Abstract Body: Anthracyclines are a key component in the management of pediatric cancers long recognized to carry significant risk of dose-dependent cardiotoxicity. Despite advancements in clinical management, considerable variation in the incidence of cardiotoxicity persists across dosing regimens suggesting modifiers exist. Recently, changes in the splicing of TNNT2, the gene encoding cardiac troponin T (cTnT), were postulated to contribute to anthracycline cardiotoxicity, potentially providing a direct link to the myofilament. Previous studies in our lab have demonstrated that the fetal isoform, cTnT1, is a potent modifier of cardiac function contributing to disease heterogeneity in animal models of cardiomyopathies. Thus, we hypothesize that the persistent expression of cTnT1 predisposes a subset of the population to anthracycline cardiomyopathy. Using molecular dynamics simulations (MD) and isothermal titration calorimetry (ITC), we assessed a range of anthracyclines for their potential to bind the cardiac thin filament (CTF). MD calculated Glide scores showed direct binding to the troponin complex. ITC indicated that this binding occurs at an order of magnitude higher affinity in complexes containing cTnT1. Stopped-flow kinetics of cTnT1 CTFs exposed to Doxorubicin showed an additive reduction in calcium dissociation rates, reinforcing our observations of direct binding to the CTF. Longitudinal 2D echocardiography of Doxorubicin treated mice (3mg/kg/week) indicated that both male and female cTnT1 mice exhibit an additive, dose-dependent reduction in cardiac systolic function compared to non-transgenic (NT) littermates. Consistent with clinical data, female mice exhibited an earlier reduction in % fractional shortening than males as well as delayed recovery after treatment cessation. Transcriptional profiling of mice treated with Doxorubicin revealed a 2- to 7-fold additive increase in type I and type II interferon signaling in cTnT1 mice above that observed in treated NT littermates. These data suggest that cTnT1 may increase binding of anthracyclines at the myofilament, eliciting accelerated cardiac dysfunction, and represent a unique, targetable genetic risk factor involved in anthracycline cardiotoxicity.