title: Site-selective labeling of a lysine residue in human serum albumin.
abstract: Conjugation to human serum albumin (HSA) has emerged as a powerful approach for extending the in vivo half-life of many small molecule and peptide/protein drugs. Current HSA conjugation strategies, however, can often yield heterogeneous mixtures with inadequate pharmacokinetics, low efficacies, and variable safety profiles. Here, we designed and synthesized analogues of TAK-242, a small molecule inhibitor of Toll-like receptor 4, that primarily reacted with a single lysine residue of HSA. These TAK-242-based cyclohexene compounds demonstrated robust reactivity, and Lys64 was identified as the primary conjugation site. A bivalent HSA conjugate was also prepared in a site-specific manner. Additionally, HSA-cyclohexene conjugates maintained higher levels of stability both in human plasma and in mice than the corresponding maleimide conjugates. This new conjugation strategy promises to broadly enhance the performance of HSA conjugates for numerous applications.
authors.affiliation: The Skaggs Institute for Chemical Biology, Department of Chemistry, and Department of Molecular and Cell Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037 (USA).
authors.forename: Shigehiro
authors.initials: S
authors.lastname: Asano
authors.forename: James T
authors.initials: JT
authors.lastname: Patterson
authors.forename: Thomas
authors.initials: T
authors.lastname: Gaj
authors.forename: Carlos F
authors.initials: CF
authors.lastname: Barbas
mesh_terms: D006801:Humans; D008239:Lysine / Q000737:chemistry*; D012709:Serum Albumin / Q000138:chemical synthesis*
chemical_list: D012709:Serum Albumin; D008239:Lysine
keywords: chemoselectivity; drug conjugates; human serum albumin; lysine labeling; site-specific conjugation