Small-Molecule KRAS Inhibitors by Tyrosine Covalent Bond Formation

Area of Science:

• Oncology
• Molecular Biology
• Drug Discovery

Background:

• KRAS mutations drive numerous cancers, but targeted therapies like sotorasib (a KRAS G12C inhibitor) address only a subset.
• KRAS protein has tyrosine residues that present potential alternative sites for covalent drug development.

Purpose of the Study:

• To identify novel covalent inhibitors targeting KRAS.
• To explore tyrosine residues as potential nucleophiles for KRAS inhibition.
• To develop new strategies for targeting KRAS-driven tumors beyond the G12C mutation.

Main Methods:

• Screening of aryl sulfonyl fluorides to identify KRAS inhibitors.
• Utilizing mass spectrometry, nucleotide exchange assays, effector binding assays, and NMR to characterize inhibitor binding.
• Employing cocrystal structures and NanoBRET assays to validate target engagement and cellular activity.

Main Results:

• Aryl sulfonyl fluoride SOF-436 was identified as a KRAS inhibitor, primarily targeting Tyr-64 and secondarily Tyr-71.
• SOF-436 inhibits KRAS nucleotide exchange and binding to SOS1 and RAF.
• Cocrystal structures revealed fragment binding to the Switch II pocket, providing a basis for Switch I/II inhibitor design.

Conclusions:

• Tyrosine residues on KRAS can serve as effective targets for covalent inhibition.
• These findings offer a new therapeutic strategy for KRAS-driven cancers, expanding treatment options.
• The identified fragments are starting points for developing novel small-molecule KRAS inhibitors.