Selectively Targeting the Kinome-Conserved Lysine of PI3Kδ as a General Approach to Covalent Kinase Inhibition

Area of Science:

• Medicinal Chemistry
• Chemical Biology
• Pharmacology

Background:

• Selective covalent kinase inhibitors are valuable tools but are limited by targeting non-conserved cysteines in ~200 kinases.
• This cysteine-targeting approach restricts the development of inhibitors for the majority of the kinome.

Purpose of the Study:

• To develop a novel strategy for selective, irreversible kinase inhibition by targeting the conserved catalytic lysine residue.
• To create selective covalent inhibitors of Phosphoinositide 3-kinase delta (PI3Kδ) as a proof of concept.

Main Methods:

• Design and synthesis of novel covalent inhibitors targeting the conserved lysine.
• In vitro biochemical assays to assess kinase inhibition and selectivity.
• Cellular assays to evaluate potency and duration of action in CD4+ T cells.
• Live-cell proteomic studies to identify off-target covalent binding.

Main Results:

• Developed selective, covalent PI3Kδ inhibitors with nanomolar potency in cellular assays.
• Achieved a duration of action exceeding 48 hours in CD4+ T cells.
• Demonstrated high selectivity over other lipid and protein kinases despite lysine conservation.
• Identified minimal off-target covalent binding in live-cell proteomic studies.

Conclusions:

• Targeting the conserved catalytic lysine residue offers a viable and generalizable strategy for selective covalent kinase inhibition.
• This approach expands the druggable kinome beyond kinases with accessible cysteines.
• The developed PI3Kδ inhibitors show promise for therapeutic applications requiring sustained target engagement.