zaprinast zaprinast zaprinast was an unsuccessful clinical drug candidate that was a precursor to the chemically related pde5 inhibitors, such as sildenafil (viagra), which successfully reached the market. it is a phosphodiesterase inhibitor, selective for the subtypes pde5, pde6, pde9 and pde11. ic50 values are 0.76, 0.15, 29.0, and 12.0 μm, respectively. zaprinast names iupac name 5-(2-propoxyphenyl)-1h-triazolopyrimidin-7(4h)-one other names m&b 22,948 identifiers cas number 37762-06-4 n 3d model (jsmol) interactive image chembl chembl28079 y chemspider 5520 y echa infocard 100.048.760 iuphar/bps 2919 pubchem cid 5722 unii gxt25d5ds0 y comptox dashboard (epa) dtxsid8045224 inchi inchi=1s/c13h13n5o2/c1-2-7-20-9-6-4-3-5-8(9)11-14-12-10(13(19)15-11)16-18-17-12/h3-6h,2,7h2,1h3,(h2,14,15,16,17,18,19) ykey: rezggxndemkiqb-uhfffaoysa-n y smiles o=c1c2=c(n=nn2)nc(c3=cc=cc=c3occc)=n1 properties chemical formula c13h13n5o2 molar mass 271.280 g·mol−1 except where otherwise noted, data are given for materials in their standard state (at 25 °c , 100 kpa). n verify (what is yn ?) infobox references zaprinast inhibits the growth of asexual blood-stage malaria parasites (p. falciparum) in vitro with an ed50 value of 35 μm, and inhibits pfpde1, a p. falciparum cgmp-specific phosphodiesterase, with an ic50 value of 3.8 μm. zaprinast has also been shown to activate the orphan g-protein coupled receptor known as gpr35, both in rats and humans, and to inhibit the mitochondrial pyruvate carrier.