Page 114 - Tyrosine-Based Bioconjugations - Jorick Bruins

Chapter 7
7.1. Short summary
Antibodies can be modified with pharmaceutical compounds for targeted therapies, and have been widely studied for drug delivery (ADCs),1 localized radiation,2 and immunotherapies.3 A key factor in generating these compounds has been the ability to modify proteins in a site-selective manner, as uncontrolled conjugation presents with unfavourable pharmacokinetics.4 Ideally, the method of conjugation relies on natural amino acids under mild conditions, and yields a single product.
Figure 1. (A) A schematic representation of SPOCQ; oxidation of a tyrosine residue by mTyr and subsequent cycloaddition with a BCN-bearing probe. (B) SPOCQ on G4Y-bearing antibody light chains for the generation of ADCs.
This thesis describes a new process for labeling of proteins in an inducible fashion, based on the selective enzymatic oxidation of tyrosine side-chains (1) by mushroom tyrosinase (mTyr).5 As most proteins, including monoclonal antibodies, do not have tyrosine residues accessible for oxidation by the bulky mushroom tyrosinase (130 kDa), selective oxidation is ensured by engineering of an exposed tyrosine tag (G4Y) on any of the protein termini. After oxidation by mTyr, a highly electrophilic quinone group (2) is generated that can readily undergo an inverse- electron demand Diels-Alder reaction (IEDDA), such as strain-promoted oxidation-controlled
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