Identification of type-II inhibitors using kinase structures

Area of Science:

• Biochemistry
• Structural Biology
• Medicinal Chemistry

Background:

• Spleen tyrosine kinase (SYK) is implicated in autoimmune diseases, allergy, and asthma.
• Designing selective small molecule inhibitors for protein kinases is challenging due to conserved ATP binding sites.
• Type-II inhibitors stabilize kinases in inactive conformations, offering a strategy for selective inhibition.

Purpose of the Study:

• To identify novel ligands targeting unique conformations of spleen tyrosine kinase (SYK).
• To apply a structure/ligand-based approach for discovering selective SYK inhibitors.
• To characterize the binding modes of newly identified SYK ligands.

Main Methods:

• Utilized public (RCSB) and proprietary (Pfizer) kinase crystal structures.
• Employed a protein structure/ligand-based drug design strategy.
• Analyzed ligand binding to DFG-out and DFG-in, C-Helix-out conformations of SYK.

Main Results:

• Discovered the first reported spleen tyrosine kinase (SYK) Type-II ligands.
• Compounds 1 and 3 bind to the DFG-out conformation of SYK.
• Compound 2 binds to a DFG-in, C-Helix-out conformation, revealing a novel hydrophobic pocket due to C-helix movement.

Conclusions:

• Successfully identified Type-II inhibitors for spleen tyrosine kinase (SYK) using a structure-based approach.
• Demonstrated the feasibility of targeting novel SYK conformations for drug discovery.
• The findings provide a foundation for developing selective SYK inhibitors for autoimmune and inflammatory conditions.