Research Area: Metabolic Disease Biological Activity: Tadalafil (Cialis) is a PDE inhibitor. Tadalafil(Cialis), which has demonstrated a high level of selectivity for PDE5 over the other phosphodiesterases, has shown efficacy in improving erectile function and sexual satisfaction in phase III trials. [1]PDE11A3, PDE11A2, and PDE11A1, which contain progressively shorter N-termini, were more sensitive than PDE11A4 to inhibition by Tadalafil(Cialis). [2]