Jan Rijn Zeevaart

Preclinical Evaluation of 68Ga-Labeled 1,4,7-Triazacyclononane-1,4,7-Triacetic Acid-Ubiquicidin as a Radioligand for PET Infection Imaging

Antimicrobial peptides such as ubiquicidin (UBI) are believed to differentiate between mammalian and bacterial or fungal cells. 99mTc-UBI29-41 was previously tested for detecting infection in humans using SPECT. For the present study, the UBI fragment UBI29-41 (TGRAKRRMQYNRR) was conjugated to 1,4,7-triazacyclononane-triacetic acid (NOTA), radiolabeled with 68Ga, and investigated in a rabbit infection model. Methods: 68Ga was obtained from a 1.85-GBq 68Ge/68Ga generator. New Zealand White rabbits were anesthetized with ketamine/medetomidine before tracer administration and placed in a clinical PET/CT scanner. 68Ga-1,4,7-triazacyclononane-1,4,7-triacetic-acid-ubiquicidin29-41 (68Ga-NOTA-UBI29-41) was formulated in saline solution, and 101 ± 41 MBq were administered intravenously. The tracer distribution was studied by PET/CT imaging in animals (a) that were healthy, (b) bearing muscular Staphylococcus aureus infections and turpentine oil-induced muscular inflammations, and (c) bearing ovalbumin-induced lung inflammations. Static PET/CT imaging was performed at different time intervals up to 120 min after injection. For calculation of target-to-nontarget ratios, standardized uptake values were normalized against healthy thigh muscle, representing nontargeted tissue. Results: PET/CT images of healthy animals showed predominant distribution in the kidneys, liver, and bladder; heart and spleen showed moderate, declining uptake, only. The biologic half-life in blood was 29 min. Urinary accumulation of 68Ga-NOTA-UBI29-41 peaked at 3.8 ± 0.91 percentage injected dose per gram (%ID) at 120 min, and 88 ± 5.2 %ID was recovered in total urine. 68Ga-NOTA-UBI29-41 imaging in (b) selectively visualized the muscular infection site and was differentiated from sterile inflammatory processes. Standardized uptake value ratios for muscles (infected/inflamed) were 2.9 ± 0.93, 2.9 ± 0.50, 3.5 ± 0.86, and 3.8 ± 0.90 at 5, 30, 60, and 90 min after injection, respectively. Rabbit lungs with asthma showed insignificant uptake. Conclusion: 68Ga-NOTA-UBI29-41 was strongly localized in bacteria-infected areas and minimally detected in a sterile inflammation area in rabbit muscles. The findings propose this compound to be an excellent first-line PET/CT tracer to allow the distinguishing of infection from inflammation.

Antimicrobial peptides: their role as infection-selective tracers for molecular imaging.

Antimicrobial peptides (AMPs) are a heterogeneous class of compounds found in a variety of organisms including humans and, so far, hundreds of these structures have been isolated and characterised. They can be described as natural microbicide, selectively cytotoxic to bacteria, whilst showing minimal cytotoxicity towards the mammalian cells of the host organism. They act by their relatively strong electrostatic attraction to the negatively charged bacterial cells and a relatively weak interaction to the eukaryote host cells. The ability of these peptides to accumulate at sites of infection combined with the minimal hosts cytotoxicity motivated for this review to highlight the role and the usefulness of AMPs for PET with emphasis on their mechanism of action and the different interactions with the bacterial cell. These details are key information for their selective properties. We also describe the strategy, design, and utilization of these peptides as potential radiopharmaceuticals as their combination with nuclear medicine modalities such as SPECT or PET would allow noninvasive whole-body examination for detection of occult infection causing, for example, fever of unknown origin.

Metal-ion speciation in blood plasma incorporating the tetraphosphonate, N,N-dimethylenephosphonate-1-hydroxy-4-aminopropilydenediphosphonate (APDDMP), in therapeutic radiopharmaceuticals

In a quest for more effective radiopharmaceuticals for pain palliation of metastatic bone cancer, this paper relates results obtained with 166Ho and 153Sm complexed to the bone seeking phosphonate, N,N-dimethylenephosphonate-1-hydroxy-4-aminopropylidenediphosphonate (APDDMP). APDDMP is synthesised from the known bone cancer pain palliation agent 1-hydroxy-3-aminopropylidenediphosphonate (APD) and was complexed to lanthanide trivalent metal ions. This work is performed to utilise the idea that the energetic beta-particle emitter, 166 Ho, coupled with phosphonate ligands such as APD and APDDMP could afford a highly effective radiopharmaceutical in the treatment of bone cancer. Complex-formation constants of APDDMP with the important blood plasma metal-ions, Ca2+, Mg2+, and Zn2+ and the trivalent lanthanides Ho3+ and Sm3+ were measured by glass electrode potentiometry at 37 degrees C and I = 150 mM. Blood plasma models were constructed using the computer code ECCLES and the results compared with those gathered from animal tests. The 166Ho-APDDMP complex was found to have little liver or bone uptake while 153Sm-APDDMP had a moderate bone uptake. This was primarily due to the high affinity of APDDMP for Ca(II). Clinical observations could be explained by the blood plasma modelling.

Metal-ion speciation in blood plasma incorporating the bisphosphonate, 1-hydroxy-4-aminopropilydenediphosphonate (APD), in therapeutic radiopharmaceuticals.

In the quest for more effective pain palliation radiopharmaceuticals for metastatic bone cancer, this paper relates results obtained with 166Ho complexed to the bone-seeking bisphosphonate, 1-hydroxy-4-aminopropililydenediphosphonate (APD). APD is itself a bone cancer pain palliation agent and this work was therefore driven by the idea that the energetic beta-particle emitter, 166Ho, coupled with APD could afford a highly effective radiopharmaceutical in the treatment of bone cancer. Complex-formation constants for important blood plasma metal-ions were measured by potentiometry or polarography at 37 degrees C and I = 150 mmol dm-3. The latter technique was used for systems where precipitates formed at ligand-to-metal ratios appropriate for potentiometry. For trivalent lanthanides, neither electrochemical technique could be used. Animal tests showed that the 166Ho-APD complex was taken up primarily by the liver due to precipitation or colloid formation.

Development of a Single Vial Kit Solution for Radiolabeling of 68Ga-DKFZ-PSMA-11 and Its Performance in Prostate Cancer Patients.

Prostate-specific membrane antigen (PSMA), a type II glycoprotein, is highly expressed in almost all prostate cancers. By playing such a universal role in the disease, PSMA provides a target for diagnostic imaging of prostate cancer using positron emission tomography/computed tomography (PET/CT). The PSMA-targeting ligand Glu-NH-CO-NH-Lys-(Ahx)-HBED-CC (DKFZ-PSMA-11) has superior imaging properties and allows for highly-specific complexation of the generator-based radioisotope Gallium-68 (68Ga). However, only module-based radiolabeling procedures are currently available. This study intended to develop a single vial kit solution to radiolabel buffered DKFZ-PSMA-11 with 68Ga. A 68Ge/68Ga-generator was utilized to yield 68GaCl3 and major aspects of the kit development were assessed, such as radiolabeling performance, quality assurance, and stability. The final product was injected into patients with prostate cancer for PET/CT imaging and the kit performance was evaluated on the basis of the expected biodistribution, lesion detection, and dose optimization. Kits containing 5 nmol DKFZ-PSMA-11 showed rapid, quantitative 68Ga-complexation and all quality measurements met the release criteria for human application. The increased precursor content did not compromise the ability of 68Ga-DKFZ-PSMA-11 PET/CT to detect primary prostate cancer and its advanced lymphatic- and metastatic lesions. The 68Ga-DKFZ-PSMA-11 kit is a robust, ready-to-use diagnostic agent in prostate cancer with high diagnostic performance.

68Ga-PSMA-HBED-CC PET imaging in breast carcinoma patients

BackgroundTo report on imaging findings using 68Ga-PSMA-HBED-CC PET in a series of 19 breast carcinoma patients.Methods68Ga-PSMA-HBED-CC PET imaging results obtained were compared to routinely performed staging examinations and analyzed as to lesion location and progesterone receptor status.ResultsOut of 81 tumor lesions identified, 84% were identified on 68Ga-PSMA-HBED-CC PET. 68Ga-PSMA-HBED-CC SUVmean values of distant metastases proved significantly higher (mean, 6.86, SD, 5.68) when compared to those of primary or local recurrences (mean, 2.45, SD, 2.55, p = 0.04) or involved lymph nodes (mean, 3.18, SD, 1.79, p = 0.011). SUVmean values of progesterone receptor-positive lesions proved not significantly different from progesterone receptor-negative lesions. SUV values derived from FDG PET/CT, available in seven patients, and 68Ga-PSMA-HBED-CC PET/CT imaging proved weakly correlated (r = 0.407, p = 0.015).Conclusions68Ga-PSMA-HBED-CC PET/CT imaging in breast carcinoma confirms the reported considerable variation of PSMA expression on human solid tumors using immunohistochemistry.

A potentiometric and differential pulse polarographic study of CdII with 1-hydroxyethylenediphosphonic acid

The complexation of the ligand 1-hydroxyethylenediphosphonic acid (HEDP) with Cd II was studied by differential pulse polarography (DPP) and glass electrode potentiometry (GEP) at fixed total ligand to total metal concentration ratios and varied pH values. Labile and non-labile metal complexes were analysed simultaneously by the use of a polarographic experimental complex formation curve (ECFC) and the calculated complex formation curve (CCFC). Complex formation curves were used for modelling of the metal‐ligand system and the refinement of stability constants. The ECFC, in which experimental parameters of only labile DPP peak are included (a shift in the peak potential and a variation in the peak height) appears to be a characteristic function for a full metal‐ligand model (labile and non-labile parts of a metal‐ligand system). The CCFC is a theoretical curve calculated for the assumed metal‐ligand model from mass-balance equations. The final model of metal species formed is the one, which is confirmed by these two experimental techniques, and for which stability constants of metal complexes obtained from DPP and GEP differ the least. Six cadmium complexes M(H4L), M(H2L), M2L, ML (all labile), ML2 (non-labile), and ML(OH) (labile) and their stability constants as log found from DPP 25.040.06, 19.560.02, 12.670.03, 7.260.02, 10.390.06 and 10.930.04, respectively, are reported. Results obtained from GEP are also reported and they differ from polarographic results only within the experimental errors typical for these techniques. # 1999 Elsevier Science B.V. All rights reserved.

Targeted radiotherapy of bone malignancies.

The severe pain associated with many disorders affecting bone account for a large proportion of cases of patient morbidity, due to the encumbrance of mobility and therefore, compromised quality of life. Skeletal metastasis is one such condition, which generally complicates the treatment of the primary cancers such as that of the breast, prostate and lung - causing intense pain and eventually even mortality. This paper presents examples of various approaches explored and proposed in the ongoing search to identify better radiopharmaceuticals for the treatment of bone disorders such as metastases. The primary objective of these developments is to alleviate the debilitating pain commonly associated with bone lesions. The efficacy of a radiotherapeutic agent intended for the treatment of diseased bone is particularly dependent on the radiation dose to the tumor cells and on the extent to which suppression of bone marrow or other critical organs can be avoided. Therefore, the design rationale requires careful consideration of the choice radionuclide and especially ensuring that the drug selectively targets the lesion or tumor site. The options pursued include the use of radioisotopes with an intrinsic affinity for bone, such as (89)Sr or (223)Ra, or the design of bone-seeking ligands, such as phosphonates, to selectively deliver the radionuclide to the target, e.g. [(153)Sm]Sm-EDTMP. A combination of the above may too be possible, where the bone seeking ligand facilitates the selective accumulation of a radionuclide, which by itself is also bone homing. In terms of therapeutic application radionuclides with various decay modes are proposed, including beta (-) emitters: (153)Sm, (89)Sr, (186)Re, (188)Re, (32)P, (177)Lu and (170)Tm; alpha (α) emitters: (223)Ra and (225)Ra; and Auger or conversion electron emitter: (117)mSn. From a purely diagnostic perspective, the radioisotopes used for imaging include the well known photon emitting (99)mTc, and positron emitters (18)F and (68)Ga. The current status in the development and application of internal radiotherapy for the palliative treatment of bone pain will be discussed, summarizing the progress made and challenges encountered in the process to realizing an effective drug candidate.

Production of 117mSn with high specific activity by cyclotron

A method to produce (117m)Sn radionuclide using accelerator production route is described. A new method is proposed to separate the (117m)Sn. Specific activities and thick target yield for (116)Cd(α,3n)(117m)Sn reaction at E(α)=35MeV bombarding energy were determined. The estimated production yield of (117m)Sn was 37.5kBq/μAh for 13.16 mg/cm(2) natural cadmium-oxide target and 410 kBq/μAh for 11.07 mg/cm(2) highly enriched (95%) (116)CdO target. The method developed for separation of (117m)Sn from Cd using anion-exchange resin (Dowex -1×8, fluorine form, 400 mesh) can achieve 98% radiochemical yield of (117m)Sn with more than 99% radionuclidic purity. The estimated specific activity is 2.4 GBq/mg that can be reached with the used irradiation conditions.

Bioaccumulation and Subchronic Toxicity of 14 nm Gold Nanoparticles in Rats

Colloidal suspensions of 14 nm gold nanoparticles (AuNPs) were repeatedly administered intravenously at three dose levels (0.9, 9 and 90 µg) to male Sprague Dawley rats weekly for 7 weeks, followed by a 14-day washout period. After sacrificing, the amount of gold was quantified in the liver, lungs, spleen, skeleton and carcass using neutron activation analysis (NAA). During the study, pre- and post (24 h) administration blood samples were collected from both the test and control groups, the latter which received an equal injection volume of normal saline. General health indicators were monitored together with markers of kidney and liver damage for acute and subchronic toxicity assessment. Histopathological assessments were done on the heart, kidneys, liver, lungs and spleen to assess any morphological changes as a result of the exposure to AuNPs. The mass measurements of all the groups showed a steady increase with no signs of overt toxicity. The liver had the highest amount of gold (µg) per gram of tissue after 56 days followed by the spleen, lungs, skeleton and carcass. Markers of kidney and liver damage showed similar trends between the pre and post samples within each group and across groups. The histopathological examination also showed no hepatotoxicity and nephrotoxicity. There was accumulation of Au in tissues after repeated dosing, albeit with no observable overt toxicity, kidney or liver damage.