Eight opponents achieve revocation of Salix’s rifaximin patent at EPO

US pharma company Salix Pharmaceuticals develops prescription drugs and medical devices that prevent and treat various gastrointestinal disorders. The current opposition proceedings centred on EP 2 350 096. The patent protects methods of treating hepatic encephalopathy — an altered level of consciousness resulting from liver failure. The main claim of the patent is the long-term use and specific dosage of the active ingredient rifaximin for treating hepatic encephalopathy.

For years, rifaximin, marketed under the brand name Xifaxan, has been known primarily as an antibiotic, used for the treatment of inflammatory bowel diseases (IBD) and diarrhoea.

A total of eight opponents attacked EP 096, which was granted in late 2019. The first opposition was filed by a straw man in August 2020, followed by others including Teva, Stada, Accord, and Alfred Tiefenbacher. In November 2022, the Opposition Division revoked the patent due to lack of inventive step. Salix appealed, but now the Boards of Appeal have upheld the first-instance decision.

EP 096 is one of four patents from the same family under attack in oppositions: the first divisional, EP 3 628 319, as well as two patents currently in the examination process EP 4 342 465 and EP3 964 066. The EPO had already revoked another related patent, dosage patent EP 2 252 148, in 2024 following oppositions by Sandoz and Teva, among others.

Conflict leads to reshuffle

Inge Hiebl, then at patent attorney firm Kraus Weisert, originally filed the patent application. The firm had worked for the pharmaceutical company Alfasigma, a licensor of Salix Pharmaceuticals, for many years. Hiebl also defended EP 096 in the first instance of the opposition proceedings.

When Kraus Weisert merged with Lederer & Keller in early 2024 to become Kraus & Lederer, a direct conflict of interest arose, as Marco Fachini from Lederer & Keller led the opposition for the second opponent as a straw man. He handed over the case to Ter Meer Steinmeister, whose partner Luigi Rumi was already leading another straw man objection in the case. Nevertheless, at the beginning of this year, Salix parted ways with Kraus & Lederer.

Salix then instructed patent attorney and London-based partner David Holland of British mixed firm Carpmaels & Ransford for the appeal at the Boards of Appeal. He is also representing the client in the appeal concerning the first divisional EP 319. Carpmaels has a long-standing relationship with Anne-Cecile Trillat, head of IP at Alphasigma. The relationship stems from her time at pharma company Chiesi. She moved to Alphasigma in 2023.

At the same time, Salix retained Thorsten Bausch of Hoffmann Eitle. He worked closely with David Holland on the case. Maiwald acted as representative in the case of EP 148, which the EPO revoked in 2024.

Salix faces straw men

Frances Lowe and Jane Hollywood from international full-service firm CMS Cameron McKenna Nabarro Olswang represented the first opponent as a straw man. The patent attorneys’ work for pharmaceutical companies such as Akebia and Sanofi in EPO oppositions is well known. For example, the team secured a success in a straw man case against one of the patents underpinning Novo Nordisk’s type 2 diabetes drug semaglutide.

Teva relied on Neil Nachshen of D Young & Co.. The patent attorney firm often represents the generics company, such as in the oppositions against apixaban patents. Irene Casalprim, then senior IP manager at Accord, led the opposition for the pharmaceutical company till she moved to Adalvo in early 2022. Accord then instructed London based name partner Adrian Murray of small Britis IP boutique Brand Murray Fuller for the remainder of the proceedings. Malte von Seebach of Hamm & Wittkopp acted for Stada and Alfred E. Tiefenbacher.

Henrik Skødt from the Danish patent attorney firm Aera filed another straw man opposition. Skødt joined the Spanish office of Bardehle Pagenberg in May. He boasts many years of experience in life sciences, including from his time in the in-house department of Novartis.