Patentability of Markush formulae

Markush formulae play a pivotal role in the field of chemical patent drafting, as they empower applicants to articulate claim families of related compounds that are centered around a shared core structure, accompanied by alternative sub-stituents. However, the breadth of these claims frequently gives rise to patentability challenges before the European Patent Office (EPO). Such challenges may take the form of unity objections during the search process, clarity issues arising from nested definitions, novelty attacks based on overlapping generic disclosures, and challenges under the disclosure-based standards that govern amendments and priority. Utilizing a doctrinal approach that is firmly rooted in the EPO Guidelines and the case law of the Boards of Appeal, this article posits that these doctrines are unified by a singular interpretative anchor point, namely that which the skilled person derives directly and unambiguously from the patent application as filed. The analysis demonstrates the manner in which this anchor functions as a foundational element in the assessment of unity, the evaluation of novelty within the context of Markush claims, and the analysis of species-focused novelty, encompassing the utilization of multiple-selection “two-list” reasoning. Furthermore, it elucidates the rigorous approach to added matter and priority, particularly in the context of diminishing lists and selection inventions. The practical implications for the drafting and prosecution are discussed in this article.