The extent of protection conferred by a European patent shall be determined by the claims [Art. 69(1) EPC; § 14 PatG]. A claim wording being as broad as possible is therefore in the interest of the applicant. Accordingly, the claim wording usually generalizes one or more concrete embodiments of the invention.

However, this practice may become critical, if the claim wording is overstretched in such a way that a skilled person – in view of the specification and even in view of his expertise – is helpless as to how to perform the invention defined in the claim beyond the practical execution embodiment. A patent claim overstretched in such a way conflicts with the requirement for patentability that the invention to be protected shall be disclosed in a manner sufficiently clear and complete to be carried out by a person skilled in the art [Art. 83 EPC; § 34(4) PatG]. Patent claims which, in this sense, have been granted erroneously may be attacked or even annihilated in opposition or invalidity proceedings by third persons. At this point it shall be emphasized that the patent claim needs to be disclosed in a manner sufficiently clear and complete to be carried out by a skilled person over the complete width of the claim, i.e. the mere reproducibility within the core area of the claimed invention according to the disclosed execution examples regularly is insufficient.

EPO’s Board of Appeal decision in the case T 1150/09 of November 14, 2013 illustrates that applicants may be confronted expeditiously surprisingly, and unforeseeable with the objection of insufficient disclosure of the invention over the complete width of the claims. In this case, patent protection has initially been granted by the EPO for a medicinal use of a PIGF-specific antibody against cancer (malignant tumor). The patented invention has been underpinned by a successful in-vivo study on mice having tumors, wherein PIGF is involved. The opponent asserted successfully that the generic term “cancer” also comprises such tumores in which the expression of PIGF as a basic prerequisite for the effectiveness of the specific antibody is not detectable.

According to the Board of Appeal the skilled person was therefore confronted with the task to initially find out which kind of cancers are appropriate for the treatment with the inventive antibody. This task could, according to the Board of Appeal, not be completed by the skilled person without undue burden. As an unfortunate result, the patent has been revoked due to infringement of Art. 83 EPC. Unfortunate because the applicant contributed an effective possibility for the treatment of PIGF-involved tumors without being rewarded with an adequate patent protection.