title: Rapid and efficient radiosynthesis of [123I]I-PK11195, a single photon emission computed tomography tracer for peripheral benzodiazepine receptors.
abstract: BACKGROUND
  [(123)I]I-PK11195 is a high-affinity single photon emission computed tomography radiotracer for peripheral benzodiazepine receptors that has previously been used to measure activated microglia and to assess neuroinflammation in the living human brain. This study investigates the radiosynthesis of [(123)I]I-PK11195 in order to develop a rapid and efficient method that obtains [(123)I]I-PK11195 with a high specific activity for in vivo animal and human imaging studies.
  
  
  METHODS
  The synthesis of [(123)I]I-PK11195 was evaluated using a solid-state interhalogen exchange method and an electrophilic iododestannylation method, where bromine and trimethylstannyl derivatives were used as precursors, respectively. In the electrophilic iododestannylation method, the oxidants peracetic acid and chloramine-T were both investigated.
  
  
  RESULTS
  Electrophilic iododestannylation produced [(123)I]I-PK11195 with a higher isolated radiochemical yield and a higher specific activity than achievable using the halogen exchange method investigated. Using chloramine-T as oxidant provided a rapid and efficient method of choice for the synthesis of [(123)I]I-PK11195.
  
  
  CONCLUSIONS
  [(123)I]I-PK11195 has been successfully synthesized via a rapid and efficient electrophilic iododestannylation method, producing [(123)I]I-PK11195 with a higher isolated radiochemical yield and a higher specific activity than previously achieved.
authors.affiliation: Department of Clinical Physics, West of Scotland Radionuclide Dispensary, Western Infirmary, Glasgow, UK. s.pimlott@clinmed.gla.ac.uk
authors.forename: Sally L
authors.initials: SL
authors.lastname: Pimlott
authors.forename: Louise
authors.initials: L
authors.lastname: Stevenson
authors.forename: David J
authors.initials: DJ
authors.lastname: Wyper
authors.forename: Andrew
authors.initials: A
authors.lastname: Sutherland
mesh_terms: D002700:Chloramines; D002851:Chromatography, High Pressure Liquid; D004355:Drug Stability; D007202:Indicators and Reagents; D007546:Isoquinolines / Q000138:chemical synthesis* / Q000302:isolation & purification; D007553:Isotope Labeling; D019275:Radiopharmaceuticals / Q000138:chemical synthesis* / Q000302:isolation & purification; D011963:Receptors, GABA-A / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D015899:Tomography, Emission-Computed, Single-Photon; D014105:Tosyl Compounds
chemical_list: D002700:Chloramines; D007202:Indicators and Reagents; D007546:Isoquinolines; D019275:Radiopharmaceuticals; D011963:Receptors, GABA-A; D014105:Tosyl Compounds; C016300:chloramine-T; C037850:PK 11195