The selective inhibition of enzymes that catalyze the conversion of arachidonic acid to inflammatory eicosanoids represents a promising approach for cancer therapy. This study, therefore, focuses on the incorporation of metabolically stable, sterically demanding, and hydrophobic carboranes into existing dual cycloxygenase‐2 (COX‐2)/5‐lipoxygenase (5‐LO) inhibitors that are key enzymes in the biosynthesis of eicosanoids. Here, the first carborane‐containing dual COX‐2/5‐LO inhibitors derived from RWJ‐63556 are presented. The replacement of the fluorophenyl moiety by meta‐ or para‐carborane resulted in five carborane‐containing derivatives 3, 6, 9, 13, and 17 that show high inhibitory activities toward COX‐2 and 5‐LO in vitro. Cell viability studies on the A375 melanoma cell line revealed that meta‐carborane derivative 3 shows higher anticancer activity compared to RWJ‐63556 based on accumulation of lipid droplets in the cells due to blockage of the COX‐2 and 5‐LO pathways, indicating a promising approach for the design of potent dual COX‐2/5‐LO inhibitors.

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The presence of inflammatory mediators in the tumor microenvironment, such as cytokines, growth factors or eicosanoids, indicate cancer-related inflammatory processes. Targeting these inflammatory mediators and related signal pathways may offer a rational strategy for the treatment of cancer. This study focuses on the incorporation of metabolically stable, sterically demanding, and hydrophobic dicarba-closo-dodecaboranes (carboranes) into dual cyclooxygenase-2 (COX-2)/5-lipoxygenase (5-LO) inhibitors that are key enzymes in the biosynthesis of eicosanoids. The di-tert-butylphenol derivative tebufelone represents a selective dual COX-2/5-LO inhibitor. The incorpo-ration of meta-or para-carborane into the tebufelone scaffold resulted in eight carborane-based tebufelone analogs that show no COX inhibition but 5-LO inhibitory activity in vitro. Cell viability studies on HT29 colon adenocarcinoma cells revealed that the observed antiproliferative effect of the para-carborane analogs of tebufelone is enhanced by structural modifications that include chain elongation in combination with introduction of a methylene spacer resulting in higher anticancer activity compared to tebufelone. Hence, this strategy proved to be a promising approach to design potent 5-LO inhibitors with potential application as cytostatic agents.

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