Smith & Nephew Plc v Convatec Technologies Inc.
| Jurisdiction | England & Wales |
| Judge | HIS HONOUR JUDGE BIRSS QC,His Honour Judge Birss QC |
| Judgment Date | 13 June 2012 |
| Neutral Citation | [2012] EWHC 1602 (Pat) |
| Docket Number | Case No: HC10 C02785 |
| Court | Chancery Division (Patents Court) |
| Date | 13 June 2012 |
[2012] EWHC 1602 (Pat)
IN THE HIGH COURT OF JUSTICE CHANCERY DIVISION
PATENTS COURT
Rolls Building
7 Rolls Buildings
London EC4A 1NL
His Honour Judge Birss QC
(Sitting as a Judge of the High Court)
Case No: HC10 C02785
James Mellor QC and Charlotte May (instructed by Bristows) for the Claimant
Piers Acland QC and Geoffrey Pritchard (instructed by Bird & Bird) for the Defendant
Hearing dates: 5th, 6th, 7th, 9th March 2012
His Honour Judge Birss QC
Contents:
| Section | Paragraph |
| Introduction | 1 |
| Background | 6 |
| The witnesses | 9 |
| The skilled person | 29 |
| The common general knowledge | 31 |
| The Patent | 39 |
| The Claim | 44 |
| Construction | 45 |
| Amendment | 55 |
| Obviousness | 101 |
| Gibbins | 106 |
| Kreidl | 160 |
| Insufficiency | 198 |
| Conclusion | 202 |
Introduction
This is an action for revocation of European Patent (UK) No. 1,343,510 entitled "Light Stabilized Antimicrobial Materials". The patent is concerned with methods of making a wound dressing which uses silver as an antimicrobial agent and which is photostable. The defendant, Convatec is the patentee. The claimant, Smith & Nephew, applies to revoke the patent on various grounds.
James Mellor QC leading Charlotte May appear for Smith & Nephew instructed by Bristows. Piers Acland QC leading Geoffrey Pritchard appear for Convatec instructed by Bird & Bird.
In the course of the proceedings Convatec conceded that the unamended patent is invalid and applied to amend. Convatec maintains that claim 1 in its amended form is valid. Convatec does not contend that the dependent claims are independently valid.
Smith & Nephew submits that the amendments sought to claim 1 are not allowable. The other issues (assuming the claim is amended) relate to the validity of claim 1 in its amended form. The issues are obviousness over two items of prior art (Gibbins and Kreidl) and an insufficiency argument. There was a third item of prior art relied on (US 2,396,515, also known as Kreidl 2) but it was not pressed.
Although there was a priority point pleaded, by the opening of the trial Convatec had accepted that the amended claim was not entitled to claim priority from the cited priority document. Accordingly the relevant date for consideration of this patent is the filing date, which is 29 th November 2001.
Background
Wound dressings have advanced over the years and in the 1990s wound dressings were developed which were intended to keep the wound surface moist. One method of achieving this aim was to use materials which formed a gel. One class of gelling wound dressing used alginate materials. Another kind used carboxymethyl cellulose (CMC).
Infection is a problem associated with wounds and consequently there is a need to both prevent and treat infection resulting from wounds. Antimicrobial agents can be used topically to achieve this result. A dry wound environment was not conducive to bacterial, fungal or viral growth. However, as gel dressings became more popular the problem of bacterial growth became more apparent. One antimicrobial agent known for many years is silver. Silver has a number of advantages for topical application including low toxicity. However there is a practical problem associated with the use of silver in wound dressings. It is light stability. This sensitivity is well known. For example the light sensitive nature of silver salts was used in photography for many years.
The patent relates to a method of preparing a light stabilized antimicrobial material for use in wound dressings and medical devices. Essentially the method is one whereby a wound dressing material can be made which comprises silver as an antimicrobial agent but which is stable in the presence of light.
The witnesses
I heard evidence from two witnesses, Professor Burrell for Smith & Nephew and Professor Kennedy for Convatec.
Prof Burrell is Professor of Chemicals and Materials Engineering at the University of Alberta, Canada. He has worked in the field of wound dressings since 1991. A particular focus of his work has been the use of silver in wound management. Prof Burrell graduated from the University of Guelph, Ontario in 1976 with a BSc in Zoology, then worked in the field of environmental Biology and completed his PhD in Biology at the University of Waterloo, Ontario in 1983. Between 1986 and 1991 Prof Burrell worked at Alcan. While at Alcan he first began to investigate wound dressings and the use of silver. He joined Westaim Corporation in 1991 and there specialised in silver dressings from 1991 to 2002. During his time at Westaim Prof Burrell worked on a product now known as Acticoat. He moved to the University of Alberta in 2002.
Acticoat has been a major advance in wound care. It is a wound dressing which incorporates silver as an antimicrobial agent. Prof Burrell has been recognised personally for the outstanding contribution to science and medicine which his Acticoat work represents. He has won a number of awards for that work including the Jonas Salk Award in 2010.
Today the Acticoat product is owned, manufactured and marketed by Smith & Nephew and as a result Prof Burrell has links to Smith & Nephew. I have no doubt that these links did not colour Prof Burrell's evidence at all.
Convatec submitted that Prof Burrell was not a good witness and that his approach was so flawed that in certain respects little or no weight can be given to his evidence. This was for two main reasons.
The first related to the Professor's evidence about ionic binding of silver to NaCMC to form AgCMC and the subsequent removal of the silver to form AgCl. This removal was sometimes called stripping. Convatec submitted that the theory was absent from Prof Burrell's first report and developed from his second through to his fourth report. It included a detailed issue concerning the solubility of AgCMC. These expert reports did not mention the Professor's own paper published in 2003 which, submitted Convatec, contained data adverse to the point the Professor was making. The submission was that Prof Burrell had no reasonable basis for not referring to the 2003 paper.
I am not convinced that from Prof Burrell's personal standpoint, it was clear that the 2003 paper was contrary to the opinion which he was advancing. The paper can certainly be read in a way which is adverse to the Professor's position on AgCMC solubility. However in my judgment the Professor's re-examination showed that from his point of view the matter was not clear cut. The Professor had obtained the data from Convatec. The paper describes the relevant material as "AgCMC" but the material may in fact have contained AgCl complexes. If so then the data reported in the paper does not relate to the solubility of AgCMC although the paper states that it does.
The re-examination showed that Prof Burrell was clearly well aware of the paper. It should have been referred to and explained in his expert report(s). However I reject the attack on the Professor as a witness based on the failure. It is clear that the reason Prof Burrell did not refer to it in evidence is because he thought he should stick to material available before the priority date. That is not right but it is an understandable error. Since the validity of patents is strictly concerned with information available at the priority date, post published material has to be treated with caution. However the point here was concerned with a simple scientific fact (the solubility of AgCMC). In order to establish a fact like that, any evidence which bears on the point is relevant regardless of when it is published. The fact the paper was post-published was not a good reason not to refer to it.
The second point related to calculations Prof Burrell had put forward as part of the obviousness case. Convatec submitted that he had taken an inconsistent approach. He did not take into account the presence of water in a silver nitrate stock solution. He had not missed the point, he had decided to ignore it because he thought it would make little difference. However Prof Burrell had taken into account other factors of a similar magnitude and in fact the silver nitrate / water point, if accepted, undermines the argument that a salt concentration within claim 1 is reached. There was a similar argument about his calculations of molar ratios. Convatec submitted that all this showed a lack of independence on the part of the witness. That goes too far in my judgment. I think the Professor should not have simply neglected the silver nitrate / water point. Since he thought of it, he should have referred to it and explained why he regarded it as irrelevant. However I regard this as a small point and reject Convatec's attempt to magnify it to this extent.
The defendant called Professor Kennedy. He obtained his BSc in Chemistry from the University of Birmingham in 1964, his PhD there in 1967 and worked as a lecturer at that institution from 1969 to 1987 and a senior lecturer from 1987 to 2001. He was director of the University of Birmingham Carbohydrate and Protein Technology Group and Director of the University of Birmingham Research Park Chembiotech Laboratories from 1987 to 2008, honorary Professor of Applied Chemistry at Glyndwr University from 1984 to the present and a director of Chembiotech Ltd. His work has included a focus on carbohydrates both monomolecular and macromolecular for many years.
Prof Kennedy's position in this case was an unusual...
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