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The phosphodiesterase inhibitor ‘war’

Sildenafil is the prototypic selective inhibitor of one of the phosphodiesterase isozymes (PDE-5) that in some ways has become Pfizer’s most successful drug. Certainly in terms of branding it has entered the modern lexicon in much the same way as Coca Cola and the Big Mac. Herein lies the rub, insofar as sildenafil is much less commonly ingested than either of these other entities and, indeed, total worldwide sales only reached $1.7 billion in 2002. The original projections for sildenafil were sales in the region of $5– 6 billion at this stage after launch. (Sales figures in this range have been achieved by two other Pfizer products, Lipitor and Celebrex). An analysis of this underperformance by sildenafil may help to define the potential role for tadalafil, vardenafil and other PDE-5 inhibitors in development.