title: Targeting osteomyelitis with complete [99mTc]besilesomab and fragmented [99mTc]sulesomab antibodies: kinetic evaluations.
abstract: BACKGROUND
  The aim of this retrospective study was to compare the targeting of "pure" osteomyelitis (i.e., without surrounding soft tissue infection) by directly 99mTc-labelled complete immunoglobulin G (IgG) monoclonal antibody (MAb) ([99mTc]besilesomab) and by directly 99mTc-labelled fragment antigen-binding (FAb) MAb ([99mTc]sulesomab) in relation to their kinetic fate. A total of 73 patients with "pure" osteomyelitis were examined with [99mTc]besilesomab, (Scintimun®, IBA/CIS bio international, Saclay, France; N.=38) and [99mTc]sulesomab (LeukoScan®, Immunomedics Inc., Morris Plains, NJ, USA; N.=35).
  
  
  METHODS
  Kinetic data were deduced from whole-body and single-photon emission computed tomographic scans, performed 10 minutes to 24 hour p.i. (region-of-interest technique [ROI]).
  
  
  RESULTS
  In targeting "pure" osteomyelitis, sensitivities at 1-4 hours were found to be higher for [99mTc]sulesomab (44% and 80% for [99mTc]besilesomab and [99mTc]sulesomab, respectively) but at significantly lower target/background (T/B) ratios than with [99mTc]besilesomab (1.8±0.3 versus 1.4±0.5 for [99mTc]besilesomab and [99mTc]sulesomab respectively; P<0.01). With [99mTc]besilesomab, there was a continuous osteomyelitis uptake over 24 hours, whereas with [99mTc]sulesomab, the maximal uptake occurred mostly within 1-4 hours, with subsequent clearance being slower for antigen-bound activity than for nonspecific background. Hence, diagnosis was possible mostly after 4h with [99mTc]sulesomab but often not before 24 hours with [99mTc]besilesomab, the later increasing significantly (P<0.01) in sensitivity (87% and 84% for [99mTc]besilesomab and [99mTc]sulesomab, respectively).
  
  
  CONCLUSIONS
  These results show that the higher sensitivity of [99mTc]sulesomab in osteomyelitis targeting at earlier p.i. times does not rely on an increased antibody uptake but on a more rapid clearance of nonspecific background activity due to faster metabolism and excretion. Intact [99mTc]besilesomab show a slow, continuous uptake, leading to higher T/B at later p.i. times, often beyond the imaging possibilities of 99mTc.
authors.affiliation: Department of Nuclear Medicine, Philipps University, Marburg, Germany - xyz750ss@gmx.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Gratz
authors.forename: Patrik
authors.initials: P
authors.lastname: Reize
authors.forename: Bendix
authors.initials: B
authors.lastname: Kemke
authors.forename: Wim U
authors.initials: WU
authors.lastname: Kampen
authors.forename: Markus
authors.initials: M
authors.lastname: Luster
authors.forename: Helmut
authors.initials: H
authors.lastname: Höffken
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000911:Antibodies, Monoclonal / Q000276:immunology* / Q000493:pharmacokinetics*; D058846:Antibodies, Monoclonal, Murine-Derived / Q000276:immunology*; D005260:Female; D006801:Humans; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D010019:Osteomyelitis / Q000000981:diagnostic imaging* / Q000378:metabolism; D012189:Retrospective Studies; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; C578104:besilesomab; C101172:Sulesomab