title: [(177)Lu]pertuzumab: experimental studies on targeting of HER-2 positive tumour cells.
abstract: OBJECTIVE
  The new antibody pertuzumab (Omnitarg) targets the dimerisation subdomain of HER-2. The purpose of this study was to analyse whether pertuzumab retains HER-2 targeting capacity after labelling with the therapeutically interesting beta emitter (177)Lu and to make initial characterizations in vitro and in vivo.
  
  
  METHODS
  Pertuzumab was conjugated with isothiocyanate-benzyl-CHX-A''-DTPA and chelated to (177)Lu. Immunoreactivity, affinity, cellular retention and internalisation were analysed using SKOV-3 cells. The affinity of non-radioactive pertuzumab was measured using a surface plasmon resonance biosensor. In vivo targeting and specific binding were assessed in Balb/c (nu/nu) mice carrying SKOV-3 xenografts. The biodistribution of (177)Lu was determined 1, 3 and 7 days after [(177)Lu]pertuzumab administration. Gamma camera images were taken after 3 days.
  
  
  RESULTS
  The immunoreactivity of [(177)Lu]pertuzumab was 85.8+/-1.3%. The affinity of non-radioactive pertuzumab was 1.8+/-1.1 nM, and that of [(177)Lu]pertuzumab, 4.1+/-0.7 nM. The cellular retention after 5 h pre-incubation was 90+/-2% at 20 h. The targeting was HER-2 specific both in vitro and in vivo, since excess amounts of non-labelled antibody inhibited the uptake of labelled antibody (p<0.0001 and p<0.01, respectively). The biodistribution and gamma camera images of (177)Lu showed extensive tumour uptake. Normal tissues had a surprisingly low uptake.
  
  
  CONCLUSIONS
  Pertuzumab was efficiently labelled with (177)Lu and showed good intracellular retention and HER-2 specific binding both in vitro and in vivo. The gamma camera images and the biodistribution study gave excellent tumour targeting results. Thus, [(177)Lu]pertuzumab is of interest for further studies aimed at radionuclide therapy.
authors.affiliation: Biomedical Radiation Sciences, Rudbeck Laboratory, Uppsala University, Uppsala, Sweden. mikael.persson@bms.uu.se
authors.forename: Mikael
authors.initials: M
authors.lastname: Persson
authors.forename: Vladimir
authors.initials: V
authors.lastname: Tolmachev
authors.forename: Karl
authors.initials: K
authors.lastname: Andersson
authors.forename: Lars
authors.initials: L
authors.lastname: Gedda
authors.forename: Mattias
authors.initials: M
authors.lastname: Sandström
authors.forename: Jörgen
authors.initials: J
authors.lastname: Carlsson
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000493:pharmacokinetics* / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized; D045744:Cell Line, Tumor; D016503:Drug Delivery Systems / Q000379:methods; D005260:Female; D006801:Humans; D008187:Lutetium / Q000737:chemistry / Q000493:pharmacokinetics* / Q000627:therapeutic use; D008657:Metabolic Clearance Rate; D051379:Mice; D008807:Mice, Inbred BALB C; D009928:Organ Specificity; D010051:Ovarian Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism*; D016499:Radioimmunotherapy / Q000379:methods; D011868:Radioisotopes / Q000737:chemistry / Q000493:pharmacokinetics* / Q000627:therapeutic use; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000493:pharmacokinetics / Q000627:therapeutic use; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D013194:Staining and Labeling; D014018:Tissue Distribution
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D008187:Lutetium; D011868:Radioisotopes; D019275:Radiopharmaceuticals; D018719:Erb-b2 Receptor Tyrosine Kinases; C485206:pertuzumab