When ET approached Sun Pharma, a spokesperson said, “As a policy, we do not comment on ongoing litigation and issues related to filed products”. A mail sent to Novartis headquarters remained unanswered at the time of going to the press. Sun told the court that through a notice in August 2007, it had explained to Novartis why it believes that the Glivec (or Gleevec as it is known in the US) patent was invalid, unenforceable and wouldn’t be infringed by its proposed generic version of the drug.The Indian drugmaker had filed an Abbreviated New Drug Application with the USFDA in June 2006 seeking permission to make and market generic versions of imatinib mesylate (strength 100 and 400 mg), Sun further claims in its plea. As Novartis did not launch the expected infringement suit against Sun Pharma within the 45-days window after it received a notice from Sun, the Indian drugmaker filed for a declaratory judgment in the US court, urging it be allowed to market a generic version of Glivec. “Sun is entitled to a declaration that all claims of the ’051 patent (related to Glivec) are not infringed and/or are invalid,” Sun’s plea filed on Friday said.Until and unless Sun obtains a court decision of non-infringement and/or invalidity on the ’051 patent, it faces the risk of incurring substantial damages for patent infringement if it commences marketing its ANDA products before the ’051 patent expires, the plea said. Novartis’ patent coverage on Glivec in the US would start expiring from Jan 2015 and different patents related to the drug would continue to expire six years after that. The '051 patent is set to expire in November 2019, according to USFDA's Orange Book.