Even by Mr Justice Arnold's normal standards his judgment in Generics (t/a Mylan) -v- Yeda and Teva  EWHC 1848 (Pat) was an epic. It stretched to over 100 pages. It seems the learned judge himself was a little self-conscious about the length given he was quick to point out, in the third of his 466 paragraphs, that when compared against a combined length of the parties' closing submissions of 947 paragraphs and 266 pages his judgment was a study in brevity.
The patent in suit, owned by Yeda and licensed to Teva, protected a pharmaceutical product called glatiiramer acetate (brand names of Copaxone) used to treat relapse-remitting multiple sclerosis. Mylan wished to 'clear the way' so that they could launch their own generic version of glatiramer acetate so they brought this action seeking revocation of the patent and a declaration of non-infringement. To be fair again to Mr Justice Arnold and the length of his judgment the case raised, in one form or another, almost the whole panoply of issues possible under the Patents Act - priority, novelty, inventive step, insufficiency, added matter and, of course, infringement. At the end of the day the Court held that the patent was not entitled to its earliest claimed priority but otherwise was valid in all respects and would be infringed were Mylan to market their intended product. So the undoubted victors were Yeda and Teva as patentee and licensee respectively.
What though is probably of most interest from a general perspective is what the judgment has to say about post-dated evidence. In other words to what extent (if any) is the inventiveness or sufficiency of a patent effected by evidence which is not available at the date of the patent but which only comes into existence at a later date.
Generally speaking the European Patent Office (EPO) has seemed to be more open to the admissibility of post-dated evidence and how to treat such evidence than has the UK courts. As is appreciated the EPO tends to adopt a so-called 'problem-and-solution' approach which requires the formulation of a "technical objective problem". The applicant must show that it is plausible that the "technical objective problem" is solved by the embodiments of the claims of his patent which in turn raises the question of how the applicant can, in an evidential sense, go about demonstrating that his invention does indeed produce the requisite technical effect to solve the problem.
At least so far as the EPO is concerned post-dated evidence can play a role in assisting the applicant demonstrate that his invention solves the stated technical problem. However there are limits. What is clear is that the post-dated evidence can not serve as the sole basis for seeking to show that the invention solves the problem (see T-1329/04). But so long as the disclosure existing in the application itself makes it plausible as at the priority date that the invention solves the problem then post-dated evidence can be adduced and relied upon to confirm, support and reinforce such a disclosure
(see by way of examples T-1336/04, T433/05, T898/05, T1452/06 and T1165/06)
The UK courts have tended in the main to be less receptive than the EPO to the admissibility of post-dated evidence. In Richardson-Vicks Inc's Patent  RPC 568 at 581 Jacob J (as he then was) stated:
"Whether or not there was synergy demonstrated by experiments conducted after the date of the patent cannot help show obviousness or non-obviousness". In Generics (UK) Ltd -v- H Lundbeck A/S [2007} RPC 32 at  Kitchin J (as he then was) stated: "A patentee cannot seek to bolster the inventive nature of his monopoly by relying on a discovery which he had not made at the time of the patent". In HGS -v- Eli Lilly  RPC 14 at  Jacob LJ said in relation to the subject of the industrial applicability of a patent "....I do not understand the reference to 'post-published evidence' to include post-published evidence establishing for the first time or adding to what the potential industrial application of the patented subject-matter may be. It is surely axiomatic that whatever the standard for susceptibility to industrial application may be, the information about it must be in the patent (supplemented if necessary by the common general knowledge of the time)."
In the instant case the parties agreed that it was necessary for the patent specification to disclose enough to the skilled reader armed with his stock of common general knowledge to persuade him that it was plausible that the invention described would work to solve the stated technical problem. If the disclosure did not reach that threshold it would be lacking and no amount of post-dated evidence designed to demonstrate the technical effect could be pitched-in to try to save it. So, in other words, the two parties accepted that the position should be as it is in the EPO pursuant to the Johns Hopkins/T-1329/04 case mentioned above.
However the parties parted company over the ability of an opponent to rely on post-published evidence to challenge the validity of a patent in circumstances where such evidence could cast doubt on whether the invention actually has the technical benefit that the skilled reader thought that it plausible it had when he notionally read the filing at the priority date. In the words of Arnold J "If a patent does disclose enough to make the invention plausible at the priority or filing date, can an opposing party come along 20 years later and say that, in light of subsequently acquired knowledge, in fact the invention does not have the technical benefit that it appeared to have ?".
Mr Justice Arnold approached his answer to his own question by stressing that the fundamental principle was that the validity of a patent should normally be judged as at its priority or application date. Whilst the UK courts in line with the EPO would be prepared to entertain post-dated evidence which served to confirm the plausibility of an existing disclosure that represented as far as they should or would go. In particular they would not re-examine on the basis of post facto evidence a disclosure accepted as plausible by the skilled reader at the priority date: "...post-dated evidence may be relied on to confirm that the disclosure in the patent either does or does not make it plausible that the invention solves the technical problem. Post-dated evidence may not be relied upon either to establish a technical effect which is not made plausible by the specification in order to rebut an allegation of obviousness or to contradict a technical effect which is made plausible by the specification in order to found an allegation of obviousness" and "...if the specification does make it plausible that the invention solves the technical problem, I do not consider that it is open to an applicant for revocation to rely upon post-dated evidence as casting doubt on this so as to place an evidential burden on the patentee to demonstrate affirmatively that the invention does solve the technical problem".
As indicated, the role (if any) of post-dated evidence in UK patent jurisprudence has been unclear for quite some time. Whilst the EPO had grappled with the issue and its case law had given clarity to its treatment of such evidence the position in the UK has been less certain. Accordingly Mr Justice Arnold's clarification and guidance is welcome and opportune as well as being on all fours with the approach of the EPO and as we all know from decisions such as that of the Supreme Court in Eli Lilly and HGS whenever possible we should align our law with that of the EPO !