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

A small library of differently substituted chromones was successfully synthesized and structurally characterized. All compounds were evaluated for their inhibitory potency and selectivity toward human cancer-associated carbonic anhydrase isoforms IX and XII, as well as the off-target isoforms I and II. Compounds 4a, 4g, 4j, and 4k selectively inhibited cancer-associated isoforms IX and XII, with no activity against the off-target isozymes I and II. Among them, compound 4k was the most potent and isozyme-selective inhibitor, with K_i 0.31 µM for hCA IX and 0.24 µM for hCA XII. To estimate drug-likeness, in silico ADMET predictions were performed, indicating that all compounds possess physicochemical and pharmacokinetic properties within the acceptable ranges. Molecular docking studies on the hCA IX isoform highlighted an optimal orientation within the binding pocket, with the chromene moiety positioned toward the zinc ion. In cellular assays 4a, 4g, 4j, and 4k selectively inhibited metabolic activity in HepG2 cells expressing hCA IX in normal conditions, whereas no activity was observed in Caco-2 cells lacking hCA IX expression.