The EPO and Partial Priority – T 0571/10 A Common Sense Decision

December 2014

Decision T0571/10 (decision date 3 June 2014) has just been published by the EPO and makes an interesting contribution to the debate on partial priority of a patent claim. 

This decision affirms decision T1222/11, and again departs from the limited interpretation of “provided that it gives rise to the claiming of a limited number of clearly defined alternative subject-matters” adopted in other Board of Appeal decisions (T1877/08, T476/09, T1443/05 and T1127/00). This condition requiring a limited number of clearly defined alternatives was first introduced by the Enlarged Board of Appeal in G2/98, although that decision was not explicit in what the term meant.

Article 88(2) of the EPC provides the possibility that a patent claim can be entitled to more than one priority.  Decision T 0571/10 refers to the FICPI memorandum (on which article 88 was based) at 4.5.5 to justify its rationale of using a “swiss cheese” approach to partial priority.  In particular, for a term in the claim that is generalised relative to the disclosure of the priority document, the generalised claim is priority-entitled for the subset of the claim scope that is clearly and unambiguously disclosed by the priority document, and everything outside that subset but within the scope of the generalised claim is not priority-entitled. 

The priority document of the patent in suit (application number 08165575.5) for T 0571/10 disclosed (i) a particular calcium salt as an active agent; and (ii) a tribasic phosphate salt in which the cation is multivalent. The particular calcium salt was generalised to a generic class including the calcium salt “or a pharmaceutically acceptable salt thereof” and the tribasic phosphate salt was generalised to an “inorganic salt”.  It was held by the Board not to be necessary that the clearly defined alternative subject matters were spelt out as such in the application (paragraph 4.5.12 of decision). The Board carved out the generalised claim filed during oral proceedings into two clearly-defined alternative subject-matters as follows:

Priority entitled:  use of pharmaceutical composition comprising the calcium salt of the generic class (dihydroxyhept-6-enoic acid) as the active ingredient and tribasic phosphate salt in which the cation is multivalent.

Not entitled to priority: use of pharmaceutical composition comprising the generic class of acid or a pharmaceutically acceptable salt thereof as the active ingredient and an inorganic salt in which the cation is multivalent, wherein the active ingredient is other than the calcium salt of the acid and the inorganic salt is other than the tribasic phosphate salt in combination.

Moreover, where the priority document is published and becomes prior art in respect of the priority claiming application having a claim entitled to partial priority, the priority document is NOT prior art in respect of the Priority-Entitled part of the claim whereas, although it is prior art in respect of the Not-Entitled-to-Priority part of the claim, that part of the claim is novel over the priority document.  Consequently, the prospect of self-collision by a “toxic priority” document is avoided.

Interestingly, T 0571/10 and T1222/11 were both associated with Board 3.3.07. This new decision is relevant to the contentious issues of toxic priority and poisonous divisionals, which arise due to the narrow interpretation of the “limited number of clearly defined alternative subject-matters” rejected, correctly in our view, in T0571/10.

This update was prepared by Dr Susan Keston,  Patent Director of our Glasgow Office and Mark Lunt , Partner in our Sheffield office. 

If you would like further advice on this or any other matter, please contact Susan at skeston@hgf.com  (Tel: +44(0) 141 229 5800), or your usual HGF representative or visit our Contact Page to get in touch with your nearest HGF office.