US Federal Circuit buries patents on diagnostic tests that rely on a naturally occurring principle

On 12 June 2015, the United States Court of Appeal for the Federal Circuit affirmed the Northern District of California’s finding that method claims for detecting cell-free fetal DNA (“cffDNA”) in maternal plasma or serum were invalid because they were not directed to patent eligible subject matter (Ariosa Diagnostics Inc v Sequenom Inc No 2014-1139, 2014-1144 (Fed Cir June 12 2015). This decision casts serious doubt over the patentability of diagnostic tests in the US that rely on a naturally occurring principle.


The inventors of the patent-in-suit (US6,258,540) discovered that the cell-free fractions (serum and plasma) of a pregnant woman’s blood contains surprisingly large amounts of cffDNA. Traditionally, this portion of the plasma or serum was discarded as medical waste. This groundbreaking discovery led to the development a non-invasive method to determine a number of fetal characteristics and abnormalities, such as Down Syndrome.

The court applied the Supreme Court’s two-step approach as laid out in Mayo Collaborative Services v Prometheus Laboratories Inc (2012) (Mayo). The court first found that the claims were directed to naturally occurring subject matter, namely cffDNA. In the second step, the court considered whether the additional elements of the claims, the methods of detecting cffDNA, were of sufficient inventive concept to “transform” the defined naturally occurring phenomenon into patent-eligible subject matter.

The court concluded that the relevant method steps (preparation and amplification of cffDNA sequences from plasma) were well understood, conventional and routine. Accordingly, the method of detecting cffDNA was not considered new and useful as specified in Section 101 of the US Patent Act, which defines patent eligible subject matter. On the contrary, the only subject matter considered new and useful at the date of the patent was the discovery of the presence of cffDNA in maternal plasma or serum, which does not represent patentable subject matter. The court therefore held that the practice of the method claims did not result in an inventive concept that transforms the natural phenomenon of cffDNA into a patentable invention.

Notably in a separate concurring judgement, Judge Linn stated that “it is hard to deny that Sequenom’s invention is truly meritorious” and that there is “no reason, in policy or statute, why this breakthrough invention should be deemed patent ineligible.” Judge Linn, however, felt the Court was bound by Mayo‘s sweeping language that left no room to distinguish the Sequenom patent from the Mayo decision.

This decision appears to confirm that the patentability in the US of a diagnostic test that uses a natural principle will depend on whether the application of the natural principle is itself novel and inventive.