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FDA Approves Roche Antibody Test as CDx for Enhertu in HER2-Low Breast Cancer Patients

NEW YORK – Roche announced on Tuesday that its antibody test has received approval from the US Food and Drug Administration to be used as a companion diagnostic for AstraZeneca and Daiichi Sankyo's Enhertu (fam-trastuzumab deruxtecan-nxki). 

The Pathway Anti-HER2/neu (4B5) Rabbit Monoclonal Primary Antibody test is intended to identify metastatic breast cancer patients with low HER2 expression that could benefit from Enhertu as a targeted treatment. Half of metastatic breast cancer patients express low levels of HER2 and have traditionally been classified as HER2-negative, but Roche's test includes a scoring algorithm that can help pathologists identify low expressors of HER2, the company said in a statement. The lower cutoff means the test can identify patients who could benefit from Enhertu, Roche added.

"Previously, metastatic breast cancer patients with a lower level of HER2 expression were considered to be part of the HER2-negative population and had no HER2-targeted treatment options," Roche Diagnostics CEO Thomas Schinecker said in a statement. "Now, they may be eligible for a HER2-targeted therapy, significantly increasing the number of patients who could have improved outcomes."

Enhertu is a specifically engineered HER2-directed antibody drug conjugate. Roche's test was used as part of the Phase III DESTINY-Breast04 trial to identify patients with tumors that expressed low levels of HER2. The trial reported a 50 percent reduction in the risk of disease recurrence or death and an overall gain of six months over standard of care in patients with low levels of HER2 expression who received Enhertu, Roche said. Enhertu received FDA approval for previously treated patients with unresectable or metastatic HER2-low breast cancer in August. 

The test is used in combination with Roche's fully automated BenchMark IHC/ISH slide staining instrument. It has received FDA approval for use as a companion diagnostic with Genentech's Herceptin (trastuzumab) and Kadcyla (ado-trastuzumab emtansine).