Phosphodiesterase-5 inhibitors for male erectile dysfunction

The success of sildenafil (Viagra®; Pfizer) as an oral therapy for male erectile dysfunction (MED) has greatly stimulated interest in phosphodiesterase (PDE)-5 inhibitors. A large number of compounds from a wide variety of structural classes have been identified as PDE5 inhibitors during the past few years. Many of them possess desirable biological and pharmaceutical profiles. Selected compounds from different structural classes have entered clinical trials for MED. Since PDE5 inhibition is now a proven mechanism for MED treatment, many of these compounds are scientifically capable of becoming drugs for MED, as evidenced by the recent launches of vardenafil (Levitra®; Bayer Yakuhin) and tadalafil (Cialis®; Lilly ICOS). However, the business environment rather than scientific merit will probably determine the journey of additional PDE5 inhibitors to the market.