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	England and Wales High Court (Patents Court) Decisions
You are here: BAILII >> Databases >> England and Wales High Court (Patents Court) Decisions >> Celltech Chiroscience Ltd. v Medimmune Inc [2002] EWHC 2167 (Patents) (28 October 2002) URL: http://www.bailii.org/ew/cases/EWHC/Patents/2002/2167.html Cite as: [2002] EWHC 2167 (Patents)

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IN THE HIGH COURT OF JUSTICE
CHANCERY DIVISION
PATENTS COURT

		Royal Courts of Justice Strand, London, WC2A 2LL
		28 October 2002

Mr Justice Jacob :

1. This preliminary point has the oddity that I have to ascertain and apply the US patent law rules as to file wrapper estoppel. The oddity comes about in this way: Celltech granted MedImmune a patent licence for most countries of the world. The licence is governed by English law and confers jurisdiction on the English Courts. Under the licence MedImmune must pay royalties if they sell a product covered by a valid claim of a particular US patent (No.5,859,205, "Adair"). In the US MedImmune sell a product called "Synagis." Celltech say, and MedImmune denies, that "Synagis" falls within the scope of the Adair patent. Celltech's case depends upon reliance of the "doctrine of equivalents". MedImmune deny generally that on the facts the doctrine could apply. But, without prejudice to that general denial, MedImmune say that Celltech are precluded from their contention by virtue of the doctrine of "file wrapper estoppel."
2. In the US the law as to how the scope of a patent is determined is different from that in Europe. In Europe the basic rule is set out in Art.69(1) of the European Patent Convention. It is that:

"The extent of the protection conferred by a European patent .. shall be determined by the terms of the claims. Nevertheless, the description and drawings shall be used to interpret the claims."

3. Art. 69 is supplemented by a Protocol on its interpretation. The Protocol does not undermine the basic rule but expands on how it is to be applied. The monopoly conferred is defined by the terms of the claims as properly interpreted using the guidance of the Protocol. There is no express provision in Europe for a doctrine of equivalents. By this I mean a rule by which there may be infringement even if the accused product falls outside the meaning of the words of the claim when understood in context. If the issue is whether a feature embodied in an alleged infringement that falls outside the primary, literal or acontextual meaning of a descriptive word or phrase in the claim is nevertheless within its language as properly interpreted, one asks the questions formulated by Hoffmann J in Improver v Remington [1990] FSR 181 at p.189. The issue remains one of construction - there is no distinct doctrine of equivalents. I remind myself of this only to ensure that the European approach is firmly put out of my mind when considering the US approach. It is not a "variant" of Art. 69 and its Protocol.
4. Thus US patent law, by contrast, does have an explicit rule about equivalents. To my mind one of the best expositions of the reason for the rule remains that of Judge Learned Hand in Royal Typewriter v Remington (1948) 168 f. 2d. 691; 77 USPQ 517 (2d Cir.):

"After all aids to interpretation have been exhausted and the scope of the claims has been enlarged as far as words can be stretched, on proper occasions courts make them cover more than their meaning can bear. If they applied the law with inexorable rigidity, they would never do this ….[But] at times they resort to the doctrine of equivalents to temper unsparing logic and prevent an infringer from stealing the benefit of the invention."

5. The same idea is to be found in Lord Reid's dissenting speech in van der Lely v Bamfords [1963] RPC 61 at p.379:

"the principle [of infringement by substitution of a mechanical equivalent for an integer of a claim] is very necessary to prevent sharp practice"

6. The US also has a further doctrine of patent law going by the name of "prosecution history (colloquially 'file wrapper') estoppel". This rule is based on the broad notion that a patentee may not go back on anything he has said or represented to the United States Patent and Trademark Office ("USPTO") in the course of prosecution of his patent.
7. Both rules are judge-made, to be ascertained from the rules laid down in the cases decided by the US Federal Courts. Of these the paramount court is the Supreme Court. The Court below that is the US Federal Court of Appeals for the Federal Circuit (the "CAFC"), a special court of appeal for the whole of the US in patent and certain other matters.
8. Foreign law is treated by our law as a question of fact. Normally it is proved by evidence from foreign lawyers. In this case such evidence has been filed. But counsel agreed that I could read the US cases without the aid of a US lawyer. Cross-examination would consist of bouncing points of argument off the experts which could just as easily be submitted to me. So it was that I found myself receiving submissions on US case law just as if I were a US District Judge.
9. In recent years the higher US courts have been much concerned with both the doctrine of equivalents and file wrapper estoppel. The basic rules as regards equivalents are now that laid down in a pair of Supreme Court cases, Markman v Westview Instruments 517 US 370 (1996) and Warner-Jenkinson v Hilton Davis 520 US 17 (1996). Markman decided that the construction of a patent claim was a question of law for the court, not a jury question. That is not to say that expert evidence is not receivable - on the contrary it is. Most patent claims these days are only intelligible to a lawyer when the background technology (and particularly the jargon of the "trade") has been explained. Hilton-Davis decided that the doctrine of equivalents remained alive and well following the 1952 revision of the US Patent Act. But it also reined in the doctrine. Justice Thomas, giving the opinion of a unanimous Supreme Court said this:

"We do, however, share the concern of the dissenters below that the doctrine of equivalents, as it has come to be applied since Graver Tank, has taken on a life of its own, unbounded by the patents claims. There can be no denying that the doctrine of equivalents, when applied broadly, conflicts with the definitional and public-notice functions of the statutory claiming requirement."

10. The reining in was achieved by adopting the solution of the late Judge Helen Nies in the CAFC. Justice Thomas expressed the modern rule thus:

"Each element contained in a patent claim is deemed material to defining the scope of the patented invention, and thus the doctrine of equivalents must be applied to individual elements of the claim, not to the invention as a whole. It is important to ensure that the application of the doctrine, even as to an individual element, is not allowed such broad play as to effectively eliminate that element in its entirety."

11. In Hilton-Davis the Supreme Court touched upon the question of file wrapper estoppel. Amongst other things it said:

"Our prior cases have consistently applied prosecution history estoppel only where claims have been amended for a limited set of reasons, and we see no substantial cause for requiring a more rigid rule invoking an estoppel regardless of the reasons for the change."

12. Notwithstanding that, in the next major case, Festo v Shoketsu Kinzoku 234 f.3d 558 (Fed.Cir 2000) the CAFC held that there was a "brightline rule" about file wrapper estoppel. The rule was this:

(1) any reason for amendment to a patent claim that is related to patentability will give rise to prosecution history estoppel;

(2) voluntary amendments are treated the same as other amendments for the purpose of prosecution history estoppel; and

(3) when amendment creates prosecution history estoppel, there is no range of equivalents available for the amended element.

13. In short if an element of a claim was amended for a patentability reason, the patentee would be confined to the literal meaning of the element. Since most claims are amended during the course of prosecution (a patent attorney would not be doing his job properly if he went in too narrow) Festo might have virtually abolished the doctrine of equivalents.
14. The brightline Festo rule depended upon there having been a disclaiming amendment. Quite apart from that, there was and is also a well-settled further rule called "argument estoppel". This applies even in the absence of claim amendment. Where the patentee has made representations to the USPTO about the scope or meaning of the claim or element of a claim, he is estopped from contending for any wider scope. This rule is stated, for instance in Texas Instruments v US International Trade Commission 988 F 2d. 1165 (Fed.Cir. 1993):

“Amendment of a claim in light of a prior art reference, however, is not the sine qua non to establish prosecution history estoppel. Unmistakable assertions made by the applicant to the Patent and Trademark Office (PTO) in support of patentability, whether or not required to secure allowance of the claim, also may operate to preclude the patentee from asserting equivalency between a limitation of the claim and a substituted structure or process step”.

It is to be noted that the test is "unmistakable assertion."

15. The claim form in this action was issued on 19^th October 2000. The particulars of claim relied upon the US law doctrine of equivalents. Festo was decided by the CAFC on 29^th November 2000. Claim 1 of the Adair patent was the result of a narrowing amendment made during the prosecution. So it is hardly surprising that the defence as originally pleaded relied on the Festo CAFC brightline rule - claim 1 had been amended. There might well be a knock-out defence. MedImmune accordingly launched an application for determination of preliminary issues. By consent Pumfrey J on March 9^th 2001 ordered trial of the following preliminary issues:

"(1) whether the Claimant is precluded from relying on the US doctrine of equivalents in these proceedings by virtue of the US doctrine of prosecution history estoppel; and

(2) whether as a result the Claimant's claim should be dismissed."

16. Before those issues could be heard, there were further developments in the US. The US Supreme Court granted certiorari (what we would call permission to appeal) in Festo. The hearing of the preliminary point was put off until the judgment in Festo was given. The Supreme Court overruled the CAFC brightline rule. I must quote a number of passages from the unanimous opinion of the Court given by Justice Kennedy:

“Prosecution history estoppel ensures that the doctrine of equivalents remains tied to its underlying purpose. Where the original application once embraced the purported equivalent but the patentee narrowed his claims to obtain the patent or to protects its validity, the patentee cannot assert that he lacked the words to describe the subject matter in question. The doctrine of equivalents is premised on language’s inability to capture the essence of innovation, but a prior application describing the precise element at issue undercuts that premise. In that instance the prosecution history has established that the inventor turned his attention to the subject matter in question, knew the words for both the broader and narrow claim, and affirmatively chose the latter”.

……….

“Based upon its experience the Court of Appeals decided that the flexible-bar rule is unworkable because it leads to excessive uncertainty and burdens legitimate innovation. For the reasons that follow, we disagree with the decision to adopt the complete bar.

Though prosecution history estoppel can bar challenges to a wide range of equivalents, its reach requires an examination of the subject matter surrendered by the narrowing amendment. The complete bar avoids this inquiry by establishing a per se rule; but that approach is inconsistent with the purpose of applying the estoppel in the first place – to hold the inventor to the representations made during the application process and the inferences that may reasonably be drawn from the amendment. By amending the application, the inventor is deemed to concede that the patent does not extend as far as the original claim. It does not follow, however, that the amended claim becomes so perfect in its description that no one could devise an equivalent. After amendment, as before, language remains an imperfect fit for invention. The narrowing amendment may demonstrate what the claim is not; but it may still fail to capture precisely what the claim is. There is no reason why a narrowing amendment should be deemed to relinquish equivalents unforeseeable at the time of the amendment and beyond a fair interpretation of what was surrendered. Nor is there any call to foreclose claims of equivalence for aspects of the invention that have only a peripheral relation to the reason the amendment was submitted. The amendment does not show that the inventor suddenly had more foresight in the drafting of claims than an inventor whose application was granted without amendments having been submitted. It shows only that he was familiar with the broader text and with the difference between the two. As a result, there is no more reason for holding the patentee to the literal terms of an amended claim than there is for abolishing the doctrine of equivalents altogether and holding every patentee to the literal terms of the patent.

This view of prosecution history estoppel is consistent with our precedents and respectful of the real practice before the PTO. While this Court has not weighed the merits of the complete bar against the flexible bar in its prior cases, we have consistently applied the doctrine in a flexible way, not a rigid one. We have considered what equivalents were surrendered during the prosecution of the patent, rather than imposing a complete bar that resorts to the very literalism the equivalents rule is designed to overcome”.

………

“They do provide, however, that when the court is unable to determine the purpose underlying a narrowing amendment – and hence a rationale for limiting the estoppel to the surrender of particular equivalents -–the court should presume that the patentee surrendered all subject matter between the broader and the narrower language.

Just as Warner-Jenkinson held that the patentee bears the burden of proving that an amendment was not made for a reason that would give rise to estoppel, we hold here that the patentee should bear the burden of showing that the amendment does not surrender the particular equivalent in question”.

……….

“The patentee, as the author of the claim language, may be expected to draft claims encompassing readily known equivalents. A patentee’s decision to narrow his claims through amendment may be presumed to be a general disclaimer of the territory between the original claim and the amended claim. Exhibit Supply, 315 U.S., at 136-137, 62 S.Ct. 513 (“By the amendment [the patentee] recognized and emphasized the difference between the two phrases and proclaimed his abandonment of all that is embraced in that difference”). There are some cases, however, where the amendment cannot reasonably be viewed as surrendering a particular equivalent. The equivalent may have been unforeseeable at the time of the application; the rationale underlying the amendment may bear no more than a tangential relation to the equivalent in question; or there may be some other reason suggesting that the patentee could not reasonably be expected to have described the insubstantial substitute in question. In those cases the patentee can overcome the presumption that prosecution history estoppel bars a finding of equivalence.

This presumption is not, then, just the complete bar by another name. Rather, it reflects the fact that the interpretation of the patent must begin with its literal claims, and the prosecution history is relevant to construing those claims. When the patentee has chosen to narrow a claim, courts may presume the amended text was composed with awareness of this rule and that the territory surrendered is not an equivalent of the territory claimed. In those instances, however, the patentee still might rebut the presumption that estoppel bars a claim of equivalence. The patentee must show that at the time of the amendment one skilled in the art could not reasonably be expected to have drafted a claim that would have literally encompassed the alleged equivalent”.

17. Even that decision did not finally determine everything about the two doctrines and their relationship. That appears from what happened next. The Supreme Court remanded the case back to the CAFC for further proceedings consistent with its opinion. On September 20^th 2002 the CAFC made an order containing the following passages:

“The Court differed with this court on the scope of equivalents available following a narrowing amendment. Whereas we had held that any narrowing amendment made for reasons related to patentability effects a complete bar to the doctrine of equivalents for the amended claim element, 234 F.3d at 563-64, 56 USPQ23d at 1868, the Court held that a narrowing amendment instead raises a rebuttable presumption that the complete bar applies”.

…….

“We must now consider what further action to take in this case. To help us in that determination, we order the parties to submit briefs on the following issues:

1. Whether rebuttal of the presumption of surrender, including issues of foreseeability, tangentialness, or reasonable expectations of those skilled in the art, is a question of law or one of fact; and what role a jury should play in determining whether a patent owner can rebut the presumption.

2. What factors are encompassed by the criteria set forth by the Supreme Court.

3. If a rebuttal determination requires factual findings, then whether, in this case, remand to the district court is necessary to determine whether Festo can rebut the presumption that any narrowing amendment surrendered the equivalent now asserted, or whether the record as it now stands is sufficient to make those determinations.

4. If remand to the district court is not necessary, then whether Festo can rebut the presumption that any narrowing amendment surrendered the equivalent now asserted”.

18. Even that may not be the end of the story. For some of the Supreme Court's observations would seem to apply whether or not a claim has been amended. Perhaps of most significance in this case, even if file wrapper estoppel did not apply, is the observation that "the patentee … may be expected to draft claims encompassing readily known equivalents". Does this apply also to unamended claims? Suppose, for instance, an unamended claim which says "nailed." And suppose screwed, riveted or glued would do just as well. Are those equivalents not covered by the doctrine of equivalents? Putting it another way is it only unforeseeable equivalents which are now covered by the doctrine? Fortunately I do not have to decide that question under the current application, though it seems that it would otherwise arise because Celltech contend that the equivalent they rely upon is obvious.
19. Thus prosecution history estoppel along with the doctrine of equivalents has become an elaborate doctrine with many facets. I am told that most patent litigation in the US currently raises disputes about one or other or both doctrines. Those who suggest similar doctrines for Europe would do well to bear this in mind - and that the prosecution file may be in any of three languages.
20. I turn to the facts in this case. To understand the amendment and what was said to the USPTO about distinguishing the prior art it is necessary to understand some of the background technology. It is explained well by the two experts who have provided me with evidence that, at least for present purposes, is uncontroversial. My exposition is largely borrowed, with gratitude, from MedImmune's skeleton argument. The embellishments are my own.
21. Antibodies, which are useful for a variety of therapeutic and research purposes, are produced by cells of the human immune system called B lymphocytes. They are protein molecules. A protein is a long chain of amino acid residues called a polypeptide. The proteins of living organisms use 20 specific amino acids. Antibodies are proteins which bind to other proteins foreign to the human body called antigens. A typical antigen would be a virus. Antigen/antibody binding depends on a close and specific physical fit between particular areas on each. The antibody "locks on" to part of the antigen, thereby disabling its invasive abilities. Antigens may be many and varied. Each particular kind will need a particular kind of antibody to disable it. When the body is invaded the B lymphocytes set about producing antibodies specific to the invading antigen. This is why it takes a little while to deal with an infection such as the common cold, and why, when antibodies have built up, it is cured.
22. Antibodies have a generally “Y” shape, though actually of course the shape is more elaborate than that. The “Y” is made from two heavy (relatively long) and light (relatively short) chains of amino acid residues. A heavy chain is about 440, and a light chain about 110 amino acids long. The Y consists of two identical heavy chains joined together for about 330 amino acids which form the trunk of the Y. The two tines of the forks (of about 110 amino acids) each have attached to them a light chain. The trunks of the Y consist of constant regions, that is to say they are the same in different antibodies. The branches are variable, i.e. different in different antibodies. In broad terms, the tips of the forks of the “Y”, where the variable regions of the heavy and light chains meet, are the parts which make the antibody “fit” with its complementary antigen. There are three loops at each tip. It is their shape and composition which make the antibody "fit" the target antigen. The regions for fitting into the antigen are called “CDRs” (complementarity determining regions). A helpful schematic diagram shows the general structure of an antibody:
23. 
     
    Illustration 1: Structural Domains of an IgG Antibody

[Diagram or picture not reproduced in HTML version - see original .rtf file to view diagram or picture]


 


24. Producing human antibodies is difficult. As a result, researchers have turned to producing antibodies in mice or other rodents. But mice antibodies themselves provoke an immune reaction in humans (the “HAMA” response). Researchers have therefore worked for some time on using antibodies which are “humanised”, being part mouse and part human. The goal is to arrive at an antibody which is still the right shape for the target antigen and is human enough not to provoke a HAMA response. In such antibodies, the mouse elements are called “donor” and the human elements are called “acceptor”.
25. There is a standard, conventional means of referring to individual specific amino acids in the protein structures of this kind of antibody. It is called the Kabat numbering system. It is used to designate a given amino acid position in an antibody by a number. In the present case, for example, “position 23” is the subject of much of the argument.
26. Part of Celltech’s argument in this case revolves around what are called “conservative substitutions”. As I said earlier, there are 20 amino acids used to make up the chain. Very generally, amino acids differ from one another in a variety of ways and to different degrees. To replace one amino acid with another which is very similar is said to make a “conservative substitution” of one for the other. Such a substitution at a non-critical part of the molecule is unlikely to make a significant difference to its function. There might be a local slight difference in shape but it does not matter. In critical areas, such as CDRs, however things are most likely different - even a conservative substitution will very probably make all the difference.
27. Celltech summarise their invention in "simple terms" in their skeleton argument:

"one takes the human antibody and grafts into it the CDRs and certain other non-CDR residues which are necessary to achieve binding. Humanised antibodies of the kind described in the patent are therefore designed to combine the best attributes of murine and human antibodies: the important binding elements from the mouse monoclonal antibody are used to target the antigen of interest and, because the remainder of the antibody contains human sequences, the human body is less likely to mount an immune response to it.

Celltech identified a specific set of positions at which it was necessary to ensure that the residue was the relevant murine residue (the so-called "donor" residue) to obtain the desired binding. This set was described in the US Adair patent [1] and claimed."

28. Thus just grafting a CDR obtained from a mouse onto an otherwise human antigen is not enough because you do not get desired binding. You need specified donor (mouse) antibodies at specified positions. These are near the CDRs. Another diagram shows where position 23 is:
Structural Location of Residues in Claim 1 of the U.S. Adair Patent

[Diagram or picture not reproduced in HTML version - see original .rtf file to view diagram or picture]

29. Now what happened during prosecution is that the USPTO cited a prior proposal called Reichmann. Celltech responded by narrowing their claims and making certain submissions. On that basis the patent was accepted. Before amendment claims 1 and 2 read:

“1. A CDR-grafted antibody heavy chain having a variable region domain comprising acceptor framework and donor antigen binding regions wherein the framework comprises donor residues at at least one of positions 6, 23 and/or 24, 48 and/or 49, 71 and/or 73, 75 and/or 76 and/or 78 and 88 and/or 91.

2. A CDR-grafted heavy chain according to Claim 1 comprising donor residues at positions 23, 24, 49, 71, 73 and 78, or at positions 23, 24 and 49.”

There was also a claim to an antibody containing such a heavy chain.

30. The claims were narrowed to an antibody containing the specified heavy chain. Nothing turns on this. But the widest form of the heavy chain was narrowed to that in the unamended claim 2. The relevant bit of the claim as granted reads:

"wherein, according to the Kabat numbering system, in said composite heavy chain: said CDRs comprise donor residues at least at residues 31 to 35, 50 to 58, and 95 to 202; and amino acid residues 6, 23, 24 and 49 at least are donor residues."

31. So prior to amendment claim 1 was to a number of alternatives. Claim 2 merely narrowed that number. It is a true "dependent" claim, that is to say a claim in the form requiring all the features of the claim from which it is dependent and the further features specified in the dependent claim. In this case, in particular prior to amendment you had to have a donor residue at at least one of positions 6,23 and 24 (7 possibilities in all). After amendment you have to have a donor residue at position 23. The other 6 possibilities were surrendered by the amendment. So were others at other positions.
32. Now it is common ground that the MedImmune product has all the elements of claim 1 of the Adair patent save in relation to position 23. There it has a residue which is not a donor residue in the strict sense, i.e. a residue which is the same as in the mouse antibody. It is an acceptor residue (i.e. one which is the same as in the human antibody). Celltech say that substituting one for the other in that position makes no difference - it is a conservative substitution and, as such within the doctrine of equivalents. MedImmune dispute that as a technical matter but say also that it does not matter because of prosecution history estoppel. The argument is put two ways, as an estoppel arising from the amendment and an estoppel arising from representations.
33. MedImmune say that by virtue of the amendment Celltech narrowed their monopoly from a case where a donor residue was optional, to one where it was mandatory. Accordingly the Festo rules apply. Although there is now a flexible bar, Celltech do not fall within any of the limbs referred to by the Supreme Court, namely unforeseeability, peripherality/tangentiality or other reason why the patentee could not reasonably have described the insubstantial substitute.
34. Celltech say that the equivalent in question, namely a conservative substitution, is simply irrelevant to the amendment made. I think they are right on this point. The amendment cut down the number of possibilities claimed. But it did not in any way cut down whether or not the claim covered equivalents of donors. Consider the case of a product which, at position 23, had an equivalent of a donor residue but did not have a donor residue at positions 6 or 24. And suppose it otherwise fell within the unamended claim. The argument for infringement of that claim would have had to be on the doctrine of equivalents. It would be exactly the same as it is now. The amendment is irrelevant.
35. One can look at the same point in another way. Festo requires one to examine what is "relinquished" or "surrendered" by the amendment. What was surrendered here is a number of possibilities. Focussing on position 23, 6 possibilities were given up. Prior to amendment an argument lay in relation to all seven possibilities that a conservative substitution would infringe by virtue of the doctrine of equivalents. All that has happened is that 6 of the possibilities have been surrendered. The surrender has no connection, no nexus, with what is alleged to be an equivalent.
36. A good example of this no nexus kind of point is to be found in the carefully reasoned judgment of Judge Breyer (the brother of the Supreme Court Justice) in Aclara Biosciences v Caliper Technologies 125 F.Supp.2d 391 (N.D. Cal. 200). This was given whilst the brightline CAFC Festo rule prevailed. The claim called for "a plurality of electrodes" to be positioned along a trench and not just at the ends of the trench, which is what the accused device had. Infringement by virtue of the equivalents doctrine was alleged. The defendant pointed out that the claim had been amended during prosecution and relied upon Festo, CAFC version. Judge Breyer held that although the amendment had been made, it "did not surrender any subject matter related to where along the trenches the electrodes should be placed." The position is the same here - the amendment did not surrender any subject matter related to an equivalent of a donor residue.
37. Mr Watson QC for MedImmune suggested that the amendment rule was wider - that once a claim had been amended the Festo rules applied to all aspects of the claim, even aspects untouched by and unrelated to the amendment. I think that is illogical and contrary to the thrust of all the reasoning in Festo. Mr Watson took me to a decision of Chief Judge Marylyn Hall Patel of the US District Court for the Northern District of California dated 21^st August 2002 in Glaxo Wellcome v Impax Laboratories. The patent had 5 sets of independent claims. Four of these were narrowed during prosecution to include the use of a sustained release material called HPMC. The other set already had that requirement and was not narrowed during prosecution. The patentee wished to assert that use of an equivalent material, HPC, in a product otherwise covered by the claims, infringed by virtue of the doctrine of equivalents. The Chief Judge held that amendment estoppel applied to all five sets of claims. So far as the amended claims are concerned there had plainly been a narrowing based on the inclusion of HPMC. So the Festo rules applied. And since HPC was an obvious equivalent the patentee was held bound and confined by the amendment. The Chief Judge took the view that the same applied to claim 1. Even though it had not in itself been amended, the amendments which had been made focussed attention on HPMC so it could not have a wider ambit in different claims.
38. I do not think this case assists Mr Watson - it is not an example of the estoppel applying to matter that was not surrendered. Likewise the case where Judge McKenna of the Southern District of New York took an opposite view of the same alleged infringement does not assist Celltech (Glaxo Wellcome v EON Labs Manufacturing August 13^th 2002). Judge McKenna held that Festo applied because there had been a narrowing amendment. His view was different from that of Chief Judge Patel because he held that the use of HPC was arguably use of an unforeseeable equivalent. That, of course, is one of the exceptions to a bar on estoppel after amendment specifically mentioned in Festo.
39. Accordingly, in this case, I hold that file wrapper estoppel does not arise by virtue of the amendment made by combining the features of claim 2 with those of claim 1. That, however, leaves the separate question of whether or not there is representation estoppel. For that purpose one has to go into what was said to the USPTO during prosecution in more detail - one does not just have to discern whether there was a narrowing amendment.
40. As I have said the amendment came about as a result of a citation of Reichmann by the USPTO. Now Reichmann had an acceptor (i.e. human) residue at position 23. The patentees said this:

"In the present claims 24 and 25 [added by amendment], it is specified that residues 23 and 24 in the heavy chain should be donor residues. However, as can be seen from [Reichmann] in the recombinant antibody shown there, residues 23 and 24 are acceptor residues."

And they correspondingly amended the claims to make it a requirement that position 23 be a donor antibody residue.

41. This, to my mind, is saying that an acceptor residue at position 23 is not within the invention. I do not think there can be any doubt about this. Moreover further representations of a similar nature were made, for instance:

"looking at the heavy chain Table, it can be seen that in all the successfully "superhumanised" antibodies produced by the applicants, in the heavy chain residues 23, 24, 31 to 25 49 to 58 and 95 to 102 are all donor residues."

42. And later on in the prosecution process they said this:

"It can thus be seen that Riechmann does not disclose a procedure which leads to an antibody as defined in the present claims. As far as the heavy chain is concerned, Reichmann does not even mention Kabat residues 23 24 and 49, let alone change them to the rat [i.e. donor] residues."

43. Exhibit RAB19 (extracts from the prosecution filed) contains this and other material which to my mind shows the patentees insisting that not only that position 23 be occupied by a donor residue but also that it be not an acceptor residue.
44. The MedImmune product has an acceptor residue at position 23. In those circumstances it seems to me inconsistent with what was said to the USPTO about the essentiality of position 23 being a donor and not an acceptor to assert infringement by equivalents. There was an unequivocal assertion to the contrary.
45. Mr Kitchin QC for Celltech urged upon me that nothing was said to the USPTO about conservative substitutions so there can be no estoppel about asserting that they infringe by the doctrine of equivalents. He further submitted that Riechmann did not discuss position 23 at all. And he relied upon the technical evidence of Dr Martin. He had read the prosecution file and opined that the patentee was surrendering a non-donor residue at position 23 but not conservative substitutions in that position.
46. I reject all these submissions. File wrapper estoppel does not require one to consider the cited prior art and work out what might have been said to distinguish it. One looks at what was said. It may be just enough to avoid it or it may go further, either by accident or on purpose. Here it may well be that Reichmann could have been distinguished in a different way - but what the patentee said is that position 23 had to be a rat (i.e. donor) residue and not an acceptor residue. He cannot now claim that an acceptor residue is within his monopoly even if it is a conservative substitution which would make no difference. As to Dr Martin's evidence, it misses the point - in particular that the patentee not only surrendered a non-donor residue at position 23 but also pointed out that Reichmann was different because he had an acceptor residue at that position. I would add this that in any event I am not impressed by the evidence - it states Dr Martin's conclusion having read the file, but does not give his reasons for that conclusion. He does not deal with what it actually says.
47. In the result I hold that reliance upon the doctrine of equivalents is precluded by file wrapper estoppel. I will hear counsel as to the appropriate order.