Guardant Health, Inc. announced that the U.S. Food and Drug Administration (FDA) has approved its Guardant360® CDx liquid biopsy test as a companion diagnostic (CDx) to select patients with unresectable or metastatic HER2-mutant non-small cell lung cancer (NSCLC) whose tumors have activating HER2 (ERBB2) mutations for treatment with ENHERTU® (fam-trastuzumab deruxtecan-nxki), a HER2-directed antibody drug conjugate (ADC) jointly developed and commercialized by Daiichi Sankyo and AstraZeneca. The approval means that Guardant360 CDx, a next generation sequencing (NGS)-based assay that detects genomic alterations using circulating tumor DNA from blood, is validated as a CDx assay to identify NSCLC patients who have an activating HER2 mutation (SNVs and exon 20 insertions) and may benefit from treatment with ENHERTU. Mutations in the HER2 gene, also called ERBB2, drive approximately 2-4% of non-squamous NSCLC.1 Non-small cell lung cancer represents about 82% of all lung cancer,2 which is the leading cause of cancer death in the U.S.