A national patent application in an EPC member state that has been filed before but only published after the effective date of a European patent application is not full prior art for assessing the novelty and inventiveness of the European patent application but may affect the validity of a national validation of the granted European patent in the EPC member state in which the national patent has been filed. To avoid this, the EPO has long allowed applicants to pursue a different/narrower set of claims for the state concerned whilst maintaining a set of claims pursuing broader protection in all other states.

Unitary Patent protection can only be obtained based on a granted European patent if the claims are the same for all of the states that would be covered by the Unitary Patent. It is accepted that Unitary Patent protection is not available for applications comprising claims that have been amended with regard to only one UPC member state to deal with a prior national rights.

Conversely, if Unitary Patent protection is obtained in the absence of knowledge of the existence of a prior national right, then a worst-case scenario could lead to the dis-allowance of Unitary Patent protection. As there are presently no provisions in the respective national patent laws of UPC member states that would allow conversion of the Unitary Patent into traditional national validations once the normal validation deadline has passed, such dis-allowance of Unitary Patent protection would have the inevitable consequence of whole sale loss of protection in UPC member states.

To guard against late discovery of prior national rights, the EPO has started on 1 September 2022 to cover national prior rights in a top-up search. The results of the top-up search will be communicated to patent applications together with the communication under Rule 71(3) EPC. Applicants are well advised to address any national prior rights uncovered in this top-up search before patent grant, given the above-discussed risk.

The above said, whilst this risk has been discussed at length by the patent profession, it is to be noted that the risk of relevant full prior art only being discovered once a patent has granted is ever present. This is one of the reasons why a large number of EPO oppositions are successful. Patent proprietors readily appreciated and accepted this risk and it is difficult to see how the risk posed by prior national rights goes beyond this accepted risk. As such, despite the excitement surrounding this topic, this is unlikely to materially influence the behaviour of patent applicants and owners, even in fast moving areas of technology. This said, intensification of the EPO top-up search is to be welcomed, given that it provides applicants with an opportunity to manage any residual risk that may have remained unidentified without it.