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The Development of a Tumour-Responsive Format for Antibody Conjugates



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Antibody-drug conjugates (ADCs) are an emerging class of targeted therapeutics which exploit the selectivity of monoclonal antibodies towards particular membrane receptors, to deliver potent cytotoxins to a desired cell type. A significant amount of research has been undertaken to improve the performance and pharmacological profile of ADCs, with a predominant focus on the constituents, format, and bioconjugate chemistry—which together influence critical factors of the ADC such as stability, pharmacokinetics, and efficacy. Significant improvements have been demonstrated by use of alternative ‘non-IgG’ ADC formats, which has facilitated greater modulation of properties such as half-life and tumour penetration. Notwithstanding, there are significant limitations with the use of smaller alternative scaffolds, such as decreased circulatory time and reduced tumour exposure. Moreover, many of the associated synthetic strategies are inflexible or require laborious optimisation.

The primary aim of the work described herein is to develop a proof-of-concept ADC format that is responsive to the conditions of the tumour microenvironment. It is proposed that a therapeutic susceptible to enzymatic fragmentation into smaller active species at the tumour site, may possess favourable circulatory and uptake profiles. The motivation behind this research is the desire that may offer a solution to resolving the challenging mutual dependency of circulatory clearance and tumour uptake to therapeutic size.

The investigations described in this thesis detail the design, synthesis, and purification of a range of chemical cross-linkers (entailing a combination of small molecule and solid-phase peptide synthesis). The ability of the linkers to cross-link antibody fragments was investigated and optimised. The synthesised cross-linked fragments (BisFabs) comprised either an identical or unique (bispecific) pairing of antibody Fab molecules. A range of cross-linked antibody fragments was synthesised on scale, and subsequently functionalised via click-chemistry with a range of payloads (e.g. fluorophores and cytotoxins). The produced conjugates were evaluated for plasma stability, cellular selectivity, antigen binding affinity, and cytotoxicity. Enzymatic cleavage of the conjugates was also demonstrated. The obtained results validate the format as a viable approach towards tumour-responsive, selective, and highly stable antibody conjugates.





Spring, David


antibody-drug conjugate, bioconjugation, biotherapeutic, bispecific, chemistry, linker, MMP


Doctor of Philosophy (PhD)

Awarding Institution

University of Cambridge
Trinity College Cambridge