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CareDx, Stanford Sue TAI Diagnostics for Patent Infringement

NEW YORK – CareDx and Stanford University on Wednesday filed a patent infringement lawsuit against TAI Diagnostics in the United States District Court for the District of Delaware, alleging that TAI's heart transplant rejection test MyTAIHeart infringes on a patent owned by Stanford and exclusively licensed to CareDx covering a method for the non-invasive diagnosis of transplant rejection.

The claims of US Patent No. 10,494,669, entitled "Non-Invasive Diagnosis of Graft Rejection in Organ Transplant Patients," are directed to a method of detecting donor-specific cell-free nucleic acids "that improves upon prior art methods, and are not directed to a natural law or natural phenomenon," CareDx's brief noted. The company also referred to a previously rendered magistrate judge's opinion on two other patents it licenses from Stanford — Patent Nos. 9,845,497 and 8,703,652 — which it said share a common specification with the '669 patent. CareDx added that the judge's opinion should apply with equal force to the claims of the '669 patent.

CareDx and Stanford are currently suing Natera for infringing on the '497 and '652 patents.

In January TAI's cofounders Michael Mitchell and Aoy Tomita-Mitchell led a team that published a research article in PLOS One describing a clinical validation study conducted by TAI and researchers at the Medical College of Wisconsin. The researchers used MyTAIHeart to quantify changes in the cell-free DNA donor fraction of blood plasma samples, and they showed that the test had a nearly 100 percent negative predictive value for heart transplant rejection.

MyTAIHeart takes a baseline signature of 94 SNPs in genomic DNA. It can then detect and quantify donor DNA in the transplant recipient's blood and calculate a donor fraction. These cell-free DNA levels serve as a biomarker of viability, with rising donor fraction indicating a potential for transplant rejection.

In its suit, CareDx pointed to this PLOS One paper and a subsequent press release from the company describing the test's methodology, as evidence that MyTAIHeart infringes on the '669 because it requires that blood samples be collected from a heart transplant recipient and used to develop a SNP profile of the donor and the recipient that focuses on 94 SNPs, and that the fraction of donor derived DNA in the recipient is determined based on this information.

The company compared those claims to certain claims in the patent, which involve genotyping a heart transplant donor to obtain a SNP profile, genotyping a heart transplant recipient to obtain a SNP profile, and performing PCR analysis on circulating cell-free DNA obtained from biological samples from the heart transplant recipient to amplify at least 10 different DNA targets and quantifying an amount of heart transplant-derived circulating cell-free DNA from the transplant using markers distinguishable between the transplant recipient and the donor.

The plaintiffs believe they are entitled to past damages for TAI's alleged infringement and have asked the court for a jury trial. They've also asked for a judgment that TAI has infringed the '669 patent and that the '669 patent is valid, as well as for damages or other monetary relief, including an order enjoining TAI from further infringement of the '669 patent, and attorneys' fees.

In an email to GenomeWeb, CareDx attorney Edward Reines of the firm Weil, Gotshal, & Manges said that the company filed the suit "to protect its intellectual property investment and market-leading products, as it has consistently done in the past."

TAI CEO Frank Langley responded to the suit by calling it "without merit" in an email to GenomeWeb, adding, "This action is consistent with CareDx's practice of attempting to stifle innovation in the transplant market by using litigation rather than engage in commercial competition."

He said TAI will issue a more detailed response to the suit in the near future.