The issue was whether the claims of a European patent granted to Kirin-Amgen, Inc. were infringed by Transkaryotic Therapies Inc. ("TKT") and Hoechst Marion Roussel Ltd in a situation where there was a remarkable similarity between the technologies employed by the two parties for producing the hormone erythropoietin.
The reasoning in the judgment has presently formed a basis for the current practice of the UK Intellectual Property Office, and other countries that take great consideration of the legal implications of British case law when assessing whether a patent has been infringed by a device or process which is equivalent to the patented invention under the doctrine of equivalents.
Kirin-Amgen, Inc. ("Amgen"), a Californian pharmaceutical company, was the proprietor of EP 0148605 relating to the production of the glycoprotein hormone erythropoietin (EPO) by recombinant DNA technology.
EPO, a previously known glycoprotein hormone, is made in the kidney and stimulates the production of red blood cells by the bone marrow.
The result was that the existing machinery for gene expression in the transfected microbial host cells operated to construct the desired product, EPO.
The Amgen technique described using exogenous DNA as a template for transcription of mRNA which is then translated into a continuous sequence of amino acid residues within the transformed microbial host cells.
The TKT technique involved introducing the necessary control sequence into the DNA within a human cell upstream from the latent EPO gene.
The principal issue in the case was whether TKT's EPO fell outside the claims of Amgen's patent suit because of the difference in the way it was made.
A recombinant polypeptide having part or all of the primary structural conformation of human or monkey erythropoietin as set forth in Table VI or Table V or any allelic variant or derivative thereof possessing the biological property of causing bone marrow cells to increase production of reticulocytes and red blood cells to increase haemoglobin synthesis or iron uptake and characterised by being the product of eucaryotic expression of an exogenous DNA sequence and which has a higher molecular weight by SDS-PAGE from erythropoietin isolated from urinary sources.
Lord Diplock expounded his new principles of "purposive construction" in the leading case of Catnic Components Ltd. v. Hill & Smith Ltd., in respect of a patent granted before 1977.
Neither should it be interpreted in the sense that the claims serve only as a guideline and that the actual protection conferred may extend to what, from a consideration of the description and drawings by a person skilled in the art, the patentee has contemplated.
On the contrary, it is to be interpreted as defining a position between these extremes which combines a fair protection for the patentee with a reasonable degree of certainty for third parties.
Before the EPC came into effect, and until the House of Lords decision in Catnic, the words and grammar of a patent claim, in the absence of ambiguity, were to be given their natural and ordinary meaning.
Lord Diplock preferred to adopt a principle of construction which actually gave effect to what the person skilled in the art would have understood the patentee to be claiming.
A corresponding United States decision which may represent the beginning of a similar tendency is Phillips v. AWH (CAFC 2005, en banc), 415 F.3d 1303 (Fed.
The principal question in that case was the extent to which a court should resort to the patent specification in seeking to ascertain the proper scope of its claims.
This case affirmed that: "Construction is objective in the sense that it is concerned with what a reasonable person to whom the utterance was addressed would have understood the author to be using the words to mean.