Background: CHRYSALIS (NCT02609776) evaluated the combination of amivantamab (ami) and lazertinib (laz) in treatment-naïve patients (pts) with epidermal growth factor receptor (EGFR)-mutated NSCLC. As previously reported, all 20 pts achieved a partial response (overall response rate of 100%) but interpretation of long-term outcomes was limited by the length of follow up (Cho Ann Oncol 2020;31:suppl_4, 1258O; Cho J Thorac Oncol 2022;17:S126, P1.16-01). Herein, we present long-term results from this treatment-naïve cohort. Methods: The treatment-naive cohort enrolled pts with EGFR exon 19 deletion (ex19del) or L858R mutated advanced NSCLC. All pts received 1050 mg IV ami (1400 mg if ≥80 kg) and 240 mg oral laz. Response was assessed by the investigator per RECIST v1.1. Circulating tumor DNA (ctDNA) was analyzed from plasma samples prior to initiation of treatment, at Cycle 3 Day 1, and at end of treatment (EOT). Results: Of the 20 pts enrolled in the treatment-naive cohort (median 62.5 years, 55% women, all Asian), 11 had EGFR ex19del and 9 had L858R NSCLC. As of Nov 15, 2022, the median follow-up and duration of treatment were 33.6 and 33.5 months, respectively. Ten (50%) pts were progression-free and remained on treatment, including 7 of 11 (64%) with ex19del and 3 of 9 (33%) with L858R. The median duration of response (DOR), median progression-free survival (PFS), and median overall survival (OS) were not estimable. The estimated landmark PFS rate was 85% at 12 months, 65% at 24 months, and 51% at 36 months. Of note, 2 (10%) pts were treated beyond progression. The longest ongoing pt has a duration of treatment of 37.2 months and DOR of 35.7 months. Treatment-related dose interruptions, reductions, and discontinuations of either ami and laz occurred in 7 (35%) pts, 8 (40%) pts, and 1 (5%) pt, respectively. The safety profile was consistent with prior reports, with predominantly on-target EGFR- or MET-related adverse events. Among the 10 pts who discontinued treatment, 4 submitted samples for ctDNA analysis at both baseline and EOT. There was 1 pt with new PIK3CA mutations, 1 with low-level HER2 amplification, 1 pt with a new CCNE1 and EGFR amplification, and 1 pt with no new mutations detected. Updated data on ctDNA at EOT may be available at the time of congress presentation. Conclusions: At a median duration of treatment of 33.5 months, median DOR, PFS, and OS have not been reached in treatment-naïve pts receiving ami+laz, with 50% remaining progression-free and on treatment. No new safety signals were identified. The ongoing phase 3 MARIPOSA study (NCT04487080) is further investigating ami+laz vs osimertinib vs laz in previously untreated, EGFR-mutated, advanced NSCLC. Clinical trial information: NCT02609776.