In a decision with important implications for the evolving field of personalized medicine, a unanimous U.S. Supreme Court on Tuesday invalidated two patents on a diagnostic test used in connection with the treatment of autoimmune diseases.

Mayo Collaborative Services v. Prometheus Laboratories Inc. pitted doctors and researchers against biotechnology and pharmaceutical companies in the ongoing debate over what is patentable subject matter.

The high court case stemmed from a patent infringement suit brought by Prometheus, the holder of patents on a diagnostic process for determining how thiopurine drugs are metabolized within the body when administered at varying dosages. Because patients metabolized the drugs differently, doctors had difficulty determining whether a particular patient’s dosage was too high or too low.

Mayo had bought and used diagnostic tests based on Prometheus’ patents, but in 2004, Mayo announced it would sell and market its own, somewhat different test. Prometheus sued, alleging patent infringement. A federal district court granted summary judgment to Mayo, ruling that the processes claimed by the patents were based on natural laws or natural phenomena and thus were not patentable. The U.S. Court of Appeals for the Federal Circuit reversed, and the Supreme Court, in Tuesday’s opinion by Justice Stephen Breyer, reversed the Federal Circuit.

Breyer said the Court has long held that laws of nature, natural phenomena and abstract ideas are not patentable because they are the basic tools of scientific and technological work. Patents on those tools, he wrote, could do more to impede innovation than to promote it. But too broad an interpretation of those exclusions, he added, could eviscerate patent law.

“The case before us lies at the intersection of these basic principles,” Breyer wrote. The Court’s precedents require that a process focused on the use of a natural law must contain other elements or a combination of elements — an “inventive concept” — to ensure that the patent amounts to more than a patent on the natural law itself.

“We find that process claims at issue here do not satisfy these conditions,” he wrote. “In particular, the steps in the claimed processes (apart from the natural laws themselves) involve well-understood, routine, conventional activity previously engaged in by researchers in the field. At the same time, upholding the patents would risk disproportionately tying up the use of the underlying natural laws, inhibiting their use in the making of further discoveries.”

The decision is “good news and bad news for the personalized-medicine industry,” said Edward Reines, a partner in Weil, Gotshal & Manges’ technology litigation practice. “It doesn’t provide clarity as to what is acceptable but it also doesn’t provide a mandate to lower courts which would wipe out all personalized medicine.”

Reines, who filed an amicus brief on behalf of several personalized-medicine companies, added, “We’re at the dawn of personalized medicine where diagnosis and therapy will be based on your personal genomic profile. The question is how much innovation we can have in this area.”

Gerald Flattmann, an intellectual property partner at Paul Hastings, said the decision should not have any major negative effect on patentees, and, in particular, on innovation in the field of personalized medicine. The justices simply decided, he said, that the process steps in the patent claims did not add enough to the laws of nature involved to make the claims patentable.

“One danger, however, will be that courts misapply the decision as broadly requiring the invalidation of any claim that recites a law of nature as one of its steps,” he said. “Such misapplication would have a profound negative impact on innovation in the field of personalized medicine and beyond since, of course, all invention is on some level based on the practical application of natural discoveries.”

The decision, however, is significant and will have “far reaching” consequences far beyond the life sciences, Reines said. “This case will be cited on patentable subject matter whether it’s software or business methods or life sciences.”

Prometheus Laboratories issued a statement: “We believe that strong patent protection is important to encourage the investment of energy and resources to develop life saving diagnostic tests and treatment protocols. Without the availability of patent protection, future healthcare will suffer as companies may opt out of new research and development. This decision will, in our view, encourage imitation, not innovation.”

Mayo’s high court counsel was Stephen Shapiro of Mayer Brown. Prometheus was represented by Richard Bress of Latham & Watkins.

Marcia Coyle can be contacted at mcoyle@alm.com.