Introduction: With multiple targeted therapies approved for anaplastic lymphoma kinase (ALK)-positive metastatic non-small cell lung cancer (NSCLC), it is increasingly important to understand outcomes with various sequences of next-generation ALK tyrosine kinase inhibitors (TKIs). We describe contemporary sequencing patterns and treatment effectiveness of first-line (1L) and second-line (2L) treatments in patients who received second-generation ALK TKIs in the 1L treatment of ALK-positive NSCLC in the United States., Methods: A cohort of adults with ALK-positive advanced NSCLC who initiated treatment with 1L alectinib or brigatinib between June 2017 and April 2021 in the Flatiron Health electronic health record-derived de-identified database were followed through April 2023. Time to treatment discontinuation (TTD) in 1L and 2L, TTD on 1L plus 2L sequential therapy (TTD2), and total time on sequential ALK TKI therapy (including beyond 2L) were evaluated., Results: Patients (N=273) were followed up for a median duration of 28.9 months. Among patients who discontinued 1L therapy, 22% died after 1L discontinuation (median time from discontinuation to death, 4.0 months) without receiving 2L therapy. Median (95% confidence interval [CI]) TTD was 21.9 (15.2-25.8) and 7.3 (5.3-10.2) months in 1L and 2L, respectively. Median (95% CI) TTD2 was 29.4 (25.1-36.1) months and total time on sequential ALK TKI treatment was 28.0 (23.6-32.9) months., Conclusions: In this large real-world study, TTD2 and the total time on sequential ALK TKIs was approximately 2.5 years. The high attrition rate from 1L to 2L and the longest clinical benefit observed with 1L therapy support using the drug with the longest 1L effectiveness up front in patients with ALK-positive advanced NSCLC., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Dr. Bauman reports consulting fees from EMD Serono and participation on an advisory board for BeiGene, Blueprint Medicine, Janssen, Lilly, Merck, Mirati, Pfizer, and Turning Point Therapeutics. Dr. G. Liu reports grant support from Amgen, AstraZeneca, Bayer, Boehringer Ingelheim, Canadian Cancer Society Research Institute, Canadian Institute of Health Research, EMD Serono, NCI (US), Pfizer, and Takeda; honoraria from AstraZeneca, EMD Serono, Pfizer, and Takeda; and participation on an advisory board for AbbVie, AstraZeneca, Bristol Myers Squibb, EMD Serono, Jazz Pharmaceuticals, Lilly, Merck, Novartis, Pfizer, and Roche. Dr. Preeshagul reports honoraria from AstraZeneca, Bristol Myers Squibb, Dava Oncology, G1 Therapeutics, Genentech, Jazz Pharmaceuticals, Novartis, OncLive, PER, Pfizer, and Takeda and a leadership role at LCRF and ASCO. Dr. S. Liu reports funding support from Pfizer; grant support from AbbVie, Alkermes, Elevation Oncology, Ellipses, Genentech, Gilead, Merck, Merus, Nuvalent, Puma Biotechnology, RAPT Therapeutics, and Turning Point Therapeutics; consulting fees and participation on advisory boards for AbbVie, Amgen, AstraZeneca, Boehringer Ingelheim, Bristol Myers Squibb, Catalyst, Daiichi Sankyo, Eisai, Elevation Oncology, Genentech/Roche, Gilead, Guardant Health, Janssen, Jazz Pharmaceuticals, Merck, Merus, Mirati, Novartis, Pfizer, Regeneron, Sanofi, Takeda, and Turning Point Therapeutics; and participation on data safety and monitoring board for Candel Therapeutics. Dr. Melosky reports honoraria from AstraZeneca, Bristol Myers Squibb, EMD Serono, Janssen, Jazz Pharmaceuticals, Merck, Novartis, Pfizer, Roche, Sanofi, and Takeda; funding support for meetings and/or travel from Janssen, Pfizer, and Sanofi; and participation on advisory boards for AstraZeneca, Bristol Myers Squibb, EMD Serono, Janssen, Jazz Pharmaceuticals, Merck, Novartis, Pfizer, Roche, Sanofi, and Takeda. Dr. Abrahami, Dr. Li, Ms. Thomaidou, and Ms. Duncan are employed by and own stocks in Pfizer. Mr. Krulewicz is employed by Pfizer and owns stock in AbbVie, Amgen, GSK, Merck, Pfizer, United Health Group, Viatris, and XLV. Dr. Rupp was employed by and owned stock in Pfizer at the time of this study. Dr. Lin has received grant support from Bayer, Elevation Oncology, Hengrui Therapeutics, Linnaeus Therapeutics, Neon Therapeutics, Novartis, Nuvalent, Relay Therapeutics, Roche, and Turning Point Therapeutics and received consulting fees from AnHeart Therapeutics, AstraZeneca, Bayer, Blueprint Medicines, Bristol Myers Squibb, C4 Therapeutics, CLaiM Therapeutics, Daiichi Sankyo, Elevation Oncology, Ellipses, Genentech, Hyku Biosciences, Merus, Mirati Therapeutics, Novartis, Nuvalent, Pfizer, Regeneron, Takeda, Turning Point Therapeutics, and Yuhan., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)