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Guardant Health Enters CDx Collaboration With Radius Health for Elacestrant in HER2- Breast Cancer

NEW YORK – Guardant Health said Thursday that it is collaborating with Radius Health to pursue regulatory approval of its Guardant360 CDx assay as a companion diagnostic for elacestrant (RAD1901), an investigational selective estrogen receptor degrader being studied in the treatment of advanced ER-positive, HER2-negative breast cancers that are resistant to CDK4/6 inhibitors in combination with hormone therapy. 

A Phase III clinical trial, EMERALD, is already underway to assess the efficacy of elacestrant versus standard-of-care endocrine therapy in the overall population, as well as in patients who have been comprehensively genotyped using the Guardant360 test and found to harbor ESR1 mutations.

Financial and other terms of the agreement were not disclosed.

Guardant360 analyzes 74 genes using cell-free tumor DNA from patient blood samples. The test is broadly covered by Medicare for use across the vast majority of advanced solid tumors, and the company has said it is also reimbursed by many private payors.

"Given breast cancer's inherent tumor heterogeneity and the high prevalence of bone metastasis in advanced disease, [Guardant360] can help overcome the challenges of tissue and bone biopsies to reveal significantly more actionable mutations, including ESR1 mutations," Guardant President AmirAli Talasaz said in a statement. "For patients with CDK4/6 resistant tumors, for whom few other treatment options exist, potential therapies such as elacestrant may represent a promising option," he added.

The partners noted that Radius and Menarini Group have signed a global licensing agreement for elacestrant under which Radius will continue to conduct and complete the ongoing EMERALD trial through filing a new drug application with the Food and Drug Administration. After that, Menarini Group will be responsible for worldwide commercialization of drug.