The impact of patent eligibility on biotech patents: A flow chart for determining patent eligibility and an immune therapy case study.

US common law recites a natural law, natural phenomenon or abstract idea as exceptions to the 4 statutory patentable categories to guard against the wholesale preemption of fundamental principles. The very recent evolutions of patent exceptions in the US may increase the difficulty of patenting and may create uncertainty in determining patent eligibility. To solve the thorny problem of eligibility, this study presents a flow chart based on the courts' decisions that can serve as a set of guidelines for determining patent eligibility. A case related to prostate cancer immune therapy is presented for discussion.