title: Zirconium-89 labeled panitumumab: a potential immuno-PET probe for HER1-expressing carcinomas.
abstract: BACKGROUND
  Anti-HER1 monoclonal antibody (mAb), panitumumab (Vectibix) is a fully human mAb approved by the FDA for the treatment of epidermal growth factor receptor (EGFR, HER1)-expressing colorectal cancers. By combining the targeted specificity of panitumumab with the quantitative in vivo imaging capabilities of PET, we evaluated the potential of (89)Zr-DFO-panitumumab PET/CT imaging and performed non-invasive, in vivo imaging of HER1 expression and estimated human dosimetry.
  
  
  METHODS
  Panitumumab was radiolabeled with (89)Zr using a derivative of desferrioxamine (DFO-Bz-NCS) and with (111)In using CHX-A" DTPA as bifunctional chelators. Comparative biodistribution/dosimetry of both radiotracers was performed in non-tumor bearing athymic nude mice (n=2 females and n=2 males) over 1-week following i.v. injection of either using (89)Zr-DFO-panitumumab or (111)In-CHX-A"-DTPA-panitumumab. Micro-PET/CT imaging of female athymic nude mice bearing human breast cancer tumors (n=5 per tumor group) with variable HER1-expression very low (BT-474), moderate (MDA-MB-231), and very high (MDA-MB-468) was performed at over 1 week following i.v. injection of (89)Zr-DFO-panitumumab.
  
  
  RESULTS
  Radiochemical yield and purity of (89)Zr-Panitumumab was >70% and >98% respectively with specific activity 150 ± 10 MBq/mg of panitumumab in a ~4 hr synthesis time. Biodistribution of (111)In-CHX-A" DTPA -panitumumab and (89)Zr-DFO-panitumumab in athymic non-tumor bearing nude mice displayed similar percent injected dose per gram of tissue with prominent accumulation of both tracers in the lymph nodes, a known clearance mechanism of panitumumab. Also exhibited was prolonged blood pool with no evidence of targeted accumulation in any organ. Human radiation dose estimates showed similar biodistributions with estimated human effective doses of 0.578 and 0.183 mSv/MBq for (89)Zr-DFO-panitumumab and (111)In-CHX-A"-DTPA-panitumumab, respectively. Given the potential quantitative and image quality advantages of PET, imaging of tumor bearing mice was only performed using (89)Zr-DFO-panitumumab. Immuno-PET imaging of (89)Zr-DFO-panitumumab in mice bearing breast cancer xenograft tumors with variable HER1 expression showed high tumor uptake (SUV >7) in the MDA-MB-468 high HER1-expressing mice and a strong correlation between HER1-expression level and tumor uptake (R(2)= 0.857, P < .001).
  
  
  CONCLUSIONS
  (89)Zr-DFO-panitumumab can prepared with high radiochemical purity and specific activity. (89)Zr-DFO-panitumumab microPET/CT showed uptake corresponding to HER-1 expression. Due to poor clearance, initial dosimetry estimates suggest that only a low dose (89)Zr-DFO-panitumumab shows favorable human dosimetry; however due to high tumor uptake, the use of (89)Zr-DFO-panitumumab is expected to be clinically feasible.
authors: ADRD, SAIC-Frederick, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA. bhattacharyyas2@mail.nih.gov
authors: Sibaprasad
authors: S
authors: Bhattacharyya
authors: Karen
authors: K
authors: Kurdziel
authors: Ling
authors: L
authors: Wei
authors: Lisa
authors: L
authors: Riffle
authors: Gurmeet
authors: G
authors: Kaur
authors: G Craig
authors: GC
authors: Hill
authors: Paula M
authors: PM
authors: Jacobs
authors: James L
authors: JL
authors: Tatum
authors: James H
authors: JH
authors: Doroshow
authors: Joseph D
authors: JD
authors: Kalen
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000493:pharmacokinetics; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic; D066246:ErbB Receptors / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D018796:Immunoconjugates / Q000737:chemistry / Q000493:pharmacokinetics; D007553:Isotope Labeling; D008297:Male; D051379:Mice; D000077544:Panitumumab; D004369:Pentetic Acid / Q000737:chemistry; D049268:Positron-Emission Tomography / Q000379:methods*; D011868:Radioisotopes; D011874:Radiometry; D015040:Zirconium
chemical_list: D000911:Antibodies, Monoclonal; D018796:Immunoconjugates; D011868:Radioisotopes; D000077544:Panitumumab; D004369:Pentetic Acid; D015040:Zirconium; C512478:EGFR protein, human; D066246:ErbB Receptors