Background: Amivantamab (ami) is a bispecific antibody targeting EGFR and MET with immune cell-directing activity, and lazertinib (laz) is a brain-penetrant, third-generation EGFR tyrosine kinase inhibitor. In a previous report, the overall response rate (ORR) of ami+laz in the post-osimertinib (osi) setting was 36%, with median duration of response of 9.6 months (Bauml JCO 2021; 39:15_suppl, 9006). Exploratory analyses suggested certain immunohistochemistry (IHC) and ctDNA-based next-generation sequencing (NGS) biomarkers may enrich for response. A prospective study was conducted to further evaluate these potential biomarkers. Methods: CHRYSALIS-2 (NCT04077463), an ongoing phase 1/1b study, examines the efficacy (ORR per RECIST v1.1) of ami+laz in patients (pts) with EGFR-mutated NSCLC. Cohort D enrolled osi-relapsed, chemotherapy-naïve pts with EGFR exon 19 deletion or L858R mutated advanced NSCLC who had tumor tissue for IHC staining and plasma for ctDNA NGS collected after their most recent therapy. Training and validation subsets identified biomarker criteria and predictive validity, respectively. A Bayesian posterior probability (biomarker positive group ORR is ≥35% and negative group ORR is ≤20%) was predefined to be ≥85% for acceptance. Results: There were 101 response-evaluable pts enrolled in Cohort D. A total of 87 pts had detectable baseline ctDNA and 77 pts had evaluable MET IHC. The training set (n = 50) identified IHC-based MET expression of 3+ staining on ≥25% of tumor cells (MET+) as a potential predictive biomarker, and the validation set (n = 27) confirmed these results. Of those with MET IHC data, 28/77 (36%) were MET+. The overall ORR for MET+ was 61% (95% CI, 41–78) and 12% (95% CI, 5–25) for MET-, with median PFS for MET+ not reached (95% CI, 4.3–NE) vs 4.1 months (95% CI, 2.8–5.7) for MET-. NGS evaluation of ctDNA did not identify predictive biomarkers meeting predetermined criteria. Of note, only 1 pt was identified by ctDNA as having MET amplification (the pt was also MET+ by IHC). Further details will be provided at the time of presentation. Conclusions: MET+ by IHC may be a predictive biomarker for response to ami+laz in the post-osi, chemotherapy-naïve setting. In contrast, molecular profiling with ctDNA failed to identify a subgroup of pts more likely to benefit. Ami+laz represents a potential chemotherapy-free option for pts with EGFR-mutated advanced NSCLC who have progressed on osi and are also MET+ by IHC. Clinical trial information: NCT04077463.