Cancer-testing company Myriad Genetics is back in the courts again. In a long-running piece of litigation, the US Supreme Court today agreed to hear arguments about the validity of Myriad’s patents covering isolated DNA of the genes BRCA1 and BRCA2.

Women can have these two genes sequenced to learn whether they carry mutations that raise their risk of breast and ovarian cancer. In the United States, access to the tests is controlled by Myriad. (In other countries, non-affiliated laboratories can test these genes as well.)

The lawsuit began in 2009 but has been considered several times this year (see ‘The great gene-patent debate’). In March, a federal appeals court ruled to uphold Myriad’s patents. Subsequently, the Supreme Court directed the appeals court to reconsider its decision in light of another patent case over medical diagnostics. In August, the appeals court again ruled that the patents were valid. After that, the Public Patent Foundation and American Civil Liberties Union petitioned the Supreme Court to reconsider aspects of the ruling.

Today, the Court decided to take up only one of the three questions it was asked to consider — whether human genes are patentable. Its decision should come sometime next year.

“It will be very useful to get a definitive ruling on some of the issues at stake,” says Hank Greely, a law professor at Stanford University in California, who focuses on biotechnology. However, even if the Court invalidates the patents, effects on other companies will depend on the Court’s reasons for doing so, he says. And Myriad is an unusual case. “Few if any companies will build their businesses around the kind of highly controlled monopoly that Myriad has sought to assert,” says Greely.

In the end, even Myriad may not be particularly affected. With its patents running out, more of Myriad’s competitive advantage is coming from another quarter — the company has been collecting data about BRCA mutations from many women for years and using that to create more accurate diagnoses. As many clinical geneticists work to find ways to share data, Myriad’s valuable, proprietary database has created an outcry (see ‘Myriad turns cancer genetic data into trade secrets‘).

The two questions that the Court did not take up address whether the court of appeals correctly considered two other controversial cases within biotech community: Mayo v. Prometheus and MedImmune v. Genentech. The former ruled that a blood test to determine appropriate drug dose was unpatentable because it stated a law of nature; the latter that a licensee could challenge the validity of a an issuer’s patent without breaking the contract. The result for Myriad is, according to the Genomics Law Report, that “the bulk of Myriad’s challenged diagnostic method patents are invalid.” That makes consideration of whether isolated DNA is patentable subject matter that much more important to Myriad.

In a statement, the Public Patent Foundation said the patents restrict access to testing. In its own statement, Myriad chief executive Peter Meldrum said that his company had devoted more than 17 years and US$500 million to developing its tests and that patents are required to drive innovation. It also stated that its prices were not overpriced and estimated that 95% of women had access to the tests through private insurance or public assistance programmes.