes for therapeutic purposes, providing an alternative solution for the cyclotron production problem. METHODS: Copper radioisotopes activities were calculated by considering proton beam irradiation of the following targets: (i) 70 Zn in the energy range 70-45 MeV; (ii) 68 Zn in the energy range 70-35 MeV; (iii) a combination of 70 Zn (70-55 MeV) and 68 Zn (55-35 MeV). The contribution of each copper radioisotope to the human-absorbed dose was estimated with OLINDA/EXM software using the biokinetic model for CuCl2 published by ICRP 53. The total absorbed dose generated by the 67/64 CuCl2 mixture, obtained through different production routes, was calculated at different times after the end of the bombardment (EOB). A simple spherical model was used to simulate tumors of different sizes containing uniformly distributed 67/64 Cu mixture and to calculate the absorbed dose of self-irradiation. The biological damage produced by 67 Cu and 64 Cu was also evaluated through cellular dosimetry and cell surviving fraction assessment using the MIRDcell code, considering two prostate cancer cell lines with different radiosensitivity. RESULTS: The absorbed dose to healthy organs and the effective dose (ED) per unit of administered activity of 67 CuCl2 are higher than those of 64 CuCl2 . Absorbed dose values per unit of administered activity of 67/64 CuCl2 mixture increase with time after the EOB because the amount of 67 Cu in the mixture increases. Survival data showed that the biological damage caused per each decay of 67 Cu is greater than that of 64 Cu, assuming that radionuclides remain accumulated in the cell cytoplasm. Sphere model calculations demonstrated that 64 Cu administered activity must be about five times higher than that of 67 Cu to obtain the same absorbed dose for tumor mass between 0.01 and 10 g and about 10 times higher for very small spheres. Consequently, the 64 CuCl2 -absorbed dose to healthy organs will reach higher values than those of 67 CuCl2 . The supplemental activity of the 67/64 CuCl2 mixture, required to get the same tumor-absorbed dose produced by 67 CuCl2 , triggers a dose increment (DI) in healthy organs. The waiting time post-EOB necessary to keep this DI below 10% (t10% ) depends on the irradiation methods employed for the production of the 67/64 CuCl2 mixture. CONCLUSIONS: A mixture of cyclotron produced 67/64 Cu radioisotopes proved to be an alternative solution for the therapeutic use of CuCl2 with minimal DI to healthy organs compared with pure 67 Cu. Irradiation of a 70 Zn+68 Zn target in the 70-35 MeV proton energy range for 185 h appears to be the best option from among all the production routes investigated, as it gives the maximum amount of activity, the shortest t10% (10 h), and less than 1% of 61 Cu and 60 Cu impurities.

Development of Novel PSMA Ligands for Imaging and Therapy with Copper Isotopes.

Prostate-specific membrane antigen (PSMA)-binding tracers have been shown to be promising agents for the specific targeting of prostate tumors. On labeling with the short-lived isotopes 18F and 68Ga, excellent molecular imaging performance is achieved. This potential could be further exploited using long-lived isotopes. Because of the favorable half-life of 64Cu, tracers labeled with this PET nuclide could solve logistic problems. Moreover, this isotope provides a theranostic pair with the therapeutic copper isotope 67Cu. Hence, 9 novel tracers that combine dedicated copper chelators with the PSMA-specific urea-based binding motif were developed. Methods: The precursors were obtained by solid-phase synthesis. The purity and molecular weight of the PSMA ligands were confirmed by high-performance liquid chromatography and liquid chromatography-mass spectrometry. The compounds were labeled with 64Cu, with a radiolabeling yield of more than 99%. Competitive cell binding assays and internalization assays were performed with C4-2 cells, a subline of the PSMA-positive cell line LNCaP (human lymph node carcinoma of the prostate). In vitro serum stability, the stability of 64Cu-CA003 in blood, and the in vivo fate of neat 64Cu-chloride or 64Cu-CA003 were determined to prove whether the stability of the radiolabeled compounds is sufficient to ensure no significant loss of copper during the targeting process. For PET imaging and biodistribution studies, a C4-2 tumor-bearing mouse model was used. Results: The radiolabeled 64Cu-PSMA ligands showed high serum stability. All PSMA ligands showed high inhibition potencies, with equilibrium inhibition constants in the low nanomolar range. 64Cu-CA003 and 64Cu-CA005 showed high internalization ratios (34.6% ± 2.8 and 18.6% ± 4.4, respectively). Both the in vitro serum stability determination and the in vivo characterization of the main radiolabeled compounds confirmed that, except for 64Cu-PSMA-617, all compounds showed high serum stability within the observation period of 24 h. Small-animal PET imaging demonstrated high tumor uptake within 20 min. Organ distribution studies confirmed high specific uptake in the tumor, with 30.8 ± 12.6 percentage injected dose (%ID)/g at 1 h after injection. Rapid clearance from the kidneys was observed-a decrease from 67.0 ± 20.9 %ID/g at 1 h after injection to 7.5 ± 8.51 %ID/g at 24 h after injection (in the case of CA003). The performance of CA003, the compound with the best preclinical properties, was assessed in a first patient. In line with its preclinical data, PET imaging resulted in clear visualization of the cancer lesions, with high contrast. Conclusion: The 64Cu-labeled PSMA ligands are promising agents to target PSMA and visualize PSMA-positive tumor lesions as shown in preclinical evaluation by small-animal PET studies, organ distribution, and a patient application. Most importantly, the images obtained at 20 h enabled delineation of unclear lesions, showing that the compounds fulfill the prerequisite for dosimetry in the course of therapy planning with 67Cu. Thus, we suggest clinical use of copper-labeled CA003 for diagnostics and radiotherapy of prostate cancer.

Advances in development of 64CuCl2 radiotracer for diagnostic imaging of copper metabolism disorders with PET / 中华核医学与分子影像杂志

Development of new radiopharmaceuticals is crucial for the advance of nuclear medicine and molecular imaging.In recent years,significant progress has been made in the development of radiopharmaceuticals based on radioactive metal nuclides such as 64Cu.Copper is a transition metal element necessary for human physiology.Disorders of copper metabolism not only cause hereditary Wilson disease and Menkes disease,but also play an important role in the development of malignant tumors.In addition to radiolabeling for probes,64Cu can be used for PET diagnostic imaging of copper metabolism disorders.64CuCl2 is a useful radiotracer that can be used to track the dynamic flow of copper ions in human body copper metabolism by PET imaging.In recent years,many preclinical and clinical studies of 64CuCl2 radiotracer have achieved good results,and have attracted a lot of attention in the field of nuclear medicine and molecular imaging.In this article,the progress in the development of 64CuCl2 as a radiotracer for PET diagnostic imaging of hereditary copper metabolism disorders and copper hypermetabolic tumors is reviewed,and further research studies and potential clinical application of 64CuCl2 PET/CT imaging is prospected.

Advances in development of 64CuCl2 radiotracer for diagnostic imaging of copper metabolism disorders with PET / 中华核医学与分子影像杂志

Development of new radiopharmaceuticals is crucial for the advance of nuclear medicine and molecular imaging. In recent years, significant progress has been made in the development of radiopharmaceuticals based on radioactive metal nuclides such as 64Cu. Copper is a transition metal element necessary for human physiology. Disorders of copper metabolism not only cause hereditary Wilson disease and Menkes disease, but also play an important role in the development of malignant tumors. In addition to radiolabeling for probes, 64Cu can be used for PET diagnostic imaging of copper metabolism disorders. 64CuCl2 is a useful radiotracer that can be used to track the dynamic flow of copper ions in human body copper metabolism by PET imaging. In recent years, many preclinical and clinical studies of 64CuCl2 radiotracer have achieved good results, and have attracted a lot of attention in the field of nuclear medicine and molecular imaging. In this article, the progress in the development of 64CuCl2 as a radiotracer for PET diagnostic imaging of hereditary copper metabolism disorders and copper hypermetabolic tumors is reviewed, and further research studies and potential clinical application of 64CuCl2 PET/CT imaging is prospected.

Production, quality control and micro PET analysis of novel solid-target based radionuclide 64 Cu / 中华核医学与分子影像杂志

Objective To briefly retrospect the production and quality control of 64 Cu(n = 9) in Department of Nuclear Medicine of Peking University Cancer Hospital in order to provide useful information for the further production and application of this novel radionuclide. Methods 64 Ni(p, n) 64 Cu nuclide re-action was used for the 64 Cu production. Firstly, a new electro-planting device for 64 Ni planting was de-signed. HM-20 cyclotron was applied to irradiate the slice for 5-8 h. 64 CuCl2 was purified, collected and in-jected into normal mice. MicroPET was conducted to monitor the metabolism in vivo. Results A new type of electro-planting device was designed and assembled. The enriched 64 Ni target showed smooth, even, dense surface and without obvious pits and cracks. High specific 64 Cu (1.3-4.1 GBq) can be collected after radio-chemical purification. 64 Cu was finally dissolved in 0.01 mol/ L HCl with high radionuclide purity (over 99.97％). MicroPET of 64 CuCl2 in normal mice showed that the radioactivity was mainly accumulated in the liver. Conclusion A new and real-time observable device for 64 Ni electro-plating has been designed and successfully used in the production of 64 Cu with high specific activity.

Radiolabeling of HTE1PA: A new monopicolinate cyclam derivative for Cu-64 phenotypic imaging. In vitro and in vivo stability studies in mice.

INTRODUCTION: HTE1PA, a monopicolinate-N-alkylated cyclam-based ligand has previously demonstrated fast complexation process, high kinetic inertness and important thermodynamic and electrochemical stability with respect to natural copper. In this work we first developed a new synthetic route to obtain HTE1PA in good yields. Then, we investigated HTE1PA chelation properties towards copper-64 and assessed in vitro and in vivo stability of the resulting compound. METHODS: Radiolabeling of HTE1PA with copper-64 was tested at different ligand concentrations in ammonium acetate medium. In vitro stability study was carried out by incubating [(64)Cu]TE1PA complex in human serum at both 37°C and 4°C; chromatographic controls were performed over 24h. Biodistribution, pharmacokinetic and hepatic metabolism of [(64)Cu]TE1PA were conducted in BALC/c mice in comparison with [(64)Cu]acetate and [(64)Cu]DOTA, used as a reference ligand. RESULTS: The promising results obtained for natural copper complexation were confirmed. HTE1PA was quantitatively radiolabeled in 15 min at room temperature. The resulting complex showed high serum stability. [(64)Cu]TE1PA induced a significant uptake in the liver and kidneys at early biodistribution time point. Nevertheless, a high speed wash out was observed at 24h leading to significantly lower uptake into the liver compared to [(64)Cu]DOTA. The metabolism study was consistent with a high resistance to transchelation as the initial uptake into liver matches with the intact form of [(64)Cu]TE1PA. CONCLUSION: Despite the partial elimination of HTE1PA - as copper-64 complex - through the hepatic route, its high selectivity for copper and its resistance to transchelation make it a promising ligand for antibody radiolabeling with either copper-64 or copper-67.