If a patentee has submitted his application in his homeland or abroad he can claim priority of his prior application for a subsequent application within one year. The advantage of claiming a priority is – amongst others – that the subsequent application preserves the date of the earlier application and, expediently, that state of the art published in between the earlier and the subsequent application is not considered for the examination for patentability of the claimed subject matter of the subsequent application.

From the viewpoint of the European Patent Office (EPO), the requirements for claiming a priority for subject matter claimed in a subsequent application is that

• the same claimed subject matter has to be evident to the skilled person from the earlier application (see G 2/98)
• the invention has to be accomplishable on the basis of the disclosure available from the earlier application (see T 81/87; T 843/03).

For applications relating to biological material which is not described in the application in a way allowing the skilled person to accomplish the invention, there is the possibility to deposit the biological material at an accredited place of deposition. If necessary, third persons can access the deposited material and accomplish the invention e.g. as license holders or in the context of the privilege to do research. However, if the deposit is not carried out until – at the latest – the date of filing the prior application, the claimed subject matter of the subsequent application which is based on the biological material cannot revert to the priority of the prior application (Numeral 1.4 of the EPO communication of July 7, 2010 on inventions, in which biological material is employed or which relate to biological material).

A recent example for this view of the EPO and the consequences thereof is the decision T 107/09 of the Technical Board of Appeal 3.3.04 of July 12, 2012 in relation with a European subsequent application claiming priority of a US-prior application.

As an essential feature, the subject matter of the claim of the European subsequent application comprised a cell line having been deposited indeed before the date of filing the European subsequent application, but after the date of filing the US prior application. As a result the Board of Appeal negated an effective claim of priority rights according to the criteria mentioned above, i.e. only the younger priority has been assigned to the European subsequent application. Due to this shift of priority, prior art initially blinded out became relevant contesting the inventive step of the claimed subject matter.

In practice this means that foreign applicants being unfamiliar with this strict view of the EPO should be advised to deposit biological material before the filing date of the prior application. This holds true, particularly, for US applicants being especially active on the field of biotechnology, as those applicants are used to their clearly more liberal “enablement-requirement” approach, according to which a later deposit of the biological material until the issuance of the US-patent is sufficient (see decision „In re Lundak“, 773 F.2d 1216, 227 U.S.P.Q. Fed.Cir. 1985).