title: Effects of Drug-Antibody Ratio on Pharmacokinetics, Biodistribution, Efficacy, and Tolerability of Antibody-Maytansinoid Conjugates.
abstract: Antibody-drug conjugates (ADCs) are being actively pursued as a treatment option for cancer following the regulatory approval of brentuximab vedotin (Adcetris) and ado-trastuzumab emtansine (Kadcyla). ADCs consist of a cytotoxic agent conjugated to a targeting antibody through a linker. The two approved ADCs (and most ADCs now in the clinic that use a microtubule disrupting agent as the payload) are heterogeneous conjugates with an average drug-to-antibody ratio (DAR) of 3-4 (potentially ranging from 0 to 8 for individual species). Ado-trastuzumab emtansine employs DM1, a semisynthetic cytotoxic payload of the maytansinoid class, which is conjugated via lysine residues of the antibody to an average DAR of 3.5. To understand the effect of DAR on the preclinical properties of ADCs using maytansinoid cytotoxic agents, we prepared a series of conjugates with a cleavable linker (M9346A-sulfo-SPDB-DM4 targeting folate receptor α (FRα)) or an uncleavable linker (J2898A-SMCC-DM1 targeting the epidermal growth factor receptor (EGFR)) with varying DAR and evaluated their biochemical characteristics, in vivo stability, efficacy, and tolerability. For both formats, a series of ADCs with DARs ranging from low (average of ∼2 and range of 0-4) to very high (average of 10 and range of 7-14) were prepared in good yield with high monomer content and low levels of free cytotoxic agent. The in vitro potency consistently increased with increasing DAR at a constant antibody concentration. We then characterized the in vivo disposition of these ADCs. Pharmacokinetic analysis showed that conjugates with an average DAR below ∼6 had comparable clearance rates, but for those with an average DAR of ∼9-10, rapid clearance was observed. Biodistribution studies in mice showed that these 9-10 DAR ADCs rapidly accumulate in the liver, with maximum localization for this organ at 24-28% percentage injected dose per gram (%ID/g) compared with 7-10% for lower-DAR conjugates (all at 2-6 h post-injection). Our preclinical findings on tolerability and efficacy suggest that maytansinoid conjugates with DAR ranging from 2 to 6 have a better therapeutic index than conjugates with very high DAR (∼9-10). These very high DAR ADCs suffer from decreased efficacy, likely due to faster clearance. These results support the use of DAR 3-4 for maytansinoid ADCs but suggest that the exploration of lower or higher DAR may be warranted depending on the biology of the target antigen.
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Xiuxia
authors.identifier: 0000-0001-9074-8124
authors.initials: X
authors.lastname: Sun
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Jose F
authors.initials: JF
authors.lastname: Ponte
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Yoder
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Rassol
authors.initials: R
authors.lastname: Laleau
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Coccia
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Leanne
authors.initials: L
authors.lastname: Lanieri
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Qifeng
authors.initials: Q
authors.lastname: Qiu
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Rui
authors.initials: R
authors.lastname: Wu
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Erica
authors.initials: E
authors.lastname: Hong
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Megan
authors.initials: M
authors.lastname: Bogalhas
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Lintao
authors.initials: L
authors.lastname: Wang
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Ling
authors.initials: L
authors.lastname: Dong
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Yulius
authors.initials: Y
authors.lastname: Setiady
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Erin K
authors.initials: EK
authors.lastname: Maloney
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Olga
authors.initials: O
authors.lastname: Ab
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Zhang
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Jan
authors.initials: J
authors.lastname: Pinkas
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Keating
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Ravi
authors.initials: R
authors.lastname: Chari
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: Hans K
authors.initials: HK
authors.lastname: Erickson
authors.affiliation: ImmunoGen, Inc. , 830 Winter Street, Waltham, Massachusetts 02451, United States.
authors.forename: John M
authors.initials: JM
authors.lastname: Lambert
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000972:Antineoplastic Agents, Phytogenic / Q000493:pharmacokinetics* / Q000494:pharmacology; D005260:Female; D006801:Humans; D018796:Immunoconjugates / Q000493:pharmacokinetics* / Q000494:pharmacology; D007624:KB Cells; D008453:Maytansine / Q000493:pharmacokinetics* / Q000494:pharmacology; D051379:Mice; D014018:Tissue Distribution; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
chemical_list: D000911:Antibodies, Monoclonal; D000972:Antineoplastic Agents, Phytogenic; D018796:Immunoconjugates; D008453:Maytansine