Structural optimization on a virtual screening hit of smoothened receptor

Area of Science:

• Medicinal Chemistry
• Molecular Biology
• Drug Discovery

Background:

• The Hedgehog (Hh) signaling pathway is crucial for embryonic development and its aberrant reactivation is implicated in various cancers.
• The Smoothened (Smo) receptor is a key target for inhibiting Hh pathway signaling in cancer therapy.
• Previous virtual screening identified a potent Hh pathway inhibitor (C794-1677) with IC50 of 47 nM.

Purpose of the Study:

• To structurally optimize the virtual screening hit C794-1677 to enhance potency and reduce lipophilicity.
• To eliminate potentially toxic pyrrole and aniline functional groups from the lead compound.
• To identify novel Smo receptor antagonists with improved drug-like properties for cancer treatment.

Main Methods:

• Structure-based drug design and molecular optimization of the Hh pathway inhibitor C794-1677.
• In vitro assays to evaluate inhibitory activity against Hh pathway activation using a Gli-responsive element (GRE) reporter gene assay.
• Assessment of compound lipophilicity (cLogP) and inhibition of Gli1 mRNA expression in NIH3T3 cells.

Main Results:

• Optimized compound 25 demonstrated a 7-fold higher potency (IC50 of 7.1 nM) compared to vismodegib.
• Compound 25 exhibited significantly reduced lipophilicity and lacked the pyrrole and aniline moieties of C794-1677.
• Compound 25 effectively inhibited Gli1 mRNA expression in cells with both wildtype and D473H mutant Smo receptors.

Conclusions:

• Structural optimization of C794-1677 yielded compound 25, a highly potent and improved Hh pathway inhibitor.
• Compound 25 represents a promising lead compound for further development as an anti-cancer therapeutic.
• The optimized compound offers a favorable profile for addressing Smo-mediated cancers.