Tadalafil (Cialis) is available as a generic in the United States. If you think "big pharma" is served by drugs going off-patent, you may want to re-evaluate your perspective.
If you want to get more reasonably unhappy with market exclusivity, look at Celgene's grip on thalidomide/lenalidomide/pomalidomide for the treatment of multiple myeloma.
If you want to get more reasonably unhappy with market exclusivity, look at Celgene's grip on thalidomide/lenalidomide/pomalidomide for the treatment of multiple myeloma.