Developing a novel strategy for site-selective amide formation at C-terminal cysteines to enable the synthesis of homogeneous state-of-the-art antibody conjugates

Project ID: 2228cd1365 (You will need this ID for your application)

UCL Lead department: Chemistry

Project Summary:

Over the years, a wide variety of methods have been established for the modification of various amino acids on peptides/proteins, e.g., Cysteine, Lysine. However, the absence of a reliable strategy for modification of the C-terminus has persisted. To the best of our knowledge, the only general method for C-terminal modification is that pioneered by Macmillian et al. (Nature Chem., 2017, 10, 205-211). However, this strategy is decarboxylative, uses an Ir photocatalyst, requires pH 3.5 for good yields and introduces a highly unnatural group onto the protein. Prima facie, the lack of methods for C-terminus modification seems logical as it is conceptually difficult to activate/react only one carboxylic acid in the presence of all others. In this project, the Chudasama and Baker research groups are proposing to develop an organic-chemistry-led first-in-class method for the site-selective modification of C-terminal cysteines. This will enable site-selective conjugation of native antibodies as the vast majority of clinically relevant antibodies bear a C-terminal cysteine (thus leading to the various applications of antibody conjugates, e.g., use in cancer imaging, therapy, diagnostics, immunotherapy, etc. whilst also providing a fundamental addition to the chemical biologist’s toolbox in a broader context). Our core concept is to utilise sulfur selective chemistries to deliver coupling reagents to the carboxylate on the C-terminus, which will then enable site-specific amide bond formation. Encouragingly, we have recently published a key preliminary result in the area (Chem. Commun., 2022, 58, 5359-5362), which sets the groundwork for application on various antibody scaffolds.

This project will develop the synthetic organic chemistry and chemical biology skills of the student whilst giving them the freedom to think and develop their project further. The standard analytical techniques (NMR, IR, LC-MS and SDS-PAGE) employed by synthetic organic chemists and chemical biologists will be a key aspect of the training within this project.