title: Development of TNKase-specific cleavable peptide-linked radioimmunoconjugates for radioimmunotherapy.
abstract: Radioimmunotherapy (RIT) is a method for selectively delivering radionuclides to cancer cells while reducing the radiation dose to normal tissues. However, because of slow clearance of MAbs, normal tissues also received radiotoxicity. One of the promising strategies is linking on-demand cleavable (ODC) peptides between radiometal chelates and the tumor targeting agents. We have tested this proof-of-concept by using ODC peptides that are designed to be cleaved only by TNKase and are resistant to cleavage by enzymes present in the plasma and the tumor. TNKase-specific peptide linkers using l- and d-amino acids were screened by OBOC combinatorial peptide libraries. One of the best peptides was linked to radiometal chelate and ChL6-MAb to prepare radioimmunoconjugate (RIC). Optimization and characterization of the linker conjugation to MAb show (a) 1-2 peptides linked to each MAb; (b) immunoreactivity >80%; (c) specific activity of the RIC 0.7-1 microCi/microg; (d) RIC stable over 7 days in human plasma; and (e) radiometal-chelated ODC peptide cleaved from the RIC in plasma by TNKase at clinical dose levels of 10 microg/ml. The percent release of radiochelate from RIC was 50% at 24h and 85% over 7 2h in vitro. This novel ODC-linked RIC could be a potential molecule for RIT.
authors.affiliation: Division of Hematology and Oncology, Internal Medicine, University of California Davis, 1508 Alhambra Blvd., Room 3100, Sacramento, CA 95816, USA.
authors.forename: Arutselvan
authors.initials: A
authors.lastname: Natarajan
authors.forename: Pappanaicken R
authors.initials: PR
authors.lastname: Kumaresan
authors.forename: Sally J
authors.initials: SJ
authors.lastname: Denardo
authors.forename: Gerald L
authors.initials: GL
authors.lastname: Denardo
authors.forename: Gary
authors.initials: G
authors.lastname: Mirick
authors.forename: Kit S
authors.initials: KS
authors.lastname: Lam
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism / Q000627:therapeutic use; D006801:Humans; D006868:Hydrolysis; D018796:Immunoconjugates / Q000627:therapeutic use*; D051379:Mice; D009369:Neoplasms / Q000276:immunology / Q000378:metabolism / Q000532:radiotherapy; D010455:Peptides / Q000737:chemistry / Q000378:metabolism / Q000627:therapeutic use*; D016499:Radioimmunotherapy / Q000379:methods; D000077785:Tenecteplase; D010959:Tissue Plasminogen Activator / Q000378:metabolism / Q000627:therapeutic use*; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; C106337:ChL6 monoclonal antibody; D018796:Immunoconjugates; D010455:Peptides; D010959:Tissue Plasminogen Activator; D000077785:Tenecteplase