Abstract 5849: Re-Phen, a novel OXPHOS enhancer that reprograms T cell mitochondrial metabolism to potentiate anti-PD-1 immunotherapy

Abstract Introduction: Immune checkpoint inhibitors fail to control most PDAC tumors. Identifying novel ways to enhance immunotherapy in PDAC is highly desired. This study aimed to evaluate a new phenformin analogue, termed Re-Phen, that targeted intratumoral dysregulated metabolism pathways. Methods: Re-Phen was encapsulated into a polymeric micellar to give MRP. 99mTc-Phen, a structurally matched radiotheranostic counterpart of Re-Phen was also synthesized and encapsulated into polymeric micelles (i.e. 99mTc-MRP) for SPECT/CT imaging and biodistribution study. 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 models murine Kras* PDAC cells. In addition, immune cells in Kras* tumor and spleen of MRP-treated mice were profiled at 5 days after initiation of treatments. Results: SPECT/CT with 99mTc-MRP and biodistribution studies revealed that MRP had higher uptake in tumor and reduced uptakes in the liver and kidneys compared to un-encapsulated Re-Phen. In vitro, Re-Phen displayed similar activity as Phen in reducing mitochondrial membrane potential. However, unlike Phen, Re-Phen reduced ROS, increased ATP production by OXPHOS instead of by glycolysis without suppress T cell proliferation. In the orthotopic Kras* model, MRP administered at a dose of 12.5 mg/kg in combination with anti-PD-1 demonstrated superior anti-tumor efficacy, achieving a long-term survival rate of 55.6%. In comparison, mice treated with MRP at 25 mg/kg plus anti-PD-1, anti-PD-1 alone, MRP (12. 5 mg/kg) alone, and untreated control achieved long-term survival rate of 33.3%, 12.5%, 0%, and 0%, respectively. In a subcutaneous Kras* PDAC model, MRP plus anti-PD-1 showed strong abscopal effect as evidenced by suppression of tumor growth in the contralateral tumors that were not treated by a local intervention with irreversible electroporation (IRE). Moreover, MRP significantly increased survival rates when combined with IRE and anti-PD1 in the subcutaneous Kras* PDAC model. The triple combination achieved an 87.5% long-term survival rate, compared to 25% with IRE alone and 25% with anti-PD1 alone. In the subcutaneous pancreatic tumor models, the combination of MRP and anti-PD1 therapy elicited a stronger immune response compared to the untreated and anti-PD1-only groups. This included an increase in CD4+ T cells, CD8+ T cells, and dendritic cells (DCs) in both tumors and spleens, along with a reduction in neutrophils. Conclusions: Re-Phen is a novel OXPHOS enhancer that induced a robust antitumor immune response, resulting in potentiation of antitumor immunotherapy. Further development of this class of drugs is warranted. Citation Format: Boping Jing, Qiuxu Teng, Guodong Zhang, Chiyi Xiong, Ping Pan, Qizhen Cao, Ningbo Zhang, Si Chen, Weiyi Peng, Chun Li. Re-Phen, a novel OXPHOS enhancer that reprograms T cell mitochondrial metabolism to potentiate anti-PD-1 immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5849.