Japan flag South Korea flag China flag

European Examiners Clarify Approach to Polymorph Claims

During their visit, the Examiners based in the pharma and chemistry directorates of the European Patent Office (EPO) explained how they examine claims directed to polymorphs.  They pointed out some common issues relating to clarity and sufficient disclosure. We provide a summary of some of the key outcomes of this meeting below, and some tips on how to prepare pharma/chemical patent applications.




Polymorphs are different crystalline forms of the same chemical compound.  They are particularly relevant to the pharmaceutical industry because the physiochemical properties of drug polymorphs can differ in ways that are important to patient administration.  A well-known polymorphism (known as allotropy) is found in the chemical element carbon – the different crystalline forms are known to us all as graphite and diamond.


The EPO considers claims such as “crystalline form II of compound X” to lack clarity – because a reference to crystalline form numbers does not reflect an accepted standard notation.  A clear claim must specify reliable parameters such as those obtained by powder X-ray diffraction and the description must describe how they are measured.


The Examiners stressed that they will find insufficient disclosure in a patent application when it does not contain a clear description of the preparation and characterisation of the polymorph.  This is especially likely when the application describes a preparation that does not look to be different or relies on seed crystals (decision T1066/03) without saying how to obtain them.


The EPO does not recognise novelty in a claim to a polymorph unless the polymorph differs from the known form in a reliable parameter.  A claim directed to a polymorph having an infra-red (IR) absorption spectrum comprising a list of absorption peaks was not necessarily novel when the polymorph appeared to differ from the known form only in that respect (T885/02).


The EPO will not recognise inventive step in a claim to a polymorph unless the presumption that its preparation is routine can be overcome, for example, by an unexpected effect over the known form or by evidence that polymorphs have been long sought without success (T777/08).


The EPO will find plural invention when polymorphs share a common feature, such as solvation, but differ in their essential crystalline form. It will, in addition, normally object to multiple independent claims directed to the same polymorph.


The Examiners particularly pointed out that they will not allow amendment (for adding subject matter) by way of a claim which selects powder X-ray diffraction reflectance peaks when those peaks are only listed in the description together with their reflectance intensities (T764/06).


Finally, the Examiners reminded us that the European Patent Convention does not allow a spectrum within a claim or a reference in the claims to a spectrum of the drawings.


TLIP advises that claims offering anything other than full characterisation by reliable parameters are becoming increasingly difficult to obtain. Further, the requirement for complete disclosure of the characterising methods appears increasingly stringent.


Please contact us at mail@tlip.co.uk for further information specific to your case.