Claim interpretation – essential integers

In August of 2002, our Supreme Court of Appeal delivered a judgment in Aktiebolag Hassle and Astrazeneca Pharmaceuticals (Pty) Ltd v Triomed (Pty) Ltd 2003 (1) SA 155 (SCA), which dealt with the principles of interpretation of claims.

The Appellants claimed infringement of a pharmaceutical product for inhibiting gastric secretion. The product was an acid sensitive active ingredient Omeprazole, having an alkaline reacting enteric coating, enabling an oral dose of Omeprazole to pass through the stomach and be delivered intact to the proximal part of the intestine, and a subcoating layer of filmforming alkaline compounds forming a barrier between the core of Omeprazole and the enteric coating.

Claim 1 of South African patent no. 87/2378 read:

  1. An oral, pharmaceutical preparation in the form of enteric coated tablets or pellets, containing omeprazole as the active ingredient characterized in that it is composed of:
    (a) alkaline core material containing omeprazole together with an alkaline reacting compound, or an alkaline salt of omeprazole optionally together with an alkaline reacting compound, and
    (b) on said alkaline core material one or more inert reacting subcoating layers comprising tablet excipients which are soluble or rapidly disintegrating in water, or polymeric, water soluble, filmforming compounds, optionally containing pH-buffering, alkaline compounds between the alkaline core material and
    (c) an outer layer, which is an enteric coating.

The allegedly infringing preparation differed from the claimed preparation only in that the subcoating layer contained a single filmforming compound.

In the court a quo, Southwood J, sitting as the Commissioner of Patents (2001 BIP 72 (CP)), applied a purely literal interpretation to the claim and held that:

In interpreting claim 1 it must be borne in mind that the function of the claim is to inform prospective rivals of the limits of the field denied to them while the patent remains in force and that it is not a function of the body of the specification to serve as an aid to interpretation. Recourse can be had to the body of the specification as an aid to interpretation only where the body of the specification provides a dictionary as to the meaning of a word or term used in the claim – Gentiruco 87D-E (BP); 614H–615A (SA); Letraset Ltd v Helios Ltd 1972 BP 243 (A) at 247C-D – or where a claim is ambiguous (in the sense of being uncertain, vague or of indefinite meaning) in order to give a reasonably certain meaning to the claim – Gentiruco at 88F-G (BP); 615F-G (SA); De Beers Industrial Diamond Division (Pty) Ltd v Ishizuka 1979 BP 135 (T) at 142E-G. These are the only exceptions to the general rule. …
[The] words must be read grammatically and in their ordinary sense to determine what the language used means. That is the primary object of interpretation since it is presumed that the inventor or patentee intended what the language means. There is no special technical meaning to be taken into account. The only issue is whether the words ‘excipients’ and ‘compounds’ are intended to mean the singular or the plural (or both the singular and the plural). …
Read grammatically and in their ordinary sense these words mean that there must be a plurality of tablet excipients or filmforming compounds of the type described.

Accordingly, Southwood J held that the patent had not been infringed.

On appeal, Nugent JA noted that in law and in the interpretation of claims “context is everything”, and applied the purposive approach as set out by Lord Diplock in the UK case of Catnic Components Ltd & Another v Hill & Smith Ltd (1982) RPC 183 (HL):

… a patent specification is a unilateral statement by the patentee, in words of his own choosing, addressed to those likely to have a practical interest in the subject matter of his invention (i.e. ‘‘skilled in the art’’), by which he informs them what he claims to be the essential features of the new product or process for which the letters patent grant him a monopoly. It is those novel features only that he claims to be essential that constitute the so-called ‘‘pith and marrow’’ of the claim. A patent specification should be given a purposive construction rather than a purely literal one derived from applying to it the kind of meticulous verbal analysis in which lawyers are too often tempted by their training to indulge. The question in each case is: whether persons with practical knowledge and experience of the kind of work in which the invention was intended to be used, would understand that strict compliance with a particular descriptive word or phrase appearing in a claim was intended by the patentee to be an essential requirement of the invention so that any variant would fall outside the monopoly claimed, even though it could have no material effect upon the way the invention worked.

The Pith & Marrow test had previously been adopted and confirmed by our Courts:

Obviously the fact that a claim incorporates a particular feature does not alone suffice to make that feature an essential one, otherwise the problem would not arise. In general, if the feature is in fact essential to the working of the claimed invention, then it must be regarded as an essential feature. On the other hand a patentee may indicate in his specification, either expressly or by implication, that he regards a particular feature as essential. And in that event it must be treated as essential and it matters not that it may not be essential to the working of the invention.

Our Courts have also consistently stressed that any purposive or realistic form of interpretation may only be applied to inessential integers. As emphasised in Stauffer at 485 A-B “[I]t is only in respect of unessential features or integers of a claim that the doctrine of infringement by the substitution of equivalents can apply. If the feature or integer for which an equivalent has been substituted is an essential part of the claimed invention, then there is no room for the doctrine of equivalents”.

Accordingly, prior to Triomed it was settled law that to infringe a patent, only the essential features, words, phrases or integers had to be satisfied. Non-essential features, words, phrases or integers could be replaced by equivalents, or excluded. It was also clear that the proper interpretation of claims comprised two distinct phases – the purposive or realistic phase and the literal phase. During the purposive phase, essential features, words, phrases or integers of a claim were identified using the Pith & Marrow test. While, during the literal phase, the meanings of all the integers were determined using the principles set out in Gentiruco AG v Firestone SA (Pty) Ltd 1972 BP 209 (A). As confirmed by Nugent JA at 160D-E, the question of essentiality was, and still is, independent of any inquiry into clarity or ambiguity:

To the extent that [the purposive construction] might have been suggested in an obiter dictum in Nampak Products Ltd and Another v Man-Dirk (Pty) Ltd 1999 (3) SA 708 (SCA) at 714A that it might be called in aid only to construe an ambiguous claim I do not think that is supported by the decisions of this Court and, in my view, it is not correct.

It is highlighted that during both phases of interpretation the inquiry revolved around the wording, or more precisely, the features, words, phrases or integers of the claim. In contrast, Nugent JA emphasised that (at 159 F-G and 160 B-D):

the language of the claim should be construed purposively, so as to extract from it the essence or the essential elements of the invention …While the claim must be construed to ascertain the intention of the inventor as conveyed by the language he has used (Gentiruco AG v Firestone SA (Pty) Ltd 1972 (1) SA 589 (A) at 614 B-C) what is sought by a purposive construction is to establish what were intended to be essential elements, or the essence, of the invention, which is not to be found by viewing each word in isolation but rather by viewing them in the context of the invention as a whole.

Accordingly, when applying the Pith & Marrow test, instead of holding that the feature, word, phrase or integer “compounds” was inessential, the Court held that a subcoating layer that consisted of more than one excipient or compound was not intended to be essential – i.e. that the element “the second compound” was inessential.

In support of this finding, the Court noted the following contradictions between the specification and the claims:

The purpose that is served by the subcoating layer or layers (for convenience I will refer hereafter to the subcoating layer or layers only in the singular) is merely to form an effective but water-soluble barrier between the alkaline core and the enteric coating. It is apparent from the claim itself that the chemical composition of the subcoating layer was considered by the inventor to be immaterial, provided only that it fulfilled the functional requirements specified in the claim, for the claim does not insist upon, or even specify, what its chemical composition should be. If the subcoating layer may consist of a mixture of any two excipients or compounds it must follow that its composition is immaterial (provided only that it has the functional characteristics specified in the claim) and there is then no apparent reason, nor could one be suggested, why it should not consist of any one of those compounds alone. The fact alone that the inventor was indifferent to the composition of the subcoating layer (provided only that it had the characteristics described in the claim) makes it most doubtful that it was intended that two or more excipients or compounds were essential elements of the invention. …
The description of the invention in the body of the specification contains no suggestion that the subcoating layer should consist of more than one excipient or compound: if anything it suggests the contrary. In describing the subcoating layer the specification says no more than that it ‘consists of one or more water soluble inert layers, optionally containing pH-buffering compounds’ and that the material for the subcoating layer ‘is chosen among the pharmaceutically acceptable, water soluble, inert compounds or polymers used for film-coating applications’. Had it been thought essential that the subcoating layer should consist of more than one compound one would have expected something to that effect to have been said. What is decisive, however, is the composition of the subcoating layer in the various examples that are given in the specification of what are said to be ‘the invention … described in detail’. In many cases the subcoating layer consists of a single compound (usually dissolved in distilled water or ethanol). That is entirely inconsistent with a construction of claim 1 that confines the invention to preparations in which the subcoating layer consists of at least two different excipients or compounds.

The effect of this subtle variation in terminology used was to divert the application of the Pith & Marrow test from features, words, phrases or integers appearing in a claim to elements described by the wording of a claim.

In this regard, it will be appreciated that a claim comprises a set of words, selected to describe the elements of an invention. Although each element is generally described by a single word or integer (“a simple integer”), a draftsman may refine the wording of a claim by combining multiple elements into a single word or integer (“a complex integer”). For instance the complex integer “motor vehicle” describes two elements – a motor and a vehicle. Furthermore, all plural words are inherently complex integers. The word “compounds” for instance represents the elements a first compound and at least a second compound. The principle is that the nature of an inessential element should not be transformed merely because it is combined with an essential element into a complex integer.

Consequently, the purposive phase of interpretation, now requires the additional step of dividing the words, in particular the complex integers, into their individual elements before applying the Pith & Marrow test to the elements to determine their essentiality.

In the instance, the complex integer “compounds” divided into at least first and second compound elements. The first compound element was clearly essential. The second compound element was not, and the word “compounds” was a hybrid. The Court was therefore correct in finding that the patent was infringed. However, the reasoning of the Court would have been clearer had the judgment in conclusion not attempted to link the second inessential element back to the hybrid word “compounds”.

It is also interesting to note that Nugent JA used subsequent claims in interpreting the claim in question. This approach was previously applied in Adcock-Ingram Pharmaceuticals Ltd v Krok Brothers Holdings (Pty) Ltd & Others 1999 BIP 260 (CP) in respect of the interpretation of an unclear integer, Multiknit 2000 (Pty) Ltd v Industrial Netting and Mining Products (Pty) Ltd 1997 BIP 97 in respect of whether an integer was essential and Rotaque (Pty) Ltd v General Mining & Finance Corporation and Chamber of Mines of SA 1986 BP 534 (A) in respect of variants of an integer. However, the court in Enka BV v EI Du Pont De Nemours & Company 1987 BP 13 (TPD) cautioned that although “dependent claims are normally narrower than the claims upon which they are dependent (this is also required by Regulation 30 of our Patents Regulations). This factual presumption cannot, however, change the ordinary meaning of the claims themselves. It is also correct that, as a matter of interpretation, it is assumed that different claims have different meanings but it is not uncommon to find a patent specification containing two claims having exactly the same scope”. Consequently, the court in GI Marketing CC v Ian Fraser-Johnston 1995 BP 362 (SCA) held that other claims should not be used in interpreting a claim, and this was the approach generally applied prior to Triomed. It is submitted that the holistic approach of Nugent JA is a welcomed revision. However, it should be noted that the authority of this judgment is limited to the purposive phase of interpretation only. The law as applicable during the literal phase remains unchanged.


The Pith & Marrow test suffered from a congenital defect in that it inquired into the essentiality of the features, words, phrases or integers of a claim. The test did not cater for complex integers that may be hybrid, in the sense that they comprise elements that are both essential and inessential. By redirecting the application of the Pith & Marrow test from the features, words, phrases or integers in a claim to elements described by the words in a claim, our Courts have remedied this defect and rendered the test applicable to all types of claims. The scope of protection has also thereby been extended since only the essential elements of a complex integer need now be satisfied.

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