Antibody drug conjugates (ADCs) are increasingly promising targeted therapies for cancer
treatments, due to the combination of antibodies with tumour selectivity and cytotoxic drugs.
Current strategies to construct ADCs suffer from heterogeneity, complexity, and high costs.
Dibromomaleimides (DBMs), a class of next generation maleimides (NGMs), have shown
ability to site-selectively bridge antibody disulfide bonds, delivering robustly stable
conjugates following maleimide hydrolysis. This work expands DBM scope by developing
trifunctional DBMs built around a lysine core, introducing multiple functionalities (such as
fluorophores) onto an antibody, which would be of significant interest for treatments of
complex diseases.
However, a problem associated with DBM-based disulfide bridging arises as disulfide
scrambling where incorrectly bridged disulfides observed in antibody hinge region, thus
forming two antibody isomers with limited homogeneity. To resolve this issue, in situ NGMbased bioconjugation has been conducted to enable simultaneous disulfide reduction and
bridging. A variety of dithiomaleimides (DTMs) has been explored to attempt to minimise
cross-reactivity to TCEP, a typical disulfide reducing agent. Compared to highly reactive DBMs,
these DTMs have attenuated reactivity, and thus can be applied during the reduction. Upon
disulfide reduction, the presence of these DTMs enables an efficient bridging and leads to a
reduction in scrambled disulfide bonds compared to conventional DBM-based bioconjugation.
However, the resultant conjugates also involve mis-bridged antibody species, therefore,
NGM-based in situ bioconjugation still needs optimisation.
Lastly, investigations on benzeneselenols as novel antibody reducing agents have been
conducted. Traditional benzeneselenols show good reducing ability but suffer from the poor
aqueous solubility and malodour. A new generation of benzeneselenols with improved
bioconjugation properties have been developed, through the synthesis of substituted aryl
derivatives with improved solubility for better compatibility with biological conditions.
Overall, this work expands the scope of DBMs and explores methods to generate more
homogeneous antibody conjugates using DBMs and related reagents
