title: SLC46A3 Is Required to Transport Catabolites of Noncleavable Antibody Maytansine Conjugates from the Lysosome to the Cytoplasm.
abstract: Antibody-drug conjugates (ADC) target cytotoxic drugs to antigen-positive cells for treating cancer. After internalization, ADCs with noncleavable linkers are catabolized to amino acid-linker-warheads within the lysosome, which then enter the cytoplasm by an unknown mechanism. We hypothesized that a lysosomal transporter was responsible for delivering noncleavable ADC catabolites into the cytoplasm. To identify candidate transporters, we performed a phenotypic shRNA screen with an anti-CD70 maytansine-based ADC. This screen revealed the lysosomal membrane protein SLC46A3, the genetic attenuation of which inhibited the potency of multiple noncleavable antibody-maytansine ADCs, including ado-trastuzumab emtansine. In contrast, the potencies of noncleavable ADCs carrying the structurally distinct monomethyl auristatin F were unaffected by SLC46A3 attenuation. Structure-activity experiments suggested that maytansine is a substrate for SLC46A3. Notably, SLC46A3 silencing led to relative increases in catabolite concentrations in the lysosome. Taken together, our results establish SLC46A3 as a direct transporter of maytansine-based catabolites from the lysosome to the cytoplasm, prompting further investigation of SLC46A3 as a predictive response marker in breast cancer specimens.
authors.affiliation: Amgen Inc., Therapeutic Innovation Unit, Seattle, Washington. kjhamblett@comcast.net.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Hamblett
authors.affiliation: Amgen Inc., Therapeutic Innovation Unit, Seattle, Washington.
authors.forename: Allison P
authors.initials: AP
authors.lastname: Jacob
authors.affiliation: Amgen Inc., Therapeutic Innovation Unit, Seattle, Washington.
authors.forename: Jesse L
authors.initials: JL
authors.lastname: Gurgel
authors.affiliation: Amgen Inc., Therapeutic Innovation Unit, Seattle, Washington.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Tometsko
authors.affiliation: Amgen Inc., Pharmacokinetics and Drug Metabolism, Seattle, Washington.
authors.forename: Brooke M
authors.initials: BM
authors.lastname: Rock
authors.affiliation: Amgen Inc., Pharmacokinetics and Drug Metabolism, Seattle, Washington.
authors.forename: Sonal K
authors.initials: SK
authors.lastname: Patel
authors.affiliation: Amgen Inc., Small Molecule Purification and Process Development, Thousand Oaks, California.
authors.forename: Robert R
authors.initials: RR
authors.lastname: Milburn
authors.affiliation: Amgen Inc., Therapeutic Discovery, Seattle, Washington.
authors.forename: Sophia
authors.initials: S
authors.lastname: Siu
authors.affiliation: Amgen Inc., Genome Analysis Unit, Seattle, Washington.
authors.forename: Seamus P
authors.initials: SP
authors.lastname: Ragan
authors.affiliation: Amgen Inc., Pharmacokinetics and Drug Metabolism, Seattle, Washington.
authors.forename: Dan A
authors.initials: DA
authors.lastname: Rock
authors.affiliation: Amgen Inc., Small Molecule Purification and Process Development, Thousand Oaks, California.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Borths
authors.affiliation: Amgen Inc., Therapeutic Discovery, Seattle, Washington.
authors.forename: Jason W
authors.initials: JW
authors.lastname: O'Neill
authors.affiliation: Amgen Inc., Clinical Immunology, South San Francisco, California.
authors.forename: Wesley S
authors.initials: WS
authors.lastname: Chang
authors.affiliation: Amgen Inc., Therapeutic Innovation Unit, Seattle, Washington.
authors.forename: Margaret F
authors.initials: MF
authors.lastname: Weidner
authors.affiliation: Amgen Inc., Small Molecule Purification and Process Development, Thousand Oaks, California.
authors.forename: Matthew M
authors.initials: MM
authors.lastname: Bio
authors.affiliation: Amgen Inc., Therapeutic Innovation Unit, Seattle, Washington.
authors.forename: Kim C
authors.initials: KC
authors.lastname: Quon
authors.affiliation: Amgen Inc., Therapeutic Innovation Unit, Seattle, Washington.
authors.forename: William C
authors.initials: WC
authors.lastname: Fanslow
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000008:administration & dosage / Q000378:metabolism*; D045744:Cell Line, Tumor; D003593:Cytoplasm / Q000378:metabolism; D016503:Drug Delivery Systems; D006801:Humans; D018796:Immunoconjugates / Q000008:administration & dosage / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism; D008453:Maytansine / Q000008:administration & dosage / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D018796:Immunoconjugates; D026901:Membrane Transport Proteins; D008453:Maytansine