Eduardo Savio

Detection, treatment, and prevention of carbapenemase-producing Enterobacteriaceae: Recommendations from an International Working Group

Abstract The prevalence of carbapenemase-producing Enterobacteriaceae (CPE) has increased during the past 10 years. Its detection is frequently difficult, because they do not always show a minimum inhibitory concentration (MIC) value for carbapenems in the resistance range. Both broth microdilution and agar dilution methods are more sensitive than disk diffusion method, Etest and automated systems. Studies on antimicrobial treatment are based on a limited number of patients; therefore, the optimal treatment is not well established. Combination therapy with two active drugs appears to be more effective than monotherapy. Combination of a carbapenem with another active agent — preferentially an aminoglycoside or colistin — could lower mortality provided that the MIC is ≤4 mg/l and probably ≤8 mg/l, and is administered in a higher-dose/prolonged-infusion regimen. An aggressive infection control and prevention strategy is recommended, including reinforcement of hand hygiene, using contact precautions and early detection of CPE through use of targeted surveillance.

Evaluation of 99mTc-glucarate as a breast cancer imaging agent in a xenograft animal model.

INTRODUCTION The use of [(99m)Tc]glucarate has been reported as an infarct-avid agent with the potential for very early detection of myocardial infarction. [(99m)Tc]Glucarate has also been postulated as an agent for non-invasive detection of tumors. The aim of our study was to develop a Glucarate kit and evaluate [(99m)Tc]glucarate as a potential cancer imaging agent in female SCID mice bearing human MDA-MB-435 breast tumors. METHODS Glucarate in a kit formulation was labeled with (99m)Tc and evaluated for radiolabelling efficiency and radiochemical purity. The Glucarate kit stability was assessed by monthly quality controls. The pharmacokinetics of [(99m)Tc]glucarate were determined in female SCID mice bearing MDA-MB-435 human breast carcinoma tumors at 0.5, 1, 2, 4 and 24 h. Nuclear imaging studies were performed with a micro-single photon emission tomography (SPECT)/computed tomography (CT) system at 2 h post injection, while magnetic resonance imaging (MRI) was employed for tumor morphology analysis and metastatic deposit localization. RESULTS The Glucarate kits exhibited a stable shelf life of 6 months. [(99m)Tc]Glucarate was obtained with radiochemical purity greater than 95%. Biodistribution studies demonstrated moderate tumor uptake coupled with high renal clearance. Tumor-to-muscle ratios were 4.85 and 5.14 at 1 and 4 h post injection. MRI analysis showed tumors with dense cellular growth and moderate central necrosis. [(99m)Tc]Glucarate uptake in the primary MDA-MB-435 shoulder tumors and metastatic lesions were clearly visualized with micro-SPECT/CT imaging. CONCLUSIONS Selective tumor uptake and rapid clearance from nontarget organs makes [(99m)Tc]glucarate a potential agent for breast cancer imaging that awaits validation in a clinical trial.

188Re radiopharmaceuticals for radiosynovectomy: evaluation and comparison of tin colloid, hydroxyapatite and tin-ferric hydroxide macroaggregates

BackgroundRadiosynovectomy is a therapy used to relieve pain and inflammation from rheumatoid arthritis and related diseases. In this study three 188Re particulate compounds were characterized according to their physico-chemical properties and their biological behavior in rabbits. The results were compared in order to establish which was the radiopharmaceutical that better fits the requirements of this kind of radiotherapy.MethodsThree radiopharmaceutical formulations, tin colloid, hydroxyapatite particles (HA) and ferric hydroxide macroaggregates coated with tin colloid (FHMA), were physically characterized (number, volume and surface of the particles). For this purpose laser diffraction methodology was used. To evaluate cavity leakage of activity the following studies in New Zealand rabbits were performed: scintigraphic images for 48 hr after intraarticular injection of each radiopharmaceutical, biodistribution at 48 hr and urine samples collection during the first 24 hr post-radiopharmaceutical administration.ResultsLabeling procedures for 188Re-HA and 188Re-Sn-FHMA were labour intensive while 188Re-Sn was easily prepared. Furthermore, 188Re-Sn colloid offered the greatest surface area in the 2–10 microm range and was obtained with a radiochemical purity over 95%, while percentage of bound activity for 188Re-HA and 188Re-Sn-FHMA were 55% and 92% respectively. Stability was verified for the three radiopharmaceuticals for 24 hr. Scintigraphic studies and biodistribution in rabbits after intraarticular administration of the radiopharmaceuticals showed relevant activity only in the knee, this being over 90% of the residual activity in the whole body at 48 hr in every case. Renal elimination of 188Re-Sn colloid and 188Re-Sn-FHMA was detected by activity measurements in urine samples, during the first 12 hr post-radiopharmaceutical injection.The percentage of activity retained in the knee was 69.1% for 188Re-Sn colloid, 55.1% for 188Re-Sn-FHMA and 33.6% for 188Re-HA.ConclusionThe 188Re-Sn colloid was easy to prepare, minimum facilities were required, was stable for 24 hr and showed minimal leakage from the joint after intraarticular injection into the rabbits knee. Furthermore, 188Re-Sn colloid has greater retention in the knee when it is compared with the other radiopharmaceuticals, so it could provide the best therapeutic effect/absorbed dose ratio for the patient.

Biological studies in animal models using [99mTc](CO)3 recombinant annexin V as diagnostic agent of apoptotic processes.

INTRODUCTION There are many diseases associated with variations in the expression of apoptosis such as organ rejection after transplantation, myocardial ischemia or infarct and neurodegenerative diseases. For this reason, the early visualization of this process is relevant to set fast and effective therapeutic strategies. METHODS The precursor was prepared according to the procedure reported by R. Alberto, R. Schibli, P. Schubiger, U. Abram, and T. Kaden [Reactions with the technetium and rhenium carbonyl complexes (NEt(4))[MX(3)(CO)(3)]. Synthesis and structure of Tc(CN-But)(3)(CO)(3)](NO(3)) and (Net(4))[Tc(2)(μ-SCH(2)CH(2)OH)(3)(CO)(3)], Polyhedron 1996;15: 1079-89]. Recombinant annexin V was incubated with [(99m)Tc](H(2)O)3(CO)(3)(+) solution, previously neutralized with buffer. Biodistribution studies were performed in 8-week-old female Wistar rats. Animals were housed and treated in compliance with institutional guidelines related to animal experimentation. Work protocol was previously approved by the Animal Ethics Committee of the university. Two groups of rats were defined. One was used as control and the other group was previously injected with 150 mg/kg ip of cyclophosphamide to induce apoptosis. RESULTS The synthesis of carbonyl precursor achieved yields higher than 90%, and the radiolabeled protein was obtained with 92% of radiochemical purity and high stability in vitro. An important uptake in apoptotic tissues was confirmed by biodistributions, scintigraphic images and histological studies. CONCLUSIONS Biodistribution studies revealed hepatobiliary elimination, high stability in vivo and important uptake in the reticuloendothelial system. In the pathologic model, higher uptake values correspond to the liver, spleen, lungs and femur. Histological studies confirmed the development of apoptosis at 8 and 24 h postinduction in the spleen and lymphocyte bulks in the peribronchial area. Scintigraphic images confirmed high uptake both the spleen and the lungs.

Physico-chemical characterisation and biological evaluation of 188-Rhenium colloids for radiosynovectomy

BackgroundRadiosynovectomy is a type of radiotherapy used to relieve pain and inflammation from rheumatoid arthritis. In this study, 188-Rhenium (188Re) colloids were characterized by physical and biological methodologies. This was used to assess which parameters of the kit formulation would be the basis in the development of a more effective radiopharmaceutical for synovectomy. Intraarticular injection in knees of rabbits assessed cavity leakage of activity.MethodsThe physical characteristics of tin (Sn) and sulphur (S) colloids were determined to assess the formulation with suitable properties. Particles were grouped in three ranges for analyzing their distribution according to their number, volume and surface. The ideal particle size range was considered to be from 2 to 10 microns. Membrane filtration and laser diffraction characterization methodologies were used.ResultsWhile membrane filtration could give misleading data, laser diffraction proportions more reliable results. The Sn colloid showed a better distribution of particle volume and surface than S colloid, in the 2 to 10 microns range. The 188Re-Sn colloid was obtained with a radiochemical purity higher than 95% after 30 minutes of autoclaving. While Sn colloid kit stability was verified for 60 days, the 188Re-Sn preparation was stable in the first 24 hrs. No significant intrabatch variability (n = 3) was detected. Biodistribution and scintigraphic studies in rabbits after intraarticular injection showed relevant activity only in knee, being 90% at 48 hours.ConclusionThe 188Re-Sn colloid is easy to prepare, is stable for 24 hours and shows minimal cavity leakage after intraarticular injection into rabbit knees, suggesting this radiotherapeutical agent has suitable physical properties for evaluation for joint treatment in humans.

Evaluation of Patients with Head and Neck Cancer by Means of 99mTc-Glucarate

Preliminary findings have suggested that 99mTc-glucarate has tumor-seeking properties. The purpose of this study was to explore the potential of this tracer to evaluate malignant head and neck tumors by means of SPECT/CT software fusion imaging. Methods: Eleven male patients with advanced head and neck carcinoma were included in the study: 9 with locally advanced disease and 2 with clinical suspicion of local relapse. Scanning started 3–6 h after the injection of 1,110 MBq of 99mTc-glucarate. Planar and SPECT images of the head, neck, and thorax were acquired. Three-dimensional images were also coregistered with CT. Results: We found 99mTc-glucarate uptake in all suspected lesions. SPECT/CT fusion imaging was helpful in all cases for topographically localizing the tracer foci. Conclusion: 99mTc-glucarate can be considered a potential tracer for the evaluation of patients with head and neck tumors.

Hydrophilic and lipophilic radiopharmaceuticals as tracers in pharmaceutical development: In vitro – In vivo studies

BackgroundScintigraphic studies have been performed to assess the release, both in vitro and in vivo, of radiotracers from tablet formulations. Four different tracers with differing physicochemical characteristics have been evaluated to assess their suitability as models for drug delivery.MethodsIn-vitro disintegration and dissolution studies have been performed at pH 1, 4 and 7. In-vivo studies have been performed by scintigraphic imaging in healthy volunteers. Two hydrophilic tracers, (99mTc-DTPA) and (99mTc-MDP), and two lipophilic tracers, (99mTc-ECD) and (99mTc-MIBI), were used as drug models.ResultsDissolution and disintegration profiles, differed depending on the drug model chosen. In vitro dissolution velocity constants indicated a probable retention of the radiotracer in the formulation. In vivo disintegration velocity constants showed important variability for each radiopharmaceutical. Pearson statistical test showed no correlation between in vitro drug release, and in vivo behaviour, for 99mTc-DTPA, 99mTc-ECD and 99mTc-MIBI. High correlation coefficients were found for 99mTc-MDP not only for in vitro dissolution and disintegration studies but also for in vivo scintigraphic studies.ConclusionScintigraphic studies have made a significant contribution to the development of drug delivery systems. It is essential, however, to choose the appropriate radiotracers as models of drug behaviour. This study has demonstrated significant differences in release patterns, depending on the model chosen. It is likely that each formulation would require the development of a specific model, rather than being able to use a generic drug model on the basis of its physicochemical characteristics.

Automated radiosynthesis of [(11)C]L-deprenyl-D2 and [(11)C]D-deprenyl using a commercial platform.

Two (11)C-labelled PET tracers, (R)-N-[(11)C]methyl-N-(3,3-dideuteropropargyl)-1-phenylpropan-2-amine ([(11)C]L-deprenyl-D2, [(11)C]DED) and (S)-N-[(11)C]methyl-N-propargyl-1-phenylpropan-2-amine ([(11)C]D-deprenyl, [(11)C]DDE) were synthesised. One step N-alkylation with [(11)C]MeI or [(11)C]MeOTf was performed using the automated platform TRACERlab® FX-C Pro. The labelled products were obtained with (37±15)% (n=10) (end of synthesis, decay corrected from [(11)C]MeI) radiochemical yields from [(11)C]MeI after 38±3min synthesis time. In all cases, radiochemical purity was over 99% when [(11)C]MeOTf was used. This synthesis using a commercial platform makes these tracers more accessible for clinical research purposes.

Dosimetry and toxicity studies of the novel sulfonamide derivative of Sulforhodamine 101([18F]SRF101) at a preclinical level.

BACKGROUND The SR101 N-(3-[18F]Fluoropropyl) sulfonamide ([18F]SRF101) is a Sulforhodamine 101 derivative that was previously synthesised by our group. The fluorescent dye SR101 has been reported as a marker of astroglia in the neocortex of rodents in vivo. OBJECTIVE The aim of this study was to perform a toxicological evaluation of [18F]SRF101 and to estimate human radiation dosimetry based on preclinical studies. METHODS Radiation dosimetry studies were conducted based on biokinetic data obtained from a mouse model. A single-dose toxicity study was carried out. The toxicological limit chosen was <100 μg, and allometric scaling with a safety factor of 100 for unlabelled SRF101 was selected. RESULTS The absorbed and effective dose estimated using OLINDA/EXM V2.0 for male and female dosimetric models presented the same tendency. The highest total absorbed dose values were for different sections of the intestines. The mean effective dose was 4.03 x10-3 mSv/MBq and 5.08 x10-3 mSv/MBq for the male and female dosimetric models, respectively, using tissue-weighting factors from ICRP-89. The toxicity study detected no changes in the organ or whole-body weight, food consumption, haematologic or clinical chemistry parameters. Moreover, lesions or abnormalities were not found during the histopathological examination. CONCLUSION The toxicological evaluation of SRF101 verified the biosafety of the radiotracer for human administration. The dosimetry calculations revealed that the radiation-associated risk of [18F]SRF101 would be of the same order as other 18F radiopharmaceuticals used in clinical applications. These study findings confirm that the novel radiotracer would be safe for use in human PET imaging.

Image-Guided Development of Heterocyclic Sulfoxides as Ligands for Tau Neurofibrillary Tangles: From First-in-Man to Second-Generation Ligands

Positron emission tomography (PET) imaging of misfolded protein aggregates that form in neurodegenerative processes of the brain is key to providing a robust marker for improved diagnosis and evaluation of treatments. We report the development of advanced radiotracer candidates based on the sulfoxide scaffold found in proton pump inhibitors (lansoprazole, prevacid) with inherent affinity to neurofibrillary tangles in Alzheimer’s disease and related disorders (e.g., dementia with Lewy bodies and the frontotemporal degeneration syndrome). First-in-man results obtained with [18F]lansoprazole and N-methyl-[18F]lansoprazole were used to guide the design of a set of 24 novel molecules with suitable properties for neuroimaging with PET. Compounds were synthesized and characterized pharmacologically, and the binding affinity of the compounds to synthetic human tau-441 fibrils was determined. Selectivity of binding was assessed using α-synuclein and β-amyloid fibrils to address the key misfolded proteins of relevance in dementia. To complete the pharmacokinetic profiling in vitro, plasma protein binding and lipophilicity were investigated. Highly potent and selective new radiotracer candidates were identified for further study.