Synthetic biology is driving a new era of medicine through the genetic programming of living cells. One particular focus has been the engineering of bacteria as therapeutic delivery systems for cancer, where microbes colonize and release payloads within tumors. Here, genetic circuits are designed to enhance spatial and temporal control of microbial behaviors for improved safety and efficacy. In this talk, I will highlight our recent efforts to develop bacterial biosensors, encapsulation strategies, and effective delivery systems for payloads ranging from cytotoxic to immunomodulatory agents. I will also discuss the progression from bacteria as single agents toward their engineered interactions with other programmable medicines using synthetic biology.