Kotaro Nagatsu

Evaluation of 89Zr-Labeled Human Anti-CD147 Monoclonal Antibody as a Positron Emission Tomography Probe in a Mouse Model of Pancreatic Cancer

Introduction Pancreatic cancer is an aggressive cancer and its prognosis remains poor. Therefore, additional effective therapy is required to augment and/or complement current therapy. CD147, high expression in pancreatic cancer, is involved in the metastatic process and is considered a good candidate for targeted therapy. CD147-specfic imaging could be useful for selection of appropriate patients. Therefore, we evaluated the potential of a fully human anti-CD147 monoclonal antibody 059-053 as a new positron emission tomography (PET) probe for pancreatic cancer. Methods CD147 expression was evaluated in four pancreatic cancer cell lines (MIA Paca-2, PANC-1, BxPC-3, and AsPC-1) and a mouse cell line A4 as a negative control. Cell binding, competitive inhibition and internalization assays were conducted with 125I-, 67Ga-, or 89Zr-labeled 059-053. In vivo biodistribution of 125I- or 89Zr-labeled 059-053 was conducted in mice bearing MIA Paca-2 and A4 tumors. PET imaging with [89Zr]059-053 was conducted in subcutaneous and orthotopic tumor mouse models. Results Among four pancreatic cancer cell lines, MIA Paca-2 cells showed the highest expression of CD147, while A4 cells had no expression. Immunohistochemical staining showed that MIA Paca-2 xenografts also highly expressed CD147 in vivo. Radiolabeled 059-053 specifically bound to MIA Paca-2 cells with high affinity, but not to A4. [89Zr]059-053 uptake in MIA Paca-2 tumors increased with time from 11.0±1.3% injected dose per gram (ID/g) at day 1 to 16.9±3.2% ID/g at day 6, while [125I]059-053 uptake was relatively low and decreased with time, suggesting that 059-053 was internalized into tumor cells in vivo and 125I was released from the cells. PET with [89Zr]059-053 clearly visualized subcutaneous and orthotopic tumors. Conclusion [89Zr]059-053 is a promising PET probe for imaging CD147 expression in pancreatic cancer and has the potential to select appropriate patients with CD147-expressing tumors who could gain benefit from anti-CD147 therapy.

Investigation of direct production of 68Ga with low energy multiparticle accelerator

Abstract Experimentally measured cross sections are presented for the natCu(α, xn)66,67,68Ga and 68Zn(p, xn)67,68Ga nuclear processes up to 36 and 20 MeV, respectively. Based on these results and the reliable cross section data available in the literature, the possible thick target yields were also calculated. Two different 68Ga production routes (Cu+α and Zn+p) are discussed in detail, especially with regard to the 66Ga and 67Ga contamination levels as a function of the target enrichment level and the incident bombarding energies. Both processes can be used for in-house 68Ga production with low (<1%) 66Ga and/or 67Ga EOB contamination using enriched 68Zn (>80%) or 65Cu (>95%) target. The maximum available yield on 100% enriched 68Zn and 65Cu (irradiation time: 2.25 h; bombarding energy: Ep=20 MeV and Eα=18 MeV) is 352.45 mCi/μA (13.04 GBq/μA) and 14.28 mCi/μA (528.36 MBq/μA), respectively.

Efficient preparation of high-quality 64Cu for routine use

INTRODUCTION Copper-64 is an attractive radionuclide for positron emission tomography and is emerging as a radiotherapeutic agent. The demand of 64Cu with low metallic impurities has increased because of its wide applications when incorporated with antibodies, peptides, and proteins. In this study, we propose a new separation method to produce high-quality 64Cu using a cation exchange column, as well as an automated separation system suitable for large-scale production. METHODS 64Cu was produced from an electrodeposited 64Ni target via the 64Ni(p,n)-reaction with a 24MeV HH+ beam at 10eμA (electrical microampere) conducted for 1-3h. The irradiated target was transported to a hot cell and disassembled remotely. 64Cu was separated by a solvent mixture of HCl and acetone on a cation-exchange resin, AG50W-X8. The chemical purity of 64Cu final product was evaluated using ion-chromatography coupled with a UV detector and inductively coupled plasma mass spectroscopy for quality as well as metallic impurities. RESULTS We obtained 64Cu in dried form at a yield of 5.2-13GBq at the end of separation, or 521±12MBq/eμAh as the final product within 2.5h of processing time. The metallic impurities were a satisfactory low level in the order of ppb. Major contaminants of Co and Ni were lower than those samples obtained by a widely accepted separation using an anion-exchange resin. CONCLUSION Using a cation-exchange resin and a systematic operation, we successfully reduced the contamination level of the 64Cu product. As a straightforward separation method, which shortened the entire processing time, we obtained a satisfactory amount of high-quality 64Cu available for routine use.

Preclinical evaluation of 89Zr-labeled human antitransferrin receptor monoclonal antibody as a PET probe using a pancreatic cancer mouse model

ObjectivePancreatic cancer is aggressive and its prognosis remains poor; thus, effective therapy is urgently needed. Transferrin receptor (TfR) is highly expressed in pancreatic cancer and is considered to be a good candidate for molecular-targeted therapy. We radiolabeled and evaluated fully human anti-TfR monoclonal antibodies as a new PET probe for evaluating the biodistribution of the anti-TfR antibody in pancreatic cancer. Materials and methodsTfR expression was evaluated in four human pancreatic cancer (MIAPaCa-2, PANC-1, BxPC-3, and AsPC-1) and murine A4 cell lines. The binding of 125I-labeled anti-TfR antibodies (TSP-A01, TSP-A02, TSP-A03, and TSP-A04) to MIAPaCa-2 cells was compared. 125I-labeled, 67Ga-labeled, and 89Zr-labeled TSP-A01 were evaluated by cell binding, competitive inhibition, and internalization assays. Biodistribution studies of 125I-labeled and 89Zr-labeled TSP-A01 were conducted in mice bearing MIAPaCa-2 and A4 tumors. PET imaging with [89Zr]TSP-A01 was carried out. ResultsMIAPaCa-2 cells showed the highest TfR expression in vitro and in vivo, whereas A4 cells showed no expression. Of the four antibodies, [125I]TSP-A01 showed the highest binding to MIAPaCa-2 cells, but not to A4 cells. The dissociation constant of TSP-A01 was 0.29 nmol/l. Uptake of radiolabeled TSP-A01, especially [89Zr]TSP-A01, was significantly higher in MIAPaCa-2 tumors than in A4 tumors. PET with [89Zr]TSP-A01 clearly visualized MIAPaCa-2 xenografts but not A4 xenografts. Conclusion[89Zr]TSP-A01 is a promising PET probe for evaluating the accumulation of anti-TfR antibody in pancreatic cancer and has the potential to facilitate the selection of appropriate patients who would benefit from anti-TfR antibody therapy.

Excitation function of (p, α) nuclear reaction on enriched 67Zn: Possibility of production of 64Cu at low energy cyclotron

Abstract The potential for production of the medically relevant 64Cu has been investigated by proton irradiation of highly enriched 67Zn targets. The excitation function of the 67Zn(p, α)64Cu a nuclear reaction was measured by the stacked-foil technique up to 30 MeV. The prediction of the TALYS code was also compared to the measured cross section results. Based on the improved database of the 67Zn(p, α)64Cu reaction, thick target yield as a function of energy was also deduced. Production possibility of 64Cu is discussed in detail, employing different energy proton beams and with regards to the 61Cu and 67Cu contamination levels as a function of the target enrichment level. By using 1 μA beam intensity, 6.3505 h irradiation time and enriched 67Zn target (64Zn ≤ 0.5%, 66Zn ≤ 9%, 67Zn ≥ 80%, 68Zn ≤ 10% and 70Zn ≤ 0.5%), the expected EOB (End Of bombardment) yields are 43.66, 88.80 and 156.14 MBq/μA at 12, 15 and 18 MeV proton energies, respectively. Application time-frames were also deduced where the total radio-copper contamination level remains below 1%.

Production of 211At by a vertical beam irradiation method

We produced (211)At by irradiating the semi-sealed encapsulated Bi target with an external vertical beam. At 28.5MeV, the yield of (211)At was 22MBq/μAh (600μCi/μAh). (211)At was recovered by dry distillation, and 80% of the produced (211)At was successfully obtained in dry Na(211)At form within 2h from the end of bombardment (EOB). The radionuclidic purity of (211)At was >99% at 5h from EOB.

An alumina ceramic target vessel for the remote production of metallic radionuclides by in situ target dissolution

INTRODUCTION As the use of metallic radionuclides increases, so does the demand for a simple production method. In this study, we demonstrated an in situ target processing concept for automated metallic radionuclide production without the use of any robotic device. METHODS An alumina ceramic vessel for a vertical irradiation system was designed and developed. The ceramic vessel was evaluated by the production of Zr-89 using an yttrium powder target. The irradiated Y was dissolved remotely in HCl in the ceramic vessel and transferred as a solution to a hotcell through a Teflon tube. The crude Zr-89 was then purified by an automated apparatus. The Zr-89 was eluted with 100 μL of oxalic acid (solution) as the final product. RESULTS The ceramic vessel gave a sufficient yield of Zr-89 (57±11MBq/μAh), showed good operability, and could be reused up to 10 times. With nominal irradiation (10μA×2h) in ~90 μL, the product (~940MBq) was obtained with >99.9% radionuclidic purity. CONCLUSION The combination of the ceramic vessel and vertical irradiation has great potential for the remote production of various metallic radionuclides.

Immuno-PET Imaging of HER3 in a Model in which HER3 Signaling Plays a Critical Role.

HER3 is overexpressed in various carcinomas including colorectal cancer (CRC), which is associated with poor prognosis, and is involved in the development of therapy resistance. Thus, an in vivo imaging technique is needed to evaluate the expression of HER3, an important therapeutic and diagnostic target. Here, we report successful HER3 PET imaging using a newly generated anti-human HER3 monoclonal antibody, Mab#58, and a mouse model of a HER3-overexpressing xenograft tumor. Furthermore, we assessed the role of HER3 signaling in CRC cancer tissue-originated spheroid (CTOS) and applied HER3 imaging to detect endogenous HER3 in CTOS-derived xenografts. Cell binding assays of 89Zr-labeled Mab#58 using the HER3-overexpressing cell line HER3/RH7777 demonstrated that [89Zr]Mab#58 specifically bound to HER3/RH7777 cells (Kd = 2.7 nM). In vivo biodistribution study in mice bearing HER3/RH7777 and its parent cell xenografts showed that tumor accumulation of [89Zr]Mab#58 in HER3/RH7777 xenografts was significantly higher than that in the control from day 1 to day 4, tending to increase from day 1 to day 4 and reaching 12.2 ± 4.5%ID/g. Radioactivity in other tissues, including the control xenograft, decreased or remained unchanged from day 1 to day 6. Positron emission tomography (PET) in the same model enabled clear visualization of HER3/RH7777 xenografts but not of RH7777 xenografts. CTOS growth assay and signaling assay revealed that CRC CTOS were dependent on HER3 signaling for their growth. In PET studies of mice bearing a CRC CTOS xenograft, the tumor was clearly visualized with [89Zr]Mab#58 but not with the 89Zr-labeled control antibody. Thus, tumor expression of HER3 was successfully visualized by PET with 89Zr-labeled anti-HER3 antibody in CTOS xenograft-bearing mice, a model that retains the properties of the patient tumor. Non-invasive targeting of HER3 by antibodies is feasible, and it is expected to be useful for cancer diagnosis and treatment.

Production cross sections of radioisotopes from 3He-particle induced nuclear reactions on natural titanium

Excitation functions were measured using the stacked-foil method for the natTi(3He,x)44mSc, 46m+gSc, 47Sc, 48Sc, 48V and 48Cr nuclear processes up to 68MeV. Our new cross-section data were compared with the earlier reported values as well as the evaluated theoretical predictions by means of the TALYS 1.6 code as compiled in the TENDL-2015 library. The new data show acceptable agreement with the previous experimental values in the overlapping energy regions, however only a partial agreement was found in the case of the results of the nuclear reaction model code. The present work not only strengthens the experimental datasets of the above processes but also provides new cross-section values above 36MeV where only one dataset is available for each reaction.

Small-scale production of 67Cu for a preclinical study via the 64Ni(α, p)67Cu channel

INTRODUCTION Copper-67 is an attractive beta emitter for targeted radionuclide therapy. However, the availability of 67Cu limits its potential use in a wide range of applications. In this study, we propose an easy small-scale production of 67Cu using 64Ni target for a preclinical study. METHODS 67Cu was produced from an electrodeposited 64Ni target via the 64Ni(α, p)67Cu-reaction with a 36 MeV alpha beam at 15 eμA (electrical microampere) conducted for 7 h. The chemical separation process of 67Cu from the 64Ni target was performed following by our routine procedure of 64Cu production using cation exchange resin, AG50W-X8, with minor modification. The target and its holder were redesigned in the preparation. RESULTS The 67Cu product was obtained with a yield of 55 ± 10 MBq at the end of bombardment (EOB), and the yield was 527 ± 96 kBq/μAh at the EOB. The copper impurity in the product was low (0.71 ± 0.21 μg) and the product was suitable for a preclinical study. CONCLUSIONS We produced 67Cu with sufficient activity and quality for a preclinical study using a 64Ni-target. This production method also showed advantages as a routine method, i.e., shorten the processing time, reducing the radiation exposure and ready target recycling, when compared with that of a conventional Zn-target used for 67Cu production.