On Nov. 21, 2003, Cialis (tadalafil), discovered through a Glaxo Wellcome and ICOS Corp. partnership, was approved by the FDA for treating erectile dysfunction (ED). In 1998, ICOS and Eli Lilly formed the Lilly ICOS joint venture to further develop and commercialize tadalafil as a treatment for ED. Cialis is a selective inhibitor of cyclic guanosine monophosphate-specific phosphodiesterase type 5 for the treatment of ED.

ICOS was founded in 1989 by Robert Nowinski, Christopher Henney and George Rathmann. The company was focused on discovering, developing and commercializing treatments for inflammation and other serious diseases. In 2006, ICOS Corporation was acquired by Eli Lilly and Co. for $2.1 billion.