Soluble guanylate cyclase (sGC) is a key enzyme in the nitric oxide (NO) signalling pathway. Riociguat is metabolized to BAY60-4552 not only via cytochrome P450 isoenzymes 3A4 (CYP3A4), CYP2C8, and CYP2J2, but also via CYP1A1, located in the liver and lungs.