On 28 July 2015, the Court of Appeal overturned the decision of Birss J in Teva v Leo Pharma. Leo’s patents relating to the treatment of psoriasis (an inflammatory skin disease) using a combination ointment (‘Dovobet Ointment’) comprising two active ingredients, calcipotriol (a vitamin D analogue) and betamethasone (a corticosteroid), and a commercially available solvent called Arlamol E, had previously been found to be invalid for obviousness by Birss J.

The key question for the Court of Appeal to consider was whether an ointment such as Leo’s Dovobet Ointment was obvious at the priority date in April 1999. Prior to this date, each active ingredient was well-established and used in the treatment of psoriasis, often being prescribed together as two topical products with different beneficial effects. However, the products could not be used at the same time. As a consequence, patient compliance in using the two products was problematic and led to clinicians calling for a combination product by the mid-90s.

The barrier to such a combination product was due to each active ingredient being unstable outside of a narrow pH range (pH ranges which did not overlap). An aqueous solvent was used in each product to buffer a pH to provide stability. It was commonly known that without water the issue of having two products with different pHs would not arise. A non-aqueous solvent was therefore needed.

One such solvent, Arlamol E, was identified by Teva in a prior art document, and Birss J had held that its use would have been obvious in 1999. Although Birss J appeared to accept evidence that a “real” formulator would not have included Arlamol E among the solvents to test (because it was not a familiar compound), he held that the “notional” formulator would have done so.

In the Court of Appeal decision, Sir Robin Jacob said that this was rather odd and that by Birss J considering "...there was a sufficient prospect of a positive result in the tests with this compound to make it worth testing" the Judge was effectively saying that the idea of including the Arlamol E in a research project amounts to obviousness. However, the ‘obvious to try’ standard requires a higher expectation of success than just the idea of including something in a research project. Including something in a project on the basis that something might turn up is not enough to make an invention obvious.

In the prior art document identified by Teva, Arlamol E had been used in a mono active product whilst the invention concerned a double active product and there was no reasonable expectation that Arlamol E would work in a combination product. Sir Robin therefore considered Birss J had erred in principle and revisited the question of obviousness de novo.

Sir Robin further identified a point of consideration he thought had been omitted by Birss J. Each party’s experts acknowledged that the invention constituted a significant advance in the treatment of patients. By resolving better patient compliance, which had been desired as early as 1995, it was therefore “...the classic sort of case where the courts have found invention over the years, a long-felt want, the desired solution and no explanation of why that solution was not done before when it could have been.” It is also interesting to note that the EPO opposition division had been provided with Birss J’s judgment and had nonetheless upheld the patent. Consequently, the Court of Appeal reversed Birss J’s finding of obviousness.