Glaxo’s critical U.S. Patent # 4,753,789 (the ‘789 patent) will be expiring on December 24, 2006 (including additional six months pediatric exclusivity), exposing U.S. Zofran market worth USD 900 million (sales in 2005) to generic drug manufactures. U.S. Patent # 4,695,578 (the ‘578 patent) covering Ondansetron hydrochloride, the active ingredient of Zofran, expired on July 25, 2005 but the ‘789 patent covering the approved indication is due to expire in next month. Interestingly, on November 07, 2006 Apotex sued U.S. regulators to block any rival from getting exclusive rights to sell generic versions of Zofran. Read More. Earlier in August 2001, Glaxo filed a patent infringement lawsuit in the U.S. District Court for the District of New Jersey against Reddy-Cheminor and Dr. Reddy’s Laboratories (DRL) alleging patent infringement of the Glaxo’s three patents including the ‘578 patent and two method of use patents, the later of which expires in December 2006. The lawsuit was result of DRL Para IV certification for Zofran tablets. In July 2003, Glaxo filed another patent infringement lawsuit against DRL in the same district court for infringement of the Glaxo’s patents related to Zofran orally disintegrating tablets followed by another lawsuit in October 2003 by Glaxo against West-ward Pharmaceuticals in the same district court for infringement of the Glaxo’s patents related to Zofran injections. Both the DRL disintegrating tablet case and West-ward case later consolidated with the earlier DRL case for Zofran tablets. However, prior to trial both DRL and West-ward withdrew their challenge to the ‘578 patent. The trial for infringement and validity of the Glaxo’s method of use and process patents got completed in June 2004 and closing arguments were heard in May 2005. Till date no decision has been announced. In March 2002, the Glaxo filed a similar action against Teva in the U.S. District Court for the District Court of Delaware alleging infringement of the two method of use patents for Zofran tablets. Teva certified invalidity or non-infringement of the two method of use patents. On August 20, 2004 the trial judge Gregory M. Sleet ruled in the favor of Glaxo, upholding the validity of method of use patents and infringed by Teva proposed ANDA product which was subsequently appealed by Teva to the Court of Appeals for the Federal Circuit (CAFC). However, Glaxo and Teva later reached a settlement agreement, the terms of which are kept confidential. In January 2003, Glaxo filed an infringement suit against Kali (now Par Pharmaceutical Company) in the U.S. District Court for the District of New Jersey involving orally disintegrating Zofran tablets. The trial judge denied Kali’s summary judgment motion and granted the Glaxo’s summary judgment motions in June 2005 and July 2005, affirming the validity of the Glaxo’s method of use patents and holding that Kali’s proposed generic product would infringe those patents. Following the district court decision, Kali filed a notice of appeal with the CAFC. Till date, no hearing date for that appeal has been announced. In June 2003, Glaxo filed an infringement action in the US District Court for the District of New Jersey against the Faulding Pharmaceutical Company (now Mayne Pharma) alleging infringement of the two method of use patents for ondansetron. Faulding case has been stayed pending decisions in the Reddy/West Ward case. Till date --- Teva, Hospira and Baxter received tentative approval for Ondansetron injection whereas Barr, Teva and Par received tentative approval for Ondansetron orally disintegrating tablets. Glenmark, Sun, Mylan, Kali, Teva and Taro received tentative approval for Ondansetron tablets. However, Kali received the FDA final approval for Zofran orally disintegrating tablets but later FDA rescinded its approval following the district court judgment that Kali’s ANDA infringes Glaxo’s unexpired patents.