Prior to this case, Pfizer owned three key patents that protect Celebrex, two of which expire at the end of May 2014, and the '048 patent, which was due to expire early in December 2015. A dispute between Pfizer and several generics companies kicked off in 2008 over the validity of the Celebrex patents, which resulted in a US appeals court invalidating a patent (US 5760068; entitled “Substituted pyrazolyl benzenesulfonamides for the treatment of inflammation”) that was a precursor to the '048 patent. The '068 patent was invalidated on grounds of 'obviousness-type double patenting', meaning that the claims in this patent overlapped with claims in the other Celebrex patents.
To try to overcome this setback, Pfizer then sought to have the '068 patent reissued by the US Patent and Trademark Office; this procedure exists to allow patentees to correct an error in a patent. This request was successful, resulting in the issuance of the '048 patent (entitled “4-[5-(4-methylphenyl)-3-(trifluoromethyl)-1H-pyrazol-1-YL]benzenesulfonamide for the treatment of inflammation or an inflammation-associated disorder”).
