But let's recap a bit. The main claim at issue is a Swiss form claim, and although this is significant for the present case, much less turns on it than in the other saga ongoing at the moment of Warner Lambert v Actavis (latest instalment here). The claim was as follows:
Use of pemetrexed disodium in the manufacture of a medicament for use in combination therapy for inhibiting tumor growth in mammals wherein said medicament is to be administered in combination with vitamin B12 or a pharmaceutical derivative thereof, said pharmaceutical derivative of vitamin B12 being hydroxocobalamin, cyano-10-chlorocobalamin, aquocobalamin perchlorate, aquo-10-chlorocobalamin perchlorate, azidocobalamin, chlorocobalamin or cobalamin.The main issue was whether this could be infringed by a different pemetrexed salt such as pemetrexed dipotassium, or by the free acid, notwithstanding that the claim said "pemetrexed disodium".
Issue 1 - Prosecution history as an aid to construction
In the first instance judgment, Arnold J drew significant support from the prosecution history of the patent when considering how broadly the claim could be construed. Floyd LJ has roundly rejected Arnold J's reasoning, stating:
58.The difficulty I feel with endorsing this reasoning is as follows. Firstly it assumes that the skilled reader will always read the prosecution history. I do not see why this should be so, given the limited value which, at least before the judgment in this case, it was generally recognised to have. Secondly, and more importantly, it suggests that the story told by the prosecution history of how the claims came to be drafted as they were will assist the court in preventing abuse of the system. To my mind this will be a very rare case indeed. Unless the acceptance of a restriction in a claim is to operate as some kind of estoppel against the patentee arguing for wider claims (a proposition for which neither side contended and which Jacob J rejected, at least on the basis of domestic estoppel, in Bristol Myers), there will always remain an issue as to whether the applicant needed to accept the restriction notwithstanding that he did so. In those circumstances, the light which the prosecution history sheds on the ultimate question of construction is likely to be extremely limited.
59.I therefore do not regard it as useful to go to the prosecution history in order to discover that the patentee accepted a restriction to his claim against an objection of lack of support in the specification. It is always open to a party attacking the patent to argue that the claims as sought to be construed by the patentee lack support in the specification: see for example American Home Products v Novartis  RPC 8 at . What purpose does it serve to illustrate this point by showing that the patentee was faced with an official objection to that effect and amended his claims in the light of it? It is still open to the patentee to say that he need not have done so, and the apparent concession he made in prosecution was wrongly made. If it is not open to the patentee so to contend, then the prosecution history is indeed creating a form of estoppel.
60.In any event, patent offices are usually concerned with patentability, not scope of protection. If an applicant were to conclude every letter by saying that he did not accept that by accepting this or that limitation he was necessarily restricting the scope of protection, no inference could be drawn from his conduct in accepting it. I would be reluctant to put the patent attorneys' profession to this unnecessary trouble.
The courts of the United Kingdom, the Netherlands and Germany certainly discourage, if they do not actually prohibit, use of the patent office file in aid of construction. There are good reasons: the meaning of the patent should not change according to whether or not the person skilled in the art has access to the file and in any case life is too short for the limited assistance which it can provide.
So Lilly was saved by the fact that the compound was to be made up in saline solution, and this fact was critical to the finding of indirect infringement by the Court of Appeal. On little facts do big cases turn.
Outcome and next steps
As a result of the finding of indirect infringement, even if not direct infringement, Floyd LJ ruled that Actavis were not entitled to a declaration (so all the issues relating to the non-UK designations of the patent became irrelevant, although in fact Floyd LJ would have agreed with Arnold J on these). Despite a flurry of post-appeal submissions, which delayed the handing down of the decision, he declined to issue a declaration in respect of direct infringement only, or a declaration that specified that Actavis would infringe if the product was to be made up (more specifically, if Actavis knows, or it is obvious in the circumstances, that the product is suitable and intended for being reconstituted) in saline in appropriate amounts to equate to a disodium salt. He declined even more strongly to issue a declaration that specified that Actavis would infringe if and only if the product was to be made up in saline in appropriate amounts to equate to a disodium salt. Any such declaration was open to being misconstrued.
However, in the meantime, Actavis had come up with a plan to specify that their product should be made up in dextrose solution rather than saline solution. They contended as a further point in their post-appeal submissions that this would require remittal to the first instance to consider whether this proposal would be sufficient to circumvent the claim, since it was possible that, notwithstanding their directions, a user might use saline instead.
On this point, the Court of Appeal granted remittal, so the case is off back to the Patents Court. So there will be more volumes of the saga to come, it seems.