As the readers of this blog are no doubt aware, patenting DNA defined only by a naturally occurring nucleotide sequence was banned by the U.S. Supreme Court in the landmark case of Association for Molecular Pathology v. Myriad Genetics, Inc. The patentee in that case attempted to patent “isolated” DNA with the natural sequence of the BRCA1 breast cancer gene. The Supreme Court believed this was an attempt to claim the natural gene itself, which it believed to be an ineligible “natural phenomenon.” Prior to this decision, newly discovered DNA sequences could be patented, so long as they were claimed to be “isolated” from their original host organism.
However, the Supreme Court opinion specifically left open the possibility that artificial methods of using natural DNA could still be patented; some of Myriad’s claims were for such methods, and their eligibility for patenting was unchallenged, and thus not directly consider by the court.
The Supreme Court in Myriad also did not consider whether properties of artificial DNA other than its sequence could distinguish it from a natural product. The patentee in Myriad had simply relied on the magic word “isolated” to draw a distinction between its invention and what is natural, and the Supreme Court was not enchanted.
Questions have lingered over to what extent artificial processes using DNA can be patented, and to what extent DNA with a natural sequence but other artificial properties can be patented. The U.S. Court of Appeals answered both questions in the October 9 decision in Roche Molecular Systems, Inc. v. Cepheid.
The invention in Cepheid arose from the discovery of unique genetic biomarkers found in the pathogenic bacterium Mycobacterium tuberculosis. M. tuberculosis is the causative agent of tuberculosis, one of the most devastating diseases. Roche patented, among other things, primer sets for polymerase chain reaction (PCR) that are complementary to the biomarker sequences, and the process of detecting the biomarkers through use of PCR.
In the past the Federal Circuit has considered other patents that claim PCR primers having natural sequences, and the process of performing PCR with them, concluding they are not patent eligible. However, this case is different: In this case the natural DNA sequence is found on a circular DNA chromosome. M. tuberculosis, like all bacteria, has a single circular chromosome, unlike eukaryotes, which have linear chromosomes. In contrast, PCR primers must be linear, or they cannot function to prime DNA polymerization during PCR.
Therefore, Roche argued that the patent claims were directed to DNA that is not identical to the natural DNA in the bacterium, and so it is not a “product of nature.” The Federal Circuit disagreed. It cited In re BRCA1- & BRCA2-Based Hereditary Cancer Test Patent Litig. for the proposition that an abbreviated segment of a longer piece of natural DNA is no different from the natural DNA. Roche pointed out that the BRCA1 & BRCA2 case involved natural DNA on a linear molecule, not natural DNA on a circular molecule, as in the case at bar. The Federal Circuit found this structural distinction to be of no importance, opining “the subject matter eligibility inquiry of primer claims hinges on comparing a claimed primer to its corresponding DNA segment on the chromosome—not the whole chromosome” (emphasis from original). This would seem to be somewhat at odds with the statement elsewhere in the opinion that the presence of a free 3’ hydroxyl group on the claimed PCR primer does not distinguish the primer from the natural DNA, as this is a chemical difference with the corresponding DNA segment. The Federal Circuit’s position could be interpreted to mean that the nucleotide sequence of the natural DNA segment is the only thing that matters, to the exclusion of any other chemical or physical property of the molecule, because courts have interpreted the nucleotide sequence to embody the “information” that is the critical function of DNA. This line of reasoning could logically be extended to ban patenting of artificial polynucleotides such as locked nucleic acid and morpholinos (although to date no court has so held). Alternatively, the decision could be read to mean eligibility requires a difference between the natural and artificial DNA that affects the functioning of the invention – in this case the circularity of the entire genome hosting the natural sequence was of no consequence to the functionality of the sequence as a PCR primer.
For the first time this decision considered whether artificial DNA with an identical sequence to what is natural, but a different higher order of structure, can be patented. This decision reaffirms that PCR performed with a primers complementing a previously unknown, but naturally occurring nucleic acid sequence, cannot be patented, regardless of whether something about the gross structure of the natural genome could have prevented its use as a primer. The reason for this conclusion seems to be that the higher level structure of the natural DNA does not affect the functioning of the claimed primer, by itself or as used in PCR. It is possible that other chemical differences between a natural DNA molecule and an artificial DNA molecule with the same sequence could still distinguish the artificial DNA from its natural counterpart.
The Roche patent in this case was drafted many years before the Supreme Court’s Myriad ban went into effect, during which time it was unquestionably patent eligible subject matter. This may be why Roche’s arguments have the definite sound of post-hoc rationalizations, because the patent was not drafted with the goal of satisfying the Myriad standard. Those present patent applicants, with the luxury of being forewarned, should consider this case a lesson. Reliance on the differences in the gross structure of the chromosome in which a natural sequence is found and the claimed DNA may be misplaced. Instead, seek to rely on differences in the primary structure (nucleotide sequence), conjugation between natural nucleic acids (DNA and RNA) with synthetic moieties (such as fluorophores, etc.), or chemical differences in the nucleotides themselves (such as LNA or triplex molecules). Last but not least, remember that the Myriad ban is not the law in most major jurisdictions outside of the United States, and consider such foreign markets when planning your patenting strategy.