Monitoring Extracellular Oxygenation Modulation with myo-inositol tripyrophosphate using EPRI

Motivation: We showed previously that multispectral optoacoustic tomography (MSOT) measures oxygen saturation (%sO2) of intravascular hemoglobin which can indirectly evaluate the effect of a radiosensitizer, inositol tripyrophosphate (ITPP), on tumor oxygenation. Electron paramagnetic resonance imaging (EPRI) could serve as a more direct biomarker by measuring the extravascular, extracellular oxygen pressure (pO2) in pre-clinical tumor models. Goal(s): Validate prior MSOT results showing decrease in hemoglobin saturation with ITPP. Approach: Use EPRI to observe extracellular oxygenation before and after treatment with ITPP compared with vehicle control. Results: Tumors treated with ITPP demonstrated lower extracellular oxygenation compared to pretreatment levels (p = 0.003). Impact: An imaging biomarker to determine how much a radiosensitizer improves tumor pO2 would dramatically impact clinical care by potentially improving response to radiotherapy and immunotherapy. EPRI could evaluate the effect of a radiosensitizer allowing for more personalized treatment approaches.