Antibody-based serology tests and PCR tests for coronavirus are being approved at a breakneck pace by the U.S. Food and Drug Administration under newly relaxed guidelines. As recently as May 8th, the FDA issued an emergency approval for another serology test for coronavirus antibodies, an immunofluorescent sandwich assay necessarily developed in under six months. Scientists also just reported the identification of neutralizing antibodies that are unique to SARS-CoV-2, which may trigger a flood of new diagnostic tests. Diagnostic tests have proven difficult to patent under recent section 101 law, yet COVID-19 has spurred the search for reliable tests, and the recent decision in Illumina may provide a way forward for inventors and investors.

Following the Supreme Court’s decision in Mayo v. Prometheus, 132 S. Ct. 1289 (2012), the outlook for patenting of diagnostic tests appeared bleak. Indeed, the Federal Circuit recently noted that it has “consistently held diagnostic claims unpatentable as directed to ineligible subject matter” in every case since Mayo, until recently. Illumina v. Ariosa, No. 2019-1419, Slip Op. at *8 (Fed. Cir. Mar. 17, 2020). Yet patenting is still a foremost concern of diagnostic inventors and investors who seek exclusivity.

A Way Forward

In Illumina the Federal Circuit provided a way to patent aspects of diagnostic methods when it found preparation steps used in a diagnostic method to be patent eligible under 35 U.S.C. § 101. This was narrowly won, however, as Judge Reyna felt the claims were not patent eligible under Mayo. Challenges therefore remain for patenting diagnostic tests.

In Mayo, the U.S. Supreme Court held that a claimed process must do more than apply “well-understood, routine, conventional activity previously engaged in by researchers in the field” to a natural law. Mayo, 132 S. Ct. at 1294. This applies even to revolutionary breakthroughs, as the Supreme Court held in Myriad. Ass’n for Molecular Pathology v. Myriad, 133 S. Ct. 2107, 2117 (2013) (“Groundbreaking, innovative, or even brilliant discovery does not by itself satisfy the § 101 inquiry.”).

The unpatentable claims in Mayo were found to merely harness the newly discovered relationship between blood levels of a drug metabolite and the drug’s efficacy and toxicity for dosage adjustments. The Court found this to improperly preempt future use of the natural phenomenon for diagnoses.

At their heart, conventional antibody tests share the current legal infirmity of most diagnostics—harnessing a natural phenomenon (e.g., the body’s generation of antibodies against coronavirus) in conjunction with known methods for detecting those antibodies. For example, most coronavirus immunity tests detect the presence of SARS-CoV-2 antibodies in serum from an individual using conventional immunofluorescent assays or ELISAs (enzyme-linked immunosorbent assays). Although their application to SARS-CoV-2 is necessarily new, both assays use well-known methods for antibody detection. According to Mayo, more would be necessary for patent eligibility.

In contrast to Mayo, in Illumina the Federal Circuit upheld the patentability of a sample preparation method that is used in diagnosing. The claims in Illumina were directed to a process of fractionating fetal DNA in maternal blood by harnessing the newly discovered natural phenomenon that fetal DNA makes up a disproportionately large percentage of the short-chain nucleic acids in maternal blood.

The question posed to the Illumina panel was whether the claims were directed to the discovery of a natural phenomenon itself, or rather, eligible subject matter that exploits the discovery of the natural phenomenon. Slip Op. at* 8-9. In response, the panel held, “This is not a diagnostic case. And it is not a method of treatment case. It is a method of preparation case.” Id. at 8. They found the claimed method distinguishable from similar, patent-ineligible diagnostic methods in the prior Sequenom case—where the inventors “discovered that cell-free fetal DNA exists, and then obtained patent claims that covered only the knowledge that it exists and a method to see that it exists.” Id. at 11. The panel in Illumina found that the claimed method “change[d] the composition of the mixture,” producing something that does not occur naturally in maternal blood, and thus “conclude[d] that the claims are not directed to that natural phenomenon but rather to a patent-eligible method that utilizes it.” Id. at 9. The panel summarized its reasoning: “The inventors here patented methods of preparing a DNA fraction. The claimed methods utilize the natural phenomenon that the inventors discovered by employing physical process steps to selectively remove larger fragments of cell-free DNA and thus enrich a mixture in cell-free fetal DNA.” Id. at 15.

An Unconventional Solution

Illumina provides a narrow way forward for patenting diagnostic methods for antibody detection. Under Mayo, the use of unconventional steps in exploiting a natural phenomenon likely render an otherwise unpatentable claim, patent eligible. Now, under Illumina, the use of conventional steps may not automatically doom patent eligibility under section 101.

As the inventors in Illumina exploited a natural phenomenon to devise a unique technical solution to the problem at hand— obtaining cell-free fetal DNA from a sample mixed with cell-free maternal DNA—can the developers of tests for coronavirus do the same? As mentioned above, it is unlikely that claims to SARS-CoV-2 diagnostic tests that merely use known methods of antibody detection would survive a section 101 challenge, as there is nothing novel in detecting antibodies to any one antigen.

However, the Illumina decision may open up possibilities for the patenting of novel inventions that either fall within the “method of preparation” exception outlined in Illumina, or that create new “carve-outs” within the section 101 jurisprudence. Antibodies to SARS-CoV-2, for example, may possess some unique, yet-to-be-determined, physicochemical properties that make them more readily isolatable from patient blood samples before the conventional detection steps are applied. This might enhance the accuracy of the diagnostic, reducing the rate of false negatives. Exploiting any unique properties of SARS-CoV-2 antibodies in sample preparation would be akin to the novel preparation steps in Illumina that rendered the claims patent eligible. While this may result in narrower claims than were patentable before Mayo, it is better than the alternative of no patent protection at all. Until the Supreme Court revisits Mayo, inventors of antibody diagnostic tests must therefore take extra care to draft patent claims commensurate with the unconventional aspects of their invention.