Gisadenafil besylate (UK 369003-26) is a potent and orally active PDE5 inhibitor (IC50=1.23 nM), 100 times more selective for PDE5 than PDE6, for the study of lower urinary tract symptoms associated with benign prostatic hyperplasia.

In vivo experiments used doxycycline-inducible HIV-1 Tat transgenic mice (GFAP-driven). Gisadenafil besylate was administered intraperitoneally at 0.25 mg/kg daily for 5 days. On day 5, a 5-minute hypercapnia challenge (5% CO₂) was applied to assess cerebrovascular reactivity. The treatment significantly improved the cortical blood flow response in Tat mice from 11.6% to 17.5%, and restored dilation of small arterioles (<25 μm) to 20.6%, though gisadenafil besylate did not recover the dilation of larger vessels[1].