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Bulletins » Reconsideration Of Claims Previously Held Invalid Barred

In the latest instalment of a prolonged and litigious saga between Eli Lilly and Genentech, the UK High Court has ruled that, with regard to their divisional patent, Genentech are estopped from revisiting arguments settled during litigation of their parent patent. However, proceedings relating to the divisional patent have been permitted to continue for undecided matters, including consideration of second medical use claims.


This decision (Lilly v Genentech [2020] EWHC 261 (Pat)) concerns a series of European patents filed by Genentech, directed towards anti-IL-17A/F antibodies, and is particularly important for Lilly’s Taltz product, marketed for the treatment of psoriasis. Taltz comprises as its active ingredient the anti-IL-17A/F antibody, ixekizumab, and is a significant product in Lilly’s portfolio. Hence, striking out these patents is of great importance to Lilly.

The UK part of the parent patent, European Patent 1641822, endured a lengthy High Court trial and, after 12 days in court and £11 million in legal fees, was found to be invalid on the grounds of lack of inventive step and insufficiency. Soon after this, the Technical Board of Appeal at the EPO upheld the decision of the Opposition Division to revoke the European parent, on the grounds that it contained added matter. This left Genentech with its divisional patent, European Patent 2784084.

Following grant, the divisional, like its parent, was met by numerous opposition and invalidity proceedings across Europe, of which the present decision forms part. Importantly for the present decision, the granted claims of the parent and divisional patents were materially the same. As such, Lilly filed to invalidate the UK divisional patent to prevent Genentech from taking a “second bite of the cherry”.

Issue Estoppel

During the present trial, Lilly cited a number of issues as being res judicata, meaning these issues had already been adjudicated and could not be tried again by the same parties. In particular, Lilly cited the principle of issue estoppel.

Issue estoppel bars a litigant from raising an issue for a second time, where said issue has already been decided and is considered “fundamental” to a decision. Genentech argued that for an issue to be fundamental the issue must be “legally indispensable to the conclusion”, hence it was argued that issue estoppel cannot apply where two alternative grounds or arguments for revocation are provided, e.g. two alternative pieces of prior art are considered to make the claims obvious, as in the case of the parent patent. The judge considered that such a conclusion would have far-reaching implications in the field of patents, where cases often turn on multiple alternative grounds of invalidity.

The balance of injustice was a significant factor in the judge’s verdict. On one hand, it was considered that preventing Genentech from revisiting the issue of inventive step might be unjust. However, to reopen this door would certainly lead to another lengthy and expensive trial and the judge concluded that this would be against the public interest and would be an injustice to Lilly. Therefore, upon consideration of this balance and the fact that Lilly sought to rely on inventive step over both pieces of prior art, issue estoppel was held to be applicable to both alternative arguments.

This result does not come as a great surprise. Injustice is key to the application of issue estoppel and the UK courts are not prone to revisiting decisions, let alone a decision that had been the result of such an onerous trial.

Abuse of Process

As well as issue estoppel, this High Court decision raises an interesting point regarding abuse of procedure. Genentech sought to amend the UK divisional patent to introduce second medical use claims for the treatment of psoriasis, repeating claims that had been rejected in the parent patent for being insufficient at the date of priority. However, Genentech argued in the present proceedings that these claims are sufficient at the date of filing, and that arguments to this effect are not barred by issue estoppel. Lilly countered that Genentech’s submissions would constitute an abuse of process.

In relation to the parent patent, Genentech also submitted that plausibility of the second medical use claims should be assessed at the date of filing. However, this submission was held to be filed too late and was rejected. Thus, Lilly argued that it would be an abuse of process for Genentech to submit this argument now, as 1) this could and should have been filed at an appropriate time in the earlier proceedings, and 2) Genentech had not provided any evidence to overcome the sufficiency objection.

On the first point, despite the lateness of the submission in the earlier action, the judge did not think that Genentech should be prevented from pursuing this argument with regard to the divisional patent. Regarding the second point, the judge considered that newly filed evidence established an arguable case that the common general knowledge had changed between the priority date and the filing date. As such, there was an argument that it was plausible for the anti-IL-17A/F antibodies of the patent to be used for the treatment of psoriasis.

Despite their initial tardiness, Genentech have obtained another chance to pursue their second medical use claims. Nevertheless, a divisional is not an absolute safety net and this case highlights the importance of submitting arguments as early as possible.

Half a bite of the cherry

Though Genentech have been barred from contesting in relation to the divisional patent issues decided with regard to the parent patent, further consideration of the plausibility of the second medical use claims at the filing date has been permitted.

This High Court decision reaffirms the position of the UK courts that divisional applications cannot be used as a second opportunity to reargue points already considered in relation to the parent patent. Though Genentech have leave to pursue the second medical use claims again in the divisional patent, this is considered to be an undecided issue. Divisionals, while strategically important, are not an outright licence for a second shot at unsuccessful claims.

We anticipate UK High Court proceedings to assess the plausibility of the second medical use claims at the date of filing to take shortly.

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