Singlet oxygen is the primary agent responsible for the therapeutic effects of photodynamic therapy (PDT). In this work, we demonstrate that singlet oxygen release due to thermal endoperoxide cycloreversion can be targeted towards specific features of selected cancer cells, and this targeted singlet oxygen delivery can serve as an effective therapeutic tool. Thus, cytotoxic singlet oxygen can be delivered regioselectively into prostate specific membrane antigen (PSMA) overexpressing lymph node carcinoma (LNCaP) cells. However, unlike typical photodynamic processes, there is no need for light or oxygen. The potential of the approach is exciting, considering the limitations on the availability of light and oxygen in deep-seated tumors.