On June 2, 2025 Guardant Health, Inc. (Nasdaq: GH), a leading precision oncology company, reported that the results of the Phase III SERENA-6 trial – sponsored by AstraZeneca – demonstrate the clinical value of the Guardant360 CDx test in a circulating tumor DNA-guided approach to detect and treat emerging resistance in 1st-line therapy ahead of radiological disease progression in breast cancer (Press release, Guardant Health, JUN 2, 2025, View Source [SID1234653659]). Study results were presented at the 2025 American Society of Clinical Oncology (ASCO) (Free ASCO Whitepaper) Annual Meeting in Chicago and were published in The New England Journal of Medicine.

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SERENA-6 is the first global, double-blind, registrational Phase III trial to use a ctDNA-guided approach to detect the emergence of endocrine resistance and inform a switch in therapy before disease progression is detected in imaging scans. The novel trial design used ctDNA monitoring with the Guardant360 liquid biopsy test at the time of routine tumor scans to identify patients for early signs of endocrine resistance and the emergence of ESR1 mutations.

"SERENA-6 is a landmark study that is creating a new paradigm using liquid biopsy to enable a switch to a new treatment as soon as you see the cancer showing signs of resistance," said Helmy Eltoukhy, Guardant Health chairman and co-CEO. "This use of the Guardant360 CDx test highlights how we are pushing the boundaries of what can be done with liquid biopsy in characterizing disease and potential drug efficacy, providing insights that could potentially change clinical practice and improve outcomes in patients with advanced breast cancer."

Following detection of an ESR1 mutation without radiological disease progression, the endocrine therapy of patients was switched to AstraZeneca’s camizestrant from ongoing treatment with an aromatase inhibitor (AI), while continuing combination with the same cyclin-dependent kinase (CDK) 4/6 inhibitor. The trial demonstrated a highly statistically significant and clinically meaningful improvement in progression-free survival (PFS) in the 1st-line treatment of patients with hormone receptor (HR)-positive, HER2-negative advanced breast cancer whose tumors had an emergent ESR1 mutation as detected by Guardant360 CDx.

About Guardant360 CDx

The first FDA-approved blood test for complete genomic testing, Guardant360 CDx is approved as a companion diagnostic fur multiple therapies in non-small cell lung cancer. It is also the only FDA-approved companion diagnostic for targeted therapy in advanced breast cancer patients with ESR1 mutations. The test is broadly covered by Medicare and commercial insurers, representing over 300 million lives. For more information, visit the Guardant360 CDx website.