This is the fourth part of a four-partite article discussing the US Federal Circuit decision in AMP v. USPTO , also known as the ACLU /Myriad "gene patenting" case ("Myriad"). Part I commenced with a description of the legal framework and an explanation of how the decision relates to the recently invigorated U.S. debate on patent eligibility, referring inter alia to the 2010 U.S. Supreme Court decision in Bilski v. Kappos and the pending certiorari in Prometheus v. Mayo (1). Before this background, Part I recited the complex procedural history of AMP v. USPTO (2) and summarized the underpinnings of the outcome, i.e. the three different opinions of the Federal Circuit judges Lourie, Moore & Bryson who comprised the panel (3). Part II continued the tale with a detailed analysis of the decision's practical implications (4), which is followed by a closer look on the chances for an ultimate Supreme Court review (5). Why a potential Supreme Court review of AMP v. USPTO would indeed be a much welcomed and necessary development was analyzed in Part III. This part elaborated on the myriad of unsolved questions raised by both AMP v. USPTO and a bulk of subsequent case law addressing the patent-eligibility of biological correlations and software-related "inventions" (6). These subsequent decisions indicate a serious split at the Federal Circuit with potentially broad implications not only for the patent eligibility of software-related patent applications and so-called "Beauregard"- claims, but also for biotech-claims directed to personalized medicine, biological correlations and compounds containing biological information. Part IV, which is to be published in issue 4, finally offers a broader discussion of the recent US patent-eligibility developments from an innovation policy perspective including brief references to recent European developments (7). This provides the basis for summarizing conclusions (8). This final part, which was completed, reviewed and accepted for publication in February 2012, also incorporates new developments that can be expected in the coming months, such as the pending certiorari decision in AMP v. USPTO and the pending Supreme Court decision in Prometheus v. Mayo.