We propose studies for the preclinical development of BJ-813, a novel agent against breast cancer. BJ-813 has significant activity in vitro (human breast cancer cell lines covering the clinical spectrum of the disease) and in xenograft models of human breast cancer in nude mice. When formulated in liposomes, BJ-813 regresses xenograft tumors. Our hypothesis is that BJ-813 can be developed into an effective therapeutic agent against breast cancer. The fact that the remarkable effect of BJ-813 against breast cancer in tumor animal models is obtained when this drug is formulated in liposomes, suggests that optimizing its formulation will lead to enhanced efficacy and safety.