Patent infringement

The life-sciences press is peppered with headlines such as 'Court holds that Ranbaxy did not infringe GSK patent' and 'Court awards Applied Medical Resources Corp., $43.5 million because Tyco Corporation had infringed Applied's patent'. But what amounts to an infringement? How does the court decide whether Ranbaxy can make its generic version of the antibiotic Ceftin or that Tyco has to pay such a large sum?

A granted patent gives the owner a monopoly: only the owner, or someone with his permission, can make, sell or use a product or process that falls within that monopoly. The scope of this monopoly is set out in the claims of the patent. Each claim — and there may be many in a single patent — sets out a number of features or elements that define the invention.

An example of a claim is 'Use of rapamycin for the preparation of a medicament for inhibiting organ- or tissue-transplant rejection in a mammal in need thereof'. This is the principal claim in a UK patent owned by American Home Products (AHP) that was the subject of litigation in the United Kingdom against Novartis in 2001. In order to infringe a claim, a product or process has to have all of the elements of the claim. So, if someone was using rapamycin to treat heart disease they would not infringe the claim, because they were not using the organ-transplant rejection element of the claim. At the other extreme, if a product falls within the literal wording of the claim then that clearly is an infringement.

The Protocol

The difficulty arises when a third party's product or process is similar to a patented invention but does not fall within the literal wording of a claim. Does the claim cover it? Under harmonized patent law in Europe, the patent should not be limited to the literal meaning of any term in a claim (the patentee should have a fair degree of protection), but the protection cannot extend outside the claims such that the claims only serve as a guideline. In the UK the court has, since 1982, applied a structured test known as the 'Protocol Questions' to apply these principles to the facts of a particular case. However, in a landmark decision of 21 October 2004 in the case of Amgen v TKT, the House of Lords held that the Protocol Questions are only really relevant to claims in which figures or measurements are used. Now the only compulsory question is, 'what would the skilled person have understood the patentee to have used the language of the claim to mean?'

In relation to the rapamycin claim, AHP argued that the term 'rapamycin' covered a derivative of rapamycin developed by Novartis. The UK decided that the term 'rapamycin', as used in the patent, meant rapamycin alone and could not be broadened to cover rapamycin derivatives (for more information see Box).

Doctrine of equivalents

The US courts take a different approach to dealing with the issue of non-literal infringement. They determine whether there is 'equivalence' between each of the elements of the accused product or process (rather than the accused product or process as a whole) and the claimed elements of the patented invention; this is the so-called 'doctrine of equivalents'. Factors that are taken into account to determine whether an element is equivalent include the purpose for which an element is used in a patent and whether persons reasonably skilled in the technology would have known of the interchangeability of an element not contained in the patent with one that was.

In the US, to prevent the unfair broadening of the scope of a claim, the doctrine is limited by a further doctrine called 'prosecution history (or file wrapper) estoppel'. This doctrine applies when a claim is amended in the course of the application for a patent — that is, during its prosecution before the US Patent & Trademark Office. If the amendment results in the narrowing of the scope of a claim, then, subject to some provisos, the patentee cannot later argue that anything falling outside the literal meaning of that element and covered by the original broader claim is an equivalent. Competitors can therefore rely on the estoppel to ensure that their own devices will not be found to infringe other patents by equivalence. This doctrine has been subject to intensive scrutiny throughout the courts in the US during the past few years in the Festo case.

Balanced protection

So, in both the UK and the US (and indeed other countries of the world), the general principle is that a claim of a patent should not be limited to the strict, literal interpretation of the words of a claim because that would unfairly limit the patentee's monopoly. But, on the other hand, a claim should not be construed so broadly as to cover devices or processes that a patentee had not considered when creating his invention and which third parties, on reading the patent, could not reasonably have supposed would fall within the claim.

Box 1: American home products versus novartis

Rapamycin was known as an antifungal antibiotic, but in 1989 Professor Sir Roy Calne discovered that it also had an immunosuppressive effect. This invention was patented under the title 'Use of rapamycin and derivatives and prodrugs thereof...', but no derivatives had been found or were described in the patent. Novartis developed the rapamycin derivative SDZ RAD, which AHP claimed infringed its patent. The UK Court of Appeal (AHP v Novartis [2001] RPC 159) held that the patent claims were limited to rapamycin alone and that Novartis' derivative, SDZ RAD, did not fall within the claims. This was because although SDZ RAD worked in the same way as rapamycin, at the time the patent was filed a skilled person could not have predicted how many derivatives would have an immunosuppressive effect or indeed whether any and/or which would. In addition, throughout the specification of the patent the word rapamycin was used to denote the molecule itself and derivatives were referred to as such. In contrast, derivatives were not mentioned in the claims.