For the first time, the FDA has approved a liquid biopsy companion diagnostic that could be run multiple times.
As part of the FDA’s approval for Guardant 360 CDx as a companion diagnostic for treatment with AstraZeneca’s breast cancer treatment ETCAMAH (camizestrant), announced by Guardant Health on Sept. 5., the agency recommended repeat testing every three months during the course of first-line treatment.
The Guardant test can identify emerging ESR1 mutations in patients with hormone receptor-positive, HER2-negative advanced or metastatic breast cancer before they appear in radiographic testing, making the patients candidates for a switch to treatment with camizestrant.
“This approval represents a landmark shift in how we define disease progression and reinforces the transformative role of liquid biopsy in guiding therapy decisions earlier at a critical moment in a breast cancer patient’s treatment journey,” Helmy Eltoukhy, Cofounder and Co-CEO of Guardant Health, said in a statement. “[This] paradigm opens a new frontier in how cancer is managed, with potential application across different diseases and therapies.”
Historically, biomarker testing in advanced cancer has most often occurred after clinical or radiographic progression. The Phase III SERENA-6 trial tested a different approach: serial Guardant360 CDx testing every three months during first-line endocrine therapy to catch emerging resistance before disease progression becomes visible on imaging.
Guardant said patients treated under the new approach had longer median progression-free survival (16 months versus 9 months) and a 47 percent reduction in the risk of deterioration in global health status and quality of life. The company estimated that 37,000 women in the US could potentially benefit from the approach.
The approval reflects a multi-year collaboration between Guardant Health and AstraZeneca; Guardant provided ESR1 mutation detection across the trial’s serial testing timepoints.
Guardant said this is Guardant360 CDx’s 29th companion diagnostic indication across multiple tumor types.