A recent decision issued by the High Court has found that a patent to the second medical use of atomoxetine for the treatment of ADHD is valid. In his judgement, Mr Justice Henry Carr provided further guidance on the relationship between plausibility, sufficiency and inventive step.

It had already been established by a number of cases (starting with Factor-9/John Hopkins (T1329/04) where the term ‘plausibility’ was first used in the context of the technical contribution test laid down by AgrEvo), that plausibility is a threshold test which can be applied to both inventive step and sufficiency.

For obviousness, Lord Hoffmann used a two-step approach in Conor Medsystems Inc v Angiotech Pharmaceuticals Inc., firstly determining whether the claimed invention was plausible before assessing if the claimed invention was obvious according to the established principles of UK law.

With regard to sufficiency, Arnold J. also adopted a two-step test (in Eli Lilly v Alzheimer Immunotherapy) with plausibility as the first step. It was first necessary to establish that the disclosure of the patent, read in conjunction with the common general knowledge of the skilled team, made it plausible that the invention would work across the claim scope, before considering whether later evidence established if the invention could be performed across the claim scope without undue burden.

This most recent atomoxetine case arose when Actavis sought revocation of Eli Lilly’s European Patent EP (UK) 0721 777 (the ‘Patent’) which claimed:

“Use of tomoxetine for the manufacture of a medicament for treating attention-deficit/hyperactivity disorder.”

Validity was challenged on the basis of lack of inventive step and insufficiency. In addition, Actavis sought to establish a squeeze argument between these two grounds based on a lack of plausibility.

In the first instance, Actavis alleged that the Patent contained ‘no more than a bald assertion that atomoxetine [was] effective and safe for the treatment of ADHD’. The Patent contained no data to support the assertions of safety and efficacy so if it was found that the Patent did disclose a theory or principle to support the claimed use, Actavis argued that this theory must be known from the prior art. The squeeze would therefore arise if Eli Lilly argued in favour of inventive step based on a lack of evidence of success in the prior art. If this was the case, then the lack of data in the application as filed must render the Patent implausible and thus insufficient.

It is well established that the test for inventive step involves (i) a determination as to whether the invention (as specified in the claims) is obvious to try and (ii) whether there would be an expectation of success. For the purposes of this test, the skilled person should be able to make a fair prediction, starting from the prior art, as to whether the invention will succeed. However, is the same true with regard to sufficiency or is the standard for plausibility different? For the squeeze argument to succeed, this must be true, and Actavis argued that plausibility, like obviousness, required a reasonable expectation that the invention would work.

To counter this argument, Eli Lilly argued that the hurdle for plausibility must be assessed on a case-by-case basis taking claim breadth into account but that in any event the threshold for plausibility must be lower than that for obviousness.

Carr J. found that plausibility was indeed dependent upon the nature of the invention, the scope of the claims, the disclosure of the specification and the common general knowledge. He observed that it would be ‘likely to be easier, as a matter of fact, to show plausibility for a claim of narrow scope,…, than for a claim of wide scope’. Taking into account the different policy considerations for sufficiency and inventive step, he found that an assessment of plausibility was not the same as an assessment of obviousness, and reaffirmed that plausibility is only a threshold test. He explicitly stated that ‘the assessment of plausibility is not the same as the standard for assessment of expectation of success in the context of obviousness.’

In conclusion, it was found that the claimed use of atomoxetine for the treatment of ADHD was plausible and that such use was inventive over the prior art, thus rejecting the squeeze between obviousness and insufficiency.

The Patent was consequently found to be valid and the claim for revocation dismissed.

The decision can be found here: http://www.bailii.org/cgi-bin/markup.cgi? doc=/ew/cases/EWHC/Patents/2015/3294.html&query=patent&method=Boolean

Practical advice – take care when relying on prior art disclosures to support plausibility so as to avoid the possibility of a squeeze attack. Include as much data as is reasonably possible having regard to the claim scope, nature of invention and common general knowledge.