Abstract 5840: Identifying drug tolerant persister to neoadjuvant osimertinib in resectable non-small cell lung cancer harbouring EGFR mutations (NORA) via single-cell RNA sequencing

Abstract Introduction: Adjuvant osimertinib is the standard of care for resected, stage IB-IIIA non-small cell lung cancer (NSCLC) harboring activating epidermal growth factor receptor (EGFR) mutation. Yet, the role of neoadjuvant osimertinib is not clear. In the NORA trial (NCT04816838), we aimed to identify the drug tolerant persister (DTP) after neoadjuvant osimertinib for surgically resectable, EGFR-mutated stage IA-IIIA NSCLC. Methods: Patients harboring EGFR Exon 19 deletion or L858R at clinical stage IA-IIIA were given 80 mg of neoadjuvant osimertinib daily for two 28-day cycles followed by surgical resection and adjuvant osimertinib for 3 years. The key exploratory endpoint was to characterize the DTP via single-cell RNA sequencing (scRNA-seq) with pre and post-osimertinib samples. Results: We performed scRNA-seq on twenty-five patients enrolled at Yonsei Cancer Center from June 2021 to March 2022. Patients with stage IA (n=8, 32%), IB (n=7, 28%), IIA (n=4, 16%), IIB (n=4, 16%), and IIIA (n=2, 8%) were included. For EGFR mutation, exon 19 del and L858R accounted for 10 (40%) patients and 15 (60%) patients, respectively. The ORR (all partial response) was 44% (n=11), major pathologic response (MPR) rate was 24% (n=6), and pathologic complete response rate was 0%. ScRNA-seq revealed a total of 252,339 cells (60 clusters) annotated as epithelial cells (10 clusters), fibroblasts (7 clusters), immune cells (17 clusters), myeloid (15 clusters), endothelial cells (11 clusters) that showed distinct enrichment in post-osimertinib samples, non-MPR, and L858R subset. We found that a distint epithelial subset, namely EP8-AGER, identified as alveolar type 1 (AT1) cells was enriched in the non-MPR subset showing activation of Wnt, Hippo, and YAP/TAZ pathway. Pseudotemporal ordering of this cluster showed activation of signaling pathway for COL4A2/COL4A3 related to structural consistuent of extracellular matrix, and RTKN2 associated with NF-κB. In the fibroblast subset, the proportion of FB6-CD74 associated with chemokine activity and NF-κB was higher in the non-MPR and L858R group. In the myeloid subset, CD8-C1-GZMK identified as CD8+ T cells with activation/effector and cytotoxic signatures was also enriched in the post-osimertinib samples. Among macrophages, 3 clusters (annotated as SELENOP+, SPP1+, PLXDC2+) showed enrichment of cholesterol metabolism with activation of apolipoprotein E that promotes conversion of proinflammatory macrophages into anti-inflammatory phenotypes. Lastly, the proportion of EC9-LYZ, annotated as scavenging endothelial cells was higher in the non-MPR and L858R group. Conclusion: Neoadjuvant osimertinib resulted in the cellular reprogramming in the tumor microenvironment, notably AT1 epithelial cell which may lead to a loop between cancer cells and fibroblasts for the generation of DTP cells. Citation Format: Jii Bum (Joy) Lee, Su-Jin Choi, Young Joon Park, Kyoung-Ho Park, Seung Hyun Yong, Hyo Sup Shim, Byung Jo Park, Chang Young Lee, Min Hee Hong, Byoung Chul Cho, Sun Min Lim. Identifying drug tolerant persister to neoadjuvant osimertinib in resectable non-small cell lung cancer harbouring EGFR mutations (NORA) via single-cell RNA sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5840.