title: Long-term stabilization of maleimide-thiol conjugates.
abstract: Michael-addition of a thiol to a maleimide is commonly used for bioconjugation of drugs to macromolecules. Indeed, both current FDA-approved antibody-drug conjugates-Brentuximab vedotin and Trastuzumab emtansine-and one approved PEGylated conjugate-Cimzia-contain a thiol-maleimide adduct. However, the ultimate in vivo fate of such adducts is to undergo disruptive cleavage by thiol exchange or stabilizing ring opening. Therapeutic efficacy of a conjugate can be compromised by thiol exchange and the released drug may show toxicities. However, if the succinimide moiety of a maleimide-thiol conjugate is hydrolyzed, the ring-opened product is stabilized toward cleavage. We determined rates of ring-opening hydrolysis and thiol exchange of a series of N-substituted succinimide thioethers formed by maleimide-thiol conjugation. Ring-opening of conjugates prepared with commonly used maleimides were too slow to serve as prevention against thiol exchange. However, ring-opening rates are greatly accelerated by electron withdrawing N-substituents, and ring-opened products have half-lives of over two years. Thus, conjugates made with electron-withdrawing maleimides may be purposefully hydrolyzed to their ring-opened counterparts in vitro to ensure in vivo stability.
authors.affiliation: ProLynx , 455 Mission Bay Blvd. South, Suite 145, San Francisco, California 94158, United States.
authors.forename: Shaun D
authors.initials: SD
authors.lastname: Fontaine
authors.forename: Ralph
authors.initials: R
authors.lastname: Reid
authors.forename: Louise
authors.initials: L
authors.lastname: Robinson
authors.forename: Gary W
authors.initials: GW
authors.lastname: Ashley
authors.forename: Daniel V
authors.initials: DV
authors.lastname: Santi
mesh_terms: D004355:Drug Stability; D007700:Kinetics; D008301:Maleimides / Q000737:chemistry*; D013379:Substrate Specificity; D013388:Succinimides / Q000737:chemistry; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D008301:Maleimides; D013388:Succinimides; D013438:Sulfhydryl Compounds; C032620:succinimide; C043592:maleimide