In a unanimous decision, the United States Supreme Court addressed the issue of patent eligibility of diagnostic method claims (Mayo v. Prometheus). This decision could have a significant impact on the fields of personalized medicine and medical diagnostics since the claims at issue, directed to a blood-testing method for optimizing a particular therapy, were invalidated because they did not define patent-eligible subject matter.

In Mayo v. Prometheus, the claims recite methods physicians may use to determine if a patient's dose of a drug used in the treatment of autoimmune diseases is too low or too high. According to the Supreme Court, such claims encompass non-patentable "laws of nature, natural phenomena, and abstract ideas".

The Supreme Court did not completely shut the door on all claims involving laws of nature, but its decision certainly creates uncertainty for diagnostic method patent claims and for the personalized medicine industry. With the use of a relative terminology such as "nothing significant", "not sufficient" or "enough", the Court's decision is vague on what is now required for patent-eligibility of claims in this field. The Court did not want to decide whether the invalidated claims might be patent eligible if their steps were less conventional, but the opinion suggests that inclusion of novel and inventive additional features might have transformed the invalidated claims in a patentable application of the natural law. However, the Court confirmed that claims to novel compositions or methods of treatment will still be eligible to patent protection.