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In an attempt to broaden a patent’s disclosure and provide Section 112 support for features that are not explicitly disclosed within the patent’s specification (such as reagents, assays, techniques, etc.), patent applications are often drafted with boilerplate language to indicate that other “conventional,” “well-known” or “routine” features may be used. But acknowledging that features of a claimed invention are conventional, well-known or routine can be detrimental to patentability. Take the Federal Circuit’s recent decision in CareDx, Inc. v. Natera, Inc., for example, in which the court held that methods for detecting organ transplant rejection were directed to “a natural law together with conventional steps to detect or quantify the manifestation of that law.” (CareDx, Inc. v. Natera, Inc., No. 2022-1027, 2022 WL 2793597, at *8 (Fed. Cir. July 18, 2022).)

The patents at issue in CareDx are said to provide “non-invasive methods of monitoring organ transplant patients for rejection that are sensitive, rapid and inexpensive.” (’652 patent at col. 1, lines 23-25.)[1] The claimed methods involve the analysis of differences (i.e., polymorphisms) in cell-free nucleic acids between the organ donor and the organ recipient. According to the patents, “the relative amount of donor-specific sequences in circulating [cell-free DNA or RNA] should provide a predictive measure of on-coming organ failure in transplant patients for many types of solid organ transplantation including, but not limited to, heart, lung, liver, and kidney.” (Id. at col. 7, lines 41-46.) Claim 1 of the ’652 patent, for example, recites:

1. A method for detecting transplant rejection, graft dysfunction, or organ failure, the method comprising:

(a) providing a sample comprising cell-free nucleic acids from a subject who has received a transplant from a donor;

(b) obtaining a genotype of donor-specific polymorphisms or a genotype of subject-specific polymorphisms, or obtaining both a genotype of donor-specific polymorphisms and subject-specific polymorphisms, to establish a polymorphism profile for detecting donor cell-free nucleic acids, wherein at least one single nucleotide polymorphism (SNP) is homozygous for the subject if the genotype comprises subject-specific polymorphisms comprising SNPs;

(c) multiplex sequencing of the cell-free nucleic acids in the sample followed by analysis of the sequencing results using the polymorphism profile to detect donor cell-free nucleic acids and subject cell-free nucleic acids; and

(d) diagnosing, predicting, or monitoring a transplant status or outcome of the subject who has received the transplant by determining a quantity of the donor cell-free nucleic acids based on the detection of the donor cell-free nucleic acids and subject cell-free nucleic acids by the multiplexed sequencing, wherein an increase in the quantity of the donor cell-free nucleic acids over time is indicative of transplant rejection, graft dysfunction or organ failure, and wherein sensitivity of the method is greater than 56% compared to sensitivity of current surveillance methods for cardiac allograft vasculopathy (CAV).

CareDx, the exclusive licensee of the ’652, ’497 and ’607 patents, sued Natera and Eurofins Viracor, Inc., (Eurofins) for patent infringement. (CareDx, Inc., No. 2022-1027, 2022 WL 2793597, at *3.)  Natera and Eurofins filed motions for summary judgment for subject matter ineligibility under Section 101. The district court granted Natera’s and Eurofins’ motions, finding that “the asserted claims were directed to the detection of natural phenomena, specifically, the presence of donor cfDNA in a transplant recipient and the correlation between donor cfDNA and transplant rejection” (CareDx, Inc., No. 2022-1027, at *4), and that “based on the specification’s numerous admissions, the claims recited only conventional techniques.” (Id.)

On appeal, CareDx argued that the claimed methods are not directed to “the discovery of a natural correlation between organ rejection and the donor’s cfDNA levels in the recipient’s blood” (id. at *5), but rather to improved measurement methods that are superior to the inadequate prior art measurement techniques. (Id.) CareDx asserted that “using digital PCR and next-generation sequencing to identify and measure donor-specific SNPs was an inventive breakthrough and that the patents claim this specific and useful application.” (Id.)

The Federal Circuit, however, did not agree and affirmed the district court’s subject matter ineligibility ruling as it found that the patents “are directed to a natural law together with conventional steps to detect or quantify the manifestation of that law.” (Id. at *8.) According to the Federal Circuit, the methods of the ’652, ’497 and ’607 patents each have the following four steps for detecting a donor’s cell-free nucleic acids from a transplant recipient’s biological sample:

  1. “Obtaining” or “providing” a “sample” from the recipient that contains cfDNA;
  2. “Genotyping” the transplant donor and/or recipient to develop “polymorphism” or “SNP” “profiles”;
  3. “Sequencing” the cfDNA from the sample using “multiplex” or “high-throughput” sequencing or performing “digital PCR”; and
  4. “Determining” or “quantifying” the amount of donor cfDNA.

(Id. at *3.)

Under step one of the Alice/Mayo inquiry, the Federal Circuit found that the claimed methods are not directed to a method of preparation or a new measurement technique, but rather to natural phenomena. (Id. at *5-7.) According to the court, “the claims boil down to collecting a bodily sample, analyzing the cfDNA using conventional techniques, including PCR, identifying naturally occurring DNA from the donor organ, and then using the natural correlation between heightened cfDNA levels and transplant health to identify a potential rejection, none of which was inventive.” (Id. at *6.) The Federal Circuit was not convinced by CareDx’s arguments that the claims were directed to improved laboratory techniques because the claims “merely recite the conventional use of existing techniques to detect naturally occurring cfDNA.” (Id. at *6.) The court stated that “the written description is replete with characterizations of the claimed techniques in terms that confirm their conventionality” (id. at *5), such as the following passage from the specification:

The practice of the present invention employs, unless otherwise indicated, conventional techniques of immunology, biochemistry, chemistry, molecular biology, microbiology, cell biology, genomics, and recombinant DNA, which are well within the skill of art.


Regarding step two of the Alice/Mayo inquiry, the Federal Circuit agreed with the district court that the claims “add nothing inventive because they merely recite standard, well-known techniques in a logical combination to detect natural phenomena.” (Id. at *7.) In reaching its conclusion, the Federal Circuit again focused on the admissions within the patents that the methods use conventional techniques and commercially available technology:

The specification admits that each step in the purported invention requires only conventional techniques and commercially available technology: (1) collecting the patient’s sample using “any technique known in the art,”  ’652 patent at col. 10 l. 11; (2) genotyping the donor and recipient to create SNP profiles using “any suitable method known in the art,” id. at col. 20 ll. 31–33; (3) sequencing the cfDNA using “well known” techniques and off-the-shelf tools, id. at col. 15 ll. 6–8, col. 15 ll. 22–67; and (4) quantifying the donor cfDNA using methods “known in the art,” id. col. 18 l. 55–col. 19 l. 2.

(Id.) According to the court, “[t]here is no genuine dispute that the claimed techniques add nothing inventive to the natural phenomenon being detected.” (Id.) The Federal Circuit therefore affirmed the district court’s ruling that the claims are ineligible under Section 101.

Patent applicants are cautioned against the use of language that characterizes parts of the invention as conventional, well-known or routine. As evidenced by the CareDx decision, such language can be detrimental to patentability, especially when subject matter eligibility is at issue. The Federal Circuit has made clear that “applying standard techniques in a standard way to observe natural phenomena does not provide an inventive concept.” (Id.)

[1] The patents at issue in CareDx were U.S. Patent No. 8,703,652 (the ’652 patent), U.S. Patent No. 9,845,497 (the ’497 patent) and U.S. Patent No. 10,329,607 (the ’607 patent), which all share a common specification.