The Federal Circuit ruled Wednesday that three Myriad Genetics Inc. breast cancer test patents are invalid for claiming patent-ineligible subject matter, another major setback for the company after the U.S. Supreme Court ruled last year that it could not patent human genes.

In a win for Ambry Genetics Corp., which makes rival breast cancer tests that Myriad accused of infringement, the appeals court ruled that Myriad’s patents on single-stranded synthetic DNA molecules known as primers used in its tests are not any different from the isolated genes that the high court ruled could not be patented.

The court said that for the purposes of patent-eligibility, it makes no difference that the primers are created synthetically, since they are structurally identical to the ends of DNA strands found in nature.

The court also invalidated Myriad’s patents on methods of detecting mutations in the BRCA1 and BRCA2 genes associated with an increased risk of breast and ovarian cancer. The patents involve ways of comparing a patient’s genes with non-cancerous genes, which the court said is nothing more than an abstract idea that cannot be patented.

“Similar concerns to the ones the Supreme Court expressed in Myriad with respect to isolated DNA exist here: allowing a patent on the comparison step could impede a great swath of research relating to the BRCA genes, and it is antithetical to the patent laws to allow these basic building blocks of scientific research to be monopolized,” the court ruled.