A Cancer Blood Test That Screens for 50 Types Just Cleared Its Biggest Hurdle Yet

Keypoints:

• GRAIL shares surged roughly 34% on September 21 after FDA staff raised no major concerns about its Galleri test
• Galleri screens for more than 50 cancer types from a single blood draw
• An FDA advisory committee formally reviews the test on September 23
• Samsung, an investor in GRAIL, has already booked tens of millions in unrealized gains
• A final FDA decision is expected in the first half of 2027

GRAIL shares jumped roughly 34% on September 21, closing at $107.97, after FDA staff reviewers released briefing documents showing no major concerns about the accuracy or safety of Galleri, the company's multi-cancer early detection blood test. 

It was the stock's largest single-day gain in more than a year. The documents come ahead of a September 23 meeting where an outside advisory panel, the Molecular and Clinical Genetics Panel, formally reviews the test's premarket approval application.

Galleri works by detecting cancer-specific methylation patterns in cell-free DNA circulating in a patient's blood, designed for adults 50 and older and covering more than 50 cancer types from one draw, including several, like pancreatic and ovarian cancer, that currently have no routine screening test at all. 

The test simply returns a positive or negative signal rather than pinpointing a specific diagnosis on its own, and the FDA's briefing documents noted it has no outstanding questions on analytical performance, study design, or the primary safety analyses.

The FDA's tone matters here beyond the stock reaction. Analysts at Mizuho described the agency's questions as focused on regulatory safeguards rather than outright rejection, a distinction that shifted investor attention away from GRAIL's ongoing cash burn and toward a realistic path to approval and insurance reimbursement, even as the stock's price-to-sales ratio of roughly 26 sits far above its three-year historical median near 10, a sign of just how much future growth is already priced in. 

Samsung Electronics and Samsung C&T, which invested $110 million in GRAIL back in June, have already booked an unrealized gain of roughly $59.5 million in three months, and Samsung C&T is separately pursuing exclusive commercialization rights for Galleri in South Korea.

If cleared, Galleri would become the first product of its kind available in the US, though the advisory panel will still weigh in on how the test's "early detection" claim should actually be labeled before any final decision, expected sometime in the first half of 2027.