Ramatroban (BAY u 3405): A Novel Dual Antagonist of TXA2 Receptor and CRTh2, a Newly Identified Prostaglandin D2 Receptor

It is known that thromboxane A 2 (TXA 2 ) contributes to various diseases such as bronchial asthma, ischemic heart disease, cerebrovascular disorders and allergic rhinitis. A number of TXA 2 synthase inhibitors and TXA 2 receptor (TP receptor) antagonists have been developed to treat these diseases. Ramatroban (BAY u 3405) was developed as a potent TP receptor antagonist with excellent efficacy against allergic rhinitis in many animal models and patients. Recent studies also revealed that ramatroban can block the newly identified PGD 2 receptor, chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTh2). PGD 2 induces migration and degranulation of eosinophils through CRTh2 and contributes to late-phase inflammation and cell damage. Accordingly, it was considered that ramatroban suppresses the late-phase inflammation via TP receptor and CRTh2 blockade. In tenns of the efficacy on vascular systems, it was revealed that ramatroban can suppress the expression of monocyte chemoattractant protein-1 (MCP-1) and adhesion molecules in endothelial cells and prevent exacerbation of inflammation by blocking these responses. According to our recent studies in hypercholesterolemic rabbits ramatroban prevents macrophage infiltration through MCP-1 downregulation and neointimal formation after balloon injury and attenuates vascular response to acetylcholine. Therefore, ramatroban may be beneficial in the treatment of atherosclerosis.