Discovery of highly potent Src SH2 binders: structure-activity studies and X-ray structures

Area of Science:

• Medicinal Chemistry
• Structural Biology
• Biochemistry

Background:

• Src SH2 domain is a key regulator in cellular signaling pathways.
• Developing potent and selective inhibitors for Src SH2 is crucial for therapeutic interventions.
• Previous studies focused on phosphotyrosine mimetics for SH2 domain binding.

Purpose of the Study:

• To optimize hydrophobic moieties of caprolactam/thiazepinone scaffolds for enhanced Src SH2 binding.
• To identify novel potent inhibitors of the Src SH2 domain.
• To elucidate the binding modes of novel inhibitors using X-ray crystallography.

Main Methods:

• Structure-based drug design and synthesis of caprolactam/thiazepinone analogs.
• In vitro biochemical assays to determine binding affinity (e.g., IC50, Kd).
• X-ray co-crystallography to determine the binding mode of inhibitors with the Src SH2 domain.

Main Results:

• Identification of two series of potent Src SH2 binders, RU 81843 and RU 79181.
• RU 81843 demonstrated high potency with an IC50 of 9 nM, significantly outperforming the reference peptide.
• X-ray structures revealed distinct binding modes for RU 81843 and RU 79181, with RU 81843 exhibiting an excellent fit within the Src SH2 domain.

Conclusions:

• Optimization of the hydrophobic moiety is critical for achieving high potency Src SH2 inhibitors.
• RU 81843 represents a promising lead compound for targeting Src SH2-mediated signaling.
• Structural insights provide a basis for further development of selective Src SH2 inhibitors.