But justices expressed doubt that merely isolating a portion of DNA from the body made something different from "products of nature," which are not eligible for patenting in the United States.
Chief Justice John G. Roberts Jr. said Myriad had simply "snipped" part of the gene sequence. It did not invent a product, but simply found a way to isolate part of the human DNA, he said.
Justice Sonia Sotomayor suggested that an isolated gene was "just nature sitting there" and none of the justices seemed to question that premise.
The case involves a lawsuit filed in 2009 against Myriad and the University of Utah by the American Civil Liberties Union and Public Patent Foundation, who sued on behalf of researchers, women's health advocates, medical groups and several cancer sufferers .
The suit challenged parts of patents granted Myriad 13 years ago on the two genes known as BRCA1 and BRCA2. It argued that, as products of nature, patents should not have been granted and that Myriad's lock on those two genes stifled development of new or alternative testing options.
Myriad, which licensed some of the disputed patents from the university, developed exclusive tests to detect mutations of the two genes that indicate a high probability of contracting breast or ovarian cancers. Such information is important in treating those cancers or even taking steps to try to prevent them.
At least three justices, Sotomayor, Stephen Breyer and Anthony Kennedy, asked about a middle ground suggested by the Obama administration. The government says the court could void parts of Myriad's patents strictly related to isolated genes, but believes that complementary DNA, or cDNA, could receive patent protection, Solicitor General Donald Verrilli Jr. told the justices.
Verrilli argued that cDNAinvolves manipulation in a laboratory outside the body that renders it substantially different than when it was in the body and, therefore, eligible for patenting.
"cDNA is a creation of the lab, it's an artificial creation," he said.
Four of Myriad's nine patent claims that are in dispute involve cDNA, and the company's attorney, Gregory A. Castanias, agreed that cDNA should be eligible for patents.
The company's cDNA "was created from hundreds of different patient samples," he said.
One area where ACLU attorney Christopher Hansen seemed to stumble was when justices pressed him on whether invalidating gene-related patents would mean companies and investors would be much less likely to pour money into research and development.
Hansen said that a company could get recognition for its work and that money for research would always be available, a statement that Kennedy said wasn't sufficient. "I don't think we can decide the case on, 'Don't worry about investment. It'll come,' " Kennedy said.
The court is expected to rule before the end of the summer.