Trading in shares of Grail is halted on Wednesday ahead of a Food and Drug Administration advisory committee meeting to discuss the diagnostic company's proposed multi-cancer blood test.

Grail is seeking FDA approval of Galleri, a blood test that aims to catch cancers before symptoms appear.

Shares of the Menlo Park, Calif., company were up 34% this week through Tuesday's close after FDA briefing documents for the meeting, released on Monday, were more favorable than investors had expected.

RBC Capital Markets analyst Dan Leonard said the briefing documents suggest the FDA is less concerned with Galleri's safety and effectiveness and more focused on how to label the commercial product.

The FDA often turns to advisory committees to obtain advice from experts who work outside of the government when a scientific, technical or policy question arises, such as whether an unapproved product is safe and effective. The agency usually follows the advice of its advisory committees but it isn't bound by the recommendations.