Weil Gotshal partner Edward Reines. Photo: Jason Doiy/ALM

Medical diagnostics patents aren't dead yet. At least, not all of them.

Last year, the U.S. Court of Appeals for the Federal Circuit and the solicitor general called on the Supreme Court to reconsider the application of Section 101 of the Patent Act to medical diagnostics. "Since Mayo, we have held every single diagnostic claim in every case before us ineligible," Judge Kimberly Moore of the U.S. Court of Appeals for the Federal Circuit wrote for herself and three other judges in Athena Diagnostics v. Mayo Collaborative. "The bottom line for diagnostics patents is problematic," Judge Todd Hughes of the U.S. Court of Appeals for the Federal Circuit wrote for himself and two others.

Of course, the Supreme Court declined to take up the case last month, and the outlook for diagnostics patents has remained dim.

But on Monday, Brisbane, California-based CareDx Inc. took a big step toward getting judicial approval of its patented AlloSure technology for assessing organ transplant rejections via a blood test. U.S. Magistrate Judge Christopher Burke of the District of Delaware recommended that two patents developed at Stanford University and licensed to CareDx be ruled eligible for patenting.

"We're delighted that the Stanford patents were upheld on Section 101 grounds given the current state of the law," said Weil, Gotshal & Manges partner Ed Reines, who represents CareDx and Stanford.

CareDx and sued San Carlos, California-based Natera Inc. and Lee's Summit, Missouri-based Eurofins Viracor Inc. last year. Natera, represented by Quinn Emanuel Urquhart & Sullivan, and Viracor, represented by Goodwin Procter, moved to dismiss. Natera argued last summer that the patents "rest entirely on observing natural phenomena inherent to organ transplants: the presence of an organ donor's nucleic acids (such as DNA) in the transplant recipient's circulation (such as blood), and a correlation of that presence to rejection of the transplanted organ by the recipient's body."

To Burke, what tipped the balance was language in the patent claim specification "repeatedly and consistently" saying that that correlation had already been well-known for a long time. "Thus, the patent explains, scientists had for years been attempting to find ways to test for and detect the presence of such donor-specific cfDNA," Burke wrote in an 11-page order.

What was invented was "a genetic fingerprint" of the organ donor that would show up in the recipient's blood if the organ were being rejected. Specifically, that would be "the use of digital PCR/high-throughput sequencing/multiplex sequencing, at certain levels of sensitivity, to identify homozygous or heterozygous [single nucleotide polymorphisms] in the blood of the transplant recipient," Burke wrote.

"It is these purportedly new, unconventional combination of steps that the claims are directed to, not the natural law itself," Burke concluded. He even threw in a cf citation to the Federal Circuit's Athena opinion for good measure.

It will now be up to U.S. District Judge Colm Connolly of the District of Delaware whether to adopt Burke's recommendation.