Eli Lilly and Company v Genentech, Inc. [2020] EWHC (Pat)
High Court applies issue estoppel and abuse of process to validity of divisional patent

This decision is the most recent development in a wider dispute between Genentech and Eli Lilly. The dispute started in 2017 when Lilly sought to revoke Genentech’s European Patent No. 1641822 (the “822 Patent”) titled “IL-17A/F heterologous peptides and therapeutic uses thereof”. It also sought a declaration of non-infringement for its blockbuster psoriasis drug Taltz®.

This judgment decided Lilly’s application for summary judgment for the revocation of Genentech’s European Patent No. 2784084 B (the “084 Patent”), a divisional of the 822 Patent.


Taltz® contains Lilly’s proprietary anti-IL-17A/F antibody ixekizumab, the result of independent research and development by Lilly. While Genentech owns a family of patents claiming the use of IL-17A/F for the treatment of psoriasis, it does not have a product related to either the 822 or 084 Patent.

In the proceedings concerning the 822 Patent (the “822 Action”), Arnold J (as he then was), revoked the 822 Patent for obviousness. Applying the principles in Warner- Lambert v Actavis [2018] UKSC 56, he also held that the claims relating to the use of IL-17A/F for the treatment of psoriasis lacked plausibility at the priority date. During the 822 Action, Genentech made an application to change the date at which plausibility was to be assessed to the filing date in light of developments in the CGK. Arnold J refused the application for case management reasons on the basis that the application was made too close to the trial date.

While Arnold J granted Genentech permission to appeal, the 822 Patent was in the interim finally revoked by the EPO for added matter (a claim rejected by Arnold J in the High Court proceedings), with the effect that the UK designation of the 822 Patent was deemed never to have existed and Genentech’s appeal fell away.

Genentech subsequently brought a fresh claim against Lilly on the basis of its divisional 084 Patent (the “084 Action”). It was agreed that for the purposes of the litigation, there was no material difference between the claims of the 822 Patent (as sought to be amended) and the 084 Patent (as sought to be amended). Lilly counterclaimed that this contravened the principle of res judicata; that the same issue should not be decided twice.

Genentech, on the other hand, argued that it had been granted leave to appeal in the 822 Action, and therefore had a reasonable prospect of success. To deny it the chance of having its arguments heard when the 822 Patent had been revoked, would amount to an injustice. This was particularly so given that the TBA had revoked the 822 Patent for added matter, an issue that was dismissed by Arnold J.


Roger Wyand QC, sitting as Deputy High Court Judge, analysed the authorities on estoppel and abuse of process at paragraphs 49 to 76 of the judgment. While he had sympathy for the position Genentech found itself in, he held it would not be in the interest of justice for a full retrial of the issues decided in the 822 Action, the combined cost of which totalled some £11 million.

However, the judge held there was one issue that would not be res judicata, this being the date on which plausibility was to be assessed. The case management reasons that prevented Genentech from running the argument in the 822 Action did not apply in the 084 Action, and he considered that there was a real prospect that Genentech could show the relevant claims were plausible at the filing date in light of developments to the CGK. Summary judgment in respect of those claims was accordingly refused.

While Lilly has successfully put a lid on most of the issues – the finding that the claims directed at the use of IL-17A/F for the treatment of psoriasis lacked plausibility at the priority date is subject to estoppel – the dispute will continue as to whether use of the antibody for the treatment of psoriasis at the filing date of the 084 Patent was plausible.

Key points to take away from the decision:

  • While the EPO system intentionally provides for the filing of divisional applications in situations where patent protection would otherwise be lost, this case illustrates the implications this can have where a patentee seeks to enforce a divisional where the parent has been invalidated.
  • The case also illustrates the important role issue estoppel plays in the UK in such circumstances, particularly in the absence of estoppel between the EPO and UK courts (an issue raised before the EPO can subsequently be raised in national proceedings, cf. the position in the US).
  • In this case, the cost of a retrial ultimately weighed heavily in the judge’s decision that issue estoppel should apply, notwithstanding the fact that Genentech lost its chance to appeal when the 822 Patent was revoked. While both Genentech and Lilly could have absorbed the costs, the absence of issue estoppel could have significant impact on a less pecunious party in the same situation.
  • Despite the judge’s robust application of the doctrine to the majority of issues Genentech wished to raise, he did leave the door open that a party should not be estopped from raising any issues not raised in earlier proceedings. It will be interesting to see if and how this affects the outcome of any similar cases in future.

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