• ESR1 mutations, a known driver of resistance to standard endocrine therapy, are present in up to 40% of ER+, HER2- advanced breast cancers¹
• ORSERDU (elacestrant) is first FDA-approved endocrine therapy innovation in more than 20 years, specifically addressing ESR1 mutations, a major unmet need
• Guardant360 CDx blood test provides comprehensive genomic profiling to identify patients with ESR1 mutations who may benefit from ORSERDU targeted therapy

Guardant Health, Inc. (Nasdaq: GH), a leading precision oncology company, announced today that the U.S. Food and Drug Administration (FDA) has approved its Guardant360^® CDx liquid biopsy test as a companion diagnostic to identify advanced or metastatic breast cancer patients with ESR1 mutations who may benefit from treatment with ORSERDU™ (elacestrant), a nonsteroidal selective estrogen receptor degrader to be commercialized by Stemline Therapeutics, Inc., a wholly-owned subsidiary of Menarini Group.

Breast cancer is the second leading cause of cancer death in women. The American Cancer Society estimates that about 297,790 new cases of invasive breast cancer will be diagnosed in women in 2023, and about 43,700 women will die from breast cancer.² ORSERDU is the first therapy to be approved by the FDA for advanced breast cancer patients with ESR1 mutations, with disease progression following at least one line of endocrine therapy. ESR1 mutations are present in approximately 40% of ER+/HER2- advanced breast cancers.

“This FDA approval is great news for breast cancer patients with ESR1 mutations, who now have, for the first time, an approved treatment for their specific type of cancer and a blood-based companion diagnostic,” said Helmy Eltoukhy, Guardant Health co-CEO. “We are pleased that the Guardant360 CDx liquid biopsy is now approved so that oncologists and their patients can access comprehensive genomic profiling to see if they are eligible to receive this therapy.”

The FDA approved Guardant360 CDx as a companion diagnostic (CDx) in conjunction with the approval of ORSERDU for postmenopausal women or adult men with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative, ESR1-mutated, advanced or metastatic breast cancer with disease progression following at least one line of endocrine therapy.

“We are proud to bring the very first treatment targeting ESR1 mutations which are present in up to 40% of ER+/HER2- advanced breast cancers,” commented Elcin Barker Ergun, CEO of Menarini Group. “We’re also pleased with the approval of the Guardant360 CDx blood test as the companion diagnostic to help oncologists identify patients who may benefit from this innovative endocrine therapy.”

The approval as a companion diagnostic for ORSERDU is Guardant Health’s fifth FDA approval for the Guardant360 CDx test and its first in breast cancer.

About ORSERDU (elacestrant)

ORSERDU is approved under the FDA’s Priority Review designation based on the results of the registrational Phase III trial EMERALD, that demonstrated statistically significant progression-free survival (PFS) with elacestrant vs SOC endocrine monotherapy (fulvestrant, letrozole, anastrozole, exemestane), meeting both primary endpoints in all patients and in those patients whose tumors harbor an ESR1-mutation. In the group with patients whose tumors had an ESR1 mutation, median PFS was doubled (3.8 vs 1.9 months), and a 45% reduction of death or progression was achieved over SOC. Safety data is consistent with the other endocrine therapies. Most of the adverse events (AEs), including nausea and musculoskeletal pain were grade 1 and 2. No hematological safety signal was observed and none of the patients in either of the two treatment arms had sinus bradycardia. For more information about ORSERDU, please visit www.orserdu.com.

About Guardant360 CDx

For oncologists, the FDA-approved Guardant360 CDx test provides comprehensive genomic results from a simple blood draw in seven days, helping them move beyond the limitations of tissue biopsies to rapidly obtain clinically relevant information in time to match patients to the optimal personalized treatment. Guardant360 CDx covers all genes recommended by the National Comprehensive Cancer Network, including those most relevant to clinical care and NSCLC treatment guidelines.

The first FDA-approved blood test for complete genomic testing, Guardant360 CDx is approved as a companion diagnostic to identify patients with non-small cell lung cancer who may benefit from treatment with TAGRISSO^® (osimertinib), RYBREVANT^® (amivantamab-vmjw), ENHERTU^® (fam-trastuzumab deruxtecan-nxki) or LUMAKRAS™ (sotorasib). It is also FDA approved to identify advanced breast cancer patients with ESR1 mutations who may benefit from treatment with ORSERDU™ (elacestrant). For more information, visit guardant360cdx.com.

Since being introduced, the Guardant360 test has become widely accepted for blood-based comprehensive genomic profiling with more than 350 peer-reviewed publications. It has been trusted by more than 12,000 oncologists, with more than 250,000 tests performed to date, and is broadly covered by Medicare and many private payers, representing over 230 million lives.

About Guardant Health

Guardant Health is a leading precision oncology company focused on helping conquer cancer globally through use of its proprietary tests, vast data sets and advanced analytics. The Guardant Health oncology platform leverages capabilities to drive commercial adoption, improve patient clinical outcomes and lower healthcare costs across all stages of the cancer care continuum. Guardant Health has commercially launched Guardant360^®, Guardant360 CDx, Guardant360 TissueNext™, Guardant360 Response™, and GuardantOMNI^® tests for advanced stage cancer patients, and Guardant Reveal™ for early-stage cancer patients. The Guardant Health screening portfolio, including the Shield^TM test, aims to address the needs of individuals eligible for cancer screening. For more information, visit guardanthealth.com and follow the company on LinkedIn and Twitter.

Forward-Looking Statements

This press 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, 2021 and in its other reports filed with 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.

References

1. Brett, J.O., Spring, L.M., Bardia, A. et al. ESR1 mutation as an emerging clinical biomarker in metastatic hormone receptor-positive breast cancer. Breast Cancer Res 23, 85 (2021). https://doi.org/10.1186/s13058-021-01462-3.
2. https://www.cancer.org/cancer/breast-cancer/about/how-common-is-breast-cancer.html. Accessed January 11, 2023.

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