Investigating Ugi/Passerini Multicomponent Reactions for the Site‐Selective Conjugation of Native Trastuzumab
Résumé
Site-selective modification of proteins has been the object of intense studies over the past decades, especially in the therapeutic field. Prominent results have been obtained with recombinant proteins, for which site-specific conjugation is made possible by the incorporation of particular amino acid residues or peptide sequences. In parallel, methods for the site-selective and site-specific conjugation of native and natural proteins are starting to thrive, allowing the controlled functionalization of various types of amino acid residues. Pursuing the efforts in this field, we planned to develop a new type of site-selective method, aiming at the simultaneous conjugation of two amino acid residues. We reasoned that this should give higher chances of developing a site-selective strategy compared to the large majority of existing methods that solely target a single residue. We opted for the Ugi four-center three-component reaction to implement this idea, with the aim of conjugating the side-chain amine and carboxylate groups of two neighbouring lysine and aspartate/glutamate. Herein, we show that this strategy can give access to valuable antibody conjugates bearing several different payloads, and limits the potential conjugation sites to only six on the model antibody trastuzumab. Posttranslational modifications of proteins is Nature's way of generating a rich and diverse proteome from a more limited genetic coding capability. First occurrences of intentional, man-made-artificial-proteins modifications using a defined chemical-thus excluding the food-related Maillard reaction for example-could be dated back to the use of formaldehyde in the tanning industry or for the production of toxoids, 1,2 which evolved later on to immunization studies using chemically-modified bovine serum albumin in the 1900s and eventually led to Landsteiner's synthetic haptenes studies. 3,4 The field of protein modification has since largely benefited from the understanding of proteins' and amino acids' structures coupled to the parallel appearance of more efficient and precise analytical tools. This finally resulted in the development of bioconjugation reagents with excellent chemoselectivity towards various amino acids' side chains groups (i.e. residue-selectivity) that translated into major applications, notably in the pharmaceutical field with the generation of protein-fluorophore adducts for trafficking studies, or the polyethyleneglycol chains functionalization (PEGylation) of proteins to give less-immunogenic and more plasma-stable conjugates. 5,6 However, site selectivity quickly emerged as the main limitation of chemoselective strategies, due to the presence of multiple copies of each type of amino acid residue at the surface of proteins. Statistic conjugation of surface-accessible lysine residues with amine-selective reagents typically results in highly heterogeneous mixtures, containing up to millions of different adducts when large proteins such as antibodies are utilised. 7,8 Each of these adducts possessing distinct physicochemical properties, such chemoselective conjugation necessarily leads to mixtures with different in-vivo pharmacokinetic properties along with virtually no reproducibility in batch-to-batch production. 9,10 Regioselective (i.e., site-specific) methods were thus developed and are currently dominated by the use of recombinant proteins, incorporating exogenous amino acid residues-natural or unnatural-or peptide sequences that can be specifically targeted by a tailored reagent or strategy. 11-13 In parallel, site-selective chemical strategies for the conjugation of native and natural proteins have also flourished over the past few years, giving rise to methods targeting various types of amino acids-e.g. lysine, cysteine, tryptophan, tyrosine-that proved to be effective on proteins of all sorts of sizes, including antibodies. 14-28 With the aim of pursuing the efforts in this field, we could not help but notice that the vast majority of previously reported strategies for the site-selective conjugation of native proteins were focused on the modification of a unique residue. We hypothesized that targeting two different amino acid side chains simultaneously would lower the enormous subset of possibilities given by single-residue bioconjugation techniques, thus increasing our chances of developing a site-selective method by minimising the number
Domaines
Chimie
Origine : Fichiers produits par l'(les) auteur(s)
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