Myriad Genetics lost its U.S. Supreme Court fight over the patentability of human genes. But the battle over Myriad’s patents is far from over.

On Oct. 10 Quest Diagnostics sued Myriad in federal court in Santa Ana, Calif., seeking a declaratory judgment that Quest’s test for cancer detecting genes doesn’t infringe Myriad’s patents for the BRCA1 and BRCA2 genes, which are related to breast and ovarian cancer. Quest’s case is at least the second of its kind filed against Myriad since September, and it comes after Myriad filed complaints in July accusing two competitors — Ambry Genetics and Gene by Gene — of infringing its patents.

The Supreme Court ruled in June that isolated human genes are products of nature and thus not patent-eligible. That ruling against Myriad appeared to clear a path for competitors to offer tests for the BRCA1 and BRCA2 genes, and a handful of companies quickly announced they would be launching such tests.

But Myriad immediately took action to protect other, related patents. In its suits against Ambry and Gene by Gene, the company argued that it still has 500 valid and enforceable claims in 24 patents underlying its BRCA tests. Both Ambry and Gene by Gene countersued in August, claiming that Myriad’s patents don’t pass muster.

Now Quest, represented by Robins, Kaplan, Miller & Ciresi, has joined the attack. Myriad’s conduct has deterred other competitors from entering the BRCA1 and BRCA2 testing market, according to Quest’s complaint. Pathway Genomics, for example, announced after the Supreme Court ruling that it planned to offer testing for the genes. But after Myriad sued Ambry and Gene by Gene, Pathway said it would delay the launch of those tests, Quest alleges.

Quest, one of the world’s largest providers of diagnostic information services and cancer diagnostics, wants a ruling that 14 of Myriad’s patents are invalid and not infringed by a two-part test that Quest intends to launch. That test, which Quest claims was developed after years of research and development and cost millions of dollars, detects hereditary alterations in the BRCA1 and BRCA2 genes.

“Myriad’s aggressive conduct has deterred other competitors from entering the BRCA1/BRCA2 genetic testing market for fear of being sued,” Quest counsel David Martinez of Robins Kaplan wrote in the complaint. (Martinez declined to comment.)

In yet another suit, Counsyl Inc., a company best known for low-cost prenatal genetic testing, is seeking to preempt Myriad claiming infringement. Counsyl tapped Daralyn Durie and Mark Lemley of Durie Tangri to sue Myriad for declaratory judgment last month in U.S. district court in San Francisco, claiming that “Myriad has asserted that any company that makes, sells, or offers to sell genetic tests and related services using the BRCA 1 and/or BRCA2 genes . . . faces the risk of suit for infringement.”

Lemley said he could not comment on the pending case.

Joshua Sarnoff, a professor of patent law at DePaul University’s College of Law, said the Supreme Court’s Myriad ruling was good news for doctors and patients. It did, however, leave uncertainty, he said. Myriad is now asserting patents and claims that were not challenged in the original suit. The Supreme Court ruling, Sarnoff said, was not entirely clear on all issues related to genetic material, so Myriad will probably assert its other patents unless and until it is told that they, too, are invalid.

“The bottom line is, we won’t really know what is patent-eligible until these issues make their way back to the Supreme Court,” Sarnoff said.