American Cyanamid Company v Ethicon Ltd

JurisdictionEngland & Wales
Judgment Date05 February 1974
Judgment citation (vLex)[1974] EWCA Civ J0205-3
CourtCourt of Appeal (Civil Division)
Date05 February 1974
American Cyanamid Company
Ethicon Limited

[1974] EWCA Civ J0205-3


Lord Justice Russell,

Lord Justice Stephenson (Not present) and

Mr Justice Foster

In The Supreme Court of Judicature

Court of Appeal

Civil Division

On appeal from Order of Mr Justice Graham

Mr STEPHEN GRATWICK, Q.C. and Mr GERALD PATERSON (instructed by Messrs Lovell, White & King) appeared on behalf of the Appellant (Defendant).

Mr ANDREW BATESON, Q.C. and Mr DAVID YOUNG (instructed by Messrs Allen & Overy) appeared on behalf of the Respondent (Plaintiff).


This is an appeal from an Order of Mr Justice Graham, who, on motion by the plaintiff, granted an interlocutory injunction restraining until trial the defendant from infringing the plaintiff's letters patent No. 1,045,518. The operation of the injunction is suspended pending the determination of this appeal against an undertaking by the defendant not to manufacture, etc., their product, such undertaking not however to prevent the defendant from carrying out clinical trials in relation thereto.


The plaintiff markets a synthetic sterile absorbable surgical suture under the brand name "Dexon". It is the product of polymerisation (by heating with a suitable catalyst) of glycolic acid and/or the cyclic dimer glycolide which is formed by driving off the water content of glycolic acid by heating. The resulting polyglycolide or polyglycolic acid may also be described as polyhydroxyacetic acid. The plaintiff's product "Dexon" is based solely on this polymer. The defendant intends to market a synthetic sterile absorbable surgical suture known as XLG under the brand name "Vicryl". This product is based upon polymerisation of glycolic acid or glycolide in the proportion of 92 moles per cent, together with lactic acid in the proportion of 8 moles per cent, the lactic acid or lactyl units in the resultant molecular chain being optically active and having a preponderance of the L — lactic acid configuration. The plaintiff's product is therefore based upon a homopolymer, in the molecular chain structure of which all units are the same — a daisy chain: whereas the defendant's product is based upon a copolymer, in the molecular chain structure of which most units are daisies but about 10 per cent are dandelions.


So far as the evidence goes at present, the plaintiff has made no experiment with a copolymer (such as that employed by the defendant) as a material for the production of a relevant suture, and Dr Frazza, who was in charge of investigations in this field for the plaintiff, in his first affidavit said in terms that pre-selection of a polymer having the biological properties required of an absorbable suture is beyond the capability of polymer and medical science. However, the prime question of infringement falls to be determined not by reference to the composition of the plaintiff's product "Dexon", but upon consideration of the defendant's product and the invention as claimed upon the proper construction of the patent in suit.


Basically here the question is whether the invention as claimed is limited to a suture the product of a homopolymer 100 per cent polyglycolic acid or polyhydroxyacetic acid: or whether it extends to embrace a suture the product of a copolymer such as that used by the defendant in which there is combined with glycolic acid or glycolide approximately 10 moles per cent of lactic acid.


Claim 1 of the patent in suit is the only one which need be recited. It is in these terms: "A sterile article for the surgical repair or replacement of living tissue, the article being readily absorbable by living tissue and being formed from a polyhydroxyacetic ester". Claim 2 referred expressly to a sterile surgical suture according to Claim 1 consisting of a solid, stretched and oriented P.H.A.E. It is the contention of the defendant that the reference only to polyhydroxyacetic ester is inherently a reference to a homopolymer and cannot be extended to embrace a copolymer produced by polymerisation of that together with some other monomer or monomers unless there be a context that compelsextension.


Dr Frazza in his first affidavit asserts that any competent technician — the man to whom the specification is addressed — would at the relevant date (1966) have understood P.H.A.E. as embracing the copolymer employed by the defendant. He further draws attention to certain passages in the body of the specification. At page 2, line 62, it is stated that P.H.A.E., sometimes referred to as polyglycolide or polyglycolic acid, "can be considered as essentially a product of polymerisation of glycolic acid, that is hydroxyacetic acid, which in simplied form is shown by the equation" — I have underlined "essentially" and "simplified form", but they are not underlined in the specification — and there is then given a formula which covers only glycolic acid and polyglycolic acid or polyglycolide. "Essentially", suggests Dr Frazza, is to be taken to indicate that the product of polymerisation is to be based "principally" upon the glycolic acid or glycolide monomer, as in the case of the defendant's XLG with its thin scattering of dandelions. He further asserts that where glycolic acid or glycolide are polymerised alone, the product is referred to as "homopolymeric polyglycolic acid" or "homopolymeric polyhydroxy acetic ester": this in support of his contention that reference simply to the polymer embraces also at least some copolymer or copolymers. He gives no specific example of this use of the word "homopolymeric": though I observe in two articles exhibited "Dexon" is described (by Bonnar) as "a linear homopolymer of glycolic acid" and (by Miln, O'Connor and Darling) as "a homopolymer of glycolic acid": contrast Anscombe and others, who do not. (These papers are in Exhibit E.J.F.3). Higgins in his patent (1950 No. 2,676,945)refers to P.H.A.E. in a manner which cannot, it appears to me, extend to a copolymer and without describing it as a homopolymer or homopolymeric.


Dr Frazza draws attention to other matters in the body of the specification in suit. Page 3, line 5, says this: "Because the fiber is from a synthetic and controllable source, with a controlled molecular weight and controlled small percentage of comonomer," — the underlining is mine — "the absorbability, stiffness, and other characteristics can be modified". I observe that if the words that I have underlined are taken as an indication of a degree of copolynerisation, it is the first such indication in point of sequence, and would seem to indicate that all fiber produced according to the invention is from a copolymer source, which would be contrary to Dr Frazza's views. I would point out that the word "modified" refers to the characteristics of the fiber: it is not a word which is applied by the patent in suit to the P.H.A.E.


The specification continues at page 3, line 10, by describing a preferred method of preparation of P.H.A.E. by polymerisation of glycol ide. After referring to the incidence in the resultant molecular chain of head to head and tail to tail linkages as probably no more than a few per cent of the total, the normal being head to tail, the specification states that "a small quantity" of various named substances nay be present during polymerisation as an end group stabiliser controlling molecular weight and viscosity — referred to loosely in argument as an anchor man: this "small quantity" is of the order of .02%. The specification then directly proceeds to state: "Small quantities of other materials may be present inthe chain, as for example, d, l-lactic acid, its optically-active forms, homologs, and analogs". Here, suggests Dr Frazza, is the plain statement of the presence within the molecular chain formed by polymerisation of just such dandelions as result from the copolymerisation in the production of XLG: a statement to be read in conjunction with the earlier reference to a controlled small percentage of comonomer at line 6. The patent in suit at page 3, line 36, refers to the description of P.H.A. esters in Lowe's patent U.S. 2,668,162, and Higgins' patent already mentioned, and at line 42 states "The processes described in the above two patents can be used for producing a polymer from which sutures can be spun". Lowe's patent basically was for the process of producing high molecular weight P.H.A.E. by heating glycolide in the presence of a catalyst. At colume 2, line 23, he states a preferred concentration of catalyst as a percentage "based upon the weight of glycolide and lactide or other lactides": and at lines 35-55 he states as follows: "The process of the present invention nay be employed with advantage to prepare copolymers of glycolide with snail quantities, e.g., up to 15%, of other lactides such as lactide and disalicylide. For example, the preparation of a copolymer of 90/10 glycolide/lactide offers two advantages over the homopolymer of glycolide. One advantage is that the melting point of the copolymer is lower than the homopolymer, being in the neighbourhood of 200° C.; and the entire reaction can be conducted at approximately the melting point of the copolymer. Operation at the lower temperatures decreases the rate of degradation of the polymer which gives a polymer of lighter color. Another advantage is that the copolymer can be successfullyquenched when being extruded into film because the copolymer is less crystalline. On the other hand, the homopolymer shows a greater tendency to crystallize on extrusion and thereby tends to form opaque areas in the film". Of five examples given by Lowe, only Example 4 combines glycolide and lactide, in the proportions 90 to 10, and there refers to "the resulting polymer", a phrase which is of course on any footing appropriate in that context. When however the claims are reached, I find it, to say the least, extremely difficult to find a...

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