Lilly Patent Particulate Form of Tadalafil

Indian Patent Office (Chennai) has lately issued an Indian patent # 224314 (the ‘314 patent) to Lilly Icos LLC for Tadalafil particulate form and method of preparation thereof. The ‘314 patent is issued against the national phase application (PCT) # IN/PCT/2002/143/CHE claiming priority from US provisional application # 60/147,048 dated August 03, 1999 which later issued as US 6,821,975 and currently listed with the US FDA Orange Book. Marketed as Cialis by Eli Lilly, Tadalafil is one of the drug that was granted exclusive marketing right (EMR) in India against the application # 85/DEL/1995 (the 1995 application) which later got stayed by the Calcutta High Court after a petition made by Mumbai-based Ajanta Pharma.

The 1995 application covered claims for Tadalafil per se and process of preparation thereof. Considering [pre-grant opposition] filed by Ajanta Pharma, the Indian Patent Office (Delhi) last year on March 22 rejected product claims for Tadalafil per se but allowed process claims. The product claims were found obvious over the US 3,917,599 (the ‘599 patent) issued to Central Drug Research Institute (CDRI). The ‘599 patent exemplified 2-substituted-1, 2, 3, 4, 6, 7, 12, 12a-octahydropyrazino [2’, 1’:6, 1] pyrido [3, 4-b] indoles which is the base structure of Tadalafil but never suggested to be useful for treatment of erectile dysfunction.