DiscoverX Zaprinast

Zaprinast is a synthetic cGMP-specific phosphodiesterase (PDE) inhibitor from which sildenafil (Viagra) was developed. It is selective for PDE5, PDE6, PDE9 and PDE11 (IC50s of 0.76, 0.15, 29, and 12 uM, respectively), and is also a GPR35 agonist. It was an unsuccessful clinical drug candidate.