This fast track Phase I/II contract will develop a 177Lu-based PSMA-targeted radiotherapy for prostate cancer. Phase I will identify a commercializable lead PSMA-targeted radiotherapy that will be advanced to manufacturing and IND-enabling studies in Phase II of this contract. Our current agent [177Lu]CTT1401 will be compared to an analog [177Lu]CTT1403 in terms of synthetic ease, in vitro performance, biodistribution, and preliminary efficacy studies. [177Lu]CTT1403 differs from [177Lu]CTT1401 in that it contains an auxiliary albumin binding motif, which is expected to exhibit a slower rate of clearance. Either [177Lu]CTT1401 or [177Lu]CTT1403 will be selected as CTT?s PSMA-targeted radiotherapeutic agent based on the following deliverables from Phase I: ? Synthetic ease, cost of goods and scalability (amenable to GMP manufacture) ? In vitro performance; cell specificity and internalization will be evaluated to ensure the modifications do not diminish the uptake and internalization of the radiotherapeutic platform in PSMA+ cells ? Biodistribution studies will be conducted to determine the effectiveness of tumor targeting as well as the pharmacokinetics of the 177Lu-labeled PSMA-targeted radiotherapeutic agents. ? Preliminary efficacy studies will be conducted to further justify the selection of one of these agents to advance to the Phase II component of this proposal