Guardant360 CDx Gains CE Mark as Camizestrant Companion Diagnostic

Guardant Health (GH ) announced on October 8, 2026 that its Guardant360 CDx test received CE-marking under Europe’s In Vitro Diagnostic Medical Devices Regulation as a companion diagnostic (CDx) to identify patients with estrogen receptor (ER)-positive, HER2-negative locally advanced or metastatic breast cancer who may benefit from treatment with Etcamah (camizestrant), AstraZeneca’s next-generation oral selective estrogen receptor degrader (SERD) and complete ER antagonist.

The Palo Alto, California-based precision oncology company said the European clearance is its 31st companion diagnostic approval and the third CDx approval for Etcamah. The approval follows prior regulatory approvals of Guardant360 CDx as a companion diagnostic for Etcamah in the United States and Japan.

With Guardant360 CDx, clinicians can test for ESR1 mutations in tumors through a blood draw ahead of disease progression, according to the company. Guardant said the approach reinforces the role of liquid biopsy in guiding therapy decisions earlier in a breast cancer patient’s treatment.

“Guardant360 CDx offers molecular insights that can support informed treatment decisions for patients with advanced breast cancer, addressing the disease before it gets out of control,” said Helmy Eltoukhy, Guardant Health chairman and co-CEO. He added that the company sees potential for this type of testing protocol in other cancer types.

Guardant describes Guardant360 CDx as the first FDA-approved liquid biopsy for comprehensive genomic profiling. According to the company, the test detects multiple genomic alterations across all solid tumors and is approved as a companion diagnostic for therapies in non-small cell lung cancer, breast cancer, and colorectal cancer.

Etcamah and the SERENA-6 Trial

AstraZeneca (AZN ) announced on July 23, 2026 that the European Commission had approved Etcamah in combination with a CDK4/6 inhibitor (palbociclib, ribociclib or abemaciclib) in the European Union, following a positive opinion from the Committee for Medicinal Products for Human Use. The drug’s EU indication covers adult patients with ER-positive, HER2-negative locally advanced or metastatic breast cancer upon detection of an ESR1 mutation and without disease progression during first-line endocrine therapy in combination with a CDK4/6 inhibitor.

According to AstraZeneca, the approval was based on results from the pivotal SERENA-6 Phase III trial, a global, double-blind, randomized study that enrolled 315 adult patients with HR-positive, HER2-negative advanced breast cancer whose tumors had an emergent ESR1 mutation. The trial used circulating tumor DNA (ctDNA) monitoring through a blood test at the time of routine tumor scans every two to three months to identify early signs of endocrine resistance via the emergence of ESR1 mutations. Following detection of an ESR1 mutation without disease progression, patients had their endocrine therapy switched from an aromatase inhibitor to Etcamah while continuing combination with the same CDK4/6 inhibitor.

In a planned interim analysis, the Etcamah combination reduced the risk of disease progression or death by 56% versus standard-of-care treatment with an aromatase inhibitor (anastrozole or letrozole) in combination with a CDK4/6 inhibitor, AstraZeneca reported, citing a hazard ratio of 0.44 (95% confidence interval: 0.31-0.60; p<0.00001). Median progression-free survival, the trial’s primary endpoint as assessed by investigators, was 16.0 months with the Etcamah combination versus 9.2 months with the aromatase inhibitor combination.

Data for the key secondary endpoints of time to second disease progression (PFS2) and overall survival were immature at the time of the interim analysis. A subsequent pre-planned analysis demonstrated a statistically significant and clinically meaningful PFS2 benefit of 25.7 months versus 19.1 months in favor of the Etcamah combination (hazard ratio 0.63; 95% confidence interval: 0.46-0.86; p=0.00373), and overall survival continued to mature in favor of the combination (hazard ratio 0.87; 95% confidence interval: 0.57-1.30), the company said, adding that the trial will continue to assess overall survival as a key secondary endpoint. The safety profile of Etcamah in combination with palbociclib, ribociclib or abemaciclib was consistent with the known safety profile of each medicine, with no new safety concerns identified and discontinuations very low and similar in both arms, according to AstraZeneca.

AstraZeneca described Etcamah as the first and only next-generation oral SERD and complete ER antagonist approved in the first-line setting and the only option in combination with all widely approved CDK4/6 inhibitors, and as the company’s 11th new medicine of the 20 it expects to launch by 2030. The recommended dose of Etcamah in combination with a CDK4/6 inhibitor is 75 mg, administered orally once daily. The company said the drug is also approved in Japan, the United Arab Emirates and Saudi Arabia based on the SERENA-6 Phase III trial, with regulatory applications under review in several other countries; as of the July 23 announcement, the U.S. application remained under Food and Drug Administration review after the agency extended its Prescription Drug User Fee Act date to review updated results from the trial.

François-Clément Bidard, professor of medical oncology at Institut Curie and Versailles University and co-principal investigator for the trial, called the EU approval “welcome news for the one in three patients in Europe with this form of advanced breast cancer whose tumours develop ESR1 mutations before disease progression.” AstraZeneca said breast cancer remains the leading cause of cancer death among women in Europe, citing more than 140,000 deaths in 2024 and more than 540,000 patients diagnosed in the same year. The company said mutations in the ESR1 gene are a key driver of endocrine resistance and are associated with poor outcomes, and that approximately 30% of patients with endocrine-sensitive HR-positive disease develop ESR1 mutations during first-line treatment before disease progression. Across the UK, France, Germany, Spain and Italy, approximately 37,000 patients with HR-positive metastatic breast cancer are treated with a medicine in the first-line setting, most frequently endocrine therapies paired with CDK4/6 inhibitors, according to the company.

Earlier FDA Approval

The European clearance follows the U.S. Food and Drug Administration’s approval of Guardant360 CDx as a companion diagnostic for camizestrant, announced by Guardant on September 4, 2026. That approval covers identification of patients with hormone receptor (HR)-positive, HER2-negative advanced or metastatic breast cancer harboring tumors with ESR1 mutations before radiographic progression, and it recommends repeat Guardant360 CDx testing every three months during therapy to detect emerging ESR1 mutations before clinical or radiographic disease progression, the company said. Guardant described the FDA approval at the time as the platform’s 29th CDx indication across multiple tumor types globally and as reflecting a multi-year collaboration with AstraZeneca focused on integrating Guardant’s products and capabilities into clinical development. The company estimated that approximately 37,000 women in the U.S. living with advanced HR-positive breast cancer being treated with an aromatase inhibitor could potentially benefit from the approach.