Abstract 7024: Simultaneous targeting of CHI3L1 and PD-1/PD-L1 axis to overcome drug resistance and immune tolerance of EGFR non-small cell lung cancer.

Abstract Background: Lung cancer is the leading cause of cancer deaths worldwide. Non-small cell lung cancer(NSCLC) accounts for 85% of all lung cancers. The overall prevalence rate of NSCLC with epidermalgrowth factor receptor (EGFR) mutations are significantly increasing in US. Oncogenic EGFR is atransmembrane protein which gets auto-phosphorylated to cause EGFR mutations (L858R, T790M, exon-19-deletion) in exon 18-21. Tyrosine kinase inhibitors (TKIs) are effectively targeted to treat mutated EGFRlung cancer. These TKIs showed favorable responses on patient’s treatments for 9-18 months but duringthe treatment, patients acquired EGFR mutations which results into the TKIs drug resistance and at thatpoint TKIs stops its efficacy for further treatment. Thus, there is a high medical unmet need for a newtherapeutic strategy to overcome drug resistance in patients with EGFR mutations. CHI3L1 expressed bymacrophages, neutrophils, epithelial cells, smooth muscle cells, chondrocytes including other immune cells.The levels of circulating CHI3L1 are increased in many malignancies including cancers of the prostate,colon, rectum, ovary, kidney, breast, glioblastomas, malignant melanoma, and lung cancer. CHI3L1contributes to pulmonary metastasis and spread via the regulation of immune-checkpoint (ICP) molecules.Our studies showed that CHI3L1 regulates and is a potent stimulator of PD-1/PD-L1 and PD-L2. CHI3L1stimulates the EGFR physiologic ligands EGF or TGF-a, a well-defined growth factors that stimulate EGFRphosphorylation. EGFR-YAP/TAZ signaling plays a growth-promoting role in cancers harboring EGFRalterations, and that inhibition of YAP/TAZ in combination with EGFR might be beneficial to prevent TKIdrug resistance and cancer recurrence. Methods: We analyzed EGFR mutant and resistant cells using techniques qPCR, protein accumulation,immuno-pull-down assay, immunofluorescence, FACS and therapeutic effect of YAP inhibitors in-vitroand in-vivo. Results: We identified that CHI3L1 augments YAP/TAZ nuclear translocation in EGFR mutant and TKIresistant cells. Also, YAP/TAZ inhibitors and agonists (Verteporfin, K-975) able to block YAP/TAZactivation and that suppress PD-1/PD-L1 in EGFR mutant and TKI resistant cells. Conclusion: These findings led us to understand that CHI3L1 and PD-1/PD-L1 axis mediated throughactivation of Hippo-YAP/TAZ signaling pathways play an essential role in TKIs drug resistance andimmune tolerance that enhances the progression of EGFR NSCLC. Additionally, simultaneous targeting ofCHI3L1 and PD-1/PD-L1 axis employing bispecific antibody (CHI3L1xPD-1) may provide a bettertherapeutic option to overcome TKI resistance and immune tolerance of EGFR NSCLC. Citation Format: Suchitra Kamle, Bing Ma, Brianna Pham, Isabella Fish, Marlo Hulnick, Taka Sadanaga, Hanseok Jeong, Mara Hofstetter, Hina Khan, Christopher Azzoli, Katerina A. Politi, Roy S. Herbst, Chun Geun Lee, Jack Elias. Simultaneous targeting of CHI3L1 and PD-1/PD-L1 axis to overcome drug resistance and immune tolerance of EGFR non-small cell lung cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 7024.