Less is more when seeking patent protection for chemical compounds possessing a therapeutic effect

Akebia Therapeutics Inc v Fibrogen, Inc [2020] EWHC 866 (Pat) (20 April 2020)
 
This case concerns important aspects of UK patent law in relation to: 

• sufficiency,

• infringement by virtue of the doctrine of equivalents, and

• threatened indirect infringement of medical use claims.

 
It is particularly relevant for those seeking to obtain protection for a number of compounds covered by a chemical formulae when a therapeutic effect is explicitly recited in the claim.
 
Akebia Therapeutics, Inc. and Otsuka Pharmaceutical Co., Ltd. sought to revoke six EP (UK) patents owned by FibroGen, Inc., in order to clear the way for launch of their drug vadadustat in the UK.  The dispute also concerned a cross-claim for threatened infringement of the same patents by FibroGen's exclusive licensee, Astellas Pharma Inc.
 
First, in relation to sufficiency, caution must be taken when drafting claims covering a large number of chemical compounds where a therapeutic effect is explicitly recited in the claim and where only a relatively small fraction of the compounds are demonstrated in the patent application to possess the claimed therapeutic effect.  The patentee must make sure that compounds falling within the structural definition of the claims possess the claimed functional features (or there is at least evidence the effect is plausible across the scope of the claims), otherwise the claims risk being invalidated by virtue of a lack of sufficiency.
 
When contemplating potential infringers, it is important to know exactly where the technical part of the invention lies.  A detailed disclosure of the invention in the application is therefore key.  Overly broad claims will encompass compounds that do not possess the technical feature(s) and overly narrow claims (such as those limited to the specific examples) will not capture competitor compounds that possess the technical feature(s) of the invention.  It is not enough to rely on the doctrine of equivalents to catch infringers, especially when the scope of the claims has been narrowed during prosecution such that the alleged infringement is no longer within the scope of the claims under normal interpretation.
 
Lastly, timeliness is key when bringing infringement actions.  FibroGen and Astellas brought the infringement action before Akebia and Otsuka had even started marketing the drug vadadustat in the UK.  The court was therefore forced to consider threatened indirect infringement of medical use claims, which meant making predictions on how the drug would be prescribed.  In this case, the court held there was no infringement.  There may have been a different outcome had the action been brought after vadadustat had been marketed in the UK and there was stronger evidence that vadadustat was being prescribed off-label for the claimed medical use.  The patentee must therefore balance the chance of success of any infringement action with the need to act early in order to prevent launch of a competitor product.
 

Practice points: 

• Make sure compounds falling within the structural definition of the claims possess the claimed functional features (or there is at least evidence the functional feature is plausible across the scope of the claims).
   

• When contemplating potential infringers, know exactly where the technical part of the invention lies, make sure there is a detailed disclosure of the invention in the application and draft claims of appropriate breadth.
   

• Balance the chance of success of any potential infringement action with the need to act early in order to prevent launch of a competitor product.