Abstract PS3-13-10: Immunomodulation of Tumor Microenvironment by Reversing Hypoxia

Abstract Background: Triple-negative breast cancer (TNBC) is an aggressive subtype with limited treatment options and higher mortality than other breast cancer subtypes. Tumor hypoxia due to rapid proliferation of cancer cells impairs T cell infiltration and function in TNBC. Although reversing tumor hypoxia has shown promise in pre-clinical tumor models, existing oxygenation strategies remain limited for clinical translation. NanO2 (NuvOx Pharma), a novel perfluorocarbon-based oxygen therapeutic composed of 2% w/v dodecafluoropentane, improves tissue oxygenation without receptor binding. It has been shown to reverse tumor hypoxia in preclinical models and in patients with Glioblastoma Multiforme. We hypothesized, that reversing hypoxia with NanO2 will change tumor microenvironment (TME) to enhance response to immunotherapy and chemotherapy. Methods: We tested NanO2 on hypoxia reversal, changes in TME in a syngeneic TNBC model (4T1 cells in BALB/c mice). Flow cytometry and IHC (CD4, CD8a, CD19, CD206, F4/80, PD-1) were used to characterize immune cell populations. In our first series of experiments we tested the effect of NanO2 with/without oxygen in 2 dosing regimens: single dose or five daily doses. Seventy mice received either saline or NanO2 intravenously, with air or O2 exposure for 17 days starting on day 5 post-tumor implantation. In the second series of experiments, we tested the effect of NanO2 in combination with immunotherapy (IT), chemotherapy (CTX, paclitaxel) or both IT and CTX. BALB/c mice were treated for three weeks starting on day 3 post-implantation with IV NanO2 (every 3 days), anti-PD-1 (200 µg IV every 5 days), Paclitaxel (2 µg/g IP every 3 days), or combinations. Due to unexpected mortality, only 26 mice reached the endpoint. Results: Treatment with NanO2 decreased hypoxic cells when combined with oxygen. In addition, it decreased PD-1 positive cells, increased CD8 cell infiltration. Tumor associated macrophages (TAMs) were also increased. PD-1 expression decreased supporting that reversing hypoxia can enhance response to IT. In addition, in the second series of experiments we demonstrated that the TME changes by NanO2 +oxygen were enhanced by IT, CTX and combination IT+CTX. Conclusions: NanO2 synergizes with immunotherapy and chemotherapy to remodel the TME to enhance anti-tumor immune responses in in vivo TNBC models. Citation Format: P. Egwon, A. Nanduru, A. Kiss, G. Cresswell, D. Roe, E. Unger, J. Johnson, P. Chalasani. Immunomodulation of Tumor Microenvironment by Reversing Hypoxia abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS3-13-10.