Pranlukast hemihydrate (ONO-1078 hemihydrate) is an antagonist of cysteinyl leukotriene receptor-1 (CysLT1) that blocks leukotrienes such as LTC4, LTD4, and LTE4, reducing bronchoconstriction and airway inflammation. It also inhibits NF-κB activation, thereby suppressing proinflammatory cytokine production (e.g., IL-6, IL-1, TNF-α) in monocytes/macrophages and T cells, contributing to its immunomodulatory effects.