Another success for Astellas and Kirkland defending Xtandi

Generics of prostate cancer drug enzalutamide remain banned from entering the UK market. The Court of Appeal in London has upheld a key patent and SPC, confirming a previous ruling by the UK High Court last autumn.

The dispute concerns EP 1 893 196 and its SPC, both covering enzalutamide — the active ingredient in Astellas’ major prostate cancer drug Xtandi. The Regents of the University of California owns EP 196, while Astellas is the licensee.

Accord, Sandoz and Teva brought a nullity action before the UK High Court which, in autumn 2024, upheld the patent in its entirety. The generics companies appealed the decision.

The parties argued that first-instance judge James Mellor had erred in his assessment of obviousness based on the expert evidence presented at trial. The judge had accepted Astellas’ argument that hindsight had influenced the expert witness’s evidence.

The Court of Appeal has now dismissed the appeal (case ID: CA-2024-002655/002675/002676). The judges emphasised that they would only intervene if the first-instance judge had erred in law or principle. The panel, led by presiding judge Richard Arnold and including Richard Snowden and Antony Zacaroli, found no error in judge Mellor’s approach. The court rejected the generics companies’ view that the patent was obvious over prior art.

In response to Astellas’ counterclaim for infringement, the generics manufacturers had previously conceded that their products would infringe the patent. However, they had argued it was invalid due to lack of inventive step. Both first and second-instance courts in the UK have now dismissed this argument.

Astellas has also successfully defended its patent in the Netherlands and Germany. In June, the District Court The Hague dismissed nullity suits filed by Accord Healthcare and Sandoz against EP 196 and its Dutch SPC. In spring, the German Federal Patent Court also upheld the German part of the patent and its SPC.