Abstract 311: Diverse biological mechanisms drive resistance to Lorlatinib in ALK-rearranged Lung Cancer

Abstract Background: ALK rearrangements occur in 3-6% of patients (pts) with lung adenocarcinoma. Lorlatinib, is a novel third generation ALK tyrosine kinase inhibitor (TKI) with proven efficacy for patients previously treated with second generation ALK TKI. Methods: The MATCH-R study is a prospective single-institution trial aiming to identify mechanisms of resistance to targeted agents and immunotherapy in pts with advanced cancer (NCT02517892). Patients that achieve an initial partial or complete response or stability of disease for at least 6 months with selected agents are included upon disease progression. Tumor biopsies are performed and serial blood samples are collected. Extensive molecular profiling with panel next-generation sequencing (NGS), whole exome sequencing (WES) and RNA sequencing (RNAseq) is performed on tumor samples. Patient-derived xenografts (PDX) in NOD scid gamma (NSG) or nude mice and patient-derived cell lines are developed. We report mechanisms of resistance in a cohort of pts with ALK-rearranged lung cancer treated with lorlatinib. Results: From June 29th 2015 to November 15th 2018, 113 pts treated with a TKI were included in the MATCH-R study, of which 14 (12%) received treatment with ALK TKI, 6 pts treated with lorlatinib and with adequate tumor biopsies for molecular analysis were included. Tumor types studied were lung adenocarcinoma (n=4), anaplastic thyroid carcinoma (ATC, n=1) and myofibroblastic inflammatory tumor (MIT, n=1). An NF2 frame-shift deletion was detected by NGS in the ATC sample and a TNIK Q674 missense mutation was detected in the MIT sample. In the four pts with lung cancer treated with lorlatinib, we identified novel ALK G1202R/F1174L compound mutations from the tumor biopsy in one case and characterized them with Ba/F3 models (ctDNA analysis will be presented). Induction of epithelial mesenchymal transition (EMT) with lorlatinib exposure was responsible for resistance in one patient-derived model and susceptible to combined ALK/SRC inhibition. This cell line also had ALK C1156Y/G1269A compound mutations, not contributing to lorlatinib resistance. In a third case, double deleterious events in NF2 were identified in temporo-spatial distinct tumor biopsies on progression to lorlatinib. We further validated the effect of these events in patient-derived cell lines developed from two different biopsies. Downstream mTOR pathway activation conferred resistance to lorlatinib, and was reversible with mTOR inhibitors. We performed NF2 knockout in H3122 cells using Crispr-Cas9 gene editing to validate these findings. The resistance mechanism to lorlatinib treatment is yet to be elucidated in one patient-derived model. Conclusions: Mechanisms of resistance to lorlatinib can be diverse and complex, involving compound mutations, EMT and bypass activation. The present evidence could provide new insights for the development of tailored treatments for patients. Citation Format: Gonzalo Recondo, Laura Mezquita, David Planchard, Anas Gazzah, Francesco Facchinetti, Ludovic Bigot, Ahsan Z. Rizvi, Jean-Paul Thiery, Jean-Yves Scoazec, Rosa L. Frias, Tony Sourisseau, Linda Mahjoubi, Justine Galissant, Aurelie Abou-Lovergne, Gilles Vassal, Rastislav Bahleda, Antoine Hollebecque, Claudio Nicotra, Maud Ngocamus, Stefan Michiels, Ludovic Lacroix, Catherine Richon, Nathalie Auger, Thierry De Baere, Frederic Deschamps, Eric Solary, Ken A. Olaussen, Eric Angevin, Alexander Eggermont, Fabrice André, Christophe Massard, Jean-Charles Soria, Benjamin Besse, Luc Friboulet. Diverse biological mechanisms drive resistance to Lorlatinib in ALK-rearranged Lung Cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 311.