27 June 2012

Every Wound Has A Silver Lining

Everyone knows that for an invention to be patentable it must be novel and not obvious. An invention is considered novel if it does not form part of the state of the art. In European patent law, the state of the art is everything that is made available to the public by means of oral or written description, by use, or in any other way, before the date of filing of the patent application. The condition of novelty is therefore a difficult one to satisfy. Added to that, the question of obviousness depends on whether a person skilled in the art would have considered the invention obvious. This so-called “inventive step” condition, like novelty, is not only difficult to satisfy, but also slightly baffling. If something was obvious to try – does that mean that the invention is obvious?

These issues were considered in a recent UK High Court action ([2012] EWHC 1602 (Pat) where the validity of a patent was challenged in part using prior art dating from 1946, some 55 years before the application date of the patent.  Did the age of the prior art affect how it could be used or how it was viewed when applied to the conditions of novelty or obviousness?

A client of ours, ConvaTec Technologies Inc, were granted a patent to a light-stabilised antimicrobial material, which concerned methods of making a fibrous wound dressing photostable by using silver as its antimicrobial agent. The background to this is that wound dressings were developed in the 1990s which achieved improved healing by keeping the wound surface moist. Infection is a problem with wounds and particularly those in moist conditions, and consequently there is a need to both prevent and treat the infection.  Silver has a number of advantages as an antimicrobial agent.  There is however a practical problem of its light-stability.  The patent concerned the solution to this problem.

The claims of the patent are limited to relatively modern materials, i.e. polymers that can be made into fibres and form a gel when they absorb exudate from the wound.  Preferred fibres are those of carboxymethyl cellulose.

Smith and Nephew sought to invalidate our client’s patent on a number of grounds including those that the invention was not new and that it was obvious.  They based their argument on an old document mainly concerned with cotton – not a gel-forming fibre albeit cellulose.  There was no question that the invention was novel over this art but what about obviousness?

It is surely common sense that the older a piece of prior art is, the harder it is to show obviousness over it.  The logic being that if it was so obvious, then why didn’t someone do it earlier? Remember: the prior art in this case was 55 years old!

The prior art document concerned preparing a light-stabilised antimicrobial bandage gauze.  As in the patent, this was achieved by using a sodium chloride solution.  The document did not mention gel-forming fibres because they didn’t exist at the time.  There were two opposing arguments.  The patentee argued that the skilled man would not have considered this art: (i) because of its age, and (ii) because of its limitation to cotton.  The skilled man would have assumed that light-stability was achieved in this old art by the silver salt being hidden in the lumen of the cotton.  Gel-forming fibres have no lumen and therefore the skilled man would not have tried the prior art method as they would not have expected it to succeed.

Smith and Nephew argued that the skilled man would have assumed that the art worked by the adsorption of silver complexes on the surface of the fibre and that too could be achieved with gel-forming fibres. The skilled man would therefore have tried the method as they would expect it to succeed.

The judge took the view that the skilled person would not know which theory was right.  To run a test and see if the prior art conditions worked for gel-forming fibres when the skilled person knows that there may either be failure or no guarantee of success is not the act of an unimaginative person.  It is the act of an inventive person.  For this reason the patent was held valid.

In this case the age of the document alone was not a reason to discount it.  It’s age did however contribute to the finding of validity because its teaching could not be directly extrapolated to modern materials.

This UK High Court decision is a notable success for Julie Mays, Partner in our chemical & life sciences team.