In Generics [UK] Limited t/a Mylan v Yeda Research & Development Co Ltd & Teva Pharmaceuticals Industries Ltd [2013] EWCA Civ 925, the Court of Appeal of England and Wales has provided clarification on the use of evidence that post-dates the priority of a patent to show whether or not the claimed invention made a plausible technical contribution


Yeda has a patent for a glatiramer acetate (GA) product (the patent) that is licensed exclusively to Teva and marketed by Teva as Copaxone. The patent relates to Copolymer 1, a polymer of a specified molecular weight range composed of four amino acids in particular ratios for the treatment of multiple sclerosis. In order to make way for its own generic GA treatment, Mylan challenged the validity of the patent for obviousness over a prior publication, referred to as "Johnson", and for lack of a technical contribution. Significantly, the

results of the Johnson phase III trial were not published until after the priority date of the patent.

At first instance, Mr Justice Arnold found the patent to be valid and infringed by Mylan’s product. Mylan was allowed to appeal, and did so.


The Court of Appeal dismissed the appeal. Although the overall decision in respect of the parties was not changed, the Court of Appeal disagreed with the High Court’s finding as to how evidence that post-dates the priority date of a patent can be used.

At first instance, Arnold J decided that post-dated evidence may be relied on to confirm that the disclosure in the patent does or does not make it plausible that the invention solves the technical problem, but not to establish a technical effect that is not made plausible by the specification nor to contradict a technical effect that is made plausible by the specification. If the specification does make it plausible that the invention solves the technical problem, Arnold J determined that the party seeking revocation cannot rely upon post-dated evidence to cast doubt on whether or not the invention does solve the technical problem. Only evidence pre-dating priority may be relied on in this situation.

The leading judgment of the Court of Appeal, delivered by Lord Justice Floyd, held that post-dated evidence (in this case, the Johnson clinical trial data) used to prove that the claimed technical contribution of a patent is implausible or is not achieved, may be used as evidence to support a finding of invalidity. Floyd LJ commented that the principle that a technical effect relied on had to be made plausible by the patent specification and could not be established for the first time by subsequent evidence, did not provide a basis for the different rule arrived at by Arnold J as to whether or not later evidence could be used to disprove an effect made credible by the specification. Arnold J was therefore incorrect to determine that, if the patent specification made a technical effect plausible, it was not open to Mylan to challenge the existence of that effect by the use of post-priority evidence.

The Court of Appeal clearly pointed out that its decision on post-dated evidence only relates to analysis of inventive step, and is independent of the rule that assessments of obviousness must be made as at the priority date of the patent. Floyd LJ commented that

The problem and solution approach to obviousness requires the court or tribunal to judge inventiveness by reference to what it is that the invention brings with it: its technical effect or advance. Like any other fact relevant to an issue, however, it must be open to being refuted. In doing so one is not judging the obviousness of the claimed invention by reference to later evidence: one is simply defining by evidence what it is that the invention is or brings with it.


This judgment is likely to give patent holders pause, as the validity of patents with plausible functionality claims covering a wide range of untested structural materials may now come under fire from post-priority feasibility studies.