Abstract C073: FOLFIRINOX with Glycogen Synthase Kinase-3 Beta (GSK-3β) Inhibitor Elraglusib and Transforming Growth Factor- β (TGFβ) Inhibitor Losartan in Untreated Metastatic Pancreatic Ductal Adenocarcinoma(PDAC): Interim analysis of safety cohort

Abstract Introduction: Epithelial-mesenchymal transition (EMT) is one of the key drivers of aggressive biology and development of chemoresistance in PDAC. Inhibition of glycogen synthase kinase 3β (GSK3β) may offer a promising novel approach for modulating dynamic EMT plasticity to overcome resistance to FOLFIRINOX (5-Fluororuacil, Irinotecan, Oxaliplatin, FFX). Methods: Cell line panels comprising both epithelial (E) and quasi-mesenchymal (QM) subtypes were used and treated with IC50 (0.3125 mM) and IC100 (1.25 mM) doses of elraglusib (ELR). Gene expression patters in response to treatment were analyzed using bulk RNA sequencing. 6 patients in the safety run-in cohort of NCT05077800 treated with standard doses of FFX, ELR and losartan were included in this interim analysis. Biopsy specimens were processed for RNA-in situ hybridization (RNA-ISH), a clinically validated assay, and Nanostring (GeoMx) spatial transcriptomics. Results: In preclinical models, exposure to the higher IC100 (1.25 mM) doses of ELR in the QM cell lines caused a shift in transcriptional expression patterns similar to the E cell line, with strong downregulation of EMT. FFX exposure alone in QM cell lines was associated with significant resistance, but addition of ELR (even at IC50 dose) caused a synergistic effect with decreased cell viability. However, in the E cell lines, there was no benefit from addition of ELR. In the safety cohort, clinical results are encouraging with a long-term (>6 month) response in 3/6 patients. 2/6 achieved partial response, 1/6 had stable disease. Nanostring (GeoMx) spatial transcriptomic profiling on available biopsy samples showed significant global gene expression changes before and after treatment. There were concordant changes in 97 differentially expressed genes (DEGs) within the epithelial compartment with treatment, similar to ELR induced changes in PDAC cell lines, with a shift in transcriptional expression patterns from QM to E subtype. Gene set enrichment analysis demonstrated downregulation of the EMT pathway, as well as decreased TGF-β signaling. RNA-ISH analysis on baseline biopsy samples showed that the two partial (best) responders had higher degrees of QM marker expression (82.58% and 63.76%). The regimen was well tolerated with no dose limiting toxicity noted in the safety cohort. Conclusion: Our experiments demonstrate that the E subtype PDAC cell lines are inherently sensitive to FFX chemotherapy with no added advantage with GSK3β inhibition. Meanwhile, GSK3β inhibition in QM cell lines induces mesenchymal to epithelial transition, thereby rendering it sensitive to FFX. The data from our safety cohort provide a clinical proof of concept that GSK-3β inhibition with ELR, in combination with FFX, may be an effective therapeutic strategy in metastatic PDAC. NCT05077800 is currently enrolling. Citation Format: Priyadarshini Pathak, Eric Lin, Ildiko Phillips, David Ting, Colin Weekes. FOLFIRINOX with Glycogen Synthase Kinase-3 Beta (GSK-3β) Inhibitor Elraglusib and Transforming Growth Factor- β (TGFβ) Inhibitor Losartan in Untreated Metastatic Pancreatic Ductal Adenocarcinoma(PDAC): Interim analysis of safety cohort [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr C073.