Protocol for Clinical GLP-1 Receptor PET/CT Imaging with [68Ga]Ga-NODAGA-Exendin-4

Imaging with radiolabeled exendin enables detection and characterization of glucagon-like peptide 1 receptors (GLP-1Rs) in vivo with high specificity. The novel radiotracer [⁶⁸Ga]Ga-NODAGA-exendin-4 forms a stable complex after a simple and fast labeling procedure. Beta-cell mass in the islets of Langerhans can be visualized using [⁶⁸Ga]Ga-NODAGA-exendin-4, which is promising for research into diabetes mellitus (DM) pathophysiology. Furthermore, this radiotracer enables very sensitive detection of insulinomas, resulting from vast overexpression of GLP-1Rs, and seems promising for the detection of focal lesions in congenital hyperinsulinism (CHI). Here, we describe the procedures involved in [⁶⁸Ga]Ga-NODAGA-exendin-4 positron emission tomography (PET)/computed tomography (CT) imaging including the radiolabeling of the NODAGA-exendin conjugate with ⁶⁸Ga, quality controls, and PET/CT.

New sensitive method for HEPES quantification in 68Ga-radiopharmaceuticals

BACKGROUND

The introduction of a GMP-certified ⁶⁸Ga-generator spurred the application of ⁶⁸Ga-radiopharmaceuticals. Several radiosynthesis of ⁶⁸Ga-radiopharmaceuticals are more efficient and robust when performed with 2-[4-(2-hydroxyethyl)piperazin-1-yl] ethanesulfonic acid (HEPES) buffer, which is considered as an impurity in the quality control (QC) procedure. Thus, prior to clinical use, QC must be conducted to ensure that HEPES does not exceed the maximum dose of 200 μg/V _Injected as described in European Pharmacopoeia (Ph Eur) for edotreotide. However, when applying the thin-layer chromatography (TLC) method described in the Ph Eur to quantify the HEPES amount present in the ⁶⁸Ga-octreotide or in the remaining ⁶⁸Ga-radiopharmaceuticals that were tested, no amount was detectable after 4 min of iodine incubation. Here we tested our modified TLC method and validate a new high-performance liquid chromatography (HPLC) method to quantify HEPES in ⁶⁸Ga-radiopharmaceuticals and compare it to the TLC-method described in Ph Eur. In addition, samples collected from various institutes were tested to evaluate whether the synthesis of different ⁶⁸Ga-radiopharmaceuticals or the use of different synthesis methods could affect the amounts of HEPES.

RESULTS

HEPES could not be detected by the TLC method described in the Ph Eur within 4 min incubation in an iodine-saturated chamber. As for our modified TLC method, only after 2 h, spots were only visible > 1 mg/mL. The HPLC method had a limit-of-quantification (LOQ) of 3 μg/mL and a limit-of-detection (LOD) of 1 μg/mL. From the three ⁶⁸Ga-radiopharmaceuticals tested, only in the [⁶⁸Ga]Ga-NODAGA-Exendin samples exceeding amounts of HEPES were found and its concentration in the [⁶⁸Ga]Ga-NODAGA-Exendin was significantly higher, when compared to [⁶⁸Ga]Ga-DOTATOC and [⁶⁸Ga]Ga-PSMA-11.

CONCLUSION

The TLC method described in Ph Eur and our modified TLC method may not be sufficiently sensitive and thus unsuitable to use for QC release. The new HPLC method was sensitive, quantitative, reproducible and suitable for QC release. With this method, we were able to determine that some ⁶⁸Ga-radiopharmaceuticals may exceed the HEPES limit of 200 μg/ V _Injected. This new analytical system would allow correcting for the maximum injected dose in order not to exceed this amount.

18th European Symposium on Radiopharmacy and Radiopharmaceuticals

OP03 Selective extraction of medically-related radionuclides from proton-irradiated thorium targets

V. Radchenko, J.W. Engle, C. Roy, J. Griswold, M.F. Nortier, E.R. Birnbaum, M. Brugh, S. Mirzadeh, K. D. John, M.E. Fassbender

OP04 Comparison of [68Ga]FSC(succ-RGD)3 and [68Ga]NODAGA-RGD for PET imaging of αvβ3 integrin expression

Chuangyan Zhai, Gerben M. Franssen, Milos Petrik, Peter Laverman, Clemens Decristoforo

OP05 A new NPY-Y1R targeting peptide for breast cancer PET imaging

Ait-Mohand Samia, Dumulon-Perreault Véronique, Guérin Brigitte

OP06 The influence of multivalency on CCK 2 receptor targeting

D. Summer, A. Kroess, C. Rangger, H. Haas, P. Laverman, F. Gerben, E. von Guggenberg, C.Decristoforo

OP07 SPECT Imaging of αvβ3 Expression by [99mTc(N)PNP43]- Bifunctional Chimeric RGD Peptide not Cross-Reacting with αvβ5

Cristina Bolzati, Nicola Salvarese, Fiorenzo Refosco, Laura Meléndez-Alafort, Debora Carpanese, Antonio Rosato, Michele Saviano, Annarita Del Gatto, Daniela Comegna, Laura Zaccaro

OP09 New dienophiles for the inverse-electron-demand Diels-Alder reaction and for pretargeted PET imaging

Emilie Billaud, Muneer Ahamed, Frederik Cleeren, Elnaz Shahbazali, Tim Noël, Volker Hessel, Alfons Verbruggen and Guy Bormans

OP10 New complexing agent for Al18F-labelling of heat-sensitive biomolecules: Synthesis and preclinical evaluation of Al18F-RESCA1-HAS

Cleeren F, Lecina J, Koole M, Verbruggen A and Bormans G

OP11 A novel versatile precursor efficient for F-18 radiolabelling via click-chemistry

B. Lugatoa, S. Stucchia, E.A. Turollaa, L. Giulianoa, S.Toddea, P. Ferraboschib

OP12 A general applicable method to quantify unidentified UV impurities in radiopharmaceuticals

R.P. Klok, M.P.J. Mooijer, N.H. Hendrikse, A.D. Windhorst

OP13 Development of [¹⁸F]Fluoro-C-glycosides to radiolabel peptides

Collet C., Petry N., Chrétien F., Karcher G., Pellegrini-Moïse N., Lamandé-Langle S.

OP14 A Microfluidic Approach for the 68Ga-labeling of PSMAHBED-CC and NODAGA-RGD

Sarah Pfaff, Cecile Philippe, Markus Mitterhauser, Marcus Hacker, Wolfgang Wadsak

OP16 Surprising reactivity of astatine in the nucleophilic substitution of aryliodonium salts: application to the radiolabeling of antibodies

François Guérard, Yong-Sok Lee, Sébastien Gouard, Kwamena Baidoo, Cyrille Alliot, Michel Chérel, Martin W. Brechbiel, Jean-François Gestin

OP17 ⁶⁴Cu-NOTA-pertuzumab F(ab')₂ fragments, a second-generation probe for PET imaging of the response of HER2-positive breast cancer to trastuzumab (Herceptin)

Lam K, Chan C, Reilly RM

OP18 Development of radiohalogenated analogues of a avb6-specific peptide for high LET particle emitter targeted radionuclide therapy of cancer

Salomé Paillas, John Marshall, Jean-Pierre Pouget, Jane Sosabowski

OP19 Ligand Specific Efficiency (LSE) as a guide in tracer optimization

Emmanuelle Briard, Yves P. Auberson, John Reilly, Mark Healy, David Sykes

OP23 The radiosynthesis of an 18F-labeled triglyceride, developed to visualize and quantify brown adipose tissue activity

Andreas Paulus, Wouter van Marken Lichtenbelt,Felix Mottaghy, Matthias Bauwens

OP24 Influence of the fluorescent dye on the tumor targeting properties of dual-labeled HBED-CC based PSMA inhibitors

Baranski, Ann-Christin, Schäfer, Martin, Bauder-Wüst, Ulrike, Haberkorn, Uwe, Eder, Matthias, Kopka, Klaus

OP25 [18F]MEL050 as a melanin PET tracer : fully automated radiosynthesis and evaluation for the detection of pigmented melanoma in mice pulmonary metastases

Chaussard M, Hosten B, Vignal N, Tsoupko-Sitnikov V, Hernio N, Hontonnou F, Merlet P, Poyet JL, Sarda-Mantel L, Rizzo-Padoin N

OP26 Design and Preclinical Evaluation of Novel Radiofluorinated PSMA Targeting Ligands Based on PSMA-617

J. Cardinale, M. Schäfer, M. Benešová, U. Bauder-Wüst, O. Seibert, F. Giesel, U. Haberkorn, M. Eder, K. Kopka

OP27 A novel radiolabeled peptide for PET imaging of prostate cancer: 64Cu-DOTHA2-PEG-RM26

Mansour Nematallah, Paquette Michel, Ait-Mohand Samia, Dumulon-Perreault Véronique, Lecomte Roger, Guérin Brigitte

OP29 Biodistribution of [¹⁸F]Amylovis®, a new radiotracer PET imaging of β-amyloid plaques

Fernandez-Maza L, Rivera-Marrero S, Prats Capote A, Parrado-Gallego A, Fernandez-Gomez I, Balcerzyk M, Sablon-Carrazana M, Perera-Pintado A, Merceron-Martinez D, Acosta-Medina E, Rodriguez-Tanty C

OP30 Synthesis and preclinical evaluation of [11C]-BA1 PET tracer for the imaging of CSF-1R

Bala Attili, Muneer Ahamed, Guy Bormans

OP31 In vivo imaging of the MCHR1 in the ventricular system via [18F]FE@SNAP

C. Philippe, M. Zeilinger, T. Scherer, C. Fürnsinn, M. Dumanic, W. Wadsak, M. Hacker, M. Mitterhauser

OP32 Synthesis of the first carbon-11 labelled P2Y12 receptor antagonist for imaging the anti-inflammatory phenotype of activated microglia

B. Janssen, D.J. Vugts, G.T. Molenaar, U. Funke, P.S. Kruijer, F. Dollé, G. Bormans, A.A. Lammertsma, A.D. Windhorst

OP33 Radiosynthesis of a selective HDAC6 inhibitor [11C]KB631 and in vitro and ex vivo evaluation

Koen Vermeulen, Muneer Ahamed, Michael Schnekenburger, Mathy Froeyen, Dag Erlend Olberg, Marc Diederich, Guy Bormansa

OP34 Improving metabolic stability of fluorine-18 labelled verapamil analogues

Raaphorst RM, Luurtsema G, Lammertsma AA, Elsinga PH, Windhorst AD

OP36 Development of a novel PET tracer for the activin receptor-like kinase 5

Lonneke Rotteveel, Uta Funke, Peter ten Dijke, Harm Jan Bogaard, Adriaan A. Lammertsma, Albert D. Windhorst

OP37 SPECT imaging and biodistribution studies of 111In-EGF-Au-PEG nanoparticles in vivo

Lei Song, Sarah Able, Nadia Falzone, Veerle Kersemans, Katherine Vallis

OP38 Melanoma targeting with [99mTc(N)(PNP3)]-labeled NAPamide derivatives: preliminary pharmacological studies

Davide Carta, Nicola Salvarese, Wiebke Sihver, Feng Gao, Hans Jürgen Pietzsch, Barbara Biondi, Paolo Ruzza, Fiorenzo Refosco, Cristina Bolzati

OP39 [⁶⁸Ga]NODAGA-RGD: cGMP synthesis and data from a phase I clinical study

Roland Haubner, Armin Finkensted, Armin Stegmair, Christine Rangger, Clemens Decristoforo, Heinz Zoller, Irene J. Virgolin

OP44 Implementation of a GMP-grade radiopharmacy facility in Maastricht

Ivo Pooters, Maartje Lotz, Roel Wierts, Felix Mottaghy, Matthias Bauwens

OP45 Setting up a GMP production of a new radiopharmaceutical

Forsback, Sarita, Bergman Jörgen, Kivelä Riikka

OP48 In vitro and in vivo evaluation of 68-gallium labeled Fe3O4-DPD nanoparticles as potential PET/MRI imaging agents

M. Karageorgou, M. Radović, C. Tsoukalas, B. Antic, M. Gazouli, M. Paravatou-Petsotas, S. Xanthopouls, M. Calamiotou, D. Stamopoulos, S. Vranješ-Durić, P. Bouziotis

OP49 Fast PET imaging of inflammation using 68Ga-citrate with Fe-containing salts of hydroxy acids

A. S. Lunev, A. A. Larenkov, K.A. Petrosova, O. E. Klementyeva, G. E. Kodina

PP01 Installation and validation of 11C-methionine synthesis

Kvernenes, O.H., Adamsen, T.C.H.

PP02 Fully automated synthesis of 68Ga-labelled peptides using the IBA Synthera® and Synthera® Extension modules

René Martin, Sebastian Weidlich, Anna-Maria Zerges, Cristiana Gameiro, Neva Lazarova, Marco Müllera

PP03 GMP compliant production of ¹⁵O-labeled water using IBA 18 MeV proton cyclotron

Gert Luurtsema, Michèl de Vries, Michel Ghyoot, Gina van der Woude, Rolf Zijlma, Rudi Dierckx, Hendrikus H. Boersma, Philip H. Elsinga

PP04 In vitro Nuclear Imaging Potential of New Subphthalocyanine and Zinc Phthalocyanine

Fatma Yurt Lambrecht, Ozge Er, Mine Ince, Cıgır Biray Avci, Cumhur Gunduz, Fatma Aslihan Sarı

PP05 Synthesis, Photodynamic Therapy Efficacy and Nuclear Imaging Potential of Zinc Phthalocyanines

Kasim Ocakoglu, Ozge Er, Onur Alp Ersoz, Fatma Yurt Lambrecht, Mine Ince, Cagla Kayabasi, Cumhur Gunduz

PP06 Radio-U(H)PLC – the Search on the Optimal Flow Cell for the γ-Detector

Torsten Kniess, Sebastian Meister, Steffen Fischer, Jörg Steinbach

PP07 Radiolabeling, characterization & biodistribution study of cysteine and its derivatives with Tc99m

Rabia Ashfaq, Saeed Iqbal, Atiq-ur-Rehman, Irfan ullah Khan

PP08 Radiolabelling of poly (lactic-co.glycolic acid) (PLGA) nanoparticles with 99mTC

R Iglesias-Jerez, Cayero-Otero, L. Martín-Banderas, A. Perera-Pintado, I. Borrego-Dorado

PP09 Development of [¹⁸F]PD-410 as a non-peptidic PET radiotracer for gastrin releasing peptide receptors

Ines Farinha-Antunes, Chantal Kwizera, Enza Lacivita, Ermelinda Lucente, Mauro Niso, Paola De Giorgio, Roberto Perrone, Nicola A. Colabufo, Philip H. Elsinga, Marcello Leopoldo

PP10 An improved nucleophilic synthesis of 2-(3,4-dimethoxyphenyl)-6-(2-[18F]fluoroethoxy) benzothiazole ([18F]FEDMBT), potential diagnostic agent for breast cancer imaging by PET

V.V. Vaulina, O.S. Fedorova, V.V. Orlovskaja, С.L. Chen, G.Y. Li, F.C. Meng, R.S. Liu, H.E. Wang, R.N. Krasikova

PP11 Internal radiation dose assessment of radiopharmaceuticals prepared with accelerator-produced 99mTc

Laura Meléndez-Alafort, Mohamed Abozeid, Guillermina Ferro-Flores, Anna Negri, Michele Bello, Nikolay Uzunov, Martha Paiusco, Juan Esposito, Antonio Rosato

PP12 A specialized five-compartmental model software for pharmacokinetic parameters calculation

Laura Meléndez-Alafort, Cristina Bolzati, Guillermina Ferro-Flores, Nicola Salvarese, Debora Carpanese, Mohamed Abozeid, Antonio Rosato, Nikolay Uzunov

PP13 Molecular imaging of the pharmacokinetic behavior of low molecular weight ¹⁸F-labeled PEtOx in comparison to ⁸⁹Zr-labeled PEtOx

Palmieri L, Verbrugghen T, Glassner M, Hoogenboom R, Staelens S, Wyffels L

PP14 Towards nucleophilic synthesis of the α-[18F]fluoropropyl-L-dihydroxyphenylalanine

V. V. Orlovskaja, O. F. Kuznetsova, O. S. Fedorova, V. I. Maleev, Yu. N. Belokon, A. Geolchanyan, A. S. Saghyan, L. Mu, R. Schibli, S. M. Ametamey, R. N. Krasikova

PP15 A convenient one-pot synthesis of [18F]clofarabine

Revunov, Evgeny, Malmquist, Jonas, Johnström, Peter, Van Valkenburgh, Juno, Steele, Dalton, Halldin, Christer, Schou, Magnus

PP16 BODIPY-estradiol conjugates as multi-modality tumor imaging agents

Samira Osati,Michel Paquette,Simon Beaudoin,Hasrat Ali,Brigitte Guerin, Jeffrey V. Leyton, Johan E. van Lier

PP17 Easy and high yielding synthesis of 68Ga-labelled HBED-PSMA and DOTA-PSMA by using a Modular-Lab Eazy automatic synthesizer

Di Iorio V, Iori M, Donati C, Lanzetta V, Capponi PC, Rubagotti S, Dreger T, Kunkel F, Asti M

PP18 Synthesis and evaluation of fusarinine C-based octadentate bifunctional chelators for zirconium-89 labelling

Chuangyan Zhai, Christine Rangger, Dominik Summer, Hubertus Haas, Clemens Decristoforo

PP19 Fully automated production of [18F]NaF using a re-configuring FDG synthesis module.

Suphansa Kijprayoon, Ananya Ruangma, Suthatip Ngokpol, Samart Tuamputsha

PP20 Extension of the Carbon-11 Small Labeling Agents Toolbox and Conjugate Addition

Ulrike Filp, Anna Pees, Carlotta Taddei, Aleksandra Pekošak, Antony D. Gee, Alex J. Poot, Albert D. Windhorst

PP21 In vitro studies on BBB penetration of pramipexole encapsulated theranostic liposomes for the therapy of Parkinson’s disease

Mine Silindir Gunay, A. Yekta Ozer, Suna Erdogan, Ipek Baysal, Denis Guilloteau, Sylvie Chalon

PP22 Factors affecting tumor uptake of 99mTc-HYNIC-VEGF165

Filippo Galli, Marco Artico, Samanta Taurone, Enrica Bianchi, Bruce D. Weintraub, Mariusz Skudlinski, Alberto Signore

PP23 Rhenium-188: a suitable radioisotope for targeted radiotherapy

Nicolas Lepareur, Nicolas Noiret, François Hindré, Franck Lacœuille, Eric Benoist, Etienne Garin

PP24 Preparation of a broad palette of 68Ga radiopharmaceuticals for clinical applications

Trejo-Ballado F, Zamora-Romo E, Manrique-Arias JC, Gama-Romero HM, Contreras-Castañon G, Tecuapetla-Chantes RG, Avila-Rodriguez MA

PP25 68Ga-peptide preparation with the use of two 68Ge/68Ga-generators

H. Kvaternik, D. Hausberger, C. Zink, B. Rumpf, R. M. Aigner

PP26 Assay of HEPES in 68Ga-peptides by HPLC

H. Kvaternik, D. Hausberger, B. Rumpf, R. M. Aigner

PP27 Preparation, in vitro and in vivo evaluation of a 99mTc(I)-Diethyl Ester (S,S)-Ethylenediamine- N,N´-DI-2-(3-Cyclohexyl) Propionic acid as a target-specific radiopharmaceutical

Drina Janković, Mladen Lakić, Aleksandar Savić, Slavica Ristić, Nadežda Nikolić, Aleksandar Vukadinović, Tibor J. Sabo, Sanja Vranješ-Đurić

PP28 90Y-labeled magnetite nanoparticles for possible application in cancer therapy

S. Vranješ-Đurić, M. Radović, D. Janković, N. Nikolić, G. F. Goya, P. Calatayud, V. Spasojević, B. Antić

PP29 Simplified automation of the GMP production of 68Ga-labelled peptides

David Goblet, Cristiana Gameiro, Neva Lazarova

PP30 Combining commercial production of multi-products in a GMP environment with Clinical & R&D activities

Cristiana Gameiro, Ian Oxley, Antero Abrunhosa, Vasko Kramer, Maria Vosjan, Arnold Spaans

PP31 ⁹⁹mTc(CO)3-labeling and Comparative In-Vivo Evaluation of Two Clicked cRGDfK Peptide Derivatives

Kusum Vats, Drishty Satpati, Haladhar D Sarma, Sharmila Banerjee

PP32 Application of AnaLig resin for 99mTc separation from molybdenum excess

Wojdowska W., Pawlak D.W., Parus L. J., Garnuszek P., Mikołajczak R.

PP33 Constraints for selection of suitable precursor for one-step automated synthesis of [18F]FECNT, the dopamine transporter ligand

Pijarowska-Kruszyna J, Jaron A, Kachniarz A, Malkowski B, Garnuszek P, Mikolajczak R

PP34 Gamma scintigraphy studies with 99mTc- amoxicillin sodium in bacterially infected and sterile inflamed rats

Derya Ilem-Ozdemir, Oya Caglayan-Orumlu, Makbule Asikoglu

PP35 Preparation of 99mTc- Amoxicillin Sodium Lyophilized Kit

Derya Ilem-Ozdemir, Oya Caglayan-Orumlu, Makbule Asikoglu

PP36 Outfits of Tracerlan FXC-PRO for 11C-Labeling

Arponen Eveliina, Helin Semi, Saarinen Timo, Vauhkala Simo, Kokkomäki Esa, Lehikoinen Pertti

PP37 Microfluidic synthesis of ω-[18F]fluoro-1-alkynes

Mariarosaria De Simone, Giancarlo Pascali, Ludovica Carzoli, Mauro Quaglierini, Mauro Telleschi, Piero A. Salvadori

PP38 Automated 18F-flumazenil production using chemically resistant disposable cassettes

Phoebe Lam, Martina Aistleitner, Reinhard Eichinger, Christoph Artner

PP39 The effect of the eluent solutions (TBAHCO3, Kryptand K2.2.2) on the radiochemical yields of 18F-Fluoromethylcholine

Surendra Nakka, Hemantha Kumara MC, Al-Qahtani Mohammed

PP40 [68Ga]Radiolabeling of short peptide that has a PET imaging potentials

Al-Qahtani, Mohammed, Al-Malki, Yousif

PP41 Is validation of radiochemical purity analysis in a public hospital in a developing country possible?

N Mambilima, SM Rubow

PP42 Improved automated radiosynthesis of [18F]FEPPA

N. Berroterán-Infante, M. Hacker, M. Mitterhauser, W. Wadsak

PP43 Synthesis and initial evaluation of Al18F-RESCA1-TATE for somatostatin receptor imaging with PET

Uta Funke, Frederik Cleeren, Joan Lecina, Rodrigo Gallardo, Alfons M. Verbruggen, Guy Bormans

PP44 Radiolabeling and SPECT/CT imaging of different polymer-decorated zein nanoparticles for oral administration

Rocío Ramos-Membrive, Ana Brotons, Gemma Quincoces, Laura Inchaurraga, Inés Luis de Redín, Verónica Morán, Berta García-García, Juan Manuel Irache, Iván Peñuelas

PP45 An analysis of the quality of 68Ga-DOTANOC radiolabelling over a 3 year period

Trabelsi, M., Cooper M.S.

PP46 In vivo biodistribution of adult human mesenchymal stem cells I (MSCS-ah) labeled with 99MTC-HMPAO administered via intravenous and intra-articular in animal model. Preliminary results

Alejandra Abella, Teodomiro Fuente, Antonio Jesús Montellano, Teresa Martínez, Ruben Rabadan, Luis Meseguer-Olmo

PP47 Synthesis of [¹⁸F]F-exendin-4 with high specific activity

Lehtiniemi P, Yim C, Mikkola K, Nuutila P, Solin O

PP48 Experimental radionuclide therapy with 177Lu-labelled cyclic minigastrin and human dosimetry estimations

von Guggenberg E, Rangger C, Mair C, Balogh L, Pöstényi Z, Pawlak D, Mikołajczak R

PP49 Synthesis of radiopharmaceuticals for cell radiolabelling using anion exchange column

Socan A, Kolenc Peitl P, Krošelj M, Rangger C, Decristoforo C

PP50 [68Ga]peptide production on commercial synthesiser mAIO

Collet C., Remy S., Didier R,Vergote T.,Karcher G., Véran N.

PP51 Dry kit formulation for efficient radiolabeling of 68Ga-PSMA

D. Pawlak, M. Maurin, P. Garnuszek, U. Karczmarczyk, R. Mikołajczak

PP52 Development of an experimental method using Cs-131 to evaluate radiobiological effects of internalized Auger-electron emitters

Pil Fredericia, Gregory Severin, Torsten Groesser, Ulli Köster, Mikael Jensen

PP53 Preclinical comparative evaluation of NOTA/NODAGA/DOTA CYCLO-RGD peptides labelled with Ga-68

R. Leonte, F. D. Puicea, A. Raicu, E. A. Min, R. Serban, G. Manda, D. Niculae

PP54 Synthesizer- and Kit-based preparation of prostate cancer imaging agent 68Ga-RM2

Marion Zerna, Hanno Schieferstein, Andre Müller, Mathias Berndt

PP55 Synthesis of pancreatic beta cell-specific [18F]fluoro-exendin-4 via strain-promoted aza-dibenzocyclooctyne/azide cycloaddition

Cheng-Bin Yim, Kirsi Mikkola, Pirjo Nuutila, Olof Solin

PP56 Automated systems for radiopharmacy

D. Seifert, J. Ráliš, O. Lebeda

PP57 Simple, suitable for everyday routine use quality control method to assess radionuclidic purity of cyclotron-produced 99mTc

Svetlana V. Selivanova, Helena Senta, Éric Lavallée, Lyne Caouette, Éric Turcotte, Roger Lecomte

PP58 Effective dose estimation using Monte Carlo simulation for patients undergoing radioiodine therapy

Marina Zdraveska Kochovska, Emilija Janjevik Ivanovska, Vesna Spasic Jokic

PP59 Chemical analysis of the rituximab radioimmunoconjugates in lyophilized formulations intended for oncological applications

Darinka Gjorgieva Ackova, Katarina Smilkov, Petre Makreski, Trajče Stafilov, Emilija Janevik-Ivanovska

PP61 The need and benefits of established radiopharmacy in developing African countries

Aschalew Alemu, Joel Munene Muchira, David Mwanza Wanjeh, Emilija Janevik-Ivanovska

PP62 University Master Program of Radiopharmacy – step forward for Good Radiopharmacy Education

Emilija Janevik-Ivanovska, Zoran Zdravev, Uday Bhonsle, Osso Júnior João Alberto, Adriano Duatti, Bistra Angelovska, Zdenka Stojanovska, Zorica Arsova Sarafinovska, Darko Bosnakovski, Darinka Gorgieva-Ackova, Katarina Smilkov, Elena Drakalska, Meera Venkatesh, Rubin Gulaboski

PP63 Synthesis and preclinical validations of a novel 18F-labelled RGD peptide prepared by ligation of a 2-cyanobenzothiazole with 1,2-aminothiol to image angiogenesis.

Didier J. Colin, James A. H. Inkster, Stéphane Germain, Yann Seimbille

Monitoring hypoxia and vasculature during bevacizumab treatment in a murine colorectal cancer model

The purpose of this study was to assess the effect of bevacizumab on vasculature and hypoxia in a colorectal tumor model. Nude mice with subcutaneous LS174T tumors were treated with bevacizumab or saline. To assess tumor properties, separate groups of mice were imaged using (18) F-Fluoromisonidazole (FMISO) and (18) F-Fluorodeoxyglucose (FDG) positron emission tomography or magnetic resonance imaging before and 2, 6 and 10 days after the start of treatment. Tumors were harvested after imaging to determine hypoxia and vascular density immunohistochemically. The T2 * time increased significantly less in the bevacizumab group. FMISO uptake increased more over time in the control group. Vessel density significantly decreased in the bevacizumab-treated group. The Carbonic anhydrase 9 (CAIX) and glucose uptake transporter 1 (GLUT1) fractions were higher in bevacizumab-treated tumors. However, the hypoxic fraction showed no significant difference. Bevacizumab led to shorter T2 * times and higher GLUT1 and CAIX expression, suggesting an increase in hypoxia and a higher glycolytic rate. This could be a mechanism of resistance to bevacizumab. The increase in hypoxia, however, could not be demonstrated by pimonidazole/FMISO, possibly because distribution of these tracers is hampered by bevacizumab-induced effects on vascular permeability and perfusion.

PET and SPECT imaging of a radiolabeled minigastrin analogue conjugated with DOTA, NOTA, and NODAGA and labeled with (64)Cu, (68)Ga, and (111)In

Cholecystokinin-2 (CCK-2) receptors, overexpressed in cancer types such as small cell lung cancers (SCLC) and medullary thyroid carcinomas (MTC), may serve as targets for peptide receptor radionuclide imaging. A variety of CCK and gastrin analogues has been developed, but a major drawback is metabolic instability or high kidney uptake. The minigastrin analogue PP-F11 has previously been shown to be a promising peptide for imaging of CCK-2 receptor positive tumors and was therefore further evaluated. The peptide was conjugated with one of the macrocyclic chelators DOTA, NOTA, or NODAGA. The peptide conjugates were then radiolabeled with either (68)Ga, (64)Cu, or (111)In. All (radio)labeled compounds were evaluated in vitro (IC50) and in vivo (biodistribution and PET/CT and SPECT/CT imaging). IC50 values were in the low nanomolar range for all compounds (0.79-1.51 nM). In the biodistribution studies, (68)Ga- and (111)In-labeled peptides showed higher tumor-to-background ratios than the (64)Cu-labeled compounds. All tested radiolabeled compounds clearly visualized the CCK2 receptor positive tumor in PET or SPECT imaging. The chelator did not seem to affect in vivo behavior of the peptide for (111)In- and (68)Ga-labeled peptides. In contrast, the biodistribution of the (64)Cu-labeled peptides showed high uptake in the liver and in other organs, most likely caused by high blood levels, probably due to dissociation of (64)Cu from the chelator and subsequent transchelation to proteins. Based on the present study, (68)Ga-DOTA-PP-F11 might be a promising radiopharmaceutical for PET/CT imaging of CCK2 receptor expressing tumors such as MTC and SCLC. Clinical studies are warranted to investigate the potential of this tracer.

Anti-CEA antibody fragments labeled with [(18)F]AlF for PET imaging of CEA-expressing tumors

A facile and rapid method to label peptides with (18)F based on chelation of [(18)F]AlF has been developed recently. Since this method requires heating to 100 °C, it cannot be used to label heat-sensitive proteins. Here, we used a two-step procedure to prepare (18)F-labeled heat-labile proteins using the [(18)F]AlF method based on hot maleimide conjugation. 1,4,7-Triazacyclononae-1,4-diacetate (NODA) containing a methyl phenylacetic acid group (MPA) functionalized with N-(2-aminoethyl)maleimide (EM) was used as a ligand which was labeled with [(18)F]AlF and then conjugated to the humanized anti-CEA antibody derivatives hMN-14-Fab', hMN-14-(scFv)2 (diabody), and a Dock-and-Lock engineered dimeric fragment hMN-14 Fab-AD2 at room temperature. The in vivo tumor targeting characteristics of the (18)F-labeled antibody derivatives were determined by PET imaging of mice with s.c. xenografts. NODA-MPAEM was radiolabeled with [(18)F]AlF at a specific activity of 29-39 MBq/nmol and a labeling efficiency of 94 ± 2%. The labeling efficiencies of the maleimide conjugation ranged from 70% to 77%, resulting in [(18)F]AlF-labeled hMN14-Fab', hMN14-Fab-AD2, or hMN14-diabody with a specific activity of 15-17 MBq/nmol. The radiolabeled conjugates were purified by gel filtration. For biodistribution and microPET imaging, antibody fragments were injected intravenously into BALB/c nude mice with s.c. CEA-expressing LS174T xenografts (right flank) and CEA-negative SK-RC-52 xenografts (left flank). All [(18)F]AlF-labeled conjugates showed specific uptake in the LS174T xenografts with a maximal tumor uptake of 4.73% ID/g at 4 h after injection. Uptake in CEA-negative SK-RC-52 xenografts was significantly lower. Tumors were clearly visualized on microPET images. Using a [(18)F]AlF-labeled maleimide functionalized chelator, antibody fragments could be radiofluorinated within 4 h at high specific activity. Here, we translated this method to preclinical PET imaging studies and showed feasibility of [(18)F]AlF-fluorinated hMN-14-Fab', [(18)F]AlF-hMN-14-Fab-AD2, and [(18)F]AlF-hMN-14-diabody for microPET imaging of CEA-expressing colonic cancer.

Quantitative multi-pinhole small-animal SPECT: uniform versus non-uniform Chang attenuation correction

Attenuation of photon flux on trajectories between the source and pinhole apertures affects the quantitative accuracy of reconstructed single-photon emission computed tomography (SPECT) images. We propose a Chang-based non-uniform attenuation correction (NUA-CT) for small-animal SPECT/CT with focusing pinhole collimation, and compare the quantitative accuracy with uniform Chang correction based on (i) body outlines extracted from x-ray CT (UA-CT) and (ii) on hand drawn body contours on the images obtained with three integrated optical cameras (UA-BC). Measurements in phantoms and rats containing known activities of isotopes were conducted for evaluation. In (125)I, (201)Tl, (99m)Tc and (111)In phantom experiments, average relative errors comparing to the gold standards measured in a dose calibrator were reduced to 5.5%, 6.8%, 4.9% and 2.8%, respectively, with NUA-CT. In animal studies, these errors were 2.1%, 3.3%, 2.0% and 2.0%, respectively. Differences in accuracy on average between results of NUA-CT, UA-CT and UA-BC were less than 2.3% in phantom studies and 3.1% in animal studies except for (125)I (3.6% and 5.1%, respectively). All methods tested provide reasonable attenuation correction and result in high quantitative accuracy. NUA-CT shows superior accuracy except for (125)I, where other factors may have more impact on the quantitative accuracy than the selected attenuation correction.

Intravenous technetium-99m labelled PEG-liposomes in horses: a safety and biodistribution study

REASONS FOR PERFORMING STUDY

Liposomes are phospholipid nanoparticles that extravasate at sites of increased vascular permeability. They have potential in equine medicine for targeted drug delivery and diagnostic imaging of infectious, inflammatory and neoplastic lesions.

OBJECTIVES

This study evaluates the safety and biodistribution of i.v. polyethyleneglycol(PEG) liposomes in normal horses.

METHODS

PEG-liposomes were prepared by the film hydration method and labelled using (99m) Tc-hexamethyl-propylene-amine-oxime. A single dose of 0.24 µmol/kg bwt (99m) Tc-PEG-liposomes and 2.4 µmol/kg bwt unlabelled PEG-liposomes was administered to 10 conscious horses via i.v. infusion at a rate of 6 µmol/min for the first 15 min and 60 µmol/min thereafter. Clinical parameters, haematology, plasma biochemistry and serum complement activity were monitored serially. Scintigraphic imaging was performed at 1, 12 and 21 h post infusion (PI). Six horses were subjected to euthanasia at 24 h PI. The percentage injected dose per kilogram of tissue was calculated for multiple organs. Results were analysed using repeated measures ANOVA.

RESULTS

Horses did not demonstrate adverse reactions during or after liposome infusion. There was a significant elevation in heart rate and respiratory rate at 20 and 25 min PI. No significant complement consumption was detected, although a trend for decreased total haemolytic complement values at 20 min PI was present. Scintigraphic studies revealed a prolonged vascular phase that lasted to 21 h PI, with a reproducible pattern of organ distribution. Biodistribution studies revealed the highest concentrations of radiopharmaceutical within the lung, kidney, liver and spleen.

CONCLUSIONS

Intravenous liposome administration appears to be safe in horses. When administered in combination with PEG-liposomes, (99m) Tc-PEG-liposomes have long circulating characteristics and a reproducible pattern of organ distribution in horses.

POTENTIAL RELEVANCE

Radiolabelled liposomes may be useful for detecting infection, inflammation and neoplasia in the horse. Liposomes have significant potential for targeted drug delivery in the horse. This study establishes the scintigraphic findings and tissue distribution of 99mTc-PEG-liposomes after i.v. administration in healthy horses.

In vivo applications of PEG liposomes: unexpected observations

Recent studies with PEG liposomes in patients have consistently shown that liposomes can induce side effects (flushing, tightness of the chest). Furthermore, the blood clearance of PEG liposomes was shown to be dose-dependent: at lipid doses lower than 1 micromol/kg, PEG liposomes do not show the long-circulation property but instead are cleared relatively rapidly from the bloodstream. Another remarkable observation was that repeated injections of PEG liposomes led to significant pharmacokinetic changes: the circulatory half-life of a second dose of radiolabeled PEG liposomes dramatically decreased when given from 5 days to up to 4 weeks after a first injection. In these three unexpected phenomena, proteins of the complement system seem to play a key role. Therefore, one has to consider that PEG liposomes are not inert drug-carrying vehicles in vivo. Pharmacological effects can occur, induced solely by using liposomal particles irrespective of the drug content.

(99m)Tc-labelled Stealth liposomal doxorubicin (Caelyx) in glioblastomas and metastatic brain tumours

British Journal of Cancer (2002) 86, 659–660. DOI: 10.1038/sj/bjc/6600093 www.bjcancer.com

© 2002 Cancer Research UK

Role of complement activation in hypersensitivity reactions to doxil and hynic PEG liposomes: experimental and clinical studies

Pegylated liposomal doxorubicin (Doxil) and 99mTc-HYNIC PEG liposomes (HPL) were reported earlier to cause hypersensitivity reactions (HSRs) in a substantial percentage of patients treated i.v. with these formulations. Here we report that (1) Doxil, HPL, pegylated phosphatidylethanolamine (PEG-PE)-containing empty liposomes matched with Doxil and HPL in size and lipid composition, and phosphatidylglycerol (PG)-containing negatively charged vesicles were potent C activators in human serum in vitro, whereas small neutral liposomes caused no C activation. (2) Doxil and other size-matched PEG-PE and/or PG-containing liposomes also caused massive cardiopulmonary distress with anaphylactoid shock in pigs via C activation, whereas equivalent neutral liposomes caused no hemodynamic changes. (3) A clinical study showed more frequent and greater C activation in patients displaying HSR than in non-reactive patients. These data suggest that liposome-induced HSRs in susceptible individuals may be due to C activation, which, in turn, is due to the presence of negatively charged PEG-PE in these vesicles.

Microscopic localization of PEG-liposomes in a rat model of focal infection

In the present study the microscopic localization of polyethylene glycol (PEG) liposomes in infected tissues was studied with both light microscopy (LM) and transmission electron microscopy (TEM) in rats with focal intramuscular Staphylococcus aureus infection. PEG-liposomes containing colloidal gold were prepared and injected intravenously in rats with focal S. aureus infection and tissues were dissected at 24 h post injection. Sections were cut and liposomes were visualized for microscopic evaluation using silver enhancement. Uptake of PEG-liposomes was visualized by both scintigraphy and LM in the abscess, liver and spleen. In the infected area, the liposomes were mainly found in the vicinity of blood vessels. TEM showed that the liposomes were localized in the macrophages and to a lesser extent in endothelial cells in the infectious tissue. In the liver, the liposomes appeared mainly localized in Kupffer cells. In the spleen, uptake was only seen in cells of the red pulp and in cells around the central arteries. Our microscopic observations indicate that uptake and retention of PEG-liposomes in the infectious focus is a result of enhanced extravasation due to increased vascular permeability and subsequent phagocytosis of PEG-liposomes by macrophages in the infected tissue.

Factors affecting the accelerated blood clearance of polyethylene glycol-liposomes upon repeated injection

Previously, we showed that long-circulating polyethylene glycol (PEG)-liposomes are cleared rapidly from the circulation when injected repeatedly in the same animal. In this article, we describe the effects of PEG-coating, the circulation time, the lipid dose, and the presence of encapsulated doxorubicin on the pharmacokinetics upon repeated injection in rats. Furthermore, the role of liver and splenic macrophages was investigated. Liposomes without PEG-coating also showed the so-called "enhanced clearance effect": blood levels at 4 h post injection decreased from 62.8 +/- 13.7% of injected dose (%ID) after the first injection to 0.54 +/- 0.21%ID after the second injection. This decrease was independent of the circulation time of the first dose. Decreasing the first lipid dose of PEG-liposomes to 0.05 micromol/kg still led to enhanced clearance of a second dose of 5 micromol/kg. No changes in pharmacokinetics were observed when the second dose was 50 micromol/kg. When hepatosplenic macrophages were depleted, no enhanced clearance of repeated liposome injections was observed. A dose of doxorubicin containing PEG-liposomes (Doxil), injected 1 week after injection of empty PEG-liposomes, was cleared rapidly from the circulation in rats. Our results indicate that hepatosplenic macrophages play an essential role in the enhanced clearance effect and that the change in pharmacokinetic behavior upon repeated injection is a general characteristic of liposomes, unrelated to the presence of PEG. Therefore, these findings may have a considerable impact on the clinical application of liposomal formulations that are administered repeatedly.

Recognition and clearance of methoxypoly(ethyleneglycol)2000-grafted liposomes by macrophages with enhanced phagocytic capacity. Implications in experimental and clinical oncology

Intravenous injection of an endotoxin-free solution of poloxamine-908 to rats can enhance the phagocytic clearance capacity of tissue macrophages, particularly those of the liver and the spleen. Such stimulated cells were able to clear a significant portion of intravenously injected methoxypoly(ethyleneglycol)2000 liposomes (mean size of 87 nm), labelled with technetium-99m via the N-hydroxysuccinimidyl hydrazine nicotinate hydrochloride derivative of distearoyl phosphatidylethanolamine, within 4 h post administration. These liposomes, otherwise, exhibit long circulatory behaviour in control animals, with poor localization to the liver and spleen. We suggest that such technetium-99m-labelled engineered vesicles may be of aid for detection of the liver and spleen macrophages with enhanced phagocytic clearance capacity by gamma scintigraphy. Alterations in the phagocytic activity of liver and spleen macrophages is known to occur during cancer. Therefore, such diagnostic procedures may prove useful for patient selection or for monitoring the progress of treatment with long circulating nanoparticles carrying anti-cancer agents, thus minimizing damage to this important line of body's defence cells, and are discussed.

The effect of molecular weight on nonspecific accumulation of (99m)T-labeled proteins in inflammatory foci

Although several proteins have been proposed and tested for scintigraphic detection of infection, the most optimal characteristics of a protein for this application have not yet been determined. Molecular weight (MW) of the protein, its charge, shape, carbohydrate content, characteristics of the radionuclide and receptor interactions are factors that could affect the in vivo behavior of the infection imaging agent. The effect of molecular weight on nonspecific accumulation of (99m)Tc-labeled proteins in inflammatory foci was studied in a rat model.

METHODS

Eleven proteins whose MWs ranged from 2.5 kDa up to 800 kDa were labeled with (99m)Tc using the hydrazinonicotinamide (HYNIC) chelator. Rats with S. aureus infection were injected i.v. with 15 MBq (99m)Tc-labeled protein. Gamma camera images were acquired and biodistribution of the radiolabel was determined ex vivo.

RESULTS

From biodistribution data no significant correlation was found between abscess uptake and molecular size of the (99m)Tc-labeled proteins that were studied. Fast blood clearance with predominant uptake in liver and spleen was found for the largest proteins (MW 669 kDa-800 kDA). For proteins of intermediate size (MW 66 kDa -206 kDa) we found relatively slow blood clearance with relatively moderate uptake in liver and spleen. For smaller proteins (MW 2.5 kDa -29 kDa) rapid blood clearance with predominant kidney uptake was observed. The abscess uptake of the (99m)Tc-labeled proteins (%ID/g, 24 h p.i.) was highest for serum proteins IgG and BSA. Abscess uptake correlated well with blood levels: r = 0.95 and 0.84 at 4 and 24 h respectively (P < 0.005). The abscess-to-muscle ratios varied from 2.1 to 17.8 at 24 h p.i. with highest values for alpha-2 macroglobulin (MW 725 kDa) and the intermediate sized proteins (MW 66-206 kDa). Gamma camera imaging showed localization of all radiotracers at the site of infection with abscess-to-background ratios (A/B) ranging from 1.4 to 7.0 (IgG) at 20 h p.i. The serum proteins IgG and BSA showed highest blood levels and best infection imaging characteristics.

CONCLUSION

Not molecular weight but blood residence time is the principal factor that determines localization of a nonspecific tracer protein in infectious foci. The ideal nonspecific infection imaging agent is a protein with a long circulatory half-life. From the proteins tested here IgG and albumin showed the best characteristics for an infection imaging agent.

Tc-99m-PEG-Liposomes for the evaluation of colitis in Crohn's disease

In the present study, the potential role of 99mTc-PEG-liposome to determine the extent and severity of active disease of Crohn's colitis was investigated. Patients suspected of having an exacerbation of Crohn's disease underwent a 99mTc-PEG-liposome scan (740 MBq, imaging at 4 and 24 h p.i.). A barium enema or endoscopy was performed as the standard verification procedure. Disease activity indices (Clinical Disease Activity Index and Van Hees Activity Index) were calculated. In seven patients positive images of colon segments affected by Crohn's colitis were obtained using 99mTc-PEG-liposomes. Only a moderate relation between 99mTc-liposome scan grading and verification procedures was found (Spearman rank r = 0.22). In accordance with previous studies, no significant correlation was found between the clinical disease activity indices and the verification procedures. This study was prematurely terminated because of unacceptable side-effects in 3 out of 9 patients, which occured almost immediately after starting the infusion. The complaints consisted of dyspnea and facial erythema. The symptoms were self-limiting when the infusion was stopped. In conclusion, the extent of Crohn's colitis can be established non-invasively with 99mTc-PEG-liposome scintigraphy. However, in view of the encountered side-effects, the PEG-liposomal preparation may have to be modified.

A 99Tcm-labelled leukotriene B4 receptor antagonist for scintigraphic detection of infection in rabbits

In a search for a rapid and accurate imaging agent for scintigraphic detection of infection and inflammation, an LTB4 receptor antagonist, 99Tcm-RP517, which contains the hydrazino nicotinamide moiety, has been developed recently. To study the in vivo behaviour of 99Tcm-RP517, rabbits with Escherichia coli infection were injected intravenously with 99Tcm-RP517. Gamma camera images were obtained and ex vivo bio-distribution was determined at several hours post-injection (p.i.). In a separate set of rabbits the choledochal duct was cannulated to quantitatively monitor the hepatobiliary clearance of the radiopharmaceutical. The receptor binding fraction of the radiolabelled RP517 exceeded 70%. Accumulation of 99Tcm-RP517 in the abscess was visualized as early as 1 h p.i. Due to rapid blood clearance (t1/2 alpha=18+/-0.6 min, t1/2 beta=6.5+/-0.4 h) and high abscess uptake, the abscess-to-muscle ratios increased with time from 7.0+/-2.3 at 1 h p.i. to 44.3+/-4.6 at 20 h p.i. The agent mainly cleared via the hepatobiliary route: 50% of the radiolabel was recovered in the small bowel at 1 h p.i., whereas 85% was found in cecum and sigmoid at 20 h p.i. In conclusion, 99Tcm-RP517 rapidly visualized E. coli abscesses in rabbits. The agent rapidly cleared from the blood, mainly via the hepatobiliary route. High abscess-to-background ratios were achieved. The accumulation in the intestines could limit the applicability of this agent for detecting infectious processes in the abdominal area. The development of a more hydrophilic analogue of 99Tcm-RP517 could improve the clinical applicability of this agent.

Radiolabeled liposomes for scintigraphic imaging

Liposomes have been investigated extensively as carriers for drugs in attempts to achieve selective deposition and/or reduced toxicity. Liposomes radiolabeled with gamma emitters such as (67)Ga, (111)In and (99m)Tc, can be used for imaging purposes. Liposomes as formulated in the past, are rapidly taken up by cells of the mononuclear phagocyte system (MPS), primarily those located in liver and spleen. The recent development of long-circulating liposomes (LCLs), yielded liposomes that oppose recognition by the MPS. The development of these LCLs with enhanced circulatory half-lives has broadened the potential of liposomes to scintigraphically visualize pathologic processes in vivo. Liposomes have been proposed for tumor imaging, infection imaging and blood pool imaging. Strategies have been developed that allow rapid, easy and efficient labeling of preformed liposomes with (111)In and (99m)Tc. There is now a vast body of preclinical evidence showing that LCLs can be used to image a wide variety of tumors as well as inflammatory lesions. The first studies in patients show that radiolabeled liposomes can image tumor and inflammatory lesions with good sensitivity and good specificity. Here, the present status of liposome-based radiopharmaceuticals for scintigraphic application is reviewed.

Preclinical and clinical evidence for disappearance of long-circulating characteristics of polyethylene glycol liposomes at low lipid dose

This study describes the effect of the lipid dose of (99m)Tc-polyethylene glycol (PEG) liposomes in the low-dose range (0. 02-1.0 micromol/kg) on the pharmacokinetics and biodistribution in rats, rabbits, and humans. The biodistribution and pharmacokinetics of (99m)Tc-PEG liposomes at various dose levels were studied in rats and rabbits with a focal Escherichia coli infection. Scintigraphic images were recorded on a gamma camera. In addition, the role of macrophages in the biodistribution of a low-dose PEG liposome injection was studied. Finally, the pharmacokinetics of (99m)Tc-PEG liposomes at two lipid dose levels was studied in four patients. At a dose level of 0.03 micromol/kg, the blood level in rats at 4 h postinjection was significantly lower than at the highest dose level (1.1 micromol/kg). The same effect was observed in rabbits where enhanced clearance was observed at a dose level of 0.02 micromol/kg. The circulatory half-life decreased from 10.4 to 3.5 h (at 1.0 and 0. 02 micromol/kg, respectively). At the lowest dose level, liposomes were mainly taken up by the liver and to a lesser extent by the spleen. Injection of a low dose of PEG liposomes in macrophage-depleted rabbits resulted in normal pharmacokinetics, suggesting involvement of macrophages in the effectuation of the rapid elimination of the liposomes from the circulation. Most importantly, the rapid clearance of low-dose PEG liposomes was also observed in humans when relatively low lipid doses were administered. This study showed that at very low lipid doses the biodistribution of PEG liposomes is dramatically altered.

Scintigraphic evaluation of experimental chronic osteomyelitis

Assessment of disease activity and disease extent in chronic osteomyelitis remains a difficult diagnostic problem. Radiography is not particularly sensitive. Scintigraphic techniques can be more helpful, but the routinely available agents lack specificity (99mTc-methylene diphosphonate [MDP], 67Ga-citrate) or are laborious to prepare (111In-leukocytes). We evaluated the performance of 2 new radiopharmaceuticals, 99mTc-polyethyleneglycol (PEG) liposomes and 99mTc-hydrazinonicotinamide (HYNIC)-immunoglobulin G (IgG), in an experimental model of chronic osteomyelitis.

METHODS

Chronic osteomyelitis was induced in rabbits by inserting S. aureus into the right reamed and washed femoral canal. The canal was closed with cement. A sham operation was performed on the left femur. Routine radiographs were obtained immediately after surgery and before scintigraphy. Four weeks after surgery, each rabbit was injected with 37 MBq 99mTc-PEG liposomes, 99mTc-HYNIC-IgG, and 99mTc-MDP on 3 consecutive days and imaged up to 4 (MDP) or 22 (liposomes and IgG) h after injection. On day 4, rabbits received either 18 MBq 111In-granulocytes or 67Ga-citrate and were imaged up to 44 h after injection. Uptake in the infected femur was determined by drawing regions of interest. Ratios of infected-to-sham-operated femur were calculated. After the last image, the rabbits were killed, and the left and right femur were scored for microbiologic and histopathologic evidence of osteomyelitis.

RESULTS

99mTc-PEG liposomes and 99mTc-HYNIC-IgG correctly identified all 6 rabbits with osteomyelitis. 11In-granulocytes and 67Ga-citrate gave equivocal results in 1 infected rabbit. 99mTc-MDP missed 1 case of osteomyelitis. The uptake in the affected region did not differ significantly between the agents, although 99mTc-MDP tended to have higher values (MDP, 4.75 +/- 1.23 percentage injected dose per gram [%ID/g]; 67Ga, 2.05 +/- 0.54 %ID/g; granulocytes, 1.56 +/- 0.83 %ID/g; liposomes, 1.75 +/- 0.76 %ID/g, and IgG, 1.96 +/- 0.27 %ID/g). The ratios of infected-to-normal femur were also not significantly different for the respective radiopharmaceuticals. Radiography visualized only severe osteomyelitis.

CONCLUSION

In this rabbit model, 99mTc-PEG liposomes and 99mTc-HYNIC-IgG performed at least as well as 111In-granulocytes and 67Ga-citrate in the localization of chronic osteomyelitis. The ease of preparation, the better image quality, and the lower radiation dose suggest that 99mTc-PEG liposomes and 99mTc-HYNIC-IgG might be suitable alternatives for 67Ga-citrate and 111In-granulocytes in the scintigraphic evaluation of osteomyelitis.

Improved imaging of infections by avidin-induced clearance of 99mTc-biotin-PEG liposomes

This article describes the preparation and optimization of biotin-polyethyleneglycol (PEG) liposomes and their application in experimental infection models to improve the scintigraphic imaging of infection and inflammation.

METHODS

Biotin was coupled to PEG-distearoylphosphatidylethanolamine (DSPE) and subsequently incorporated in the PEG liposomes. Biotinylated liposomes were radiolabeled with 99mTc-hydrazinonicotinamide. In vitro binding studies were performed to find the optimal biotin concentration in the liposomes. In rats the biodistribution of the 99mTc-biotin-PEG liposomes was compared with the biodistribution of normal (nonbiotinylated) 99mTc-PEG liposomes. Furthermore, in vivo studies in rats were performed to study both the effect of the biotin content and the optimal avidin dose for efficient clearance of the liposomes. Liposomes containing 0.5 or 1.0 mol% biotin-PEG-DSPE were compared in rats with a Staphylococcus aureus infection in the left calf muscle. Avidin was injected 4 h after injection of the liposomes.

RESULTS

Biotinylation of the liposomes did not affect their in vivo behavior. All biotin-PEG liposome formulations tested showed good in vitro avidin binding with 50% inhibitory concentrations ranging from 36 to 8 micromol/L. With avidin doses higher than 100 microg, both preparations rapidly cleared from the circulation. As a result, abscess-to-blood ratios increased 5-fold. To illustrate the potential of the avidin-induced clearance of radiolabeled PEG liposomes, we also studied the 99mTc-biotin-PEG liposomes in rabbits with a subcutaneous S. aureus abscess. The infection was visualized only after injection of 100 microg avidin.

CONCLUSION

This study shows that biotin-coated 99mTc-PEG liposomes in combination with the injection of avidin can lead to improved imaging of infection or inflammation localized especially in regions with high blood-pool activity.

99mTc-PEG liposomes for the scintigraphic detection of infection and inflammation: clinical evaluation

Polyethyleneglycol (PEG) liposomes have been shown to be excellent vehicles for scintigraphic imaging of infection and inflammation in various experimental models. In this article we report on a series of patients with possible infectious and inflammatory disease in whom the performance of 99mTc-PEG liposomes was evaluated. The results of 99mTc-PEG liposome scintigraphy were directly compared with those of 111In-immunoglobulin G (IgG) scintigraphy.

METHODS

Thirty-five patients (22 men, 13 women; mean age, 51 y; range, 20-76 y), suspected of having infectious or inflammatory disease, received 740 MBq 99mTc-PEG liposomes intravenously. Imaging was performed at 4 and 24 h after injection. Patients received 75 MBq 111In-IgG 24 h after administration of the liposomes. The scintigraphic results were compared and verified by culture, biopsy, surgery, and follow-up of at least 6 mo.

RESULTS

Of the 16 proven infections and inflammations, 15 were detected by 99mTc-PEG liposome scintigraphy: soft-tissue infection (n = 3), septic arthritis (n = 3), autoimmune polyarthritis (n = 2), infected hip prosthesis (n = 1), infected osteosynthesis (n = 1), spondylodiscitis (n = 1), infected aortic prosthesis (n = 1), colitis (n = 1), abdominal abscess (n = 1), and pneumonia (n = 1). 99mTc-PEG liposome and 111In-IgG scintigraphy both missed 1 case of endocarditis. In addition, an 111In-IgG scan of a patient with mild soft-tissue infection was false-negative. Concordantly false-positive scans were recorded from 2 patients, both with uninfected pseudarthrosis and focal signs of sterile inflammation. During liposomal administration, 1 patient experienced flushing and chest tightness, which rapidly disappeared after lowering the infusion rate. No other adverse events were observed.

CONCLUSION

This clinical evaluation of 99mTc-PEG liposomes shows that focal infection and inflammation can be adequately imaged with this new agent. The performance of 99mTc-PEG liposomes is at least as effective as that of 111In-IgG. With the simple and safe preparation and the physical and logistic advantages of a 99mTc label, 99mTc-PEG liposomes could be an attractive agent for infection or inflammation imaging.

Accelerated blood clearance and altered biodistribution of repeated injections of sterically stabilized liposomes

Sterically stabilized liposomes are considered promising carriers of therapeutic agents because they can facilitate controlled release of the drugs, thereby reducing drug-related toxicity and/or targeted delivery of drugs. Herein, we studied the pharmacokinetics and biodistribution of repeated injections of radiolabeled polyethyleneglycol (PEG) liposomes. Weekly injections of (99m)Tc-PEG liposomes dramatically influenced the circulatory half-life in rats. Biodistribution 4 h after the second dose showed a significantly reduced blood content (from 52.6 +/- 3.7 to 0.6 +/- 0.1% injected dose (ID), P <.01) accompanied by a highly increased uptake in the liver (from 8.1 +/- 0.8 to 46.2 +/- 9.8%ID, P <.01) and in the spleen (from 2.2 +/- 0.2 to 5.3 +/- 0.7%ID, P <.01). At subsequent injections the effect was less pronounced: after the fourth dose, the pharmacokinetics of the radiolabel had almost returned to normal. The same phenomenon was observed in a rhesus monkey, but not in mice. The enhanced blood clearance of the PEG liposomes also was observed in rats after transfusion of serum from rats that had received PEG liposomes 1 week earlier, indicating that the enhanced blood clearance was caused by a soluble serum factor. This serum factor was a heat-labile molecule that coeluted on a size exclusion column with a 150-kDa protein. In summary, i.v. administration of sterically stabilized PEG liposomes significantly altered the pharmacokinetic behavior of subsequently injected PEG liposomes in a time- and frequency-dependent manner. The observed phenomenon may have important implications for the repeated administration of sterically stabilized liposomes for targeted drug delivery.

Scintigraphic imaging of bacterial and fungal infection in granulocytopenic rats

Scintigraphic imaging in granulocytopenic patients can be very useful to detect and localize infections, which often do not show localizing signs and symptoms. We studied the potential of 99mTc-labeled polyethylene glycol (PEG)-coated liposomes and 99mTc-labeled IgG to image bacterial and fungal infection in a granulocytopenic rat model. 67Ga-citrate was used as a reference agent.

METHODS

99mTc-PEG-liposomes, 99mTc-hydrazinonicotinate (HYNIC)-IgG or 67Ga-citrate was administered to granulocytopenic rats with a Staphylococcus aureus abscess or with unilateral invasive pulmonary aspergillosis. Imaging and biodistribution studies were performed.

RESULTS

All agents visualized the S. aureus infection from 1 h after injection onward. However, only with 99mTc-PEG-liposomes and with 99mTc-HYNIC-IgG did activity in the infectious foci increase with time up to 24 h. 99mTc-PEG-liposomes and 99mTc-HYNIC-IgG showed significantly higher accumulation in the infectious focus compared with 67Ga-citrate (1.33+/-0.31 and 1.40+/-0.16 percentage injected dose per gram [%ID/g], respectively, versus 0.31+/-0.04 %ID/g 24 h after injection; P<0.05). At 24 h after injection, abscess-to-muscle ratios were highest for 99mTc-liposomes (72.1+/-19.1), followed by 99mTc-HYNIC-IgG (18.3+/-3.3) and 67Ga-citrate (4.4+/-0.7). In pulmonary aspergillosis, both 99mTc-PEG-liposomes and 99mTC-HYNIC-IgG showed significantly higher uptake in the infected lung than did 67Ga-citrate (3.6+/-0.4 and 8.3+/-0.8 %ID/g, respectively, versus 1.3 %ID/g at 24 h after injection; P<0.05).

CONCLUSION

99mTc-PEG-liposomes and 99mTc-HYNIC-IgG performed better than did 67Ga-citrate in the localization of peripheral bacterial infection and fungal infection in the lung in granulocytopenic rats. The high focal uptake and high target-to-nontarget ratios of 99mTc-PEG-liposomes and 99mTc-HYNIC-IgG indicate that both radiopharmaceuticals may become valuable agents to image infection in granulocytopenic patients.

Liposomes for scintigraphic detection of infection and inflammation

Liposomes are small vesicles consisting of one or more concentric lipid bilayers enclosing discrete aqueous spaces. Liposomes potentially serve as carriers for radiolabels to visualize pathological processes scintigraphically. Research performed during the last two decades has revealed insight on the characteristics of liposomes with regard to their tissue distribution after i.v. injection. Various approaches have been developed to radiolabel liposomes with gamma-emitting radionuclides such as Ga-67, In-111 and Tc-99m. Preferably, liposomes are labeled according to the 'after-loading' method. The radionuclide can either be encapsulated in the aqueous interior or coupled to the lipid bilayer. The potential of radiolabeled liposomes to image infectious and inflammatory foci has been demonstrated in a variety of preclinical studies. Recently, a study in patients suspected of having infectious or inflammatory disease has been initiated. Preliminary clinically results exemplify the potential of Tc-99m-PEG liposomes to image infection and inflammation.

Imaging experimental intraabdominal abscesses with 99mTc-PEG liposomes and 99mTc-HYNIC IgG

OBJECTIVE

To evaluate the accuracy of technetium-99m-labeled polyethylene glycol-coated liposomes (99mTc-PEG liposomes) and technetium-99m-labeled nonspecific human immunoglobulin G (99mTc-HYNIC IgG) for the scintigraphic detection of experimental intraabdominal abscesses in comparison with that of a standard agent, gallium-67 citrate.

BACKGROUND

Scintigraphic imaging techniques can be very useful for the rapid and accurate localization of intraabdominal abscesses. Two newly developed radiolabeled agents, 99mTc-PEG liposomes and 99mTc-HYNIC IgG, have shown to be excellent agents for imaging experimental focal infection, but have not yet been studied in the detection of abdominal abscesses.

METHODS

Intraabdominal abscesses were induced in 42 rats using the cecal ligation and puncture technique. Seven days later, randomized groups of rats received 99mTc-PEG liposomes, 99mTc-HYNIC IgG, or 67Ga citrate intravenously. The rats were imaged up to 24 hours after the injection. The biodistribution of the radiolabel was determined by counting dissected tissues ex vivo. Macroscopic intraabdominal abnormalities and focal uptake on the images were independently scored on a semiquantitative scale.

RESULTS

99mTc-PEG liposomes provided the earliest scintigraphic visualization of the abscess (as soon as 2 hours after the injection vs. 4 hours for the other two agents). Liposomes, IgG, and gallium all showed similarly high absolute uptake in the abscess. Focal uptake of liposomes and gallium correlated best with the extent of the macroscopic abnormalities.

CONCLUSIONS

99mTc-PEG liposomes and 99mTc-HYNIC IgG performed at least as well as the standard agent, 67Ga citrate, in the detection of experimental intraabdominal abscesses, with obvious advantages such as lower radiation exposure and more favorable physical properties. Of the two technetium agents, the liposomes seemed to be superior, providing the earliest diagnostic image and the best correlation with the inflammatory abnormalities. In addition, the preferential localization of radiolabeled PEG liposomes holds promise for targeted delivery of liposome-encapsulated drugs.

A novel method to label liposomes with 99mTc by the hydrazino nicotinyl derivative

In this study a new 99mTc labeling method for polyethyleneglycol (PEG)-coated liposomes is described. The in vitro and in vivo characteristics were compared with the conventional 99mTc-HMPAO-labeled PEG-coated liposomes.

METHODS

PEG-coated liposomes were labeled with 99mTc by the hydrazino nicotinyl (HYNIC) derivative of distearoylphosphatidyl-ethanolamine (DSPE) and compared with PEG-coated liposomes labeled with 99mTc-HMPAO. In vitro stability tests were performed. Biodistribution and imaging characteristics of both liposomal preparations were determined in rats with Staphylococcus aureus infection in the left calf muscle.

RESULTS

Per liposome, 230 hydrazine groups were incorporated. The labeling efficiency of the 99mTc-HYNIC liposomes was greater than 95%, so no postlabeling purification was required, in contrast to the 99mTc-HMPAO liposomes. The 99mTc-HYNIC liposomes showed greater in vitro stability than the conventional 99mTc-HMPAO liposomes. Abscess uptake of the 99mTc-HYNIC liposomes was significantly greater (1.74+/-0.38%ID/g versus 1.26+/-0.29%ID/g, 24 h postinjection, P < 0.03). Furthermore, kidney uptake of the 99mTc-HYNIC liposomes was one third of the uptake of the 99mTc-HMPAO liposomes (0.79+/-0.07%ID/g versus 2.47+/-0.35%ID/g, 24 h postinjection, P < 0.0001).

CONCLUSION

This new 99mTc-HYNIC-based labeling method for liposomes is rapid, efficient and easy to perform. Most importantly, the 99mTc-labeled liposomes have an improved stability and in vivo characteristics. The new labeling method is a major step forward toward a radiopharmaceutical for infection imaging that can be prepared in a one-step procedure within 15 min at room temperature and thus can be applied in every routine clinical practice.

Technetium-99m-labeled liposomes to image experimental colitis in rabbits: comparison with technetium-99m-HMPAO-granulocytes and technetium-99m-HYNIC-IgG

Scintigraphic techniques are routinely used for the evaluation of the extent and severity of inflammatory bowel disease. Currently, the radiopharmaceutical of choice is 99mTc-hexamethyl propyleneamine oxime (HMPAO)-leukocytes. We studied the imaging potential of two recently developed 99mTc-labeled agents, polyethylene glycol (PEG)-coated liposomes and hydrazinonicotinate (HYNIC) IgG, in a rabbit model of acute colitis, and compared them with that of 99mTc-labeled, granulocyte-enriched (>90%), white blood cells.

METHODS

Acute colitis was induced in rabbits by retrograde instillation of trinitrobenzene sulfonic acid. After 48 hr, 37 MBq of each radiopharmaceutical was administered intravenously. Gamma camera images were taken at 0, 1, 2, 4, 10 and 24 hr. At 4 and 24 hr postinjection, groups of rabbits were killed, and the uptake of the radiolabel in the dissected tissues was determined. For each affected 5-cm segment, the colitis index (CI, affected-to-normal-colon-uptake ratio) was calculated and correlated to the macroscopically scored severity of inflammation.

RESULTS

All three agents visualized the colitis lesions within 1 hr postinjection. The CI correlated with the severity of the abnormalities. With increasing severity, the CI at 4 hr postinjection for liposomes was 3.89+/-0.73, 4.41+/-0.47 and 5.76+/-0.65; for IgG 1.67+/-0.08, 3.92+/-0.44 and 6.14+/-0.65; and for granulocytes 2.90+/-0.09, 6.15+/-0.96 and 9.36+/-3.35. For liposomes, the CI further increased during 24-hr postinjection to 6.56+/-0.84, 8.50+/-0.53 and 10.61+/-1.34, respectively. The CI for the other two agents did not change significantly with time.

CONCLUSION

In this rabbit model, 99mTc-labeled granulocytes, IgG and liposomes all rapidly visualized colonic inflammation. Granulocytes and liposomes showed the highest CI. Technetium-99m-labeled PEG-liposomes may be an attractive alternative for labeled leukocytes to image inflammatory bowel disease, because they can be prepared off the shelf and no handling of blood is required.

In vivo expression of interleukin-1 receptors during various experimentally induced inflammatory conditions

Systemically administered interleukin-1 (IL-1) has been shown to preferentially bind to IL-1 receptors (IL-1Rs) in inflammation. Using radiolabeled IL-1alpha and molecular methods to assess gene expression for these receptors, the in vivo behavior of these receptors was investigated in a number of experimental inflammatory conditions. The uptake of 125I-labeled IL-1alpha in inflammatory foci significantly correlated with the mRNA expression for the type I and type II IL-1Rs (P < .05). Type II IL-1R mRNA showed a greater increase in expression than type I IL-1R mRNA. In neutropenic mice, inflammatory lesions, which are devoid of granulocytes, significantly lower 125I-labeled IL-1alpha uptake (P < .001), and type II IL-1R mRNA expression (P < .005) was found. Thus, there is strong up-regulation of IL-1Rs at sites of focal inflammation. Of interest, this mainly involved the type II IL-1R on granulocytes, which is not involved in signal transduction.

Identical transcriptional control of the divergently transcribed prtP and prtM genes that are required for proteinase production in lactococcus lactis SK11

We have investigated transcriptional regulation of the divergently transcribed genes required for proteinase production (prtP and prtM) of Lactococcus lactis SK11. Their promoters partially overlap and are arranged in a face-to-face configuration. The medium-dependent activities of both prtP and prtM promoters were analyzed by quantitative primer extension studies and beta-glucuronidase assays with L. lactis MG1363 cells harboring transcriptional gene fusions of each promoter with the promoterless beta-glucuronidase gene (gusA) from Escherichia coli. High-level production of prtP- or prtM-specific mRNAs was found after the growth of cells in media with low peptide concentrations, while increases in peptide concentrations resulted in an approximately eightfold decrease in mRNA production. Furthermore, prtP and prtM promoters exhibited similar efficiencies under different growth conditions. Deletion analysis of the prt promoter region showed that all the information needed for full activity and regulation of the prtP and prtM promoters is retained within a 90-bp region which includes both transcription initiation sites. An inverted repeat sequence positioned around the prtP and prtM transcription initiation sites was disrupted by either deletion or insertion of a small DNA sequence to analyze their effects on the activities of both prtP and prtM promoters. The mutations affected the activities of these promoters only marginally at low peptide concentrations but resulted in 1.5- to 5-fold derepression at high peptide concentrations. These results indicate that the expression of both prtM and prtP genes is controlled in an identical manner via a control mechanism capable of repressing transcription initiation at high peptide concentrations.

Medium-dependent regulation of proteinase gene expression in Lactococcus lactis: control of transcription initiation by specific dipeptides

Transcriptional gene fusions with the Escherichia coli beta-glucuronidase gene (gusA) were used to study the medium- and growth-dependent expression of the divergently transcribed genes involved in proteinase production (prtP and prtM) of Lactococcus lactis SK11. The results show that both the prtP and prtM genes are controlled at the transcriptional level by the peptide content of the medium and, to a lesser extent, by the growth rate. A more than 10-fold regulation in beta-glucuronidase activity was observed for both prtP and prtM promoters in batch and continuous cultures. The level of expression of the prtP and prtM promoters was high in whey permeate medium with relatively low concentrations of peptides, whereas at increased concentrations the expression of the promoters was repressed. The lowest level of expression was observed in peptide- and amino acid-rich laboratory media, such as glucose-M17 and MRS. The addition of specific dipeptides, such as leucylproline and prolylleucine, to the growth medium negatively affected the expression of the prtP-gusA fusions. The repression by dipeptides was not observed in mutants defective in the uptake of di-tripeptides, indicating that the internal concentration of dipeptides or derivatives is important in the regulation of proteinase production.