Site-Selective Protein Conjugation by a Multicomponent Ugi Reaction

Ilias Koutsopetras, Valentine Vaur, Rania Benazza, Hélène Diemer, Charlotte Sornay, Yağmur Ersoy, Léa Rochet, Carmen Longo, Oscar Hernandez-Alba, Stéphane Erb, Alexandre Detappe, Arne Skerra, Alain Wagner, Sarah Cianferani, Guilhem Chaubet

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


The chemical bioconjugation of proteins has seen tremendous applications in the past decades, with the booming of antibody-drug conjugates and their use in oncology. While genetic engineering has permitted to produce bespoke proteins featuring key (un−)natural amino acid residues poised for site-selective modifications, the conjugation of native proteins is riddled with selectivity issues. Chemoselective strategies are plentiful and enable the precise modification of virtually any residue with a reactive side-chain; site-selective methods are less common and usually most effective on small and medium-sized proteins. In this context, we studied the application of the Ugi multicomponent reaction for the site-selective conjugation of amine and carboxylate groups on proteins, and antibodies in particular. Through an in-depth mechanistic methodology work supported by peptide mapping studies, we managed to develop a set of conditions allowing the highly selective modification of antibodies bearing N-terminal glutamate and aspartate residues. We demonstrated that this strategy did not alter their affinity toward their target antigen and produced an antibody-drug conjugate with subnanomolar potency. Excitingly, we showed that the high site selectivity of our strategy was maintained on other protein formats, especially on anticalins, for which directed mutagenesis helped to highlight the key importance of a single lysine residue.

Original languageEnglish
Article numbere202303242
JournalChemistry - A European Journal
Issue number14
StatePublished - 7 Mar 2024


  • Bioconjugation
  • chemical biology
  • multicomponent reactions
  • proteins
  • site-selectivity


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