Patent

Infringement - Infringement by making

Ranbaxy (UK) Ltd v AstraZeneca AB: Chancery Division, Patents Court: 15 July 2011

The defendant company, which was the only supplier of esomeprazole in the United Kingdom, owned patent EP 1 020 461 (the patent) which covered one of the defendant's drugs called Nexium, used to treat gastric related disease. The active ingredient of Nexium was magnesium esomeprazole, the magnesium salt of the S enantiomer (the (-) enantiomer) of the racemic mixture known as omeprazole which had itself been introduced onto the market under the brand name Losec in 1988.

The patent was granted on 22 July 2009 upon a divisional application which had been published on 19 July 2000 and had a filing date of 27 May 1994. It described the use of magnesium esomeprazole with a high optical purity such that the ratio of the S enantiomer to the R enantiomer (the (+) enantiomer) had to be ≥ 99.9/0.1. That optical purity was expressed in terms of enantiomeric excess (e.e.), namely the fraction of the compound present as the major enantiomer less the fraction of the compound present as the minor enantiomer. Hence the patent explained the magnesium esomeprazole had to have an optical purity of ≥ 99.8% e.e. That was a bulk characteristic of the compound.

The parent application was published on 17 May 1995 and granted as EP 0 652 872 on 8 November 2000. The patent was said to address the desirability to obtain compounds with improved pharmacokinetic and metabolic properties which would give an improved therapeutic profile such as a lower degree of inter-individual variation. 

The invention was said to provide such compounds, those being novel salts of single enantiomers of omeprazole.

The patent's specification described and claimed the use of magnesium esomeprazole which was 'essentially free' of the magnesium salt of the R enantiomer. On 9 December 2006, the Board of Appeal of the EPO held that patent invalid for lack of inventive step. Claims 1 to 8 were all drafted in conventional Swiss form with each of claims 3 to 8 directed to the use of magnesium esomeprazole with an optical purity of ≥ 99.8% e.e. for the manufacture of medicaments for the treatment of different or increasingly specific conditions.

Swiss form claims were introduced under the EPC 1973 to address the exclusion from patentability of methods of treatment of humans or animals. Article 52(4) of the EPC 1973 provided that: '(4) Methods for treatment of the human or animal body by surgery or therapy and diagnostic methods practised on the human or animal body shall not be regarded as inventions which are susceptible of industrial application within the meaning of paragraph 1.

This provision shall not apply to products, in particular substances or compositions, for use in any of these methods'. Article 54(5) of the EPC 1973 provided that the inventor of a first medical indication could obtain purpose limited product protection for a known substance or composition without having to restrict himself to the substance or composition when in a form technically adapted to a therapeutic purpose. Claim 1 was directed to the use of magnesium esomeprazole with an optical purity of ≥ 99.8% e.e. for the manufacture of a medicament for the inhibition of gastric acid secretion (see [26] of the judgment). Claim 9 was directed to optically pure magnesium esomeprazole and was in conventional product claim form. Claim 10 was directed to a product for use in therapy, the characteristic form for a claim for the use of a known product in a method referred to in art 52(4) EPC 1973.

Claim 11 was directed to a product for use in the treatment of a specific condition as defined in claims 3 to 8, as contemplated by art 54(5) EPC 1973, as revised by EPC 2000 (EPC 2000), which came into force on 13 December 2007. The exclusion contained in art 52(4) EPC 1973 was moved to art 53(c) EPC 2000, reflecting an appreciation that such methods were excluded from patentability for ethical and public health reasons rather than lack of industrial applicability. Article 54(5) EPC 2000 expressly allowed further patent protection of substances or compositions already known as medicines provided their use in a method under art 53(c) EPC 2000 was specific and not comprised in the state of the art.

Claims 12 and 13 were dependent upon claims 9 to 11 and directed to a salt and composition respectively. The claimant company wished to import a product made in India which it believed did not infringe the patent and for which it expected to secure regulatory approval in the course of July 2011. If it was successful in that claim it would be free to sell that product without competition from other generic suppliers.b For the purposes of the instant proceedings, there was no dispute that the process of manufacture began with magnesium esomeprazole with an optical purity of ≥ 99.8% e.e.

There was also no dispute that the process involved the addition of a quantity of omeprazole racemate such that the finished product no longer contained magnesium esomeprazole of that optical purity. In those circumstances, the defendant contended that claim 1 was infringed. It argued that the product which the claimant wished to import was the direct product of a process in which magnesium esomeprazole with an optical purity of ≥ 99.8% e.e. was used to make a medicament for the inhibition of gastric acid secretion. The claimant, on the other hand, contended that claim 1 was not infringed: the product which it wished to import had not been formulated using, and did not contain, magnesium esomeprazole with an optical purity of ≥ 99.8% e.e. The claim and counterclaim therefore depended upon the proper interpretation of claim 1.

The claimant commenced proceedings, seeking a declaration of non-infringement and revocation of the patent. The defendant counterclaimed for infringement of the patent. It was directed that the infringement issues in the action should be tried as preliminary issues.

The defendant's case was that a process claim was not limited to the manufacture of specific products but extended to the use of the claimed process to make any product. Claim 1 was a process claim which was used if a magnesium salt of esomeprazole with an optical purity of ≥ 99.8% e.e. was used for the manufacture of a medicament for the inhibition of gastric acid secretion irrespective of whether or not the medicament contained magnesium esomeprazole at all. Put another way, it claimed that the claimant was seeking to rewrite claim 1 by inserting a limitation which it did not at that time contain.

The claimant contended that, construed purposively, claim 1 was directed to the process of making a medicament containing magnesium esomeprazole with an optical purity of ≥ 99.8% e.e. and the teaching of the patent was to that effect. Moreover, the skilled person would recognise that claim 1 was a Swiss form claim and that such claims were in substance directed to the protection of a new therapeutic use of a medicament containing a known active compound and it followed that the medicament had to contain that compound.

Against that background, it fell to be determined what the skilled person would have understood the words of claim 1 to mean; those words had to be construed purposively in the context of the specification. The court ruled.

It was well established that the skilled person read the specification in the light of the common general knowledge and appreciating that its purpose was to describe and demarcate an invention, namely a practical idea for a new product or process. From that approach, the following points emerged, namely first, the words of the claim were to be construed having regard to the patentee's purpose as set out in the rest of the specification.

Secondly, the exercise was one of interpretation of the words of the claim. It followed that it was not permissible simply to ignore an integer of the claim; nor was it permissible to write a new integer into the claim. Thirdly, it was generally reasonable to infer the patentee had intended the various claims to have a meaning different from each other, and so to have some effect. Fourthly, a patent specification was not a document inter rusticos. Accordingly, the skilled person would be taken to have known the basic drafting conventions used to frame a patent and its claims. Further, the skilled person would generally understand a Swiss form claim to mean that the medicament should contain the active ingredient for which the new and inventive use had been found (see [36]-[41], [54] of the judgment).

In the instant case, the skilled person would consider the meaning of claim 1 to be tolerably clear. Recognising the teaching of the specification that magnesium esomeprazole with an optical purity of ≥ 99.8% e.e. was new, he would nevertheless understand claim 1 to be directed to the use of such magnesium esomeprazole to manufacture a medicament which contained that active ingredient.

That understanding would, however, be reinforced by the skilled person’s appreciation that the claims fell into various sets, namely product claims, product for use claims, Swiss form claims, and as permitted under the EPC 2000, product for specific use claims. Claim 1, as a Swiss form claim, and forming as it did the first of a cascade of claims directed to the use of optically pure magnesium esomeprazole to manufacture a medicament for the treatment of different or more specific uses, would, naturally be understood as requiring the medicament to contain the active ingredient for which the claimed use had been found (see [67]-69] of the judgment).

The claimant was entitled to its declaration of non-infringement and the defendant's counterclaim for infringement failed (see [73] of the judgment).

Kirin-Amgen Inc v Hoechst Marion Roussel Ltd; Hoechst Marion Roussel Ltd v Kirin-Amgen [2004] All ER (D) 286 (Oct) applied; Actavis UK Ltd v Merck & Co Inc [2008] All ER (D) 290 (May) considered; Virgin Atlantic Airways Ltd v Premium Aircraft Interiors UK Ltd [2009] All ER (D) 235 (Oct) applied.

John Baldwin QC and Mark Chacksfield (instructed by S J Berwin LLP) for the claimant. Henry Carr QC and Miles Copeland (instructed by Bristows) for the defendant.