Development of lysine-targeted irreversible inhibitors of PI3Kδ

Rights statement
Awarding institution
  • University of Strathclyde
Date of award
  • 2018
Thesis identifier
  • T15980
Person Identifier (Local)
  • 201474584
Qualification Level
Qualification Name
Department, School or Faculty
  • Targeted covalent inhibition of poorly conserved cysteine residues for kinase inhibition has increased in popularity over recent years. Whilst these inhibitors are often highly successful, studies have shown that only ~40% of human kinases are amenable to this approach. Furthermore, cysteine point-mutations present common resistance mechanisms to these drugs. This thesis explores the concept of targeting the catalytically essential lysine of the kinase, which is conserved throughout the human kinome, for selective covalent inhibition. The validity of this approach is exemplified with the lipid kinase phosphoinositide 3-kinase delta (PI3Kδ), as it has been implicated in a range of diseases, and is not amenable to traditional cysteine-targeting. An activated ester motif was identified that was able to covalently modify this lysine residue, on non-selective scaffolds. These scaffolds were then optimised by exploration of the hingebinder, back-pocket, and electrophilic warhead to afford a series of indazole-based inhibitors that showed nanomolar potency and >100-fold selectivity in biochemical assays. The best series of inhibitors were then progressed to a full kinetic analysis to understand the mechanism of binding to PI3Kδ. The lead inhibitor, possessing a para-fluorophenolic ester warhead, showed evidence of target engagement in CD4+ T-cells in the sub-nanomolar range with an extended duration of action. Additionally, this inhibitor showed minimal off-target engagement in chemoproteomic studies in Ramos cells. In summary, this thesis discloses the development of the first selective irreversible inhibitor of PI3Kδ. This supports the hypothesis that covalent inhibition of kinases can be achieved by targeting a highly conserved lysine residue, opening the door to covalent targeting of kinases not possessing reactive cysteine residues. Additionally, this inhibitor may have applications in the design of long-acting therapeutics for kinase-mediated diseases. Finally, this concept may also offer a way of overcoming cysteine point-mutations as an acquired resistance mechanism to currently available targeted covalent inhibitors.
Advisor / supervisor
  • Campos, Sébastien
  • Murphy, John
Resource Type
  • Previously held under moratorium in Chemistry department (GSK) from 12th April 2018 until 18 June 2021.
Embargo Note
  • This thesis is restricted to Strathclyde users only until 12th April 2023.
  • The electronic version of this thesis is currently under moratorium due to a licensing issue. If you are the author of this thesis, please contact the Library to resolve this issue.