title: Engineered anti-CD70 antibody-drug conjugate with increased therapeutic index.
abstract: An anti-CD70 antibody conjugated to monomethylauristatin F (MMAF) via a valine-citrulline dipeptide containing linker has been shown previously to have potent antitumor activity in renal cell cancer xenograft studies. Here, we generated a panel of humanized anti-CD70 antibody IgG variants and conjugated them to MMAF to study the effect of isotype (IgG1, IgG2, and IgG4) and Fcgamma receptor binding on antibody-drug conjugate properties. All IgG variants bound CD70+ 786-O cells with an apparent affinity of approximately 1 nmol/L, and drug conjugation did not impair antigen binding. The parent anti-CD70 IgG1 bound to human FcgammaRI and FcgammaRIIIA V158 and mouse FcgammaRIV and this binding was not impaired by drug conjugation. In contrast, binding to these Fcgamma receptors was greatly reduced or abolished in the variant, IgG1v1, containing the previously described mutations, E233P:L234V:L235A. All conjugates had potent cytotoxic activity against six different antigen-positive cancer cell lines in vitro with IC50 values of 30 to 540 pmol/L. The IgGv1 conjugate with MMAF displayed improved antitumor activity compared with other conjugates in 786-O and UMRC3 models of renal cell cancer and in the DBTRG05-MG glioblastoma model. All conjugates were tolerated to > or =40 mg/kg in mice. Thus, the IgG1v1 MMAF conjugate has an increased therapeutic index compared with the parent IgG1 conjugate. The improved antitumor activity of the IgG1v1 auristatin conjugates may relate to increased exposure as suggested by pharmacokinetic analysis. The strategy used here for enhancing the therapeutic index of antibody-drug conjugates is independent of the antigen-binding variable domains and potentially applicable to other antibodies.
authors.affiliation: Seattle Genetics, Inc., 21823 30th Drive Southeast, Bothell, WA 98021, USA.
authors.forename: Charlotte F
authors.initials: CF
authors.lastname: McDonagh
authors.forename: Kristine M
authors.initials: KM
authors.lastname: Kim
authors.forename: Eileen
authors.initials: E
authors.lastname: Turcott
authors.forename: Lindsay L
authors.initials: LL
authors.lastname: Brown
authors.forename: Lori
authors.initials: L
authors.lastname: Westendorf
authors.forename: Tiffany
authors.initials: T
authors.lastname: Feist
authors.forename: Django
authors.initials: D
authors.lastname: Sussman
authors.forename: Ivan
authors.initials: I
authors.lastname: Stone
authors.forename: Martha
authors.initials: M
authors.lastname: Anderson
authors.forename: Jamie
authors.initials: J
authors.lastname: Miyamoto
authors.forename: Robert
authors.initials: R
authors.lastname: Lyon
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Alley
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Gerber
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Carter
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics / Q000627:therapeutic use*; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics / Q000627:therapeutic use*; D053282:CD27 Ligand / Q000276:immunology*; D045744:Cell Line, Tumor; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D005260:Female; D006801:Humans; D018796:Immunoconjugates / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics / Q000627:therapeutic use*; D007074:Immunoglobulin G / Q000276:immunology; D051379:Mice; D008819:Mice, Nude; D008958:Models, Molecular; D015202:Protein Engineering; D017452:Receptors, IgG / Q000276:immunology; D023041:Xenograft Model Antitumor Assays
chemical_list: D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; D053282:CD27 Ligand; D018796:Immunoconjugates; D007074:Immunoglobulin G; D017452:Receptors, IgG