Hyderabad: Multinational drug majors Pfizer and AstraZeneca have filed separate patent infringement cases against city-based Pharma Company Hetero Drugs in two different US courts.

While Pfizer dragged Hetero to court for violating patents of its blockbuster drug Viagra, which is used for the treatment of impotence, AstraZeneca filed a patent infringement suit seeking an order restraining the generic drug maker from launching a generic version of its 'Nexium' drug, which is used for the treatment of acid-related diseases, before the patent expiry.

The patents for Viagra and Nexium will expire on October 22, 2019, and August 3, 2015, respectively.

When contacted, a senior official of Hetero termed the development as routine.

"Our processes are non-infringing and have been developed for launch only after patent expiry. While it necessitates us to file ANDAs before patent expiry, it is routine for the
originators to challenge filings in the interim," said Hetero Drugs Director (Marketing) Srinivas Reddy.

"There are many examples of filing this kind of patent suits in US where the judgement went against the plaintiffs," he added.

Pfizer filed a petition in the district court for the Southern District of New York alleging that Hetero's generic version will infringe Viagra's patent.

Hetero filed an Abbreviated New Drug Application (ANDA) for its generic Viagra drug with the US Food and Drug Administration on June 17.

Pfizer requested the court to issue a permanent injunction order against the Hyderabad drug-maker from selling, making or importing the generic version until the expiry of the patent for Viagra, which cloaked revenues of USD 1.93 billion worldwide in 2010.

According to Pfizer, Viagra worldwide revenues increased 2 per cent in 2010, compared to 2009.

In the USA, Viagra revenues increased 3 per cent in 2010, compared to 2009.

Viagra began facing generic competition in Spain and Finland in December, 2009. AstraZeneca, which filed a patent infringement case against Hetero, alleged that the generic drug-maker violated three patents for Nexium, which are valid until August 3,

Hetero, in a Notice Letter to AstraZeneca on June 17, notified that it had submitted an ANDA to the FDA seeking the approval to manufacture, use, offer to sell and sell the
generic version of Nexium.

AstraZeneca requested the United States District Court for the District of New Jersey to declare that the effective date of any approval of Hetero's ANDA for Esomeprazole Magnesium delayed release capsules (20 mg and 40 mg) must not be before the expiration date of the last patent-in-suit that is infringed, including pediatric exclusivity relating to the patent.

According to AstraZeneca, Nexium saw revenues of nearly USD 5 billion in 2010 worldwide.