UK: Words Of The Patentee’s Own Choosing

Last Updated: 15 July 2003

BASF AG v. SmithKline Beecham PLC

Court of Appeal (Aldous & Sedley L.JJ, Lindsay J.)

[2003] ECWA Civ 872


SmithKline Beecham ("SB") have a patent for paroxetine hydrochloride anhydrate ("PHA") with low levels of bound organic solvents and ways of producing them. This was an appeal from a decision of Mr Justice Pumfrey in an action to revoke the patent for lack of novelty and obviousness. Pumfrey J. found many of the claims invalid, but some claims survived. Both parties appealed. The Court of Appeal judgements are not revolutionary but have some interesting features. They emphasises the ever important issues of construction and it restates the law on novelty.


Paroxetine hydrochloride is an antidepressant drug sold in the UK under the trade name Seroxat. SmithKline Beecham ("SB") had developed a method of producing paroxetine hydrochloride anhydrate ("PHA") using organic solvents in which the resulting PHA contained lower levels of bound solvent than had been possible before. SB also claimed to have found new forms of PHA.

SB’s UK Patent GB 2 297 550 acknowledged that PHA in a particular form (designated Form Z) was known but only as a solvate of PHA in propan-2-ol. Two technical contributions are claimed in the patent. One is the discovery of a method of preparing PHA substantially free of bound propan-2-ol and the other is the discovery of four new forms of PHA (designated as Forms A, B, C and D).

In fact the prior art did disclose a method that produced Form A, but used acetone as a solvent. Form A produced by the prior method contained bound acetone, but not, of course, bound propan-2-ol, which was not use in the method at all.

Because of this disclosure, the construction of Claim 3 of the patent which read :

Paroxetine hydrochloride anhydrate substantially free of bound propan-2-ol in Form A; ……

became of vital importance.

BASF argued it meant what it said. It merely required the PHA to be substantially free of bound propan-2-ol and accordingly claim 3 was anticipated by the disclosure of PHA in Form A containing bound acetone.

SB argued that the patent used the terms "bound propan-2-ol" and "bound organic solvent" interchangeably and the former expression in claim 3 should be read only as an example being used to denote the wider class, a grammatical construction called a "synecdoche" as Aldous LJ pointed out. SB also argued following a dictum of Lord Davey in Parkinson v. Simon (1895) 12 RPC 403 that any ambiguity in the claim should be resolved by a construction which would uphold the patent not one that would invalidate it.


In a separate judgement by Lord Justice Sedley, with which Lord Justice Aldous expressly agreed, the court rejected the idea that ambiguity in claims should be resolved to make them valid rather than invalid. Construction is governed by Article 69(1) of the European Patent Convention and the Protocol to it. The claims are to be construed to give a fair degree of protection to the patentee and reasonable certainty to the public. It would be incompatible with this principle simply to resolve ambiguities in favour of the patentee.

By the same token a patentee is not to be construed like a deed or a written contract so that ambiguities are construed contra proferentem. To construe ambiguities against the patentee may well be unfair to the patentee.

The court rejected SB’s argument that "substantially free of bound propan-2-ol" was a synecdoche and should be construed as "substantially free of (any) bound organic solvent". The patent could be construed so as to give the words their ordinary meaning without doing violence to the language. The patent claimed one aspect of the technical contribution to be the elimination of bound propan-2-ol. As Aldous LJ stated, the reader would know "that the patentee claimed his monopoly in words of his own choosing".

There is, in the judgement of Aldous LJ, a useful restatement of the law on anticipation, particularly the requirement for the prior document to be an enabling disclosure. BASF argued that the requirement for a disclosure to amount to an enabling disclosure was the same for anticipation as it was when considering sufficiency. Aldous LJ did not accept this part of the BASF arguments.

Much turned on a particular example of the preparation of paroxetine hydrochloride given in a prior specification SB said the example would produce the hemihydrate so the prior example was not an enabling disclosure; it did not put Form A of PHA in the public domain. BASF argued the opposite. Both parties did experiments, purportedly to reproduce the prior art example.

The court preferred both the argument and experiments of SB. BASF’s experiments were criticised by the court for departing from the instructions of the example in a way that a skilled man at the priority date would not have done. For this reason the court upheld the decision of Pumfrey J that certain of the claims for methods of producing PHA were valid.

One of the criticisms levelled at BASF in the judgement was that they did not produce as a witness the person who had devised the experiments on which they relied. The experiments were only supported by BASF’s expert, who was seeking to justify the way the experiments were devised after the event.


As in almost every patent case that reaches the courts, a critical issue is the construction of the claims of the patent. The well known quotation from the opinion of Lord Diplock in Catnic that a patent is a statement by the patentee "in words of his own choosing" is used in argument, usually by a defendant seeking to construe the patent against the patentee.

In this case Aldous LJ used the words of Lord Diplock as part of the reasons for rejecting the case of SB that the construction of claim 3 should depart from the plain meaning of the words. To that extent, the case supports the use by the defendant of Lord Diplock’s phrase to hold the patentee to a limited meaning.

But the case also rejects the extreme view that any doubt about the meaning of the words of a patent must be construed against the patentee whose words they are.

This Hot Topic contains information of general interest about current legal issues, but does not give legal advice

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