Teva knocked back by Leo in psoriasis patent dispute

A patent can fail for a number of reasons.

Obviousness is one of the more difficult ones to call. It requires you to put yourself into the mindset of the relevant technical expert before the patented invention was filed. You then have to assess whether you would have come up with the invention in the light of published material.

A recent decision about a psoriasis treatment (Teva UK Ltd v Leo Pharma A/S) highlights some of the pitfalls that await you in making an assessment of this kind.

Speciality pharma company Leo Pharma developed a novel treatment for the skin condition psoriasis and filed patent protection in 1999. Their new formulation combined two known compounds for treating the condition with a new, non-water based solvent.

At the heart of the claimed invention was bringing together two active ingredients that had previously had to be kept separate. This was because each one was only stable within a particular pH range. Putting them together in a water-based solution would inevitably mean that one or the other would degrade because it was outside its stable acidity range. This meant that for years the two ingredients had to be applied as separate ointments – tiresome and difficult for the end user.

Then Leo came up with a formulation using a solvent that was not water-based – Arlamol E. The combined product, Dovobet Ointment, was launched in 2002. It proved to be more acceptable for patients to use and was a success.

Teva wanted to sell a generic version of the combination product. It challenged Leo's patents in the UK (with parallel challenges in Europe, the US and Canada). Initially, Teva succeeded. Relying on an earlier Upjohn patent that described use of steroids dissolved in Arlamol E, Teva persuaded the judge that Leo's patents were obvious. But the appeal court disagreed.


  • The judge had separated the theoretical skilled person from the real formulator tackling the problem. That person would in reality have tried to use familiar solvents rather than trying something new.
  • The judge had said that Arlamol E fitted the bill and so would have been tried. But there was nothing to make Arlamol E stand out from a range of possible candidates - 'possible inclusion of something within a research programme on the basis you will find out more and something might turn up is not enough'.
  • The judge concluded that there was a good prospect of success with this solvent – it would be worth testing. This ‘obvious to try' line of argument can work, but you need a higher expectation of success than here, where Arlamol E was just one of a list of non-aqueous solvents.

Crucially, Leo had found a solution to a problem that had persisted for a number of years, and produced a formulation that offered a recognised advance in treatment. It was entitled to protection.

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