Concerted efforts have led to the development of medical countermeasures against acute radiation toxicity in victims of a radiological accident or nuclear terrorism, thereby significantly increasing the chance of survival if such a radiological event were to occur today. However, survivors of acute radiation toxicities may develop delayed injuries that become clinically apparent months to years after exposure. Cardiovascular disease is one of the main sources of morbidity and mortality in survivors of acute exposure to ionizing radiation. Nearly ten percent of Japanese atomic bomb survivors died of cardiovascular disease, and cancer patients undergoing thoracic radiation therapy (RT) involving cardiac exposures exhibit a 1.7- to 2-fold greater heart disease mortality. In several reports, patients treated with RT for esophageal cancer exhibited a 1-in-3 chance of pericardial effusion with median occurrence post-treatment of only 6 months. Since clinical reversal of radiation-induced cardiovascular disease is difficult, if not impossible once a survivor becomes symptomatic, it is critical to identify such injuries sooner so that the proper interventions can begin. Therefore, availability of a blood-based test that would predict risk for delayed radiation injuries such as in the heart in asymptomatic victims of radiation incidents is an urgent and unmet need. Herein, we propose to extend our SBIR Phase I work to further develop our multi-omics-based CardioWatch biomarker assay. In our Phase I effort, the CardioWatch panel predicted radiation-induced heart disease in mouse models of exposure to gamma-rays (AUC >90%). Furthermore, biomarkers in this panel were also found to be dysregulated in serum of non-human primates (NHP) 3-6 days after partial body irradiation. Finally, the panel was verified in a cohort of patients that developed cardiac complications following RT for esophageal cancer. In the proposed Phase II study, we will conduct a rigorous analytic validation of the CardioWatch assay, followed by blinded validation in test samples from rat models as well as longitudinally collected samples from an elite survivor cohort of NHPs (N=56, sampling at 3 time points) and a cohort of esophageal cancer patients (N=45) undergoing RT with monitoring for cardiac outcomes. FDA biomarker qualification guidance will be sought at all steps to ensure successful completion of technical objectives compliant with guidelines for evaluating commercialization potential of biomarker-based tests. The final product of this study will be a multi-omics biomarker assay replete with detailed standard operating procedures and a software algorithm (MetaboWatch) with a graphical user interface provides interpretation of biomarker data and an overall risk score. Cross-validation among a spectrum of biological samples will establish and solidify performance measurements for the CardioWatch assay at independent clinical sites for future clinical use. The CardioWatch assay cou...