Guardant Health, Inc (NASDAQ:GH) shares are trading lower on Tuesday after the U.S. Food and Drug Administration (FDA) announced a review of AstraZeneca Plc's (NASDAQ:AZN) application for camizestrant for advanced breast cancer.

In briefing documents, the agency panel appeared concerned about the trial design, measurement of progression-free survival (PFS), and immature overall survival (OS) results, which may not achieve statistical significance.

FDA Raises Concerns

The FDA has raised multiple concerns about the interpretation of results from the SERENA-6 trial evaluating camizestrant in HR-positive, HER2-negative advanced breast cancer, despite the study meeting its progression-free survival (PFS) endpoint.

Regulators said uncertainties remain around whether early treatment switching based on ESR1 mutation detection provides meaningful clinical benefit.

The study used Guardant Health’s FDA-approved Guardant360 CDx assay to detect ESR1 mutations detected in ctDNA.

The FDA did not approve the Guardant360 device for detecting ESR1m in patients with HR+HER2- ABC who are receiving an AI and a CDK4/6 inhibitor for ≥ 6 months (as used in SERENA-6).

A Premarket Approval (PMA) supplement for the Guardant360 device is under review in CDRH concurrently with the NDA for camizestrant.