Doctors have been diagnosing patients for centuries. So you might suspect this work can't be patented. After all, physicians base their diagnoses on natural phenomena, which are unpatentable under longstanding Supreme Court precedents.
More and more often, however, physicians are using technology to help make their diagnoses. This technology is patentable.
Tale of Two Patents
Prometheus arises from two patents on methods of using thiopurine drugs to treat autoimmune diseases. These drugs need to be administered carefully; too low a dose is ineffective, while too high a dose is toxic.
The Federal Circuit saw things differently. It held, in 2009, that the claimed methods were patentable subject matter.
Law of the Land
This issue isn't settled yet. "Mayo intends to file a petition for certiorari," says Jonathan Singer, a Fish & Richardson principal who is representing Mayo in this litigation. "For Mayo, the case is important for the principle for which it will ultimately stand: whether doctors can freely use natural relationships in the treatment of their patients. It's widely perceived as a biotech case of national importance. It's been up to the Supreme Court once before, and they have certainly shown a real interest in this issue."