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Title: The development of divinyl-heteroaryl linkers for the synthesis of stable and functional antibody-drug conjugates
Author: Walsh, Stephen
ISNI:       0000 0004 7972 9864
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2019
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Antibody-drug conjugates (ADCs) are a class of targeted therapeutics that utilise the exquisite selectivity of antibodies for membrane receptors to selectively deliver cytotoxic warheads to specific cell types, such as cancer cells. Much effort has been invested in recent years to deliver ADCs with improved pharmacokinetics, toxicology and overall pharmacological profiles over early generation ADCs. In particular, advances in linkage strategies through antibody engineering or enzymatic modification have yielded homogeneous ADC products with defined modification sites and stable linkages. Despite significant advances in this regard, these strategies are typically laborious and low-yielding, and the immunogenicity of these unnatural modifications is still unclear. The primary aim of this work was to obtain a linker technology that yields homogeneous, stable and functional ADCs from native antibodies. To this end, cysteine bridging strategies, whereby a bis-reactive scaffold covalently cross-links the two cysteines of a reduced disulfide, were identified as a reported method to produce homogeneous and functional ADCs. However, a limited number of these reagents have been described in the literature and it was postulated that an expansion of the toolbox of these reagents would be beneficial to the ADC research community. This report details the development of a novel set of divinylpyrimidine (DVP) cysteine bridging linkers. Early investigations into divinylpyridine reagents were initially conducted, but disappointingly, were deemed to have insufficient reactivity to enable efficient antibody disulfide rebridging. Alteration of the divinyl-heteroaryl scaffold by switching to a pyrimidine core was then explored. In the first instance, monovinylpyrimidine small molecule models demonstrated the improved reactivity of the scaffold, while maintaining the stability and chemoselectivity that was observed with the vinylpyridine reagents. DVP linkers including a dual-functional DVP were then readily prepared and were shown to efficiently rebridge the reduced disulfides of native antibodies, antibody fragments and other disulfide-containing proteins. Functionalisation of the protein substrates with biologically-relevant moieties (e.g. cytotoxins, fluorophores) could be achieved either before rebridging with a pre-functionalised linker or after rebridging through bioorthogonal chemistry. In addition, the receptor affinity and cellular selectivity of the antibodies were unaffected by rebridging and the antibody conjugates displayed exceptional stability in human plasma over two weeks. Critically, ADCs synthesised through DVP conjugation demonstrated highly potent and selective cytotoxicity in a series of in vitro cellular assays.
Supervisor: Spring, David Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Chemistry ; antibody-drug conjugates ; bioconjugation