Riociguat (Rio)

Riociguat is a novel drug that is in clinical development by Bayer. It is a stimulator of soluble guanylate cyclase (sGC). At the moment Phase III clinical trials investigate the use of riociguat as a new approach to treat two forms of pulmonary hypertension (PH): chronic thromboembolic pulmonary hypertension (CTEPH) and pulmonary arterial hypertension (PAH). Riociguat constitutes the first drug of a novel class of sGC stimulators. In healthy individuals nitric oxide (NO) acts as a signalling molecule on vascular smooth muscle cells to induce vasodilation. NO binds to soluble guanylate cyclase (sGC) and mediates the synthesis of the secondary messenger cyclic guanosine monophosphate (cGMP). sGC forms heterodimers consisting of a larger alpha-subunit and a smaller haem-binding beta-subunit. Riociguat can cause fetal harm and is therefore contraindicated in pregnant women.