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A macroporous styrene–divinylbenzene copolymer containing N-methylglucamine groups was selected for a new 68Ge/68Ga generator system. This resin packed into a column effectively adsorbed the parent nuclide 68Ge. The daughter 68Ga was eluted from the resin with a solution of a low-affinity gallium chelating ligand such as citric or phosphoric acid. The 68Ge leakage was less than 0.0004% of the 68Ge adsorbed on the resin. By simple mixing of transferrin and desferoxamine conjugated HSA and IgG with the eluate from the column, 68Ga-labeling was completed in high yield. [Copyright &y& Elsevier]

Gallium-68 (68Ga) is a important positron-emitting radionuclide available for positron emission tomography. Since the 68Ga is prepared by decay of germanium-68 (68Ge) having a long half-life, separation of 68Ga from 68Ge is essential for the utilization of 68Ga. In this study, a macroporous styrene-divinylbenzene copolymer containing N-methylglucamine groups (R-MGlu) was selected as an adsorbent for 68Ge. This resin effectively and rapidly adsorbed 68Ge above pH 5. By a batch method, 0.1 mol l−1 trisodium citrate eluted over 90% of 68Ga built up in the resin by decay of 68Ge on the resin, although distilled water did not elute the 68Ga. A solution of ethylenediaminetetraacetic acid or desferroxamine at a lower concentration also desorbed the 68Ga in higher yield. These results indicated that 68Ga was eluted by the formation of a complex with a suitable ligand. When 0.1 mol l−1 sodium citrate was used as the eluting agent by a column method, most of the 68Ga on the R-MGlu was recovered using 0.1 mol l−1 sodium citrate, while the 68Ge leakage was less than 0.0004% of the 68Ge adsorbed on R-MGlu. [Copyright &y& Elsevier]

Radionuclide imaging and therapy are promising methods for controlling systemic cancers; however, their clinical application has been limited by excessive radionuclide accumulation in healthy tissues. To minimize radionuclide accumulation in non-cancerous tissues while ensuring sufficient build up in tumors, we aimed to develop a method that controlled the in vivo dynamics of radionuclides post-administration. To this end, we describe a novel strategy that combines liposomes, a potent carrier system for drug delivery, with unique radionuclide-ligand complexes based on 111 In-ethylenedicysteine. Conventional 111 In-ligand-complexes-carrying liposomes delivered substantial amounts of radionuclides to tumors; however, they also accumulated in the liver and spleen. In contrast, 111 In-ethylenedicysteine-carrying liposomes greatly reduced non-specific accumulation, while being retained selectively at high doses within tumors. Liposomes were rapidly broken down in the liver, releasing encapsulated 111 In-ligand complexes. Among the chelates used, only 111 In-ethylenedicysteine could escape from the liver and be excreted in the urine. Instead, most liposomes remained intact in tumors, retaining the radionuclide-ligand complexes within them. Therefore, high tumor accumulation was obtained regardless of the type of 111 In-ligand complexes in the liposomes. In vivo single photon emission computed tomography/computed tomography imaging with 111 In-ethylenedicysteine-carrying liposomes accurately revealed tumor-selective radionuclide retention with little background. Hence, our new strategy could greatly enhance tumor-to-healthy tissue ratios, improve diagnostic imaging, boost therapeutic efficacy, reduce toxicity to healthy tissues, and facilitate radionuclide imaging and therapy., Competing Interests: Declaration of Competing Interest The authors have no relevant financial or non-financial interests to disclose., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The interposition of a cleavable linkage by enzymes on the renal brush border membrane constitutes a promising approach for reducing the renal radioactivity levels of radiolabeled low-molecular-weight antibody fragments and constructs (LMW Abs). Herein, we applied the molecular design to 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-based reagents for radiotheranostic applications with trivalent radiometals. DOTA or a derivative thereof was conjugated to a Fab through an FGK linkage ([ 111 In]In-DO3A i Bu-Bn-FGK-Fab or [ 111 In]In-DOTA-Bn-FGK-Fab). When injected into mice, both generated radiometabolites, [ 111 In]In-DO3A i Bu-Bn-F and [ 111 In]In-DOTA-Bn-F, by the angiotensin-converting enzyme at similar rates. Both exhibited significantly lower renal radioactivity levels than a 111 In-labeled Fab prepared by the conventional procedure ([ 111 In]In-DOTA-Bn-SCN-Fab). The different elimination rates of each radiometabolite from the kidney significantly affected the renal radioactivity levels. [ 111 In]In-DO3A i Bu-Bn-FGK-Fab preferentially reduced the renal localization without impairing tumor accumulation. These findings would pave the way for developing a DOTA-based radiotheranostic platform for LMW Abs bearing cleavable linkers for renal brush border enzymes.

Chemotherapy for peritoneal dissemination is poorly effective owing to limited drug transfer from the blood to the intraperitoneal (i.p.) compartment after intravenous (i.v.) administration. i.p. chemotherapy has been investigated to improve drug delivery to tumors; however, the efficacy continues to be debated. As anticancer drugs have low molecular weight and are rapidly excreted through the peritoneal blood vessels, maintaining the i.p. concentration as high as expected is a challenge. In this study, we examined whether i.p. administration is an efficient route of administration of high-molecular-weight immune checkpoint inhibitors (ICIs) for the treatment of peritoneal dissemination using a model of peritoneal disseminated carcinoma. After i.p. administration, the amount of anti-PD-L1 antibody transferred into i.p. tumors increased by approximately eight folds compared to that after i.v. administration. Intratumoral distribution analysis revealed that anti-PD-L1 antibodies were delivered directly from the i.p. space to the surface of tumor tissue, and that they deeply penetrated the tumor tissues after i.p. administration; in contrast, after i.v. administration, anti-PD-L1 antibodies were only distributed around blood vessels in tumor tissues via the enhanced permeability and retention (EPR) effect. Owing to the enhanced delivery, the therapeutic efficacy of anti-PD-L1 antibody in the peritoneal dissemination models was also improved after i.p. administration compared to that after i.v. administration. This is the first study to clearly demonstrate an EPR-independent delivery of ICIs to i.p. tumors by which ICIs were delivered in a massive amount to the tumor tissue via direct penetration after i.p. administration., Competing Interests: Declaration of Competing Interest Authors declare that they have no competing interests in this research., (Copyright © 2022 Elsevier B.V. All rights reserved.)

1,4,7,10-Tetraazacyclododecane-1,4,7-triacetic acid (DO3A) has been used to prepare 68 Ga-labeled probes for the diagnostic counterpart of radiotheranostic applications. While DO3A provides stable complexes with therapeutic radionuclides such as 90 Y, 177 Lu, and 225 Ac, further improvement of the in vivo stability of the Ga-DO3A complex is required. Considering the high stability of an intact Ga-DOTA complex, the stability of Ga complexes of DOTA and DO3A derivatives, including benzyl-DOTA (Bn-DOTA), was evaluated to gain fundamental knowledge for developing the next-generation radiotheranostic probes using 68 Ga as a diagnostic counterpart. Following the complexation reaction to prepare 67 Ga-labeled DOTA and DO3A derivatives, the stability of the resulting 67 Ga-labeled compounds was evaluated in murine plasma and apo-transferrin challenge. [ 67 Ga]Ga-Bn-DOTA produced two isomers, and one of the isomers exhibited the highest stability among the tested complexes. The X-ray crystallography showed that the less stable isomer of Ga-Bn-DOTA suggested an N 3 O 3 coordination geometry, while Ga-DOTA and Ga-Bn-DO3A show N 4 O 2 coordination. To further evaluate the stability, a synthetic somatostatin analogue, [Tyr 3 ]octreotide (TOC), was used as a model peptide, and p -COOH-Bn-DOTA and DO3A were conjugated with TOC to prepare DOTA-Bn-TOC and DOTATOC. [ 67 Ga]Ga-DOTA-Bn-TOC also yielded two isomers with varying stability, and one isomer exhibited significantly higher stability than [ 67 Ga]Ga-DOTATOC both in vitro and in vivo . These findings indicate that para -substituted Bn-DOTA would constitute a suitable chelating agent for developing next-generation radiotheranostic probes, although high-performance liquid chromatography purification is needed. Thus, further chemical modification on the Bn-DOTA molecule is also needed to avoid the formation of a Ga complex with the N 3 O 3 configuration., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Introduction: Radiolabeled peptides and low-molecular-weight (LMW) polypeptides show high and persistent radioactivity levels in the kidney. To develop a DOTA-based bifunctional chelating agent that provides a radiometabolite with a rapid elimination rate from the kidney, a para-carboxyl Bn-DOTA (p-COOH-Bn-DOTA) was designed, synthesized, and evaluated., Methods: A precursor compound, p-COOH-Bn-DOTA( t Bu) 4 , was synthesized in 9 steps using N-Boc-p-iodo-L-phenylalanine as the starting material. A synthetic somatostatin analog (TOC) was used as a representative peptide metabolized in the renal lysosomes. p-COOH-Bn-DOTA-conjugated TOC (DOTA-Bn-TOC) was synthesized by the conventional solid-phase peptide synthesis using p-COOH-Bn-DOTA( t Bu) 4 . DOTA-tris( t Bu ester) was also conjugated with TOC to prepare DOTATOC. 111 In-labeling of the peptides was conducted under similar conditions. The radiochemical conversions, stability against apo-transferrin (apoTf), and in vivo behaviors were compared., Results: [ 111 In]In-DOTA-Bn-TOC was obtained with higher radiochemical conversions than [ 111 In]In-DOTATOC. Both 111 In-labeled TOC derivatives remained stable against apoTf. In biodistribution studies, [ 111 In]In-DOTA-Bn-TOC exhibited higher initial uptake in the kidney, followed by a faster elimination rate of radioactivity into the urine than [ 111 In]In-DOTATOC. The metabolic studies showed that the shorter residence time of the radiometabolite from [ 111 In]In-DOTA-Bn-TOC was responsible for the renal radioactivity decline., Conclusion: p-COOH-Bn-DOTA provides stable 111 In-labeled peptides in high yields at low peptide concentrations. p-COOH-Bn-DOTA also provides a radiometabolite with a short residence time in the kidney. Such characteristics would render p-COOH-Bn-DOTA useful to the future application to radiolabeled LMW polypeptides with low renal radioactivity levels., Competing Interests: Declaration of competing interest The authors declare no competing financial interest., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Prostate cancer frequently metastasizes to the bone. Because patients with bone metastases suffer from skeletal-related events, the diagnosis and treatment of bone metastases in the early stage are important. In this study, to improve the sensitivity of detecting bone metastases in patients with prostate cancer, we designed, synthesized, and evaluated a multifunctional radiotracer, [ 67 Ga]Ga-D 11 -PSMA-617 ([ 67 Ga]3), with an undeca-aspartic acid as a bone-seeking moiety between [ 67 Ga]Ga-DOTA and a prostate-specific membrane antigen (PSMA) ligand based on the lysine-urea-glutamate motif. [ 67 Ga]3 showed a high affinity for hydroxyapatite and high uptake in PSMA-positive LNCaP cells. Moreover, in biodistribution experiments using tumor-bearing mice, [ 67 Ga]3 exhibited high accumulation in the bone and PSMA-positive tumor although the accumulation of [ 67 Ga]3 in the PSMA-positive tumor was lower than that of [ 67 Ga]Ga-PSMA-617. This study provides valuable information for developing radiotheranostic probes combining multiple carriers with different mechanisms., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Neuroinflammation and oxidative stress are hallmarks of neurodegenerative diseases. Microglia, the major important regulators of neuroinflammation, are activated in response to excessive generation of reactive oxygen species (ROS) from damaged cells and resulting in elevated and sustained damages. However, the relationship between microglia and ROS-regulatory system in the early stages of neuroinflammation prior to the appearance of neuronal damages have not been elucidated in detail. In this study, we analyzed the time-dependent changes in ROS generation during acute neuroinflammation in rats that were given an intrastriatal injection of lipopolysaccharide (LPS). We evaluated the effects of minocycline, an anti-inflammatory antibiotic, and N,N'-dimethylthiourea (DMTU), a radical scavenger, to understand the correlation between activated microglia and ROS generation. Ex vivo fluorescence imaging using dihydroethidium (DHE) clearly demonstrated an increased ROS level in the infused side of striatum in the rats treated with LPS. The level of ROS was changed in time-dependent manner, and the highest level of ROS was observed on day 3 after the infusion of LPS. Immunohistochemical studies revealed that time-dependent changes in ROS generation were well correlated to the presence of activated microglia. The inhibition of microglial activation by minocycline remarkably reduced ROS levels in the LPS-injected striatum, which indicated that the increased ROS generation caused by LPS was induced by activated microglia. DMTU decreased ROS generation and resulted in remarkable inhibitory effect on microglial activation. This study demonstrated that ROS generation during acute neuroinflammation induced by LPS was considerably associated with microglial activation, in an intact rat brain. The results provides a basis for understanding the interaction of ROS-regulatory system and activated microglia during neuroinflammation underlying neurodegenerative diseases., Competing Interests: Declaration of competing interest The authors declare that they have no competing of interest., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

The high in vivo stability of 2,2-dihydroxymethyl-3-[ 18 F]fluoropropyl-2-nitroimidazole ([ 18 F]DiFA) prompted us to evaluate neopentyl as a scaffold to prepare a radiotheranostic system with radioiodine and astatine. Three DiFA analogues with one, two, or without a hydroxyl group were synthesized. While all 125 I-labeled compounds remained stable against nucleophilic substitution, only a 125 I-labeled neopentyl glycol was stable against cytochrome P450 (CYP)-mediated metabolism and showed high stability against in vivo deiodination. 211 At-labeled neopentyl glycol also remained stable against both nucleophilic substitution and CYP-mediated metabolism. 211 At-labeled neopentyl glycol showed the biodistribution profiles similar to those of its radioiodinated counterpart in contrast to the 125 I/ 211 At-labeled benzoate pair. The urine analyses confirmed that 211 At-labeled neopentyl glycol was excreted in the urine as a glucuronide conjugate with the absence of free [ 211 At]At - . These findings indicate that neopentyl glycol would constitute a promising scaffold to prepare a radiotheranostic system with radioiodine and 211 At.

Purpose: Our study aimed to elucidate the intracellular processes associated with quinolinic acid (QA)-induced brain injury by acquiring semiquantitative fluorescent images of reactive oxygen species (ROS) generation and positron emission tomography (PET) images of mitochondrial complex I (MC-I) activity., Methods: Ex vivo fluorescent imaging with dihydroethidium (DHE) and PET scans with 18 F-BCPP-EF were conducted at 3 h and 24 h after QA injection into the rat striatum. Immunohistochemical studies were performed 24 h after QA injection into the rat brain using monoclonal antibodies against neuronal nuclei (NeuN) and CD11b., Results: A strong DHE-derived fluorescent signal was detected in a focal area within the QA-injected striatum 3 h after QA injection, and increased fluorescent signal spread throughout the striatum and parts of the cerebral cortex after 24 h. By contrast, 18 F-BCPP-EF uptake in the QA-injected rat brain was unchanged after 3 h and markedly decreased after 24 h, not only in the striatum but also in the cerebral hemisphere. The fluorescent signal in the striatum 24 h after QA injection colocalised with microglial marker expression., Conclusions: We successfully obtained functional images of focal ROS generation during the early period of excitotoxic injury, and microglial ROS generation and mitochondrial dysfunction were observed during the progression of the inflammatory response. Both ex vivo DHE imaging and in vivo 18 F-BCPP-EF-PET were sufficiently sensitive to detect the respective processes of QA-induced brain damage. Our study contributes to the functional imaging of multiple events during the pathological process., (© 2021. The Author(s).)

The high and persistent radioactivity levels in the kidney constitute a long-unsettled problem of radiolabeled peptides and low molecular weight (LMW) polypeptides, especially when they are labeled with metallic radionuclides. To address the issue, we proposed an approach to liberate a radiometabolite of urinary excretion from covalently conjugated antibody Fab fragments, used as a representative LMW polypeptide, by the action of enzymes present on the brush border membrane of renal tubules. In this review, The history of our approach, starting from radioiodine to metallic radionuclides such as 188 Re, 99m Tc, 67/68 Ga, and 111 In, will be briefly described. The future perspective of this approach will also be described., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The high and persistent renal radioactivity levels after injection of radiolabeled low-molecular-weight polypeptides constitute a significant problem for their diagnostic and therapeutic applications, especially when they are labeled with metallic radionuclides. To improve the renal radioactivity levels of technetium-99m ( 99m Tc)-labeled Fab fragments, a mercaptoacetyltriglycine (MAG 3 )-based new bifunctional chelating agent with a cleavable glycyl-phenylalanyl-lysine (GFK) linkage, MAG 3 -GFK-suc-TFP, was designed, synthesized, and evaluated. 99m Tc-labeled Fab was obtained by reacting MAG 3 -GFK-Fab conjugate with 99m Tc-glucarate. The GFK linkage remained stable in plasma but was cleaved by enzymes on the renal brush border membrane. The comparative biodistribution studies with indium-111 ( 111 In)-labeled Fab using SCN-CHX-A″-DTPA showed that while both radiolabeled Fabs exhibited similar elimination rates from the blood, [ 99m Tc]Tc-MAG 3 -GFK-Fab registered much lower renal radioactivity levels from 30 min post-injection onward due to the release and subsequent urinary excretion of [ 99m Tc]Tc-MAG 3 -Gly. However, [ 99m Tc]Tc-MAG 3 -GFK-Fab showed an increase in the intestinal radioactivity levels with the time that was not observed with 111 In-labeled Fab. The analysis of the intestinal contents suggested the redistribution of [ 99m Tc]Tc-MAG 3 -Gly to the intestine. The retrospective comparison of [ 99m Tc]Tc-MAG 3 -GFK-Fab with the radiolabeled Fabs so far prepared under the identical concept suggested that some portion of [ 99m Tc]Tc-MAG 3 -Gly was generated after the coated vesicle formation and they were excreted into the blood, and subsequently redistributed in the intestine via hepatobiliary excretion. In conclusion, MAG 3 -GFK-suc-TFP provided 99m Tc-labeled Fabs that exhibit low renal radioactivity shortly after injection by the post-labeling procedure. The present study indicated that, contrary to our earlier proposal, the generation of the radiometabolites would proceed not only during the internalization process of the parental antibody fragments but also after coated vesicle formation. This study also showed that the intracellular behaviors of radiometabolites played crucial roles in the elimination rates and the routes of the radioactivity from the kidney.

Introduction: Targeted α-radionuclide therapy has attracted attention as a promising therapy for refractory cancers. However, the application is limited to certain types of cancer. Since L-type amino acid transporter 1 (LAT1) is highly expressed in various human cancers, we prepared an LAT1-selective α-radionuclide-labeled amino acid analog, 2-[ 211 At]astato-α-methyl-L-phenylalanine (2-[ 211 At]AAMP), and evaluated its potential as a therapeutic agent., Methods: 2-[ 211 At]AAMP was prepared from the stannyl precursor. Stability of 2-[ 211 At]AAMP was evaluated both in vitro and in vivo. In vitro studies using an LAT1-expressing human ovarian cancer cell line, SKOV3, were performed to evaluate cellular uptake and cytotoxicity of 2-[ 211 At]AAMP. Biodistribution and therapeutic studies in SKOV3-bearing mice were performed after intravenous injection of 2-[ 211 At]AAMP., Results: 2-[ 211 At]AAMP was stable in murine plasma in vitro and excreted intact into urine. Cellular uptake of 2-[ 211 At]AAMP was inhibited by treatment with an LAT1-selective inhibitor. After 24 h incubation, 2-[ 211 At]AAMP suppressed clonogenic growth at 10 kBq/ml, and induced cell death and DNA double-strand breaks at 25 kBq/ml. When injected into mice, 2-[ 211 At]AAMP exhibited peak accumulation in the tumor at 30 min postinjection, and radioactivity levels in the tumor were retained up to 60 min. The majority of the radioactivity was rapidly eliminated from the body into urine in an intact form immediately after injection. 2-[ 211 At]AAMP significantly improved the survival of mice (P < 0.05) without serious side effects., Conclusion: 2-[ 211 At]AAMP showed α-radiation-dependent cellular growth inhibition after it was taken up via LAT1. In addition, 2-[ 211 At]AAMP had a beneficial effect on survival in vivo. These findings suggest that 2-[ 211 At]AAMP would be useful for the treatment of LAT1-positive cancer., Advances in Knowledge and Implications for Patient Care: This is the first report of an LAT1-targeting radiopharmaceutical for α-radionuclide therapy; this agent would be applicable for the treatment of various types of cancer., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Introduction: 99m Tc-labeled hexavalent probes can be readily synthesized by the coordination of six equivalent isocyanide ligands towards Tc I , and alkyl isocyanide ligands have been extensively used for preparing such probes. However, high ligand concentration (>1 mM) is generally required due to their insufficient coordination ability to Tc I ., Methods and Results: In this study, we revealed that aryl isocyanide ligands, which have greater π-accepting ability compared with alkyl ones, provided 99m Tc-labeled hexavalent probes in high radiochemical yields (>95%) even at low ligand concentration (50 μM). We applied this finding to the synthesis of a 99m Tc-labeled hexavalent RGD probe, targeting integrin α v β 3 . This 99m Tc-labeled probe was prepared in a 5 min reaction at ligand concentration of 50 μM, and exhibited high tumor localization in vivo without post-labeling purification., Conclusion: The present findings indicate that aryl isocyanide ligands would be a useful precursor to a variety of 99m Tc-labeled hexavalent targeting probes for molecular imaging of saturable systems., Advances in Knowledge: Aryl isocyanide is a better precursor than alkyl isocyanide for preparing 99m Tc-labeled hexavalent targeting probe., Implication for Patient Care: This work provides a straightforward method to prepare molecular imaging agents of high target uptake, which would facilitate nuclear medicine imaging in clinical settings., Competing Interests: Declaration of competing interest The authors declare no competing financial interest., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The accumulation of 99m Tc-labeled probes targeting saturable systems of the body is hindered by the presence of a large excess of unlabeled ligands needed to ensure high radiochemical yields in a short reaction time. To address the issue, we recently reported a novel concept of a metal-coordination-mediated synthesis of a bivalent 99m Tc-labeled probe from a monovalent ligand using d-penicillamine (Pen) as a chelating molecule and c(RGDfK) as a model targeting device. The Pen-conjugated c(RGDfK) via a hexanoate linkage (Pen-Hx-c(RGDfK)) provided a bivalent [ 99m Tc]Tc-[(Pen-Hx-c(RGDfK)) 2 that possessed much higher integrin α v β 3 binding affinity than Pen-Hx-c(RGDfK) and visualized a murine tumor without purification. However, high radioactivity levels were observed in the abdominal regions, which necessitated improved pharmacokinetics of the probes for practical applications. In this study, a pharmacokinetic (PK) modifier was introduced to manipulate the pharmacokinetics of the 99m Tc-Pen 2 -based bivalent probe. The Hx linkage in Pen-Hx-c(RGDfK) was replaced with acetyl-d-serine-d-serine-glycine (Ac-ssG) or hexanoyl-d-serine-d-serine-d-serine (Hx-sss) to prepare Pen-Ac-ssG-c(RGDfK) or Pen-Hx-sss-c(RGDfK). Pen-Ac-ssG-c(RGDfK) impaired the complexation ability of Pen-Hx-c(RGDfK), and a monovalent 99m Tc-labeled compound was generated at low ligand concentration. However, Pen-Hx-sss-c(RGDfK) provided the objective bivalent 99m Tc-labeled probe in high radiochemical yields at a concentration similar to that of Pen-Hx-c(RGDfK). [ 99m Tc]Tc-[Pen-Hx-sss-c(RGDfK)] 2 also possessed stability and integrin α v β 3 binding affinity similar to those of [ 99m Tc]Tc-[Pen-Hx-c(RGDfK)] 2 . As a result, [ 99m Tc]Tc-[Pen-Hx-sss-c(RGDfK)] 2 exhibited tumor and abdominal radioactivity levels similar to and significantly lower than those of [ 99m Tc]Tc-[Pen-Hx-c(RGDfK)] 2 . These findings indicate the incorporation of a tripeptide PK modifier to Pen-Hx-c(RGDfK) preserved the complexation ability and improved the pharmacokinetics of the resulting 99m Tc-labeled bivalent probe without impairing the targeting ability. Thus, the [Pen-Hx-(PK modifier)-(targeting device)] would constitute a basic formulation for preparing the 99m Tc-Pen 2 -based bivalent probes for imaging saturable targets of the body.

Dihydromethidine (DHM) labeled with 18F at the para position of the peripheral benzene ring was designed as a positron emission tomography (PET) radiotracer for non-invasive imaging of reactive oxygen species (ROS). This compound readily crosses the blood-brain barrier and is oxidized by ROS, and the oxidation product is retained intracellularly. PET imaging of ROS-producing rat brain microinfused with sodium nitroprusside identified specific brain regions with high ROS concentrations. This tracer should be useful for studies of the pathophysiological roles of ROS, and in the diagnosis of neurodegenerative diseases.

Background: Recently, antiprogrammed cell death protein 1 (aPD-1) and antiprogrammed death-ligand 1 (aPD-L1) monoclonal antibodies (mAbs) have been approved. Even though aPD-1 and aPD-L1 mAbs target the same PD-1/PD-L1 axis, it is still unclear whether both mAbs exert equivalent pharmacological activity in patients who are sensitive to PD-1/PD-L1 blockade therapy, as there is no direct comparison of their pharmacokinetics (PK) and antitumor effects. Therefore, we evaluated the differences between both mAbs in PK and therapeutic effects in PD-1/PD-L1 blockade-sensitive mouse models., Methods: Herein, murine breast MM48 and colon MC38 xenografts were used to analyze the pharmacological activity of aPD-1 and aPD-L1 mAbs. The PK of the mAbs in the tumor-bearing mice was investigated at low and high doses using two radioisotopes (Indium-111 and Iodine-125) to evaluate the accumulation and degradation of the mAbs., Results: aPD-1 mAb showed antitumor effect in a dose-dependent manner, indicating that the tumor model was sensitive to PD-1/PD-L1 blockade therapy, whereas aPD-L1 mAb failed to suppress tumor growth. The PK study showed that aPD-L1 mAb was accumulated largely in normal organs such as the spleen, liver, and kidney, resulting in low blood concentration and low distributions to tumors at a low dose, even though the tumors expressed PD-L1. Sufficient accumulation of aPD-L1 mAb in tumors was achieved by administration at a high dose owing to the saturation of target-mediated binding in healthy organs. However, degradation of aPD-L1 mAb in tumors was greater than that of aPD-1 mAb, which resulted in poor outcome presumably due to less inhibition of PD-L1 by aPD-L1 mAb than that of PD-1 by aPD-1 mAb., Conclusion: According to the PK studies, aPD-1 mAb showed linear PK, whereas aPD-L1 mAb showed non-linear PK between low and high doses. Collectively, the poor PK characteristics of aPD-L1 mAb caused lower antitumor activity than of aPD-1 mAb. These results clearly indicated that aPD-L1 mAb required higher doses than aPD-1 mAb in clinical setting. Thus, targeting of PD-1 would be more advantageous than PD-L1 in terms of PK., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

The diaminedithiol (N 2 S 2 ) tetradentate ligand constitutes a useful chelating molecule for preparing 99m Tc-labeled compounds of high in vivo stability in high radiochemical yields. However, since the thiol groups in the N 2 S 2 ligand are easy to be oxidized to disulfide bonds, they need to be protected with an appropriate protecting group, which hinders the broad applications of the N 2 S 2 ligand for radiopharmaceuticals. In this study, a Zn chelate of N 2 S 2 was evaluated as a precursor for purification-free 99m Tc-labeled N 2 S 2 under the mild and simple procedure. Zn-N 2 S 2 was prepared by reacting Zn acetate with N 2 S 2 , and the Zn-N 2 S 2 remained stable under aerobic conditions at room temperature. 99m Tc-N 2 S 2 was obtained over 90% radiochemical yields at room temperature by a one-pot reaction, consisting of Zn-N 2 S 2 (10 -5 M), 99m TcO 4 - , ethylenediaminetetraacetic acid (EDTA), and a reducing agent (Sn 2+ ) at pH = 5.5 to 7.5. 99m Tc-N 2 S 2 was also obtained over 90% radiochemical yields when the reaction was conducted in the presence of an equimolar amount of IgG antibody. These findings indicate the Zn complex of N 2 S 2 ligand constitutes a stable and useful precursor to prepare 99m Tc-labeled N 2 S 2 compounds in high yields under the mild and simple procedure.

C-X-C chemokine receptor type 4 (CXCR4) constitutes a promising target for tumor diagnosis and therapy. Herein, we evaluate a new 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-conjugated CXCR4 antagonist derived from LY2510924, FRM001, and its metal complexes as CXCR4-targeting probes. FRM001 was synthesized by modifying the C-terminus of LY2510924 with maleimido-mono-amide-DOTA via a cysteine linker. FRM001 exhibited CXCR4-specific binding with an affinity similar to that of the parental LY2510924. The binding affinity of FRM001 remained unchanged after complexation with Ga, Lu, and Y. The internalization of 67 Ga-FRM001 into the cells was hardly observed. In mice biodistribution studies, 67 Ga-FRM001 exhibited high accumulation in the tumor and the liver with rapid elimination rates from the blood. The hepatic accumulation of 67 Ga-FRM001 was preferentially and significantly reduced by co-injecting a CXCR4 antagonist, AMD3100. The C-terminal-modified LY2510924 would constitute a versatile scaffold to develop CXCR4-targeting probes or therapeutics for tumor imaging or therapy.

The presence of excess unlabeled ligands in the injectate hinders the target uptake of 99m Tc-labeled targeting vectors. To address the issue, we previously developed a chemical design which provides a 99m Tc-labeled trivalent RGD probe upon CN-βAla-Gly-Gly-c(RGDfK) (L β ) coordination to [ 99m Tc][Tc(CO) 3 ] + core at pH 6.0. In this study, we extended our coordination mediated synthesis of the trivalent RGD probe to that of a tetravalent one. Our initial attempts reacting L β with [ 99m Tc][Tc(CO) 3 ] + core at pH 8.0 failed to provide [ 99m Tc][Tc(CO) 2 (L β ) 4 ] + due to the formation of multiple side products. A γ-aminobutylic acid (GABA) based isonitrile ligand CN-GABA-Gly-Gly-c(RGDfK) (L G ), on the other hand, avoided the side reaction and selectively provided [ 99m Tc][Tc(CO) 2 (L G ) 4 ] + ( 99m Tc-[L G ] 4 ) at pH 8.0. 99m Tc-[L G ] 4 exhibited higher binding affinity to integrin α v β 3 than its unlabeled ligand, and visualized U87MG tumor without tedious post-labeling purification. These results indicate that the metal coordination-mediated syntheses of 99m Tc-labeled multivalent probes have been successfully applied to a tetravalent one, which would allow a wider range of choices for designing novel 99m Tc-labeled multivalent probes of high in vivo target uptake., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Positron emission tomography (PET) imaging with 18 F-labeled α-methyl-substituted amino acids exerts significant influence on differential diagnosis of malignant tumors and tumor-like lesions. Exclusive uptake via L-type amino acid transporter 1 (LAT1), a tumor-specific transporter, accounts for their excellent tumor specificity and low background accumulation. However, further refinement and optimization in their tumor accumulation and pharmacokinetics are sorely needed. To address these issues, we newly designed 18 F-labeled α-methyl-phenylalanine ( 18 F-FAMP) regioisomers (2-, 3-, or 4- 18 F-FAMP) and stereoisomers (L- or D-form), and we comprehensively evaluated their potential as tumor-imaging agents. 18 F-FAMPs were prepared from α-methyl phenylalanine by electrophilic radiofluorination and purified by reversed-phase HPLC. In biodistribution studies on normal mice, L-2- 18 F-FAMP and the three D- 18 F-FAMPs showed faster blood clearance and lower renal accumulation than L-3- 18 F-FAMP or L-4- 18 F-FAMP. In LS180 human colorectal cancer cell line xenograft mice, L-2- 18 F-FAMP exhibited significantly higher tumor accumulation than the D- 18 F-FAMPs or a clinically relevant tracer, L-3- 18 F-α-methyl-tyrosine ( 18 F-FAMT) ( p < 0.05). The renal accumulation levels of L-2- 18 F-FAMP were significantly lower than that of 18 F-FAMT ( p < 0.01). LAT-1 specificity of L-2- 18 F-FAMP was validated in the cellular uptake studies. The PET imaging with L-2- 18 F-FAMP clearly visualized the tumor as early as 1 h after injection, and the high tumor accumulation level was retained for 3 h. These findings suggest that L-2- 18 F-FAMP constitutes a potential PET tracer for tumor-specific imaging.

Inflammation after myocardial infarction (MI) may be a major factor influencing ventricular remodeling, leading to congestive heart failure and arrhythmia. Therefore, inflammation in the heart needs to be monitored. Tenascin-C (TNC) is an extracellular matrix molecule not normally expressed, but it is strongly upregulated when associated with active inflammation. Based on this characteristic, we successfully imaged in vivo inflammatory lesions in rat models using 111 Indium ( 111 In)-labeled anti-TNC antibodies. The aim of the present study was to further assess the applicability of this molecular imaging probe to detect inflammatory activity in primate hearts.We generated an MI model of cynomolgus monkeys (Macaca fascicularis) by coronary artery ligation and performed dual-isotope single-photon emission computed tomography (SPECT) imaging with an 111 In-labeled anti-TNC antibody Fab' fragment ( 111 In-TNC Fab') and 99m technetium methoxy-isobutyl isonitrile ( 99m Tc-MIBI). Dual autoradiography was used to compare the uptake of 111 In-TNC Fab' with histology and immunostaining for TNC. Dual-isotope SPECT showed the regional myocardial uptake of 111 In-TNC Fab' complementary to a defect in the perfusion image by 99m Tc-MIBI. The high radioactivity of 111 In-TNC Fab' by autoradiography corresponded to immunostaining for TNC, which was observed in inflammatory lesions at the border zone between the infarcted and non-infarcted areas of the left ventricle and at the epi/pericarditis lesions of the right ventricle. These results demonstrate the potential of 111 In-TNC-Fab' imaging to monitor myocardial injury and inflammation and suggest the feasibility of the non-invasive detection of cardiac inflammation following acute MI in a preclinical stage before testing in humans.

Objective: Oxidative stress plays an important role in the onset of many neuronal and peripheral disorders. We examined the feasibility of obtaining semiquantitative fluorescent images of reactive oxygen species (ROS) generation in mouse brain and kidney utilizing a planar laser scanner and dihydroethidium (DHE)., Methods: To investigate ROS generation in brain, sodium nitroprusside was injected into the striatum. Dihydroethidium was injected into the tail vein. After DHE injection, tissue slices were analyzed utilizing a planar laser scanner. For kidney study, cis-diamminedichloroplatinum [II] (cisplatin) was intraperitoneally administrated into mice., Results: Clear and semiquantitative fluorescent images of ROS generation in the mouse brain and kidney were obtained. Furthermore, the fluorescence intensity was stable and not affected by fading. Sodium nitroprusside induced approximately 6 times the fluorescence accumulation in the brain. Cisplatin caused renal injury in all mice, and in comparison with control mice, more than 10 times fluorescence accumulation was observed in the renal medulla with tubular necrosis and vacuolization., Conclusions: We successfully obtained ex vivo semiquantitative fluorescent images of ROS generation utilizing a planar laser scanner and DHE. This simple method is useful for ROS detection in several ROS-related animal models and would be applicable to a variety of biochemical processes.

Macrophage mannose receptor (MMR/CD206) is a promising target for the detection and identification of sentinel lymph node (SLN). MMR-targeting probes have been developed using mannosylated dextran, however, impairment of efficient targeting of SLN was often caused because of retention of injection site in which macrophages and dendritic cells exist. In this study, we prepared new MMR-targeting probes from yeast mannan (85 kDa), and its bioditribution was investigated. In-vivo evaluation showed that 11.9% of injected dose of 99m Tc-labeled mannan-S-cysteines ( 99m Tc-MSCs) was accumulated in popliteal lymph node (the SLN in this model), however, significant level of radioactivity (approximately 80%) was remained in injection site. Interestingly, 99m Tc-labeled low molecular weight mannan-S-cysteine mannan ( 99m Tc-LSC) prepared from 50 and 25 kDa mannan showed a decreased specific accumulation of 99m Tc-LSC in the popliteal lymph node, while the radioactivity at the injection site remained unchanged. These results suggest that the molecular size, or nature/shape of the sugar chain is important for the specific accumulation of 99m Tc-MSC in popliteal lymph node.

A large excess of unlabeled ligands over gallium-67 ( 67 Ga) provides 67 Ga-labeled probes with high radiochemical yields in a short reaction time. However, the unlabeled ligands hinder target accumulation of radiolabeled probes by competing for target molecules. To circumvent the problem, we investigated the way to prepare 67 Ga-labeled multivalent probes from monovalent ligands. The reaction of a bi- or tridentate ligand with [ 67 Ga]Ga-citrate resulted in 67 Ga-labeled probes of insufficient stability. However, the reaction of [ 67 Ga]Ga-citrate with a mixture of RGD-conjugated salicylaldehyde and triamine provided a 67 Ga-labeled trivalent probe with stability sufficient for in vivo applications. Since the free Schiff base ligand decomposed rapidly upon injection, the 67 Ga-labeled trivalent probe visualized the murine tumor without postlabeling purification, which was not achieved with a 67 Ga-labeled trivalent probe from a trivalent ligand. These findings indicate the availability of Schiff base ligands to prepare 67 Ga-labeled trivalent probes by a simple radiolabeling procedure.

Purpose: This study was undertaken to evaluate the renal radioactivity levels of a newly designed 67 Ga-labeled antibody fragment with a linkage cleaved by enzymes present on the brush border membrane (BBM) lining the lumen of the renal tubule. Experimental Design: 67 Ga-labeled S-2-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (SCN-Bn-NOTA) was conjugated with an antibody Fab fragment through a Met-Val-Lys linkage ( 67 Ga-NOTA-MVK-Fab) considering that a Met-Val sequence is a substrate of enzymes on the renal BBM and 67 Ga-NOTA-Met is excreted from the kidney into the urine. The enzymatic recognition of the linkage was evaluated with a low-molecular-weight 67 Ga-NOTA-Met-Val-Lys derivative. Biodistribution of radioactivity after injection of 67 Ga-NOTA-MVK-Fab into mice was compared with 67 Ga-NOTA-conjugated Fab fragments through a Met-Ile linkage that liberates 67 Ga-NOTA-Met ( 67 Ga-NOTA-MI-Fab) or a conventional thiourea linkage ( 67 Ga-NOTA-Fab). Results: The MVK linkage remained stable in plasma and was recognized by enzymes on renal BBM to liberate 67 Ga-NOTA-Met. When injected into mice, all three 67 Ga-labeled Fab exhibited similar blood clearance rates and tumor accumulation. Significant differences were observed in the kidney where 67 Ga-NOTA-MVK-Fab registered the lowest renal radioactivity levels from early postinjection time ( P < 0.05), followed by 67 Ga-NOTA-MI-Fab, which was well reflected in the SPECT/CT images. Conclusions: These findings indicated that our proposal of liberating a radiolabeled compound to urinary excretion from antibody fragments at the renal BBM to reduce the renal radioactivity levels was applicable to 67/68 Ga-labeled antibody fragments. Because antibody fragments and constructs share similar metabolic fates in the kidney, the present labeling procedure would also apply to a variety of antibody fragments and constructs of interest. Clin Cancer Res; 24(14); 3309-16. ©2018 AACR ., (©2018 American Association for Cancer Research.)

The obstructive renal radioactivity after injection of antibody fragments/constructs labeled with metallic radionuclides would be improved by liberating a radiometal chelate of urinary excretion from the antibody molecules by enzymes on the renal brush border membrane (BBM). A tripeptide GFK sequence was newly evaluated as an enzyme-cleavable linkage and conjugated to a 99m Tc chelate of an isonicotinic acid derivative of 2-picolylglycine ( 99m Tc-IPG). 99m Tc-IPG-glycine was liberated from 99m Tc-IPG-GFK by the enzymes, while 99m Tc-IPG-GK (where the tripeptide GFK was substituted with a dipeptide GK) did not. When injected into mice, 99m Tc-IPG-GFK-conjugated Fab exhibited lower renal radioactivity levels than directly radioiodinated Fab shortly after injection without reducing the tumor radioactivity levels, due to a release and excretion of 99m Tc-IPG-glycine by enzymes present on the renal BBM. These findings would provide insights to develop antibody fragments/constructs labeled with metallic radionuclides of the clinical relevance for improved renal radioactivity levels.

In this study, we synthesized of a series of 2-phenyl- and 2-pyridyl-imidazo[1,2- a]pyridine derivatives and examine their suitability as novel probes for single-photon emission computed tomography (SPECT)-based imaging of β-amyloid (Aβ). Among the 11 evaluated compounds, 10 showed moderate affinity to Aβ(1-42) aggregates, exhibiting half-maximal inhibitory concentrations (IC 50 ) of 14.7 ± 6.07-87.6 ± 39.8 nM. In vitro autoradiography indicated that 123 I-labeled triazole-substituted derivatives displayed highly selective binding to Aβ plaques in the hippocampal region of Alzheimer's disease (AD)-affected brain. Moreover, biodistribution studies performed on normal rats demonstrated that all 123 I-labeled probes featured high initial uptake into the brain followed by a rapid washout and were thus well suited for imaging Aβ plaques, with the highest selectivity observed for a 1 H-1,2,3-triazole-substituted 2-pyridyl-imidazopyridine derivative, [ 123 I]ABC577. This compound showed good kinetics in rat brain as well as moderate in vivo stability in rats and is thus a promising SPECT imaging probe for AD in clinical settings.

In the synthesis of technetium-99m ( 99m Tc) labeled target-specific ligands, the presence of a large excess of unlabeled ligands over 99m Tc in the injectate hinders target accumulation of 99m Tc-labeled ligands by competing for target molecules. To circumvent the problem, we recently developed a concept of the metal coordination-mediated multivalency, and proved the concept with a 99m Tc-labeled trivalent compound [ 99m Tc(CO) 3 (CN-RGD) 3 ] + . In this study, D-penicillamine (Pen) was selected as a chelating molecule and a cyclic RGDfK peptide was conjugated to Pen via a hexanoic linkage (Pen-Ahx-c(RGDfK)). 99m Tc complexation reaction, and the stability, integrin α v β 3 binding affinity, and biodistribution of the 99m Tc-labeled probe were investigated to evaluate the applicability of the concept to bivalent probes. 99m Tc-[Pen-Ahx-c(RGDfK)] 2 was obtained over 95% radiochemical yields under low Pen-Ahx-c(RGDfK) concentration (50 μM). 99m Tc-[Pen-Ahx-c(RGDfK)] 2 showed approximately 10-times higher integrin α v β 3 binding affinity than the monovalent compounds, Pen-Ahx-c(RGDfK) and c(RGDyV). In biodistribution studies, the tumor accumulation of 99m Tc-[Pen-Ahx-c(RGDfK)] 2 was decreased to 77% and 43% of HPLC-purified (Pen-Ahx-c(RGDfK)-free) 99m Tc-[Pen-Ahx-c(RGDfK)] 2 by the presence of 5 nmol of unlabeled Pen-Ahx-c(RGDfK) and Re-[Pen-Ahx-c(RGDfK)] 2 , respectively. 99m Tc-[Pen-Ahx-c(RGDfK)] 2 provided tumor image without removing unlabeled ligand, while a 99m Tc-labeled monovalent probe prepared from a monovalent ligand could not. These findings indicate the availability of the design concept to prepare 99m Tc-labeled bivalent probes with a variety of 99m Tc core and other metallic radionuclides of clinical relevance.

Introduction: 111 In-DTPA-d-Phe 1 -octreotide scintigraphy is an important method of detecting neuroendocrine tumors. We previously reported that a new derivative of 111 In-DTPA-d-Phe 1 -octreotide, 111 In-DTPA-d-Phe -1 -Asp 0 -d-Phe 1 -octreotide, accomplished the reduction of prolonged renal accumulation of radioactivity. The aim of this study was to evaluate the tumor accumulation of 111 In-DTPA-d-Phe -1 -Asp 0 -d-Phe 1 -octreotide in vitro and in vivo by comparing it with 111 In-DTPA-d-Phe 1 -octreotide., Methods: The tumor accumulation of this octreotide derivative was determined by measuring its uptake using cultured AR42J cells in vitro and biodistribution studies in vivo. The distribution of the radiotracer and the extent of somatostatin receptor-specific uptake in the tumor were estimated by a counting method using AR42J tumor-bearing mice. The radioactive metabolite species in the tumor and kidney were identified by HPLC analyses at 3 and 24h post-injection of the 111 In-DTPA-conjugated peptide., Results: In both cases, in vitro and in vivo, the tumor radioactivity levels of 111 In-DTPA-d-Phe -1 -Asp 0 -d-Phe 1 -octreotide were approximately 2-4 times higher than those of 111 In-DTPA-d-Phe 1 -octreotide. On in vitro cellular uptake inhibition and radioreceptor assay, 111 In-DTPA-d-Phe -1 -Asp 0 -d-Phe 1 -octreotide exhibited a binding affinity to somatostatin receptor highly similar to that of 111 In-DTPA-d-Phe 1 -octreotide. As the additional cellular uptake of 111 In-DTPA-d-Phe -1 -Asp 0 -d-Phe 1 -octreotide was significantly lower at low temperature than at 37°C, it was considered that a cellular uptake pathway is involved in energy-dependent endocytotic processes. In the radiometabolite analysis of 111 In-DTPA-d-Phe -1 -Asp 0 -d-Phe 1 -octreotide, 111 In-DTPA-d-Phe-Asp-OH was a major metabolite in the tumor at 24h post-injection., Conclusion: 111 In-DTPA-d-Phe -1 -Asp 0 -d-Phe 1 -octreotide exhibited higher tumor accumulation and persistence of tumor radioactivity than 111 In-DTPA-d-Phe 1 -octreotide. We reasoned that this higher tumor accumulation would not be based on the receptor affinity but on a receptor-mediated endocytotic process involved in temperature-dependent cellular uptake. The present study demonstrated the great potential of the pharmaceutical development of a new radiolabeled peptide with high tumor accumulation and low renal radioactivity by the chemical modification of 111 In-DTPA-d-Phe 1 -octreotide., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Upregulated monocarboxylate transporters (MCTs) in tumors are considered diagnostic imaging targets. Herein, we synthesized the positron emission tomography probe candidates coumarin analogs 2 and 3, and showed 55 times higher affinity of 2 for MCTs than a representative MCT inhibitor. Whereas [ 11 C]2 showed low tumor accumulation, probably due to adduct formation with plasma proteins, [ 11 C]2 showed high initial brain uptake, suggesting that the scaffold of 2 has properties that are preferable in imaging probes for the astrocyte-neuron lactate shuttle. Although further optimization of 2 is required, our findings can be used to inform the development of MCT-targeted imaging agents., (Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Introduction: Radiolabeled octreotide derivatives have been studied as diagnostic and therapeutic agents for somatostatin receptor-positive tumors. To prevent unnecessary radiation exposure during their clinical application, the present study aimed to develop radiolabeled peptides which could reduce radioactivity levels in the kidney at both early and late post-injection time points by introducing a negative charge with an acidic amino acid such as L-aspartic acid (Asp) at a suitable position in 111 In-DTPA-conjugated octreotide derivatives., Methods: Biodistribution of the radioactivity was evaluated in normal mice after administration of a novel radiolabeled peptide by a counting method. The radiolabeled species remaining in the kidney were identified by comparing their HPLC data with those obtained by alternative synthesis., Results: The designed and synthesized radiolabeled peptide 111 In-DTPA-d-Phe -1 -Asp 0 -d-Phe 1 -octreotide exhibited significantly lower renal radioactivity levels than those of the known 111 In-DTPA-d-Phe 1 -octreotide at 3 and 24h post-injection. The radiolabeled species in the kidney at 24h after the injection of new octreotide derivative represented 111 In-DTPA-d-Phe-OH and 111 In-DTPA-d-Phe-Asp-OH as the metabolites. Their radiometabolites and intact 111 In-DTPA-conjugated octreotide derivative were observed in urine within 24h post-injection., Conclusion: The present study provided a new example of an 111 In-DTPA-conjugated octreotide derivative having the characteristics of both reduced renal uptake and shortened residence time of radioactivity in the kidney. It is considered that this kinetic control was achieved by introducing a negative charge on the octreotide derivative thereby suppressing the reabsorption in the renal tubules and affording the radiometabolites with appropriate lipophilicity., (Copyright © 2017 Elsevier Inc. All rights reserved.)

L-[methyl-11C]Methionine (11C-Met) is useful for estimating the therapeutic efficacy of particle radiotherapy at early stages of the treatment. Given the short half-life of 11C, the development of longer-lived 18F- and 123I-labeled probes that afford diagnostic information similar to 11C-Met, are being sought. Tumor uptake of 11C-Met is involved in many cellular functions such as amino acid transport System-L, protein synthesis, and transmethylation. Among these processes, since the energy-dependent intracellular functions involved with 11C-Met are more reflective of the radiotherapeutic effects, we evaluated the activity of the amino acid transport System-A as an another energy-dependent cellular function in order to estimate radiotherapeutic effects. In this study, using a carbon-ion beam as the radiation source, the activity of System-A was evaluated by a specific System-A substrate, alpha-[1-14C]-methyl-aminoisobutyric acid (14C-MeAIB). Cellular growth and the accumulation of 14C-MeAIB or 14C-Met were evaluated over time in vitro in cultured human salivary gland (HSG) tumor cells (3-Gy) or in vivo in murine xenografts of HSG tumors (6- or 25-Gy) before and after irradiation with the carbon-ion beam. Post 3-Gy irradiation, in vitro accumulation of 14C-Met and 14C-MeAIB decreased over a 5-day period. In xenografts of HSG tumors in mice, tumor re-growth was observed in vivo on day-10 after a 6-Gy irradiation dose, but no re-growth was detected after the 25-Gy irradiation dose. Consistent with the growth results, the in vivo tumor accumulation of 14C-MeAIB did not decrease after the 6-Gy irradiation dose, whereas a significant decrease was observed after the 25-Gy irradiation dose. These results indicate that the activity of energy dependent System-A transporter may reflect the therapeutic efficacy of carbon-ion radiotherapy and suggests that longer half-life radionuclide-labeled probes for System-A may also provide widely available probes to evaluate the effects of particle radiotherapy on tumors at early stage of the treatment.

Metallic radionuclides provide target-specific radiolabeled probes for molecular imaging in radiochemical yields sufficient for administration to subjects without purification. However, unlabeled ligands in the injectate can compete for targeted molecules with radiolabeled probes, which eventually necessitates postlabeling purification. Herein we describe a "1 to 3" design to circumvent the issue by taking advantage of inherent coordination properties of technetium-99m ((99m)Tc). A monovalent RGD ligand possessing an isonitrile as a coordinating moiety (CN-RGD) was reacted with [(99m)Tc(CO)3(OH2)3](+) to prepare [(99m)Tc(CO)3(CN-RGD)3](+) in over 95% radiochemical yields. This complex exhibited higher integrin αvβ3 binding affinity than its unlabeled monovalent ligand, primarily due to its multivalency. This compound visualized a murine tumor without removing unlabeled ligands, while a (99m)Tc-labeled monovalent probe derived from a monovalent ligand could not. The metal coordination-mediated synthesis of radiolabeled multivalent probes thereby can be a useful approach for preparing ready-to-use target-specific probes labeled with (99m)Tc and other metallic radionuclides of interest.

This survey was performed in order to investigate the incidence of adverse reactions to radiopharmaceuticals in FY2014 in Japan. It was based on the responses to questionnaires sent to nuclear medicine institutions. The reply was obtained from 992 institutions among 1,244 to which the questionnaire had been sent. Nine cases of adverse reactions were reported. A total of 1,091,011 radiopharmaceutical administrations were reported. The incidence of adverse reactions per 100,000 case was 0.8. Three cases of deficient products were reported, and the incidence of deficient products per 100,000 case was 0.3.

Unlabelled: Radiolabeled amino acids are superior PET tracers for the imaging of malignant tumors, and amino acids labeled with (76)Br, an attractive positron emitter because of its relatively long half-life (16.2 h), could potentially be a widely usable tumor imaging tracer. In this study, in consideration of its stability and tumor specificity, we designed two (76)Br-labeled amino acid derivatives, 2-(76)Br-bromo-α-methyl-l-phenylalanine (2-(76)Br-BAMP) and 4-(76)Br-bromo-α-methyl-l-phenylalanine (4-(76)Br-BAMP), and investigated their potential as tumor imaging agents., Methods: Both (76)Br- and (77)Br-labeled amino acid derivatives were prepared. We performed in vitro and in vivo stability studies and cellular uptake studies using the LS180 colon adenocarcinoma cell line. Biodistribution studies in normal mice and in LS180 tumor-bearing mice were performed, and the tumors were imaged with a small-animal PET scanner., Results: Both (77)Br-BAMPs were stable in the plasma and in the murine body. Although both (77)Br-BAMPs were taken up by LS180 cells and the uptake was inhibited by L-type amino acid transporter 1 inhibitors, 2-(77)Br-BAMP exhibited higher uptake than 4-(77)Br-BAMP. In the biodistribution studies, 2-(77)Br-BAMP showed more rapid blood clearance and lower renal accumulation than 4-(77)Br-BAMP. More than 90% of the injected radioactivity was excreted in the urine by 6 h after the injection of 2-(77)Br-BAMP. High tumor accumulation of 2-(77)Br-BAMP was observed in tumor-bearing mice, and PET imaging with 2-(76)Br-BAMP enabled clear visualization of the tumors., Conclusion: 2-(77)Br-BAMP exhibited preferred pharmacokinetics and high LS180 tumor accumulation, and 2-(76)Br-BAMP enabled clear visualization of the tumors by PET imaging. These findings suggest that 2-(76)Br-BAMP could constitute a potential new PET tracer for tumor imaging and may eventually enable the wider use of amino acid tracers., (© 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.)

α-(11) C-Methyl amino acids are useful tools for biological imaging studies. However, a robust procedure for the labeling of amino acids has not yet been established. In this study, the (11) C-methylation of Schiff-base-activated α-amino acid derivatives has been optimized for the radiosynthesis of various α-(11) C-methyl amino acids. The benzophenone imine analog of methyl 2-amino butyrate was (11) C-methylated with [(11) C]methyl iodide following its initial deprotonation with potassium tert-butoxide (KOtBu). The use of an alternative base such as tetrabutylammonium fluoride, triethylamine, and 1,8-diazabicyclo[5.4.0]undec-7-ene did not result in the (11) C-methylated product. Furthermore, the KOtBu-promoted (11) C-methylation of the Schiff-base-activated amino acid analog was enhanced by the addition of 1,2,4,5-tetramethoxybenzene or 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and inhibited by the addition of 1,10-phenanthroline. These results suggest that inhibition of radical generation induced by KOtBu improves the α-(11) C-methylation of the Schiff-base-activated amino acids. The addition of a mixture of KOtBu and TEMPO to a solution of Schiff-base-activated amino acid ester and [(11) C]methyl iodide provided optimal results, and the tert-butyl ester and benzophenone imine groups could be readily hydrolyzed to give the desired α-(11) C-methyl amino acids with a high radiochemical conversion. This strategy could be readily applied to the synthesis of other α-(11) C-methyl amino acids., (Copyright © 2015 John Wiley & Sons, Ltd.)

The high and persistent radioactivity at the injection site hinders the accuracy and expansion of sentinel lymph node (SLN) mapping. We investigated the mechanism underlying the undesirable radioactivity after subcutaneous injection of (99m)Tc-labeled mannosylated dextran ((99m)Tc(CO)3-DCM20), a SLN mapping agent targeting mannose receptors on macrophages and dendritic cells, in a mouse model. Biodistribution studies were performed 1 h after subcutaneous injection of (99m)Tc(CO)3-DCM20 from the rear footpad of mice in the presence of varying molar amounts of DCM20 or DC15, a modified dextran without mannose. Biodistribution studies were also conducted after subcutaneous injection of [(125)I]radioiodinated mannosyl-neoglycoalbumin ((125)I-NMA) from the rear footpad. The distribution of fluorescence-labeled DCM20 and DC15 at the injection site was also compared 1 h after subcutaneous injection by immunofluorescent histochemistry. The radioactivity levels of (99m)Tc(CO)3-DCM20 at the injection site and popliteal lymph node, a SLN in this model, decreased with an increase in the molar amounts of DCM20, whereas no significant changes in biodistribution were observed after injection of (99m)Tc(CO)3-DCM20 with varying molar amounts of DC15. (125)I-NMA exhibited rapid elimination of radioactivity from both the popliteal lymph node and the injection site. The fluorescence-labeled DCM20 colocalized well with CD68-positive cells such as macrophages and dendritic cells at the injection site. While partial colocalization was observed between DC15 and CD68-positive cells, the signal intensity was very weak. These findings suggest that specific binding of (99m)Tc(CO)3-DCM20 to the mannose receptor on macrophages and dendritic cells would be responsible for the sustained radioactivity levels at the injection site. These results also imply that discriminated blockage of (99m)Tc(CO)3-DCM20 binding to mannose receptors at the injection sites would reduce the radioactivity at the injection site.

This survey was performed in order to investigate the incidence of adverse reactions to radiopharmaceuticals in FY2013 in Japan. It was based on responses to questionnaires sent to nuclear medicine institutions. The reply was obtained from 997 institutions among 1,249 to which the questionnaire had been sent. Eight cases of adverse reactions were reported. A total of 1,056,876 radiopharmaceutical administrations was reported. The incidence of adverse reactions per 100,000 cases was 0.8. One case of defect products was reported, and the incidence of defect products per 100,000 cases was 0.1.

Intrinsic drug resistance occurs in many renal carcinomas and is associated with increased expression of multidrug resistant proteins, which inhibits intracellular drug accumulation. Multidrug resistant protein 1, also known as P-glycoprotein, is a membrane drug efflux pump belonging to the ATP-binding cassette (ABC) transporter superfamily. ABC Sub-family B Member 2 (ABCG2) is widely distributed and is involved in the multidrug resistant phenotype. Sunitinib is a tyrosine kinase inhibitor used to treat kidney cancer that disrupts signaling pathways responsible for abnormal cancer cell proliferation and tumor angiogenesis. Multiple drug resistance is important in tyrosine kinase inhibitor-induced resistance. We hypothesized that inhibition of multidrug resistant transporters by elacridar (dual inhibitor of P-glycoprotein and ABCG 2) might overcome sunitinib resistance in experimental renal cell carcinoma. Human renal carcinoma cell lines 786-O, ACHN, and Caki-1 were treated with sunitinib or elacridar alone, or in combination. We showed that elacridar significantly enhanced sunitinib cytotoxicity in 786-O cells. P-glycoprotein activity, confirmed by P-glycoprotein function assay, was found to be inhibited by elacridar. ABCG2 expression was low in all renal carcinoma cell lines, and was suppressed only by combination treatment in 786-O cells. ABCG2 function was inhibited by sunitinib alone or combination with elacridar but not elacridar alone. These findings suggest that sunitinib resistance involves multidrug resistance transporters, and in combination with elacridar, can be reversed in renal carcinoma cells by P-glycoprotein inhibition., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Background: Hepatic mitochondrial dysfunction has been implicated in pathological conditions leading to non-alcoholic steatohepatitis (NASH). Technetium-99 m-2-methoxyisobutyl-isonitrile ((99m)Tc-MIBI), a lipophilic cationic myocardial perfusion agent, is retained in the mitochondria depending on membrane potential. The aim of this study was to investigate the feasibility of (99m)Tc-MIBI for evaluating the hepatic mitochondrial dysfunction induced by methionine-choline-deficient (MCD) diet in mice., Methods: Male C57Black6J/jcl mice were fed a MCD diet for up to 4 weeks. SPECT scan (N =6) with (99m)Tc-MIBI was performed at 2 and 4 weeks after MCD diet. Mice were imaged with small-animal SPECT/CT under isoflurane anesthesia. Radioactivity concentrations of the liver were measured, and the time of maximum (T max) and the elimination half-life (T 1/2) were evaluated. After SPECT scan, liver histopathology was analyzed to evaluate steatosis and inflammation. Non-alcoholic fatty liver disease (NAFLD) activity score was obtained from the histological score of hepatic steatosis and inflammation. Blood biochemistry and hepatic ATP content were also measured (N =5 to 6)., Results: Plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were significantly elevated at 2 and 4 weeks after MCD diet. A decrease in hepatic ATP content was also observed in MCD-fed mice. (99m)Tc-MIBI SPECT imaging clearly showed the decrease of hepatic (99m)Tc-MIBI retention in MCD-fed mice compared to control mice. T 1/2 after (99m)Tc-MIBI injection was significantly decreased in the liver of MCD-fed mice (control, MCD 2 weeks, and MCD 4 weeks, T 1/2 = 57.6, 37.6, and 19.8 min, respectively), although no change in T max was observed in MCD-fed mice. SPECT data and histological score showed that the negative correlation (r = -0.74, p <0.05) between T 1/2 and NAFLD activity score was significant., Conclusions: Hepatic (99m)Tc-MIBI elimination was increased with increase in NAFLD activity score (NAS) in mice fed MCD diet for 2 and 4 weeks. These results suggest that (99m)Tc-MIBI SPECT imaging might be useful for detecting hepatic mitochondrial dysfunction induced by steatosis and inflammation such as NAFLD or NASH.