Abstract A096: Re-Phen, a phenformin analogue potentiates anti-PD-1 immunotherapy by enhancing T cell mitochondrial energetics

Abstract Introduction: Immune checkpoint inhibitors have limited efficacy in treating most pancreatic ductal adenocarcinoma (PDAC) tumors. Novel strategies to enhance immunotherapy in PDAC are urgently needed. This study investigates a new rhenium tricarbonyl phenformin complex, termed Re-Phen, designed to target mitochondrial metabolic pathways. Methods: Re-Phen was synthesized from phenformin and (NEt4)2[Re(CO)3Br3], Re-Phen was further encapsulated in a stable polymeric micelles (M-Re-Phen) to enable systemic administration. The effects of Re-Phen on mitochondrial membrane potential, generation of reactive oxygen species (ROS), and ATP production were studies in vitro with both tumor cells and T cells. Antitumor efficacy of MRP in combination with anti-PD-1 was studied in both subcutaneous and orthotopic inoculated murine Kras* PDAC cells with inducible KrasG12D mutation. In addition, immune cells in Kras* tumor and spleen of MRP-treated mice were profiled at 5 days after initiation of treatments. Single-cell RNA sequencing was performed to explore the mechanism by which Re-Phen acts as an immune adjuvant. Additionally, immune cell profiles in Kras* tumors were analyzed by flow cytometry five days after treatment initiation in MRP-treated mice. Results: In vitro, Re-Phen more potently reduced mitochondrial membrane potential than phenformin. However, Re-Phen but not phenformin reduced ROS level. Real-time ATP production rate analysis showed that unlike phenformin, which is known to inhibit oxidative phosphorylation (OXPHOS) and reduce mitochondrial ATP production, Re-Phen increased mitochondrial ATP production without affecting ATP generation by glycolysis, suggesting that Re-Phen and phenformin may act through distinct mechanisms on T cell metabolic programs. In the orthotopic Kras* model, M-Re-Phen administered intravenously at a dose of 12.5 mg/kg in combination with intraperitoneally injected anti-PD-1 significantly prolonged media survival compared to untreated control. Single-cell sequencing analysis indicated that Re-Phen combined with anti-PD-1 inhibited epithelial-mesenchymal transition (EMT), promoted antigen processing, increased the proportion of CD8+ T cells, and enhanced mitochondrial metabolism within CD8+ T cells. These findings were corroborated by increased CD8+ T cells observed in flow cytometry study. Conclusions: Re-Phen is a novel phenformin analogue that reprogramed T cell OXPHOS activity and bioenergetics while inhibiting tumor cell EMT, resulting in increased anti-tumor immunity in combination with anti-PD-1 immunotherapy. Further development of this class of drugs is warranted. Citation Format: Boping Jing, Qiuxu Teng, Guodong Zhang, Chiyi Xiong, Ping Pan, Qizhen Cao, Amir Gholizadeh, Diana Chow, Ningbo Zheng, Si Chen, Weiyi Peng, Chun Li. Re-Phen, a phenformin analogue potentiates anti-PD-1 immunotherapy by enhancing T cell mitochondrial energetics [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research—Emerging Science Driving Transformative Solutions; Boston, MA; 2025 Sep 28-Oct 1; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl_3):Abstract nr A096.