title: Improved targeting of an anti-epidermal growth factor receptor variant III monoclonal antibody in tumor xenografts after labeling using N-succinimidyl 5-iodo-3-pyridinecarboxylate.
abstract: Monoclonal antibody (mAb) L8A4, specific for the tumor-associated mutant epidermal growth factor receptor variant III (EGFRvII), is internalized and degraded after cell binding. Four paired-label experiments were performed in athymic mice bearing EGFRvIII-positive xenografts to determine the suitability of N-succinimidyl 3-iodo-5-pyridinecarboxylate (SIPC) for labeling this internalizing mAb. In mice with HC2 20 d2 xenografts, tumor uptake reached a maximum of 32.7 +/- 2.0% injected dose/g when labeled using SIPC, a value significantly higher (P < 0.05, paired t test) than that observed when L8A4 was labeled using lodogen (24.4 +/- 2.2% injected dose/g). The specificity of mAb uptake in HC2 20 d2 and U87MG(delta)EGFR xenografts was measured in separate experiments by coadministration of L8A4 and nonspecific, isotype-matched P3X63Ag8 mAb, both radioiodinated using SIPC. Tumor localization indices were approximately 10 or more by 72 h, a degree of specificity 3-4 times higher than that reported previously when labeling was performed using the tyramine cellobiose (TCB) method. In a final study directly comparing L8A4 labeled using SIPC and TCB, similar tumor levels were obtained (SIPC, 33.7 +/- 6.1% injected dose/g at 24 h; TCB, 37.8 +/- 6.7% injected dose/g at 24 h); however, tumor-to-tissue ratios for the liver, spleen, and kidneys were 3 times higher with SIPC at later time points. These results suggest that SIPC is a promising method for labeling this anti-EGFRvIII mAb and possibly other mAbs that internalize after binding.
authors.affiliation: Department of Pathology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Reist
authors.forename: G E
authors.initials: GE
authors.lastname: Archer
authors.forename: C J
authors.initials: CJ
authors.lastname: Wikstrand
authors.forename: D D
authors.initials: DD
authors.lastname: Bigner
authors.forename: M R
authors.initials: MR
authors.lastname: Zalutsky
mesh_terms: D016475:3T3 Cells / Q000378:metabolism; D000345:Affinity Labels; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism / Q000493:pharmacokinetics / Q000627:therapeutic use*; D000918:Antibody Specificity; D066246:ErbB Receptors / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D009539:Nicotinic Acids / Q000493:pharmacokinetics*; D013388:Succinimides / Q000493:pharmacokinetics*; D014018:Tissue Distribution; D014183:Transplantation, Heterologous; D014439:Tyramine / Q000493:pharmacokinetics
chemical_list: D000345:Affinity Labels; D000911:Antibodies, Monoclonal; D009539:Nicotinic Acids; D013388:Succinimides; C069228:N-succinimidyl-5-iodo-3-pyridinecarboxylic acid; D066246:ErbB Receptors; D014439:Tyramine