Riociguat is a first-in-class, orally available drug that is being developed as a treatment for CTEPH and PAH.
It stimulates soluble guanylate cyclase (sGC), a key component of the nitric oxide signalling pathway that binds nitric oxide and increases synthesis of the second messenger cyclic guanosine monophosphate
. Riociguat has a dual mode of action; it increases the sensitivity of sGC to endogenous nitric oxide by stabilising the binding of nitric oxide to the prosthetic haem group on sGC, and it can also increase sGC activity independently of nitric oxide
. The nitric oxide independent action of riociguat distinguishes it from phosphodiesterase-5 inhibitors, which require nitric oxide to function and may have limited effect in the presence of very low nitric oxide levels.
The therapeutic potential of riociguat was first demonstrated in mice and rats with established pulmonary hypertension; treatment with riociguat led to partial reversal of pulmonary hypertension, vascular remodelling and cardiac hypertrophy in these models .