Clinical Validation of Companion Diagnostics for the Selection of Patients with Non–Small Cell Lung Cancer Tumors Harboring Epidermal Growth Factor Receptor Exon 20 Insertion Mutations for Treatment with Amivantamab

Amivantamab, an epidermal growth factor receptor (EGFR)–c-Met bispecific antibody, targets activating/resistance EGFR mutations and MET mutations/amplifications. In the ongoing CHRYSALIS study (ClinicalTrials.gov Identifier: NCT02609776), amivantamab demonstrated antitumor activity in patients with non–small cell lung cancer harboring EGFR exon 20 insertion mutations (ex20ins) that progressed on or after platinum-based chemotherapy, a population in which amivantamab use has been approved by the US Food and Drug Administration. This bridging study clinically validated two novel candidate companion diagnostics (CDx) for use in detecting EGFR ex20ins in plasma and tumor tissue, Guardant360 CDx and Oncomine Dx Target Test (ODxT), respectively. From the 81 patients in the CHRYSALIS efficacy population, 78 plasma and 51 tissue samples were tested. Guardant360 CDx identified 62 positive (16 negative), and ODxT identified 39 positive (3 negative), samples with EGFR ex20ins. Baseline demographic and clinical characteristics were similar between the CHRYSALIS-, Guardant360 CDx–, and ODxT–identified populations. Agreement with local PCR/next-generation sequencing tests used for enrollment into CHRYSALIS demonstrated high adjusted negative (99.6% and 99.9%) and positive (100% for both) predictive values with the Guardant360 CDx and ODxT tests, respectively. Overall response rates were comparable between the CHRYSALIS, Guardant360 CDx, and ODxT populations. Both the plasma- and tissue-based diagnostic tests provided accurate, comprehensive, and complementary approaches to identifying patients with EGFR ex20ins who could benefit from amivantamab therapy.