Incontinence Drug Ruling Offers Key Patent Drafting Lessons

(November 2, 2023, 11:33 AM GMT) --
George McCubbin
George McCubbin
On Oct. 17, the High Court of Justice of England and Wales handed down the long-awaited judgment in Astellas Pharma Industries Ltd. v. Teva Pharmaceutical Industries Ltd. and Sandoz Ltd., some 14 months after trial.

The case concerned the patent infringement action commenced by Astellas against Teva and Sandoz, in relation to their proposed generic mirabegron tablets, which are used to treat overactive bladder syndrome.

The case highlights some important points to remember for patent drafting and litigation strategy, and the interaction between the two.

Context of the Dispute

The defendants Teva and Sandoz propose to launch generic mirabegron, which was sold by Astellas under the brand name Betmiga. They had earlier challenged the validity of a method of treatment under European Patent 1 559 427, or EP'427, owned by Astellas, which claimed "a remedy for use in the treatment of overactive bladder comprising [mirabegron]."

Judge Richard Meade of the High Court found EP'427 to be valid and infringed at first instance, which was upheld by the Court of Appeal of England and Wales in July.[1]

Thus, Teva and Sandoz will be held off the market until expiry of the supplementary protection certificate over EP'417, which extends protection until around December 2027 into early 2028, depending on the country.

Separately, Astellas asserted another patent against Teva and Sandoz in separate proceedings before the High Court, called EP 2 345 410, or EP'410, which is a modified release formulation patent with a priority date of 2008. EP'410 would extend Astellas' exclusivity over Betmiga until around September 2029.

In response, Teva and Sandoz alleged that the patent was invalid for insufficiency and obviousness, arguing that the claims of EP'410 were excessively broad and exceeded any relevant technical contribution to the art, and not infringed by their proposed products. This patent is the subject of the recent decision.

Summary of the Proceedings

EP'410 allegedly reduced the "food effect" associated with conventional formulations of mirabegron.

Food effect refers to possible pharmacokinetic differences between patients in fed and fasted states.

The claims of EP'410 recite a modified release formulation of mirabegron comprising specified additives and having a prescribed drug dissolution rate.

Teva did not contest that its original proposed product would infringe EP'410, but argued that its new formulation would not and brought a claim for a declaration of noninfringement, which was not determined at trial. Sandoz contested infringement by its product.

In summary, the case before the High Court turned on the correct construction of claim 1 of the patent.

Judge James Mellor found that — on his construction of EP'410 — the patent as amended was valid, but not infringed.

Conversely, if his construction was incorrect — and under the construction proposed by the patentee itself — then EP'410 was infringed but invalid. This is a win for Teva and Sandoz, given their loss in relation to the method of treatment patent EP'427.

Takeaways From the Decision

Although this decision is highly fact-specific, it is a reminder that the consequences of patent drafting have to be carefully considered.

As explained in the sections below, Astellas was put in an unenviable position: to adopt a construction that made proving infringement challenging, or to adopt a construction that led to a finding of invalidity.

The decision highlights why considering infringement of claims is as important an aspect of drafting patents as considering their own validity.

In addition, the decision reinforces the importance of developing alternative case strategies. Especially on infringement, Astellas did not present any evidence on what would happen if the contrary construction position was adopted by the court, which it ultimately was.

For example, expert evidence on how infringement might be demonstrated on the basis that Sandoz admitted that it does not conduct comparative studies against conventional formulations, but only equivalence studies against the originator reference product.

Key Aspects of the Decision

In this case, the three main considerations in any patent action — (1) construction, (2) validity and (3) infringement — were all intertwined.

As discussed below, the success of the generics in this case can be traced back to this interrelationship.

Construction of Claim 1

The issue on construction related to whether or not the term "pharmaceutical composition for modified release" in claim 1 required a reduction in food effect.

The claim, as amended by Astellas, does not refer to food effect at all and the only functional limitation relates to a drug dissolution rate test.

However, the description of the patent provides a definition of the term that notes "the drug release is controlled to the extent that the effects by food are reduced," which was further defined to refer to a reduction in the parameter Cmax — the peak concentration of drug in body plasma — compared to a conventional formulation.

This is why Astellas was pushing for a construction of the claim that ignored this language.

If reduction in food effect was considered to be an integer of the claim, then infringement would have to be demonstrated by showing a reduction in Cmax, which may require in vivo studies.

Thus, Astellas argued that claim 1 only required that the formulation had the recited composition and satisfied the claimed dissolution test.

Conversely, Teva and Sandoz argued, and the court accepted, that the outcome — reduction of food effect — is an element of the claim.

Judge Mellor could not understand why Astellas would have "carefully set out a defined term and then not use or apply it", unless its definition was intended.

On Astellas' argument that such a construction may require costly and time-consuming in vivo studies, which involve testing with living subjects, to prove infringement, Judge Mellor had little sympathy observing it was for them to draft the patent in a way to avoid such requirements.

This is a reminder that the English courts will place paramount emphasis of the language actually chosen in the patent, and so its implications for validity and infringement, and the interplay between the two, must be carefully considered.

Grounds of Invalidity

On the ground of insufficiency, Teva and Sandoz argued that it was not plausible that the invention worked with substantially all formulations falling within the scope of claim 1, on the basis of the sole experimental example in the patent that presents pharmacokinetic data in humans.

After a highly detailed analysis of the description of the patent and the expert evidence, Judge Mellor did not agree. He observed that the threshold for plausibility was low, requiring "some reason for supposing" that the outcome in the claim is true, as put by Justice Jonathan Sumption in the 2018 U.K. Supreme Court case Warner-Lambert Co. LLC v Generics U.K. Ltd.

In relation to the inventive step, all three pieces of prior art relied upon aspects of an oral controlled absorption system developed in the early 2000s by a company now part of Astellas.

Judge Mellor had to grapple with heated dispute between the parties as to the meaning and impact of the various prior art documents.

The finding of obviousness depended on which construction of claim 1 was accepted.

On Astellas' own construction, which did not require the amelioration of food effect as an integer, EP'410 would be obvious in light of the prior art, whereas on Teva and Sandoz's construction, it would not be, because such documents did not disclose this feature.

As the court preferred Teva and Sandoz's construction, the patent was valid.


As foreshadowed above, the adoption of the construction requiring a reduction in food effect, as defined by Cmax, was going to make life difficult for Astellas on infringement.

A finding in relation to Teva's revised product formulation could not be determined at trial and will subsequently have to be assessed.

Sandoz had disputed that its proposed product fell within the scope of the claims and Judge Mellor agreed that, on his construction of the claims, infringement had not been established as there was no evidence of the reduction of food effect by the Sandoz formulation as compared to a conventional formulation of the drug.

This is because Astellas had only argued an infringement case based on their own proposed construction of the claim, which was not adopted.

Astellas even tried to issue a last-minute application for disclosure against Sandoz, which was later withdrawn.


The case shows how decisions made during patent drafting and litigation can influence the outcome of the action.

Had Astellas not included the impugned definition in the patent, food effect would not have been a feature of the claim and infringement would have been established.

Conversely, on the construction adopted by the court, Astellas may have established infringement if it had adduced expert evidence that, for example, by demonstrating bioequivalence to their product Betmiga, the generics must have met the relevant parameter Cmax parameter.

Thus, Astellas is left with another valid patent in its mirabegron arsenal, but one that may be more difficult to assert against generics. This is because it requires the comparison of in vivo pharmacokinetic data of the generic product against a conventional formulation of the drug, unless it has confidence that it can convince a court with expert evidence such as the kind suggested above.

However, given that this patent is still valid, the saga is unfinished and there may be yet further debate on the infringement of EP'410.

George McCubbin is a senior associate at Herbert Smith Freehills LLP.

The opinions expressed are those of the author(s) and do not necessarily reflect the views of their employer, its clients, or Portfolio Media Inc., or any of its or their respective affiliates. This article is for general information purposes and is not intended to be and should not be taken as legal advice.

[1] Teva Pharmaceutical Industries Ltd & Anor v Astellas Pharma Inc [2023] EWCA Civ 880.

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