A split panel of the US Court of Appeals for the Federal Circuit held on February 6 that claims to an assay for diagnosing myasthenia gravis are not patent eligible because they are directed to a natural law. The majority decision in Athena Diagnostics v. Mayo Collaborative Services is in line with a series of decisions by the Federal Circuit in which diagnostic method claims were found to be not patent eligible.

Athena is the exclusive licensee of US Patent No. 7,267,820, which is based upon the discovery that autoantibodies to the MuSK protein cause myasthenia gravis. The ’820 patent claims methods for diagnosing myasthenia gravis by detecting MuSK autoantibodies. Claim 9 of the ’820 patent describes a specific test for MuSK autoantibodies using a radioimmunoassay, and was the most specific claim considered by the court. According to claim 9, MuSK is radioactively labeled with Iodine-125, a radioactive isotope of Iodine, and then contacted with a bodily fluid. If the bodily fluid contains MuSK autoantibodies, the autoantibodies and Iodine-125-labeled protein will form immune complexes. The immune complexes are collected and then monitored for the presence of the radioactive label, which indicates a diagnosis of myasthenia gravis.

Patent eligibility is analyzed under a two-step test set forth by the US Supreme Court in Mayo and Alice. The first step is to determine whether the claims are directed to a natural law, abstract idea, or other patent-ineligible subject matter. The second step asks whether the claims contain an inventive concept that transforms the claims into a patent-eligible application of the underlying ineligible subject matter.

The majority opinion authored by Judge Alan Lourie focused on claim 9 as it was the most specific one at issue. In the first step, the majority identified “the correlation between the presence of naturally-occurring MuSK autoantibodies in bodily fluid and MuSK related neurological diseases like [myasthenia gravis]” as a natural law because it “exists in nature apart from any human action.” The majority determined that the claims are “directed to a natural law because the claimed advance was only in the discovery of a natural law, and that the additional recited steps only apply conventional techniques to detect that natural law.” In the second step, the majority recognized that the additional steps did not represent “an inventive application beyond the discovery of the natural law itself” because the patent itself described the detection steps as standard techniques in the art.

Judge Pauline Newman dissented. In her view, the majority’s analysis of patent-eligibility was incorrect because the court should have considered the claims as a whole, including all their elements and limitations. Judge Newman concluded that viewed as such, the claims are for a novel multistep method of diagnosis, not a law of nature. In Judge Newman’s opinion, it was incorrect for the majority to separate the claim steps according to whether they are performed using conventional techniques, and then to ignore the presence of the conventional steps in the analysis. Section 101 does not turn on whether any claim steps are “standard techniques,” according to Judge Newman. “The appropriate analysis of the role of conventional steps in claims to a new method is under Sections 102 and 103, not Section 101.”

The split decision in Athena reflects competing views on the application of the Mayo test to diagnostic method claims, but the outcome of the case is patent ineligibility in yet another diagnostic method case.