The Indian patent of Champix, Pfizer's non-nicotine prescription drug for smoking cessation sold in the US as Chantix, is facing a challenge from Dr Reddy's Laboratories, it is learnt.
Dr Reddy's has filed a post-grant opposition with the India Patent Office against the approval of Patent No 204091 covering the freebase of varenicline and its tartrate salt, the active ingredient of Chantix, according to sources. The product, which was launched in India in February 2008, had received the Indian patent corresponding of Orange Book listed US patent nos 6,890,927 and 7,265,119.
Dr Reddy's, on May 2008, opposed the patent claims on four grounds. The company alleged that the claims as granted in India are broader than the claims filed in the international application and the alleged invention relating to vareinicline is neither novel nor inventive as it has already been claimed in a prior Indian patent application. The international application claimed only the tartrate salt of varenicline whereas the Indian patent claims the freebase, stated the company.
The company also added that 'the alleged invention relating to the tartrate salt of varenicline squarely falls within the ambit of Section 3(d) i.e. the said invention is merely a new form of a known substance', informed Dr Reddy's spokesperson. Pfizer has filed a reply to the opposition and the matter is yet to come up for hearing before the Mumbai Patent office, added the company.
Varenicline tartate, the only marketed and approved drug with the particular mechanism, first mimics a low dose of nicotine to ease the withdrawal and then blocks nicotine from binding with receptors, making the nicotine action ineffective. Thus, the product will block the nicotin boost even when the person smokes.
However, the US FDA has issued safety alert on the drug for triggering suicidal thoughts and aggressive and erratic behaviour in users of the product. Harmful side-effects like serious accidents and falls, potentially lethal cardiac rhythm disturbances, severe skin reactions, acute myocardial infarction, seizures, diabetes, psychosis and aggression are also reported with varenicline usage. In the 4th quarter of 2007 varenicline accounted for 988 serious injuries in the U.S. reported to the FDA, more than any other individual drug in this time period. In Canada, the drug regulators received 818 reports of adverse reactions associated with the medication from 2006 to October 31, 2008.
Despite the serious concerns raised world over about the safety of the drug, Pfizer launched the product in India in less than two years of its launch in the US. Champix was priced at Rs 9,500 for a 12-week therapy in India. Of late, in 2009, the drug regulatory body of India has sought post marketing analysis on the drug to take an account of the safety of Champix.
Pfizer Ltd, the Indian arm of the global pharma leader, is building the market in India through Champ clubs and collaborating with more health care firms. India has a tobacco-related disease burden of over Rs 24,000 crore, and by 2010 it is estimated that over one million Indians will die of smoking-related diseases.