A cancer startup that wants to build a blood test to screen for cancer is seeking to raise at least $1 billion.

Grail was created in January 2016 by gene-sequencing giant Illumina, funded by a group of Silicon Valley investors including Jeff Bezos, Bill Gates, and Google Ventures, raising $100 million at the time.

Now, it’s looking for at least $1 billion for its Series B round. The company said in a release that it’s “received indications of interest to invest.” The news comes ahead of a major healthcare investor conference in San Francisco.

“This raise, when completed, will provide Grail the resources to develop its first products and embark on the large-scale trials required to demonstrate the stringent performance requirements of a cancer screening test,” Grail chairman Jay Flatley said in a statement Thursday.

The idea behind a cancer-screening test is to identify the tiny bits of cancer DNA that are hanging out in our blood but currently undetectable. If Grail is successful, it’ll be the first to pull off a cancer-detecting blood test that works proactively. The concept is similar to liquid biopsy tests, which use blood samples to sequences genetic information in that blood to figure out how tumors are responding to a certain cancer therapy.

With one simple blood draw, Grail's plan is to sequence and screen for those bits with the hope that it will help catch cancer before it starts to be a full-blown problem.

But getting a test that will be accurate will take a lot of time and require huge clinical trials. Fast Company reported one trial that will take place in the United Kingdom with as many as 500,000 people. Another trial, called the Circulating Cell-free Genome Atlas study, launched in December 2016.