Covalent Inhibition by a Natural Product-Inspired Latent Electrophile

Area of Science:

• Chemical Biology
• Medicinal Chemistry
• Proteomics

Background:

• Targeting specific protein cysteines is crucial for developing covalent probes and drugs.
• 3-Bromo-4,5-dihydroisoxazole (BDHI) is a synthetically accessible electrophilic moiety inspired by natural products.
• Previous studies showed BDHI reacts with nucleophilic cysteines in purified enzymes.

Purpose of the Study:

• To define the global cysteine reactivity and selectivity of BDHI-functionalized chemical fragments.
• To compare BDHI's cysteine engagement profile with that of haloacetamide electrophiles.
• To explore the utility of BDHI in covalent ligand discovery and drug design.

Main Methods:

• Competitive chemoproteomic profiling was used to assess cysteine reactivity.
• BDHI's selectivity was mapped across the human proteome.
• BDHI was utilized in the design of Bruton's tyrosine kinase (BTK) inhibitors.

Main Results:

• BDHI effectively engages reactive cysteine residues in the human proteome.
• The selectivity profile of BDHI differs from haloacetamide electrophiles.
• BDHI forms covalent conjugates with GSTP1 and PIN1, validated anticancer targets.
• BDHI was successfully incorporated into BTK inhibitor design.

Conclusions:

• BDHI exhibits distinct cysteine reactivity and selectivity, offering a valuable tool for covalent ligand discovery.
• The tunable binding element of BDHI allows for restricted and selective protein engagement.
• BDHI represents a promising electrophilic moiety for developing novel covalent drugs and chemical probes.