title: Preclinical evaluation of two 68Ga-siderophores as potential radiopharmaceuticals for Aspergillus fumigatus infection imaging.
abstract: OBJECTIVE
  Invasive pulmonary aspergillosis is mainly caused by Aspergillus fumigatus, and is one of the major causes of morbidity and mortality in immunocompromised patients. The mortality associated with invasive pulmonary aspergillosis remains high, mainly due to the difficulties and limitations in diagnosis. We have shown that siderophores can be labelled with (68)Ga and can be used for PET imaging of A. fumigatus infection in rats. Here we report on the further evaluation of the most promising (68)Ga-siderophore candidates, triacetylfusarinine (TAFC) and ferrioxamine E (FOXE).
  
  
  METHODS
  Siderophores were labelled with (68)Ga using acetate buffer. Log P, protein binding and stability values were determined. Uptake by A. fumigatus was studied in vitro in cultures with high and low iron loads. In vivo biodistribution was determined in normal mice and an infection model was established using neutropenic rats inoculated with A. fumigatus. Static and dynamic μPET imaging was performed and correlated with CT images, and lung infection was evaluated ex vivo.
  
  
  RESULTS
  (68)Ga-siderophores were labelled with high radiochemical purity and specific activity. (68)Ga-TAFC and (68)Ga-FOXE showed high uptake by A. fumigatus in iron-deficient cultures. In normal mice, (68)Ga-TAFC and (68)Ga-FOXE showed rapid renal excretion with high metabolic stability. In the rat infection model focal lung uptake was detected by μPET with both compounds and increased with severity of the infection, correlating with abnormal CT images.
  
  
  CONCLUSIONS
  (68)Ga-TAFC and (68)Ga-FOXE displayed excellent in vitro stability and high uptake by A. fumigatus. Both compounds showed excellent pharmacokinetics, highly selective accumulation in infected lung tissue and good correlation with severity of disease in a rat infection model, which makes them promising agents for A. fumigatus infection imaging.
authors.affiliation: Clinical Department of Nuclear Medicine, Innsbruck Medical University, Innsbruck, Austria. milospetrik@seznam.cz
authors.forename: Milos
authors.initials: M
authors.lastname: Petrik
authors.forename: Gerben M
authors.initials: GM
authors.lastname: Franssen
authors.forename: Hubertus
authors.initials: H
authors.lastname: Haas
authors.forename: Peter
authors.initials: P
authors.lastname: Laverman
authors.forename: Caroline
authors.initials: C
authors.lastname: Hörtnagl
authors.forename: Markus
authors.initials: M
authors.lastname: Schrettl
authors.forename: Anna
authors.initials: A
authors.lastname: Helbok
authors.forename: Cornelia
authors.initials: C
authors.lastname: Lass-Flörl
authors.forename: Clemens
authors.initials: C
authors.lastname: Decristoforo
mesh_terms: D000818:Animals; D001232:Aspergillus fumigatus / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D005290:Ferric Compounds / Q000493:pharmacokinetics; D005710:Gallium Radioisotopes; D006877:Hydroxamic Acids / Q000493:pharmacokinetics; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010456:Peptides, Cyclic / Q000493:pharmacokinetics; D049268:Positron-Emission Tomography; D055732:Pulmonary Aspergillosis / Q000000981:diagnostic imaging* / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D051381:Rats; D011917:Rats, Inbred Lew; D017262:Siderophores / Q000493:pharmacokinetics*; D014018:Tissue Distribution
chemical_list: D005290:Ferric Compounds; D005710:Gallium Radioisotopes; D006877:Hydroxamic Acids; D010456:Peptides, Cyclic; D019275:Radiopharmaceuticals; D017262:Siderophores; C017508:ferrioxamine E; C012694:N(alpha)-acetylfusarinines