PJ34 is a phenanthridinone derivative that acts as a competitive poly(ADP)-ribose polymerase (PARP) inhibitor. PJ34 exhibits cardioprotective, neuroprotective, anticancer, and anti-diabetic activities. In in vitro and in vivo models of oxygen glucose deprivation, PJ34 protects against stroke-related ischemic brain injury. This compound is also cardioprotective against myocardial infarction, decreasing infarct size and postsystolic shortening. In diabetic NOD mice, PJ34 decreased insulitis, beta-cell destruction, and diabetes incidence by decreasing islet IFN-γ expression and inducing apoptosis in islet-infiltrating leukocytes. In mouse models of allergic encephalitis, PJ34 exhibits protective benefit by shifting the immune response from a pro-inflammatory Th1-mediated response to an anti-inflammatory Th2-mediated response. Additionally, in a variety of cancer cell lines, PJ34 induces G2/M phase mitotic arrest and caspase-depedent apoptosis, potentially due to direct antagonism of Pim-1 kinase.