Abstract CT218: Phase II open label trial of Minnelide™ in patients with chemotherapy refractory metastatic pancreatic cancer

Abstract

Abstract Background: Triptolide and its water-soluble prodrug, Minnelide™, have shown promising activity against pancreatic ductal adenocarcinoma (PDAC) in both in vitro and in vivo experiments. Triptolide induces apoptosis in pancreatic cancer cells by different pathways, including caspase-dependent apoptotic death and caspase -independent autophagic death. It inhibits the activity of the TFIIH general transcription factor complex and modulates the transcriptional landscape of both the stroma and cancer cell compartments. In the epithelial tumour compartment, triptolide down-regulates key transcription factors such as c-MYC. Preclinical investigations indicate significant activity against super enhancer targets. In the phase I clinical trial of Minnelide™ activity in highly refractory metastatic pancreatic carcinoma was observed. Hence, we undertook this study in patients with chemotherapy refractory metastatic PDAC. Our aims were to determine clinical anticancer effects, and to define effects of the drug on super enhancer expression and downstream effects. Methods: Eligibility criteria included stage IV PDAC progressing on standard chemotherapy, Karnofsky performance status ≥ 70%, and measurable disease by RECIST 1.1. Planned sample size was up to 35 patients with interim analysis after the first 18 evaluable patients, aiming for at least a 20% difference in DCR (10% v 30%). Minnelide™ 0.67 mg/m2 was administered intravenously over 30 minutes on days 1-21, followed by a 7-day rest period in a 28-day cycle. Exploratory objectives included: analyses of paired tumour biopsies for changes in immune cell infiltration, stromal activation, chromatin accessibility, proteomics and metabolism. Results: 17 patients were treated. There were no RECIST responses or stable disease. However, evidence of activity was observed in 4 of 15 evaluable patients. This activity included progression after 117 days treatment in 1 patient and reductions in CT tumour size or FDG-PET uptake and/or significant decreases in circulating CA19.9 levels in 3 others. Minnelide was generally well tolerated. Treatment related toxicities > 3 were: neutropenia 4 patients and cerebellar ataxia 1 patient.Exploratory analyses included ATAC-Seq on paired biopsies where gene ontology analyses showed downregulation of genes negatively regulating cell cycle and upregulation of genes controlling cell cycle checkpoints. Other exploratory analyses will be presented. Conclusions: The study identified a tolerable drug dose and evidence of activity in a highly chemotherapy-refractory population which provides encouraging proof for the principle of targeting TFIIH in human PDAC. Supported by SU2C, Cancer Research UK, Lustgarten Foundation Citation Format: David Propper, Erkut Borazanci, Peter J. O'Dwyer, Daniel Von Hoff, Joseph Hartlebury, Corina E. Antal, Gerard I. Evan, HaiYong Han, Michael Downes, Ronald Evans, Joshua Rabinowitz, Emmanuel Petricoin, Ashok Saluja, Mohana Velagapudi, Hitendra Patel. Phase II open label trial of Minnelide™ in patients with chemotherapy refractory metastatic pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT218.