Galectin-8N-Selective 4-Halophenylphthalazinone-Galactals Double π-Stack in a Unique Pocket.

Area of Science:

• Biochemistry
• Medicinal Chemistry
• Structural Biology

Background:

• Galectin-8 possesses two distinct carbohydrate recognition domains (CRDs).
• Targeted inhibition of specific CRDs is crucial for understanding galectin-8 functions and developing therapeutics.

Purpose of the Study:

• To design and discover potent and selective inhibitors targeting galectin-8's carbohydrate recognition domains.
• To develop tool compounds for galectin-8 biology studies and potential drug development.

Main Methods:

• Structure-guided design of glycomimetic-heterocycle hybrid ligands.
• Biochemical assays to determine binding affinity (K_d) and selectivity against various galectins.
• X-ray crystallography to elucidate ligand-protein interactions at high resolution (1.30 Å).
• In vitro ADME (Absorption, Distribution, Metabolism, Excretion) studies including LogD, permeability, and stability assessments.

Main Results:

• A 4-(p-bromophenyl)phthalazinone derivative demonstrated a 34 μM K_d for galectin-8N (N-terminal CRD).
• This compound exhibited high selectivity, showing no binding to galectin-8C and other tested galectins, with >40-fold selectivity over galectin-4C.
• X-ray structure revealed specific interactions within the galectin-8N-specific sub-pocket, explaining the observed selectivity.
• Favorable physicochemical properties (LogD) and good passive permeability were observed.
• Promising chemical, microsomal, and plasma stability were confirmed.

Conclusions:

• Novel glycomimetic-heterocycle hybrids are potent and selective inhibitors of galectin-8N.
• The identified compounds serve as valuable tool compounds for galectin-8 research.
• These molecules represent promising candidates for hit-to-lead optimization in drug discovery.