Patent thicket asserted by Salix against Norwich in the rifaximin district court cases

Rifaximin illustrates the anticompetitive gamesmanship that patents with double patenting rejections and terminal disclaimers enable. When Norwich filed an ANDA to market generic rifaximin, Salix asserted a thicket with 26 patents including 19 that had terminal disclaimers. The court ordered Salix to narrow its contentions before trial and the company presented evidence of infringement for only seven of the 26 patents initially asserted. The case concluded in 2022 with the invalidation of four of the seven patents that reached trial, including two that claimed methods of treating IBS. In 2023, the USPTO granted Salix two new terminally disclaimed patents claiming methods of treating IBS in females. Salix then asserted the newer IBS patents against Norwich in 2024, delaying generic competition for several more years while Americans pay among the highest prices in the world for rifaximin. Read the Generation Patient report on how patent thickets increase costs and delay access for young adult patients.