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Experts and skilled addressee come to the fore in UK Patents Court Eloxatin decision

On 19 May 2006, Mr Justice Pumfrey of the UK
High Court (Patents Court) handed down his decision in Mayne Pharma v
Debiopharm SA & Sanofi-Synthélabo
[2006] EWHC 1123 (Pat)

Take home

Mayne Pharma had sought revocation and declarations of
non-infringement in relation to EP0943331 and EP1308454 owned by Sanofi and Debiopharm
respectively. Both patents were held
not-infringed and revoked.
An important aspect of the case was the nature of the skilled
addressee of the patents and the testimony given by expert witnesses for each


As is always the case, the
nature of the skilled addressee was largely driven by the associated common
general knowledge that they would bring to the construction and validity of
the relevant patents.

Naturally, Sanofi argued that
the skilled addressee was a general organometallic
chemist, while Mayne argued that the addressee had at least knowledge of
other platinum-based anti-cancer compounds.

Mr Justice
Pumfrey commented:

‘…this is one of those
cases where it is important to bear in mind that those primarily interested
in the invention will be employees of pharmaceutical companies interested in
improving, or making for the first time, pharmaceutical compositions
containing oxaliplatin…’

“…It is not sensible
not to attribute to the skilled person the common general knowledge of those
presently engaged in the manufacture and formulation of platinum-based

As a result,
Mr Justice Pumfrey held that Mayne’s characterization of the skilled
addressee was correct and proceeded on the basis that Mayne’s expert
was well qualified to give evidence on the perspective of such a person. In contrast, Mr Justice Pumfrey appears to
have been unimpressed by the testimony of Sanofi’s leading expert and
stated in relation to one contention about the obviousness of EP ’454
— ‘I remain surprised and unconvinced by the contention he

Mr Justice
Pumfrey repeated several sizeable sections of the expert’s
cross-examination transcript in the judgment to explain his conclusions.


The patent dispute relates to Sanofi-Aventis’ leading
oncology drug – Eloxatin® (Oxaliplatin).

Mayne had
originally sought revocation and declarations of non-infringement of ten
patents. By the time that evidence was
exchanged, the scope of the dispute had narrowed to four patents, and in
respect of two of those Sanofi declined to file any evidence. Consequently,
the issues of infringement and validity were to be decided by Mr Justice
Pumfrey in respect of EP(UK) 0943331 (“’331”) and EP(UK)
1308454 (“’454”).

It became
apparent during the trial that it would be difficult for Sanofi to maintain
the allegation of infringement in relation to the ‘331 patent and it
was formally withdrawn. Accordingly, the judgment deals with the validity of ’331 and with both infringement
and validity of ’454.

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