title: Engineering anti-Lewis-Y hu3S193 antibodies with improved therapeutic ratio for radioimmunotherapy of epithelial cancers.
abstract: BACKGROUND
  The aim of the study was to explore Fc mutations of a humanised anti-Lewis-Y antibody (IgG1) hu3S193 as a strategy to improve therapeutic ratios for therapeutic payload delivery.
  
  
  METHODS
  Four hu3S193 variants (I253A, H310A, H435A and I253A/H310A) were generated via site-directed mutagenesis and radiolabelled with diagnostic isotopes iodine-125 or indium-111. Biodistribution studies in Lewis-Y-positive tumour-bearing mice were used to calculate the dose in tumours and organs for therapeutic isotopes (iodine-131, yttrium-90 and lutetium-177).
  
  
  RESULTS
  (111)In-labelled I253A and H435A showed similar slow kinetics (t 1/2β, 63.2 and 62.2 h, respectively) and a maximum tumour uptake of 33.11 ± 4.05 and 33.69 ± 3.77 percentage injected dose per gramme (%ID/g), respectively. (111)In-labelled I253A/H310A cleared fastest (t 1/2β, 9.1 h) with the lowest maximum tumour uptake (23.72 ± 0.85 %ID/g). The highest increase in tumour-to-blood area under the curve (AUC) ratio was observed with the metal-labelled mutants ((90)Y and (177)Lu). (177)Lu-CHX-A" DTPA-hu3S193 I253A/H310A (6:1) showed the highest tumour-to-blood AUC ratio compared to wild type (3:1) and other variants and doubling of calculated dose to tumour based on red marrow dose constraints.
  
  
  CONCLUSIONS
  These results suggest that hu3S193 Fc can be engineered with improved therapeutic ratios for (90)Y- and (177)Lu-based therapy, with the best candidate being hu3S193 I253A/H310A for (177)Lu-based therapy.
authors.affiliation: Tumour Targeting Laboratory, Ludwig Institute for Cancer Research and Olivia Newton-John Cancer Research Institute, Melbourne, VIC, Australia.|School of Cancer Medicine, La Trobe University, Melbourne, VIC, Australia.
authors.forename: Ingrid J G
authors.initials: IJ
authors.lastname: Burvenich
authors.affiliation: Tumour Targeting Laboratory, Ludwig Institute for Cancer Research and Olivia Newton-John Cancer Research Institute, Melbourne, VIC, Australia.
authors.forename: Fook-Thean
authors.initials: FT
authors.lastname: Lee
authors.affiliation: School of Cancer Medicine, La Trobe University, Melbourne, VIC, Australia.|Department of Molecular Imaging and Therapy, Austin Health, Melbourne, Australia.
authors.forename: Graeme J
authors.initials: GJ
authors.lastname: O'Keefe
authors.affiliation: Tumour Targeting Laboratory, Ludwig Institute for Cancer Research and Olivia Newton-John Cancer Research Institute, Melbourne, VIC, Australia.
authors.forename: Dahna
authors.initials: D
authors.lastname: Makris
authors.affiliation: Tumour Targeting Laboratory, Ludwig Institute for Cancer Research and Olivia Newton-John Cancer Research Institute, Melbourne, VIC, Australia.
authors.forename: Diana
authors.initials: D
authors.lastname: Cao
authors.affiliation: Department of Molecular Imaging and Therapy, Austin Health, Melbourne, Australia.
authors.forename: Sylvia
authors.initials: S
authors.lastname: Gong
authors.affiliation: Tumour Targeting Laboratory, Ludwig Institute for Cancer Research and Olivia Newton-John Cancer Research Institute, Melbourne, VIC, Australia.
authors.forename: Angela
authors.initials: A
authors.lastname: Rigopoulos
authors.affiliation: Tumour Targeting Laboratory, Ludwig Institute for Cancer Research and Olivia Newton-John Cancer Research Institute, Melbourne, VIC, Australia.
authors.forename: Laura C
authors.initials: LC
authors.lastname: Allan
authors.affiliation: Radioimmune and Inorganic Chemistry Section, Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA.
authors.forename: Martin W
authors.initials: MW
authors.lastname: Brechbiel
authors.affiliation: Tumour Targeting Laboratory, Ludwig Institute for Cancer Research and Olivia Newton-John Cancer Research Institute, Melbourne, VIC, Australia.
authors.forename: Zhanqi
authors.initials: Z
authors.lastname: Liu
authors.affiliation: School of Science, RMIT University, Bundoora, VIC, Australia.|Centre for Biomedical Research, Burnet Institute, Melbourne, VIC, Australia.|Department of Immunology, Monash University, Melbourne, VIC, Australia.|Department of Surgery Austin Health, University of Melbourne, Heidelberg, VIC, Australia.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Ramsland
authors.affiliation: Tumour Targeting Laboratory, Ludwig Institute for Cancer Research and Olivia Newton-John Cancer Research Institute, Melbourne, VIC, Australia. andrew.scott@onjcri.org.au.|School of Cancer Medicine, La Trobe University, Melbourne, VIC, Australia. andrew.scott@onjcri.org.au.|Department of Molecular Imaging and Therapy, Austin Health, Melbourne, Australia. andrew.scott@onjcri.org.au.|Faculty of Medicine, University of Melbourne, Melbourne, VIC, Australia. andrew.scott@onjcri.org.au.|Olivia Newton-John Cancer Research Institute, 145-163 Studley Road, Heidelberg, VIC, 3084, Australia. andrew.scott@onjcri.org.au.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Scott
keywords: Antibody engineering; Lewis-Y; Payload delivery; Small animal imaging; Therapeutic ratio