As an exploratory analysis, the concordance of CLDN18.2 positivity (defined as ≥ 75% of tumor cells demonstrating moderate-to-strong membranous CLDN18 staining) or the concordance of any CLDN18 staining (defined as ≥ 1% of tumor cells demonstrating moderate-to-strong membranous CLDN18 staining) was assessed in a subset of pair-matched samples consisting of archival tumor samples, which were collected any time before treatment, and baseline tumor samples, which were collected within 3 months before first study treatment (cohorts 1A and 2 of the ILUSTRO study, n = 23; phase 1 study, n = 13). This evidence concerns the gene CLDN18 and neoplasm.