Antibodies can be defined by the process of their production, i.e. either by the immunisation protocol of a non-human animal with a well-characterised antigen or by the specific cell line used to produce them; for more details see F-IV, 4.12.
However, such a product-by-process definition, based on the immunisation by an antigen comprising a sequence less than 100% identical to a defined sequence does not fulfil the requirements of Art. 84 because the use of variants renders the scope of the antibodies obtained by the immunisation process unclear.
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/g_ii_5_6_1_5.htm
Date retrieved: 17 May 2021