Chromones as Nonclassical Inhibitors of Carbonic Anhydrase IX and XII Isoforms: Probing Chromone-Based Derivatives

Area of Science:

• Medicinal Chemistry
• Biochemistry
• Pharmacology

Background:

• Carbonic anhydrases (CAs) are enzymes implicated in various physiological processes, with specific isoforms linked to cancer development.
• Human carbonic anhydrase IX (hCA IX) and XII (hCA XII) are cancer-associated isoforms overexpressed in several tumors.
• Developing selective inhibitors for these isoforms is a key strategy for targeted cancer therapy.

Purpose of the Study:

• To synthesize and characterize a library of novel chromone derivatives.
• To evaluate the inhibitory potency and selectivity of these compounds against cancer-associated (hCA IX, hCA XII) and off-target (hCA I, hCA II) human carbonic anhydrase isoforms.
• To assess the drug-likeness and binding interactions of the most promising compounds.

Main Methods:

• Chemical synthesis and structural characterization of chromone derivatives.
• In vitro enzymatic assays to determine inhibitory constants (K_i) against purified carbonic anhydrase isoforms.
• In silico ADMET predictions for drug-likeness assessment.
• Molecular docking studies to elucidate binding modes within the hCA IX active site.
• Cellular assays using HepG2 and Caco-2 cell lines to evaluate metabolic inhibition.

Main Results:

• A library of novel chromone compounds was successfully synthesized.
• Compounds 4a, 4g, 4j, and 4k exhibited selective inhibition of hCA IX and hCA XII, with no significant activity against hCA I and hCA II.
• Compound 4k emerged as the most potent and selective inhibitor, with K_i values of 0.31 µM for hCA IX and 0.24 µM for hCA XII.
• In silico analyses indicated favorable ADMET properties for all synthesized compounds.
• Molecular docking revealed optimal binding of the chromone moiety towards the zinc ion in hCA IX.
• Cellular assays confirmed selective inhibition of metabolic activity in hCA IX-expressing HepG2 cells, but not in hCA IX-deficient Caco-2 cells.

Conclusions:

• The synthesized chromone derivatives represent a promising class of selective inhibitors for cancer-associated carbonic anhydrase isoforms IX and XII.
• Compound 4k is a potent and highly selective inhibitor with potential for further development as an anti-cancer therapeutic agent.
• The findings support the role of hCA IX as a therapeutic target in cancer and validate the chromone scaffold for designing selective CA inhibitors.