zaprinast

Zaprinast is a **selective inhibitor of cGMP-specific phosphodiesterases (PDEs)**, most notably **PDE5 and PDE6**, with moderate or weak inhibition of other isoforms such as PDE9, PDE10, and PDE11[1][3][5]. It was a **precursor compound in the development of sildenafil (Viagra)** but did not proceed to clinical approval[5]. Zaprinast enhances the vasodilatory effects of nitric oxide by prolonging cGMP-mediated signaling[1][4]. In addition to PDE inhibition, Zaprinast has been shown to **activate the orphan G-protein coupled receptor GPR35** and is a **potent inhibitor of the mitochondrial pyruvate carrier (MPC)**, independently of PDE inhibition[1][3][5]. Pharmacological studies demonstrated renal vascular and neuroprotective effects in animal models, as well as effects on metabolic pathways related to mitochondrial transport and amino acid metabolism[2][3][4][5].

Other names

1,2,6,7-tetrahydro-1-methyl-7-oxo-1H-pyrazolo[4,3-d]pyrimidin-5-yl-4-benzamide