The Supreme Court dismissed an appeal by Ranbaxy Laboratories Limited, Ranbaxy Europe Limited and Ranbaxy Ireland Limited over whether correspondence with European and Danish patent offices could be admitted as evidence in their patent dispute with Warner Lambert Company.
The appeal concerned a preliminary evidential issue, not whether Ranbaxy’s proposed product infringed the patent. The companies seek to market atorvastatin calcium, a single enantiomer. Warner Lambert owns Irish Patent 60014 for the cholesterol-reduction product Lipitor, which the judgment describes as a racemate. Ranbaxy argued that the patent claims covered racemates but not single enantiomers; Warner Lambert’s defence said the patent also covered Ranbaxy’s proposed product.
Ranbaxy sought discovery of documents referred to in its reply to the defence, including letters said to represent that corresponding patents were confined to racemates. A High Court judge ruled that the documents were inadmissible. On appeal, Ranbaxy pursued only four letters: three to the European Patent Office, dated 20 June 1995, 10 June 1996 and 31 January 1990, and one to the Danish Patent Office, dated 18 May 1993. For the purpose of deciding admissibility, the Supreme Court accepted Ranbaxy’s proposed interpretation of those letters and that they referred to patents corresponding to the Irish patent.
The judgment explained that patent claims are construed objectively through the understanding of a skilled addressee. Evidence of a patentee’s intention, including indirect evidence said to show that intention, is generally inadmissible. Ranbaxy submitted that the letters could instead show the views of skilled patent agents. The Court held that the agents wrote on behalf of the patentee, expressing the construction it wished to put on the claims; they were not giving independent expert opinions. The Court also distinguished earlier English authority involving correspondence that discussed experiments conducted in response to official observations.
Mr Justice McCracken concluded that the letters were expressions of the patentee’s opinion about claim construction and were inadmissible. The Court dismissed the appeal. It did not decide the ultimate scope of the patent or whether Ranbaxy’s proposed product infringed it.