Liarozole HCl is a benzimidazole derivative with antineoplastic activity. As a retinoic acid metabolism blocking agent, liarozole inhibits CYP450-dependent all-trans-retinoic acid (ATRA)-4-hydroxylase, leading to an increase in endogenous ATRA production, inhibition of cell proliferation, and induction of cell differentiation. It also inhibits aromatase.