124I-labeled anti-CD147 antibody for noninvasive detection of CD147-positive pan-cancers: construction and preclinical studies.

Extracellular matrix metalloproteinase inducer CD147 is a glycoprotein on the cell surface. There is minimal expression of CD147 in normal epithelial and fetal tissues, but it is highly expressed in a number of aggressive tumors. CD147 has been implicated in pan-cancer immunity and progression. With the development of CD147-targeting therapeutic strategy, accurate detection of CD147 expression in tumors and its changes during the therapy is necessary. In this study we constructed a novel radiotracer by labeling the anti-CD147 mAb with radionuclide 124/125I (124/125I-anti-CD147) for noninvasive detection of CD147 expression in pan-cancers, and characterized its physicochemical properties, affinity, metabolic characteristics, biodistribution and immunoPET imaging with 124I-IgG and 18F-FDG as controls. By examining the expression of CD147 in cancer cell lines, we found high CD147 expression in colon cancer cells LS174T, FADU human pharyngeal squamous cancer cells and 22RV1 human prostate cancer cells, and low expression of CD147 in human pancreatic cancer cells ASPC1 and human gastric cancer cells BGC823. 124/125I-anti-CD147 was prepared using N-bromine succinimide (NBS) as oxidant and purified by PD-10 column. Its radiochemical purity (RCP) was over 99% and maintained over 85% in saline or 5% human serum albumin (HSA) for more than 7 d; the RCP of 125I-anti-CD147 in blood was over 90% at 3 h post injection (p.i.) in healthy mice. The Kd value of 125I-anti-CD147 to CD147 protein was 6.344 nM, while that of 125I-IgG was over 100 nM. 125I-anti-CD147 showed much greater uptake in CD147 high-expression cancer cells compared to CD147 low-expression cancer cells. After intravenous injection in healthy mice, 125I-anti-CD147 showed high initial uptake in blood pool and liver, the uptake was decreased with time. The biological half-life of distribution and clearance phases in healthy mice were 0.63 h and 19.60 h, respectively. The effective dose of 124I-anti-CD147 was estimated as 0.104 mSv/MBq. We conducted immunoPET imaging in tumor-bearing mice, and demonstrated a significantly higher tumor-to-muscle ratio of 124I-anti-CD147 compared to that of 124I-IgG and 18F-FDG in CD147 (+) tumors. The expression levels of CD147 in cells and tumors were positively correlated with the maximum standardized uptake value (SUVmax) (P < 0.01). In conclusion, 124/125I-anti-CD147 displays high affinity to CD147, and represents potential for the imaging of CD147-positive tumors. The development of 124I-anti-CD147 may provide new insights into the regulation of tumor microenvironment and formulation of precision diagnosis and treatment programs for tumors.

An iodine­labelled Antibody-drug conjugate PET probe for noninvasive monitoring of Nectin-4 expression in urothelial carcinoma.

BACKGROUND AND PURPOSE: Some kinds of antibody-drug conjugate (ADC) with high affinity to Nectin-4 have demonstrated breakthrough progress in the third-line setting for bladder cancer. However, many patients are still difficult to benefit from treatment based on the heterogeneity of tumour. As the most advanced auxiliary treatment technology, treatment visualization can most intuitively predict the effectiveness of drug treatment, and timely detect the occurrence of drug resistance. Among them, nuclear medicine molecular probes play an important role in this field. METHODS: 124/125I-EV was prepared by labelling Enfortumad Vedetin (EV), an ADC drugs widely used in clinic targeted Nectin-4, with Na124/125I using N-bromine succinimide as oxidant. The radiochemical purity was analyzed via radio-TLC and bioactivity was measured by enzyme-linked immunosorbent assay. Cell uptake assay and small-animal PET imaging were performed to verified the specificity and targeting. KEY RESULTS: 124/125I-EV was prepared with high labeling yield and radiochemical purity. ELISA assays demonstrated that 124I-EV maintained the same high bioactivity as EV with significantly higher uptake in SW780 cells (Nectin-4 positive, 4.05 ± 0.32 %IA/5 × 105 cells at 8 h) than that in T24 cells (Nectin-4 negative, 1.34 ± 0.18 %IA/5 × 105 cells, p < 0.001). In PET imaging, 124I-EV had a significantly higher accumulation in SW780 tumour than that in T24 tumour and the uptake in SW780 tumour could be specifically blocked when co-injected with cold EV. The signal-to-noise ratio at the tumour site gradually increased with time, and peaked at 72 h. CONCLUSION AND IMPLICATIONS: 124I-EV was successfully prepared with high specificity and binding affinity of Nectin-4. This radioactive probe completely simulates the internal circulation of ADC drugs and tumour uptake and retention, which will greatly improve the clinical application of ADC therapy.

Construction and preclinical evaluation of a zirconium-89 labelled monoclonal antibody targeting PD-L2 in lung cancer.

OBJECTIVES: The aim of this study was to design a novel tracer targeting programmed cell death-ligand 2 (PD-L2) to dynamically monitor PD-L2 expression and perform preclinical screening to identify patients who may benefit from immune checkpoint inhibitor therapy (ICI) therapy. METHODS: 89Zr labelling of DFO-conjugated PD-L2 antibody (ATL2) was carried out in Na2CO3 buffer at pH 7 (37 °C, 1 h). In vitro stability was analysed using radio-thin layer chromatography (radio-TLC). The affinity of [89Zr]Zr-DFO-ATL2 was evaluated by radio-ELISA. Cell uptake, pharmacokinetic, and biodistribution experiments were used to evaluate the biological properties. Micro-PET/CT imaging with [89Zr]Zr-DFO-ATL2 was conducted at different time points. Immunohistochemical and HE staining studies were carried out using tumour tissues from tumour-bearing mice. RESULTS: The radiochemical yield of [89Zr]Zr-DFO-ATL2 was 65.6 ± 3.9%, and the radiochemical purity (RCP) of the tracer was greater than 99%. The tracer maintained relatively high stability and had a high affinity for the PD-L2 protein (Kd = 31.85 nM, R2 = 0.94). The uptake of [89Zr]Zr-DFO-ATL2 in A549-PD-L2 cells was higher than that in A549 cells at each time point. Micro-PET/CT showed significant uptake in the tumour region of mice bearing tumours derived from A549-PD-L2 (SUVmax = 3.53 ± 0.09 at 96 h) and H2228 (SUVmax = 2.30 ± 0.12 at 48 h) cells. CONCLUSION: The high tumour uptake at early imaging time points demonstrates the feasibility of applying [89Zr]Zr-DFO-ATL2 to image PD-L2 expression in tumours and is encouraging for further clinical application in the screening of patients who may benefit from ICI therapy.

Preparation and Application of a Bioorganic Nanoparticle-Enhanced PDL1-Targeted Small-Molecule Probe.

Programmed death ligand 1 (PDL1) is a specific molecular target for the diagnosis and immunotherapy of solid tumors. PET imaging can be used for noninvasive assessments of PDL1 expression in tumors to aid in therapy selection. The most frequently reported small-molecule radiotracer of PDL1 is limited by low imaging specificity, short residence time, and singular functionality. Here, we combined a biocompatible melanin nanoprobe with the PDL1-binding peptide WL12 to construct a novel radiotracer, 124I-WPMN, to enhance PDL1 targeting. The radiochemical purity of 124I-WPMN was >95%, and uptake in A549PDL1 cells was 1.49 ± 0.08% at 2 h. The uptake was blocked by WL12 (0.39 ± 0.03%, P < 0.0001). This novel radiotracer showed a higher affinity for PDL1 (Kd = 18.5 nM) than 68Ga-NOTA-WL12 (Kd = 24.0 nM). Micro-PET/CT imaging demonstrated specific uptake and a high signal-to-noise ratio in an A549PDL1 xenograft mouse model with a tumor-to-muscle ratio of 27.31 ± 7.03 at 2 h. The levels increased or remained steady for more than 72 h, and tumor uptake was significantly higher than 68Ga-NOTA-WL12, at 6.08 ± 0.62 at 2 h. Prolonged retention of 124I-WPMN makes it possible to conduct PET/MRI imaging over long periods and to perform various imaging techniques. A clear advantage of 124I-WPMN over 68Ga-NOTA-WL12 was observed for PDL1-targeted PET imaging after nanoparticle modification, supporting the utility of 124I-WPMN PET imaging as an effective diagnostic tool for optimizing PDL1-targeted therapies.

Construction and Preclinical Evaluation of a 124/125I-Labeled Specific Antibody Targeting PD-L2 in Lung Cancer.

Programmed cell death-ligand 2 (PD-L2) is an important emerging molecule of the immune checkpoint, which is closely related to the prognosis of patients with immune checkpoint inhibitor (ICI) therapy. The quantification of PD-L2 can provide a potential reference for patients who benefit from ICI treatment. In this study, we used iodine isotope (nat/124/125I)-labeled PD-L2 antibody (ATL2) to noninvasively detect PD-L2 expression in mice with human lung adenocarcinoma A549 cell lines. The radiochemical yields of 125I-ATL2 and 124I-ATL2 were 73.56 ± 3.72% and 69.46 ± 2.05%, respectively. The radiochemical purity (RCP) of the tracers was more than 99%. The positive cell line A549-PDL2 was constructed by lentivirus. Western blot, immunofluorescence, and flow cytometry indicated that the A549-PDL2 cells showed a higher PD-L2 protein level than the A549 cells. The dissociation constant of 125I-ATL2 binding to the PD-L2 protein was 7.25 nM. Cellular uptake experiments confirmed that the uptake of 125I-ATL2 in A549-PDL2 cells was higher than that in A549 cells at each time point (P < 0.0001). Micro-PET/CT showed significant uptake in the tumor region of A549-PDL2 tumor-bearing mice 24 h postinjection of 124I-ATL2 compared with that of other groups (SUVmax = 0.75 ± 0.06, 0.19 ± 0.07, and 0.27 ± 0.05, respectively). Consistently, the biodistribution of the tracers at 24 h postinjection showed a higher tumor uptake in A549-PDL2 mice (7.11 ± 0.38 %ID/g for 124I-ATL2 in A549-PDL2 mice vs 2.72 ± 0.15 %ID/g for 124I-ATL2 in A549 mice vs 3.89 ± 0.65 %ID/g for 124I-IgG in A549-PDL2 mice). The dosimetry estimation by using Olinda software showed that the effective dose of 124I-ATL2 was 3.62 × 10-2 mSv/MBq, which is within the range of acceptable doses. Immunohistochemical results further confirmed that the expression of PD-L2 in the tumor tissues of A549-PDL2-bearing mice was higher than that of the A549 model mice. In conclusion, the development of 124/125I-ATL2 provides the first noninvasive quantification of PD-L2 expression in lung cancer by molecular imaging, which provides a new reference for screening potential beneficiaries of ICI therapy.

Preclinical evaluation and first in human study of Al18F radiolabeled ODAP-urea-based PSMA targeting ligand for PET imaging of prostate cancer.

Purpose: This study aimed to introduce a novel [18F]AlF-labeled ODAP-Urea-based Prostate-specific membrane antigen (PSMA) probe, named [18F]AlF-PSMA-137, which was derived from the successful modification of glutamate-like functional group. The preclinically physical and biological characteristics of the probe were analyzed. Polit clinical PET/CT translation was performed to analyze its feasibility in clinical diagnosis of prostate cancer. Methods: [18F]AlF-PSMA-137 was maturely labeled with the [18F]AlF2+ labeling technique. It was analyzed by radio-HPLC for radiochemical purity and stability analysis in vitro and in vivo. The PSMA specificity was investigated in PSMA-positive (LNCaP) and PSMA-negative (PC3) cells, and the binding affinity was evaluated in LNCaP cells. Micro-PET/CT imaging was performed in mice bearing LNCaP or PC3 tumors. Thirteen patients with newly diagnosed prostate cancer were included for [18F]AlF-PSMA-137 PET/CT imaging. Physiologic biodistribution and tumor burden were semi-quantitatively evaluated and the radiation dosimetry of [18F]AlF-PSMA-137 was estimated. Results: The radiochemical yield of [18F]AlF-PSMA-137 was 54.2 ± 10.7% (n = 16) with the radiochemical purity over 99% and the specific activity of 26.36 ± 7.33 GBq/µmol. The binding affinity to PSMA was 2.11 ± 0.63 nM. [18F]AlF-PSMA-137 showed high cell/tumor uptake which can be specifically blocked by PSMA inhibitor. According to the biodistribution in patients, [18F]AlF-PSMA-137 was mainly accumulated in kidneys, lacrimal glands, parotid glands, submandibular glands and liver which was similar to the extensive Glu-Ureas based probes. A total of 81 lesions were detected in PET/CT imaging and over 91% of lesions increased between 1 h p.i. (SUVmean: 10.98 ± 18.12) and 2 h p.i. (SUVmean: 14.25 ± 21.28) (p < 0.001). Additionally, the probe showed intensive accumulation in lesions which provided excellent imaging contrast with the high tumor-to-muscle ratio of 15.57 ± 27.21 at 1 h p.i. and 25.42 ± 36.60 at 2 h p.i. (p < 0.001), respectively. The effective dose of [18F]AlF-PSMA-137 was estimated as 0.0119 ± 0.0009 mSv/MBq. Conclusion: An ODAP-Urea-based PSMA probe [18F]AlF-PSMA-137 was successfully prepared with high specificity and binding affinity to PSMA. Micro-PET/CT imaging study demonstrated its feasibility for prostate cancer imaging. Pilot clinical study showed its potential for delay-imaging and prostate cancer detection.

Evaluation of 68Ga- and 177Lu-Labeled HZ20 Angiotensin-Converting Enzyme 2-Targeting Peptides for Tumor-Specific Imaging.

Angiotensin-converting enzyme 2 (ACE2) is closely related to tumor formation. We developed the radiolabeled peptide pair 68Ga/177Lu-labeled 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-conjugated DX600 (68Ga/177Lu-HZ20), for the targeting and mapping of ACE2-overexpressing tumors. 68Ga/177Lu-HZ20 was prepared with a routine labeling method. HepG2ACE2+/HepG2WT cell lines were used to evaluate the specificity of 68Ga/177Lu-HZ20. Pharmacokinetics, biodistribution, and micro-PET/CT and -SPECT/CT imaging were performed, and radiation dosimetry was estimated. Immunohistochemistry (IHC) staining was performed to assess the expression of ACE2 in tumors. The radiolabeling yields of 68Ga/177Lu-HZ20 were 88.49 ± 8.57% (n > 10) and 84.71 ± 9.75% (n > 10), with specific activities of (18.74 ± 3.72) × 106 and (17.85 ± 1.62) × 106 GBq/mol, respectively. 68Ga/177Lu-HZ20 showed significant differences in the cellular uptake of HepG2ACE2+/HepG2WT cells and fast clearance in KM mice. Moreover, HepG2ACE2+ tumors were clearly visualized in 68Ga/177Lu-HZ20 micro-PET/SPECT images. Based on micro-PET/CT, the standard uptake value (SUVmax) of HepG2ACE2+ tumors was 0.66 ± 0.02 at 30 min postinjection, IHC confirmed the high expression of ACE2 in HepG2ACE2+ tumors. In PET/CT images, the SUVmean of volunteer 1 was higher than the 18F-FDG value in the same lesion. 68Ga/177Lu-HZ20 was successfully obtained and showed high and specific uptake in tumors overexpressing ACE2. They may serve as paired probes for ACE2-targeting theranostics.

Construction of an Iodine-Labeled CS1001 Antibody for Targeting PD-L1 Detection and Comparison with Low-Molecular-Peptide Micro-PET Imaging.

Programmed death-1 (PD-1) and programmed death ligand-1 (PD-L1), the research focus in immune checkpoint regulation, play an important role in tumor immunotherapy. Inhibitors of this pathway are also the focus of tumor immunotherapy research. The PD-1/PD-L1 pathway can be blocked by selective binding to PD-L1. Clinical trials have been conducted in a variety of patients with advanced solid tumors. CS1001 is a high-affinity humanized full-length anti-PD-L1 monoclonal antibody with great clinical significance. We constructed a PD-L1-targeted radioactive molecular probe, 124/125I-labeled full-length antibody CS1001, and evaluated its binding specificity and targeting ability to PD-L1 in tumor cells and tumor models. Additionally, a comparison study with 68Ga-WL12, a PD-L1 targeting peptide, was conducted. The binding potency of 125I-CS1001 to human PD-L1 was evaluated by enzyme-linked immunosorbent assay (ELISA), and the Kd value was 52.1 ± 19.3 nM. The cellular uptake of 125I-CS1001 was examined in Chinese hamster ovary cells (CHO) and CHO expressing human PD-L1 (CHO-hPD-L1). At 2 h, the uptake values of 125I-CS1001 in CHO-hPD-L1 without blocking and in the presence of 0.1 mg non-radiolabeled CS1001 were 3.60 ± 0.08 and 0.09 ± 0.005 (%AD/2 × 105 cells, p < 0.001). Micro-PET imaging was performed between 8 to 192 h after injection of 124I-CS1001 into normal KM mice and CHO-hPD-L1 and HeLa tumor models. The standard uptake value (SUV) of relevant organs in PET images was calculated by drawing regions of interest (ROI). SUVmean of CHO-hPD-L1 tumors was significantly higher than that of HeLa tumors at 48 h (1.98 ± 0.04 vs 0.73 ± 0.14, p = 0.005). The SUVmean of 124I-CS1001 in CHO-hPD-L1 tumors at 48 h was higher than that of 68Ga-WL12 in CHO-hPD-L1 tumors at 0.5 h (1.98 ± 0.04 vs 1.09 ± 0.1 SUVmean, p = 0.007). In conclusion, this work provides a new method for monitoring and evaluating the in vivo expression of PD-L1 in tumors.

Noninvasive Mapping of Angiotensin Converting Enzyme-2 in Pigeons Using Micro Positron Emission Tomography.

The ACE2 receptor, as the potential entrance site of SARS-CoV-2-affected cells, plays a crucial role in spreading infection. The DX600 peptide is a competitive inhibitor of ACE2. We previously constructed the 68Ga-labeled DOTA-DX600 (also known as 68Ga-HZ20) peptide and confirmed its ACE2 binding ability both in vitro and in vivo. In this research, we aimed to investigate the noninvasive mapping of ACE2 expression in fowl using 68Ga-HZ20 micro-PET. We chose pigeons as an animal model and first studied the administration method of 68Ga-HZ20 by direct site injection or intravenous injection. Then, the dynamic micro-PET scan of 68Ga-HZ20 was conducted at 0-40 min. Additionally, 18F-FDG was used for comparison. Finally, the pigeons were sacrificed, and the main organs were collected for further immunoPET and IHC staining. Micro PET/CT imaging results showed that 68Ga-HZ20 uptake was distributed from the heart at the preliminary injection to the kidneys, liver, stomach, and lungs over time, where the highest uptake was observed in the kidneys (SUVmax = 6.95, 20 min) and lung (SUVmax = 1.11, 20 min). Immunohistochemical experiments were carried out on its main organs. Compared to the SUVmax data, the IHC results showed that ACE2 was highly expressed in both kidneys and intestines, and the optimal imaging time was determined to be 20 min after injection through correlation analysis. These results indicated that 68Ga-HZ20 is a potential target molecule for SARS-CoV-2 in fowl, which is worthy of promotion and further study.

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.

First-in-Humans Evaluation of a PD-L1-Binding Peptide PET Radiotracer in Non-Small Cell Lung Cancer Patients.

68Ga-NOTA-WL12 is a peptide-based PET imaging agent. We conducted a first-in-human study of 68Ga-NOTA-WL12 for PET to study the in vivo biodistribution, metabolism, radiation dosimetry, safety, and potential for quantifying programmed death ligand-1 (PD-L1) expression levels in patients with advanced non-small cell lung cancer (NSCLC). Methods: In vitro assessment of the PD-L1 expression and cellular uptake of 68Ga-NOTA-WL12 was performed, followed by in vivo evaluation of 68Ga-NOTA-WL12 uptake in mouse models with tumors. Nine patients with NSCLC with lesions expressing PD-L1 were enrolled and monitored for adverse events during the study. 68Ga-NOTA-WL12 and paired 18F-FDG PET/CT imaging were performed. Uptake (SUV, SUL [SUVlean], and kBq/mL) values of tumors and normal organs were obtained. Radiopharmaceutical biodistribution, radiation dosimetry, and the relationship of tumor uptake to PD-L1 expression were evaluated. Follow-up 18F-FDG PET/CT was performed in patients who had undergone treatment with a combination of pembrolizumab with chemotherapy. Results:68Ga-NOTA-WL12 exhibited PD-L1-specific uptake in vitro and in PD-L1-positive tumors in vivo. 68Ga-NOTA-WL12 PET imaging proved safe with acceptable radiation dosimetry. Physiologic tracer uptake was mainly visible in the liver, spleen, small intestine, and kidney. Tumors were clearly visible, particularly in the lungs, with a tumor-to-lung ratio of 4.45 ± 1.89 at 1 h. One hour was a suitable time point for image acquisition because no significant differences were noted in tumor-to-background ratios between 1 and 2 h. A strong, positive correlation was found between tumor uptake (SUVpeak) and PD-L1 immunohistochemistry results (r = 0.9349; P = 0.002). 68Ga-NOTA-WL12 and 18F-FDG PET studies suggest that PD-L1 PET before therapy may indicate the therapeutic efficacy of pembrolizumab plus chemotherapy combination treatment. Conclusion: Our first-in-human findings demonstrate the safety and feasibility of 68Ga-NOTA-WL12 for noninvasive, in vivo detection of tumor PD-L1 expression levels, indicating potential benefits for clinical PD-L1 therapy.

SARS-CoV-2 receptor binding domain radio-probe: a non-invasive approach for angiotensin-converting enzyme 2 mapping in mice.

The spike protein of SARS-CoV-2 interacts with angiotensin-converting enzyme 2 (ACE2) of human respiratory epithelial cells, which leads to infection. Furthermore, low-dose radiation has been found to reduce inflammation and aid the curing of COVID-19. The receptor binding domain (RBD), a recombinant spike protein with a His tag at the C-terminus, binds to ACE2 in human body. We thus constructed a radioiodinated RBD as a molecule-targeted probe to non-invasively explore ACE2 expression in vivo, and to investigate radiotherapy pathway for inhibiting ACE2. RBD was labeled with [124I]NaI using an N-bromosuccinimide (NBS)-mediated method, and 124I-RBD was obtained after purification with a specific activity of 28.9 GBq/nmol. Its radiochemical purity was (RCP) over 90% in saline for 5 days. The dissociation constant of 124I-RBD binding to hACE2 was 75.7 nM. The uptake of 124I-RBD by HeLaACE+ cells at 2 h was 2.96% ± 0.35%, which could be substantially blocked by an excessive amount of RBD, and drop to 1.71% ± 0.23%. In BALB/c mice, the biodistribution of 124I-RBD after intravenous injection showed a moderate metabolism rate, and its 24 h-post injection (p.i.) organ distribution was similar to the expression profile in body. Micro-PET imaging of mice after intrapulmonary injection showed high uptake of lung at 1, 4, 24 h p.i.. In conclusion, the experimental results demonstrate the potential of 124I-RBD as a novel targeted molecular probe for COVID-19. This probe may be used for non-invasive ACE2 mapping in mammals.

Application Analysis of 124I-PPMN for Enhanced Retention in Tumors of Prostate Cancer Xenograft Mice.

BACKGROUND: In recent years, nuclear medicine imaging and therapy for prostate cancer have radically changed through the introduction of radiolabeled prostate-specific membrane antigen (PSMA)-binding peptides. However, these small molecular probes have some inherent limitations, including high nephrotoxicity and short circulation time, which limits their utility in biological systems. METHODS AND RESULTS: In this study, organic melanin nanoparticles were used to directly label the long half-life radionuclide 124I (t1/2=100.8 h), and PSMA small molecular groups were efficiently bonded on the surface of nanoparticles to construct the PSMA-targeted long-retention nanoprobe 124I-PPMN, which has the potential to increase tumor uptake and prolong residence time. The results showed that the nanoprobe could substantially aggregate in the tumors of prostate cancer xenograft mice and was visible for more than 72 h. Positron Emission Computed Tomography (PET) imaging showed that the nanoprobe could be used for precise imaging of prostate cancer with high expression of PSMA. In addition, organic melanin nanoparticles labeled with an elemental radionuclide achieved a stable, metal-free structure. Cell experiments and mouse toxicity experiments indicated that the nanoprobe has high safety. CONCLUSION: The new nanoprobe constructed in this study has high specificity and biocompatibility. In the future, combined with the multifunctional potential of melanin nanoparticles, this nanoprobe is expected to be used in the integrated theranostics of prostate cancer.

Molecular PET/CT Profiling of ACE2 Expression In Vivo: Implications for Infection and Outcome from SARS-CoV-2.

Rapid progress has been made to identify and study the causative agent leading to coronavirus disease 2019 (COVID-19) but many questions including who is most susceptible and what determines severity remain unanswered. Angiotensin-converting enzyme 2 (ACE2) is a key factor in the infection process of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). In this study, molecularly specific positron emission tomography imaging agents for targeting ACE2 are first developed, and these novel agents are evaluated in vitro, in preclinical model systems, and in a first-in-human translational ACE2 imaging of healthy volunteers and a SARS-CoV-2 recovered patient (NCT04422457). ACE2 expression levels in different organs in live subjects are quantitatively delineated and observable differences are measured in the patient recovered from COVID-19. Surprising sites of uptake in the breast, reproductive system and very low uptake in pulmonary tissues are reported. This novel method can add a unique tool to facilitate SARS-CoV-2 related research and improve understanding of this enigmatic disease. Molecular imaging provides quantitative annotation of ACE2, the SARS-CoV-2 entry receptor, to noninvasively monitor organs impacted by the COVID-19.

64Cu-PSMA-BCH: a new radiotracer for delayed PET imaging of prostate cancer.

PURPOSE: Develop a 64Cu labeled radiopharmaceutical targeting prostate specific membrane antigen (PSMA) and investigate its application for prostate cancer imaging. METHODS: 64Cu-PSMA-BCH was prepared and investigated for stability, PSMA specificity, and micro-PET imaging. With the approval of Ethics Committee of Beijing Cancer Hospital (No. 2017KT97), PET/CT imaging in 4 patients with suspected prostate cancer was performed and the radiation dosimetry was estimated. Then, PSMA PET-ultrasound image-guided biopsies were performed on 3 patients and the fine needle aspirates were further performed for autoradiography and immunohistochemistry analysis. RESULTS: 64Cu-PSMA-BCH was prepared with high radiochemical yield and stability. In vivo study showed higher uptake in PSMA ( +) 22Rv1 cells than PSMA ( -) PC-3 cells (5.59 ± 0.36 and 1.97 ± 0.22 IA%/106 cells at 1 h). It accumulated in 22Rv1 tumor with increasing radioactivity uptake and T/N ratios from 1 to 24 h post-injection. In patients with suspected prostate cancer, SUVmax and T/N ratios increased within 24 h post-injection. Compared with image at 1 h post-injection, more tumor lesions were detected at 6 h and 24 h post-injection. The human organ radiation dosimetry showed gallbladder wall was most critical, liver and kidneys were followed, and the whole-body effective dose was 0.0292 mSv/MBq. Two fine needle aspirates obtained by PET-ultrasound-guided targeted biopsy showed high radioactive signal by autoradiography, with 100% PSMA expression in cytoplasm and 30% expression in nucleus. CONCLUSION: 64Cu-PSMA-BCH was PSMA specific and showed high stability in vivo with lower uptake in liver than 64Cu-PSMA-617. Biodistribution in mice and PCa patients showed similar profile compared with other PSMA ligands and it was safe with moderate effective dosimetry. The increased tumor uptake and T/N ratios by delayed imaging may facilitate the detection of small lesions and guiding targeted biopsies.

A Highly Specific Multiple Enhancement Theranostic Nanoprobe for PET/MRI/PAI Image-Guided Radioisotope Combined Photothermal Therapy in Prostate Cancer.

An integrated molecular probe for combined tumor-targeted multimodal imaging and therapy in the era of precision medicine requires a multiplexed platform that simultaneously has high targeting specificity, versatile conjugation capability, and biocompatibility. Here, a novel biocompatible melanin nanoprobe (PMNs-II-813) coupled with a highly specific prostate-specific membrane antigen small molecule inhibitor is developed for the targeted multimodal diagnosis and treatment of prostate cancer. The melanin nanoparticles demonstrate photoacoustic imaging and photothermal therapy (PTT) functionalities via strong near-infrared absorption. The imaging contrast agents 89 Zr and Mn2+ are stably conjugated to the nanoparticles for positron emission tomography (PET) and magnetic resonance imaging (MRI). Fusion PET/MRI with PMNs-II-813 enables the monitoring of treatment effects in real time and lasts for more than 1 week, demonstrating the capability for multimodal theranostics in prostate cancer. Labeling with a therapeutic radionuclide, 131 I, simultaneously endows the nanoprobe with the capability for radioisotope therapy (RIT) and PTT under triple-modal imaging guidance. Combined PTT and RIT has an inhibitory effect on prostate cancer growth (tumor inhibition rate of ≈93% 20 days after treatment), which is significantly better than that with the single treatment. Overall, it is believed that PMNs-II-813 has potential for clinical translation to treat prostate cancer.

Dynamic PET/CT Imaging of 68Ga-FAPI-04 in Chinese Subjects.

This study aims to further explore dynamic 68Ga-FAPI-04 PET/CT imaging of healthy Chinese subjects and lung cancer patients. Moreover, the variability of 68Ga-FAPI-04 uptake in normal organs was measured to provide a basis for analyzing its biological distribution, interpreting auxiliary images, determining the reliability of image quantification, and monitoring treatment. Six patients (3 subjects without tumors and 3 lung cancer patients) separately underwent 68Ga-FAPI-04 and 2-[18F]FDG PET/CT imaging within 1 week. The biodistribution and internal radiation dosimetry were reported and compared with data previously obtained from Caucasian patients. Moreover, the mean SUV (standardized uptake value) was normalized to body mass or to lean body mass (SUL), and the coefficients of variation (CVs) were calculated and compared for each volume of interest. The average whole-body effective dose was calculated to be 1.27E-02 mSv/MBq, which was comparable with previously reported results of 68Ga-FAPI-04 probes. Furthermore, the SUVmean was slightly higher than the SULmean in most organs; however, the CV of the SULmean for most organs was higher than that of the SUVmean at later time points. In the liver, the CV of the SUVmean was lower (12.7%) than that of the SULmean and was similar to the CV for corresponding 2-[18F]FDG PET/CT value (11.8%). In addition, 68Ga-FAPI-04 PET/CT showed good efficacy for diagnosing lung cancer patients in this study. A comparison of the radiation dosimetry obtained before from a Caucasian population demonstrated no clinically significant differences between these two populations after 68Ga-FAPI-04 injection. The variability in most organs was slightly lower for SUVmean than for SULmean, suggesting that SUVmean may be the preferable parameter for quantifying images obtained with 68Ga-FAPI-04. In addition, 68Ga-FAPI-04 PET/CT imaging is expected to be a promising tool for diagnosing lung cancer.

Noninvasive evaluation of PD-L1 expression using Copper 64 labeled peptide WL12 by micro-PET imaging in Chinese hamster ovary cell tumor model.

As an indicative biomarker for immunotherapy, PD-L1 plays an important role in the clinical decision-making of the immune checkpoint blockade therapy. PET imaging through radiotracer can real-timely, quantitatively, and non-invasively assess the expression of PD-L1 in tumors. Here, we reported a copper-64 radiolabeled NOTA-WL12, 64Cu-NOTA-WL12, and preliminarily evaluated its application in non-invasively detecting the PD-L1 expression.64Cu-NOTA-WL12 was produced with high radiochemical yield (>90%), radiochemical purity (>98%), and specific activity (20 MBq/nmol). 64Cu-NOTA-WL12 showed high in vitro stability and high binding affinity to the PD-L1 (KD ≈ 3.012 nM). The micro-positron emission tomography/computerized tomography (micro-PET/CT) imaging indicated that 64Cu-NOTA-WL12 was specifically accumulated in the tumor with PD-L1 expression. All results demonstrated that 64Cu-NOTA-WL12 holds great potential for noninvasive evaluation of PD-L1 expression levels.

Synthesis, preclinical evaluation, and a pilot clinical imaging study of [18F]AlF-NOTA-JR11 for neuroendocrine neoplasms compared with [68Ga]Ga-DOTA-TATE.

PURPOSE: A [18F]AlF-labeled somatostatin receptor (SSTR) antagonist was developed for imaging of neuroendocrine neoplasms (NENs), evaluated and compared with [68Ga]Ga-DOTA-TATE. METHOD: [18F]AlF-NOTA-JR11 was synthesized manually and qualified with high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS). The cellular uptake, internalization, and saturation binding were performed with HEK293-SSTR2 cells. Biodistribution and micro-PET imaging were carried out with HEK293-SSTR2 tumor-bearing mice. [18F]AlF-NOTA-JR11 PET/MR imaging and [68Ga]Ga-DOTA-TATE PET/CT were performed with ten patients of NEN at 50~60 min post-injection (p.i.). Normal organ biodistribution and tumor detectability were evaluated. RESULT: [18F]AlF-NOTA-JR11(24~36 GBq/µmol) was prepared within 30 min and 51.35 ± 3.30% (n > 10)of radiochemical yield. The radiochemical purity was 98.74 ± 1.24% (n > 10). Two stereoisomers were found and confirmed by LC-MS. The cellular uptake of [18F]AlF-NOTA-JR11 and [68Ga]Ga-DOTA-TATE were 4.50 ± 0.31 and 4.50 ± 0.13 %AD/105 cells at 30 min, and the internalization at 37 °C of [18F]AlF-NOTA-JR11 (5.47 ± 0.32% at 60 min) was significantly lower than [68Ga]Ga-DOTA-TATE (66.89 ± 1.62% at 60 min). The affinity of [18F]AlF-NOTA-JR11 (Kd = 11.59 ± 1.31 nM) was slightly lower than [68Ga]Ga-DOTA-TATE (Kd = 7.36 ± 1.02 nM); [18F]AlF-NOTA-JR11 showed high uptake in tumor (9.02 ± 0.92 %ID/g at 60 min p.i.) which can be blocked by 50 µg of NOTA-JR11 (3.40 ± 1.64 %ID/g at 60 min p.i.); the result was coincident with micro-PET imaging. Imaging study of NEN patients showed that more lesions were found only by [18F]AlF-NOTA-JR11 (n = 67 vs. 1 only by [68Ga]Ga-DOTA-TATE), and the uptakes of [18F]AlF-NOTA-JR11 in majority normal organs were significantly lower than [68Ga]Ga-DOTA-TATE. The target to nontarget of maximum of standard uptake value (SUVmax) of [18F]AlF-NOTA-JR11 in liver lesions were significantly higher than those of [68Ga]Ga-DOTA-TATE. CONCLUSION: Qualitied [18F]AlF-NOTA-JR11 is prepared conveniently with reasonable yield, and it can bind SSTR2 specifically with high affinity. Excellent imaging capability of [18F]AlF-NOTA-JR11 for NENs is superior to [68Ga]Ga-DOTA-TATE, especially in digestive system. It has a great potential for imaging of NENs.