Since the first marketing authorisation for a monoclonal antibody (Mab) in the 1980s, the patent system has never stopped adding the fuel of interest to the fire of Mabs ingenuity.
In view of the ever-increasing pace of technological progress in this highly competitive field, patent applications are often filed at the stage of Mab prototypes. Patent claims have naturally adapted to this practice in order to attempt to protect not only the Mab prototypes but also downstream developments. In this context, claims based on sequence identity are often sought after by applicants.
However, the EPO practice concerning Mab sequence identity appears rather variable, all the more so given that there is no official guideline in this area. A journey through Board of Appeal decisions and examination files nonetheless enables certain conclusions to be drawn in order for applicants to be in a better position to handle examination proceedings.
Firstly, complementarity-determining regions (CDRs) are intangible for the EPO: a claim focused on a degree of identity of CDR sequences is generally not allowed in Europe. Secondly, two main forms of sequence identity claim seem to be accepted by the EPO. The first form consists of applying the degree of identity to a region broader than the CDRs while specifying that said degree of identity does not apply to CDR sequences. This type of claim has been accepted by the Board of Appeal in the decision T 0516/11. The second form consists of associating the degree of identity with at least one functional feature, which has been encouraged by the Board of Appeal in the decision T 2101/09. This strategy can be particularly useful when the functional characteristic is a reflection of an unexpected property that justifies inventive step.
Thus, it is recommended to define the degree of identity in different ways and to provide fallback positions to combine degree of identity with functional features. It is nevertheless necessary to ensure that all the combinations contemplated have direct and unambiguous support in the original application to satisfy the requirements of Article 123(2) EPC.
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