Guardant Health Japan receives regulatory approval of Guardant360® CDx liquid biopsy as first companion diagnostic for camizestrant in ESR1-mutated advanced breast cancer in Japan
April 27, 2026
Approval reinforces the growing role of ESR1 mutation testing and liquid biopsy in precision endocrine therapy
TOKYO — Guardant Health Japan Corp. today announced that the Ministry of Health, Labour and Welfare (MHLW) has approved Guardant360® CDx on 21 April 2026 as a companion diagnostic to identify ESR1 mutations in patients with hormone receptor (HR)–positive, HER2-negative breast cancer, who may be eligible for treatment with camizestrant. Guardant360® CDx comprehensive genomic profiling panel is the first companion diagnostic approved for camizestrant, an investigational agent currently under regulatory review in Japan.
ESR1 mutations commonly cause resistance to endocrine therapy in patients with HR-positive advanced breast cancer1. Approximately 30% of patients with endocrine sensitive HR-positive breast cancer develop ESR1 mutations during first-line treatment without disease progression2. Detecting these mutations can help inform optimal treatment selection.
“ESR1 mutations are now recognized as a critical mechanism of endocrine resistance in advanced breast cancer, making accurate and timely detection increasingly important,” said Simran Singh, CEO of Guardant Health AMEA. “As the first companion diagnostic approved for camizestrant in Japan, Guardant360 CDx reinforces the growing role of liquid biopsy in enabling biomarker-driven treatment decisions for patients in Japan.”
Clinical results from the Phase III SERENA-6 trial demonstrated that patients with advanced HR-positive breast cancer with an emergent ESR1 tumor mutation who switched to camizestrant while continuing with the same CDK4/6 inhibitor had a highly statistically significant and clinically meaningful improvement in median progression-free survival from 9.2 months to 16.0 months, compared with continuing standard aromatase inhibitor therapy with a CDK4/6 inhibitor2.
This approval further strengthens the clinical adoption of blood-based ESR1 mutation testing in Japan and supports identification of ESR1 mutations that may inform endocrine therapy decisions, consistent with approved indications. Camizestrant is an investigational, potent, next-generation oral selective estrogen receptor degrader (SERD) and complete estrogen receptor (ER) antagonist that is currently in Phase III trials for the treatment of HR-positive breast cancer.
Guardant360® CDx was approved by MHLW in March 2022 for comprehensive genomic profiling in patients with advanced solid tumors. The test is approved as a companion diagnostic for multiple cancer drugs approved in Japan. Testing under the national health insurance system is available at cancer genome core hospitals, cancer genome hub hospitals, and affiliated cancer genome medical institutions designated by MHLW. Please refer to Annex A for the list of approved companion diagnostics.
References:
- Dustin D, Gu G, Fuqua SAW. ESR1 mutations in breast cancer. Cancer. 2019;125(21):3714-3728. doi:10.1002/cncr.32345
- Camizestrant reduced the risk of disease progression or death by 56% in patients with advanced HRpositive breast cancer with an emergent ESR1 tumour mutation in SERENA-6 Phase III trial. AstraZeneca. Published online June 1, 2025. Accessed April 13, 2026. https://www.astrazeneca.com/media-centre/pressreleases/2025/camizestrant-reduced-the-risk-of-disease-progression-or-death-by-56-in-patients-withadvanced-hr-positive-breast-cancer-with-an-emergent-esr1-tumour-mutation-in-serena-6-phase-iii-trial.html.
About Guardant360® CDx
Guardant360® CDx is a liquid biopsy test that uses next generation sequencing to analyse circulating tumour DNA (ctDNA), which is produced when tumours shed small pieces of their genetic material into the bloodstream. The test provides comprehensive genomic profiling results from a simple blood draw, helping oncologists move beyond the limitations of tissue biopsies to obtain clinically relevant information in time to match patients to the optimal personalized treatment.
About Guardant Health
Guardant Health is a leading precision oncology company focused on guarding wellness and giving every person more time free from cancer. Founded in 2012, Guardant is transforming patient care and accelerating new cancer therapies by providing critical insights into what drives disease through its advanced blood and tissue tests, real-world data and AI analytics. Guardant tests help improve outcomes across all stages of care, including screening to find cancer early, monitoring for recurrence in early-stage cancer, and treatment selection for patients with advanced cancer*. For more information, please visit https://guardanthealthjapan.com and follow the company on LinkedIn.
* The complete portfolio of Guardant Health products may not be available in all regions.
Forward-Looking Statements
This news release contains forward-looking statements within the meaning of federal securities laws, including statements regarding the potential utilities, values, benefits and advantages of Guardant Health’s liquid biopsy tests or assays, which involve risks and uncertainties that could cause the actual results to differ materially from the anticipated results and expectations expressed in these forward-looking statements. These statements are based on current expectations, forecasts and assumptions, and actual outcomes and results could differ materially from these statements due to a number of factors. These and additional risks and uncertainties that could affect Guardant Health’s financial and operating results and cause actual results to differ materially from those indicated by the forward-looking statements made in this press release include those discussed under the captions “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operation” and elsewhere in its Annual Report on Form 10-K for the year ended December 31, 2024 and in its other reports filed with or furnished to the Securities and Exchange Commission. The forward-looking statements in this press release are based on information available to Guardant Health as of the date hereof, and Guardant Health disclaims any obligation to update any forward-looking statements provided to reflect any change in its expectations or any change in events, conditions, or circumstances on which any such statement is based, except as required by law. These forward-looking statements should not be relied upon as representing Guardant Health’s views as of any date subsequent to the date of this press release.
Annex A
List of Approved Companion Diagnostics in Japan
| Biomarker | Cancer | Companion Diagnostic |
|---|---|---|
| KRAS G12C | Non-small cell lung cancer (NSCLC) | sotorasib |
| ERBB2 (HER2) mutation | trastuzumab deruxtecan | |
| EGFR exon 20 insertion mutation | amivantamab-vmjw | |
| ESR1 mutation | Breast cancer | imlunestrant and camizestrant |
| BRAF V600E | Colorectal cancer | encorafenib, binimetinib, and cetuximab |
| encorafenib and cetuximab | ||
| KRAS/NRAS wild-type | cetuximab | |
| panitumumab | ||
| ERBB2 copy number alteration (HER2 gene amplification positive) | trastuzumab and pertuzumab | |
| Solid tumor | trastuzumab deruxtecan | |
| MSI-High | Colorectal cancer | nivolumab |
| Solid tumor | pembrolizumab |
Note: Underlined item has been added with this approval.