FDA Staff See No Major Safety Issues With Grail's Galleri
FDA reviewers identified no major safety or accuracy concerns with Grail's Galleri multi-cancer early detection blood test.
FDA staff members have raised no major safety or accuracy concerns about Grail's Galleri multi-cancer early detection blood test in documents prepared for an upcoming advisory committee meeting. The prescription test is intended to screen adults aged 50 and older for early signs of multiple cancer types through a single blood sample.
In a briefing document released ahead of the meeting, agency staff noted that most cancer deaths in the U.S. Come from cancer types lacking guideline-recommended screening programs. "Blood-based multicancer detection tests offer the potential to detect multiple types of cancer through a single blood draw," they wrote. They stated that tests like Galleri could help address an unmet need by finding cancers that would otherwise go undetected, while also cautioning that risks from false positive and false negative results must be carefully considered.
Review Focus and Trial Data
The FDA's neutral review focused on performance and safety data from two studies: the PATHFINDER 2 trial and the first year of the NHS-Galleri trial. PATHFINDER 2 evaluated the safety of diagnostic workups triggered by a Galleri result and assessed test performance in screening-eligible individuals. The NHS-Galleri study is a prospective, randomized controlled trial in the U.K. Involving participants aged 50-77 with no signs of cancer, designed to assess the test's performance in population screening.
Notably, the FDA briefing did not address a key outcome from the NHS-Galleri study presented in May. That data showed the trial failed to meet its primary goal of reducing late-stage (III or IV) cancers across a dozen tumor types with no existing screening tests, though it did detect more early-stage (I and II) cancers.
Reported Test Performance Metrics
The briefing document presented specific performance metrics from the two studies for a 12-month period.
| Metric | PATHFINDER 2 Result | NHS-Galleri Trial Result |
|---|---|---|
| Sensitivity | 35.0% | 31.6% |
| Specificity | 99.85% | 99.74% |
| Positive Predictive Value (PPV) | 77.0% | 66.2% |
| Negative Predictive Value (NPV) | 99.07% | 98.89% |
| Cancer Signal Origin (CSO) Accuracy | 94.3% | 91.9% |
Advisory Committee's Upcoming Vote
On Wednesday, the FDA's Molecular and Clinical Genetics Panel will vote on several critical questions. They will determine if there is reasonable assurance that Galleri is safe and effective for patients meeting the proposed criteria. The panel will also decide if the test's benefits outweigh its risks for those patients.
The FDA will further seek the committee's advice on appropriate test labeling. This includes discussions on warnings, risk mitigation strategies, and how to clearly communicate the test's performance and limitations to both healthcare providers and patients. The agency typically follows the recommendations of its advisory committees, though it is not required to do so.
