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Itchy combinations and the power of common general knowledge

28 November 2014

The decision by Mr Justice Birss in the Patents Court in the case of Teva UK Limited and Teva Pharmaceuticals Limited (Teva) v Leo Pharma A/S and Leo Laboratories Limited (Leo) (See here), relates to a combination treatment for psoriasis and provides an interesting commentary on the assessment of obviousness and common general knowledge in such inventions.

The two patents involved concern Leo’s treatment which is a non-aqueous formulation comprising a combination of a corticosteroid (e.g. betamethasone) and a vitamin D analogue (e.g. calcipotriol), together with a specific solvent (polyoxypropylene). Leo marketed the product in the UK with substantial sales. Teva wanted to sell a generic version.

Both corticosteroids and vitamin D analogues were already known for the treatment of psoriasis, but had not previously been combined in a single formulation. Providing the two actives in a single formulation was expected to improve patient compliance compared to patients using separate formulations. However, differing pH stability profiles, meant that the components could not simply be added together in an aqueous formulation. Leo’s invention lay in their finding that the actives could be combined by using a non-aqueous formulation with a particular solvent, which acted to stabilise the composition.

Teva contended that both of Leo’s EP (UK) patents to the formulation were invalid for obviousness, insufficiency and added subject matter. Birss J’s Decision focusses on Teva’s obviousness attack, which was based on a combination of the common general knowledge and an earlier US patent which disclosed anti-inflammatory preparations containing polyoxypropylene 15 stearyl ether.

Based upon the testimony of expert witnesses from both sides, Birss J built up a detailed picture of the common general knowledge in the art and the skilled person (in this case actually a team of a skilled clinician and a skilled formulator of pharmaceutical compositions). Birss J agreed that, starting from the common general knowledge, the skilled person (in particular, the skilled clinician) would have had an obvious desire to develop a combination treatment to encourage patient compliance. Acknowledging that the skilled formulator would have been aware of the incompatibility of the pH profiles of the two components, Birss J concluded that the solution of using a non-aqueous formulation would also have formed part of the skilled person’s common general knowledge. Combining the two active compounds in a single non-aqueous treatment was therefore deemed to be entirely obvious.

In relation to the specific solvent used by Leo (polyoxypropylene), it was acknowledged that at the time of the invention this was not a compound a skilled person would have been aware of from their common general knowledge. However, the solvent was known from the US patent which was held to be a document that a skilled person would not have ignored or dismissed.

The fact that the solvent did not have a well-established track record in pharmaceutical formulations was not found to have been sufficient to put the formulator off including the solvent in routine tests. Indeed, Birss J noted that it had been listed in the FDA’s inactive ingredient guide and had therefore been approved for use by a regulator. Birss J concluded that, based on what the skilled formulator knew at the time, there was a sufficient prospect of a positive result with this solvent to make it worth testing and it would have been obvious to do so.

The Judgement also touched on the possibility that the solvent may have been an inventive selection as Leo provided evidence that a polyethylene glycol solvent did not work. However, it appears that this is the only other solvent Leo tested and, in the absence of other comparative data, this argument was not found to be compelling. Birss J consequently found both patents invalid for a lack of inventive step.

It seems that Leo may have had the misfortune to hit on an appropriate solvent early in their development process – if they could have provided more comparative data, their formulation may have been deemed to be an inventive selection. Inventors in the field of combination inventions may benefit from devoting more time to comparative studies.


Helen Henderson
Life Sciences & Chemistry Group

If you require further information on anything covered in this briefing, please contact Helen Henderson (; +44 1179 253 030) or your usual contact at the firm.

This publication is a general summary of the law. It should not replace legal advice tailored to your specific circumstances.

© Withers & Rogers LLP, November 2014