US Pharm. 2010;35:50. 

Synthon Pharmaceuticals, Inc., was sued by Eli Lilly and Company and Icos Corporation after filing an Abbreviated New Drug Application (ANDA) for tadalafil 20 mg--a generic bioequivalent of Lilly's and United Therapeutics' Adcirca tablets for the treatment of pulmonary arterial hypertension to improve exercise ability. Synthon indicated that it is the “Single First Filer” of an ANDA with a Paragraph IV certification for Adcirca (tadalafil) tablets, 20 mg. As a result, Synthon is expected to be eligible for 180 days of Hatch-Waxman exclusivity.