The case related to the validity of a European patent to Roquette Freres. The patent described processes for synthesising a sugar substitute maltitol by hydrogenation of maltose. A key feature of the patent was that a known by-product of the hydrogenation process, maltotriitol, was found (surprisingly, of course) to affect the crystal formation of the resulting maltitol. At low matotriitol concentrations, a bipyramidal crystal form would tend to result, while at higher concentrations a prismatic form would instead result. Controlling the type and proportion of these crystal forms could be useful in affecting how the resulting product behaved, such as in terms of its flow behaviour. The patent was granted with 10 claims but, after opposition, only one claim was left, being: “The use of maltotriitol to modify or control the form of maltitol crystals”.
At first instance, the judge found that the claimed invention was invalid for a number of reasons, one being that it lacked novelty over a prior disclosed process involving hydrogenation of maltose, in which maltotriito would be inevitably modify or control the form of maltitol crystals.
Did this mean that the prior art disclosed the use of maltotriitol to modify or control the form of the resulting maltitol crystals?
The judge effectively held that it did, after construing the words of the claim (in particular those in italics). The issue on appeal was then principally one of construction.
Lord Justice Lloyd did a precise meticulous verbal analysis. The issue was whether the claim required a deliberate modification of the maltotriitol content in order to vary the crystal forms in the resulting maltitol. Lord Justice found that it did not in light of what was disclosed in the rest of the specification. So in a very roundabout way, a meaning of the claim was arrived at that agreed with that of the judge. The appeal was dismissed.