title: Yttrium-90/indium-111-DOTA-peptide-chimeric L6: pharmacokinetics, dosimetry and initial results in patients with incurable breast cancer.
abstract: BACKGROUND
  Radioimmunotherapy (RIT) using 131I-Chimeric L6 (ChL6) antibody has shown therapeutic promise for patients with breast cancer. To enhance this potential, a novel immunoconjugate was developed that targets adenocarcinomas like breast cancer and tightly binds yttrium-90 (90Y) for therapy and indium-111 (111In) for imaging. The radioimmunoconjugate consists of a macrocyclic chelator (DOTA) linked to ChL6 by a catabolizable peptide. 90Y-DOTA-peptide-ChL6 was designed to minimize the radiation dose to critical normal tissues, thereby improving the therapeutic index.
  
  
  METHODS
  Three patients with incurable metastatic breast cancer received 90Y/111In-DOTA-peptide-ChL6 for 5 pharmacokinetics/dosimetry studies and one of these patients also received 2 therapy doses. Quantitative imaging of 111In and in vitro assay of 90Y and 111In in blood urine and bone marrow samples were obtained.
  
  
  RESULTS
  90Y/111In-DOTA-peptide-ChL6 was prepared at high purity and was stable in vivo. Assays of bone marrow revealed no evidence for escape of 90Y or 111In from the chelate. 111In imaging of tumors was excellent, providing a therapeutic index for tumor to marrow radiation as high as 229 to 1. 90Y and 111In provided comparable pharmacokinetics, as did tracer and therapeutic doses of radioimmunoconjugates. One patients that received 2 therapeutic doses of 90Y-DOTA-peptide-ChL6 showed regression of tumors and tumor markers. Toxicities were relatively minor and no anti-globulin response developed despite 5 immunoconjugate infusions.
  
  
  CONCLUSIONS
  This first study in patients of radioimmunoconjugates with a catabolizable linker between the metal chelator and the antibody confirmed that these novel 90Y/111In-DOTA-peptide-ChL6 radioimmunoconjugates have significant potential. Tracer doses of 111In-DOTA-peptide-ChL6 for imaging predicted the behavior of therapeutic doses of 90Y-DOTA-peptide-ChL6. The latter radioimmunoconjugate induced regression of tumors and tumor markers without significant toxicity. When compared to earlier 131I-ChL6 dosimetry, 90Y-DOTA-peptide-ChL6 provided a therapeutic index several times better.
authors.affiliation: Division of Hematology/Oncology, University of California Davis Medical Center, Sacramento.
authors.forename: S J
authors.initials: SJ
authors.lastname: Denardo
authors.forename: C M
authors.initials: CM
authors.lastname: Richman
authors.forename: D S
authors.initials: DS
authors.lastname: Goldstein
authors.forename: S
authors.initials: S
authors.lastname: Shen
authors.forename: Q
authors.initials: Q
authors.lastname: Salako
authors.forename: D L
authors.initials: DL
authors.lastname: Kukis
authors.forename: C F
authors.initials: CF
authors.lastname: Meares
authors.forename: A
authors.initials: A
authors.lastname: Yuan
authors.forename: J L
authors.initials: JL
authors.lastname: Welborn
authors.forename: G L
authors.initials: GL
authors.lastname: Denardo
mesh_terms: D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics / Q000627:therapeutic use*; D014408:Biomarkers, Tumor / Q000032:analysis; D001853:Bone Marrow / Q000000981:diagnostic imaging; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D007205:Indium Radioisotopes / Q000493:pharmacokinetics / Q000627:therapeutic use*; D008657:Metabolic Clearance Rate; D009362:Neoplasm Metastasis; D009367:Neoplasm Staging; D016719:Radioimmunodetection / Q000009:adverse effects; D016499:Radioimmunotherapy / Q000009:adverse effects; D011993:Recombinant Fusion Proteins; D014018:Tissue Distribution; D014055:Tomography, Emission-Computed; D014057:Tomography, X-Ray Computed; D015021:Yttrium Radioisotopes / Q000493:pharmacokinetics / Q000627:therapeutic use*
chemical_list: D000911:Antibodies, Monoclonal; D014408:Biomarkers, Tumor; C106337:ChL6 monoclonal antibody; D007205:Indium Radioisotopes; D011993:Recombinant Fusion Proteins; D015021:Yttrium Radioisotopes