OBJECTIVES/GOALS: Although the approval of immune checkpoint inhibitors (ICIs) revolutionized the treatment of metastatic breast cancer (BC), yet about 30% remain unresponsive. Since the potency of ICIs depends on the efficient presentation of tumor-specific antigens by cancer cells, compounds which increase such presentation could increase efficacy of ICIs. METHODS/STUDY POPULATION: A library of the ester and urethane derivatives of polyether ionophore antibiotic, monensin (MON) has been synthesized. MTT cell viability assays were performed on the panel of human and mouse BC cell lines, and non-cancerous breast epithelial cells to determine IC50 values of MON and its derivatives. Selectivity Indexes were calculated to identify the most selective compounds towards cancer versus non-cancer cells. Major Histocompatibility Complex (MHC) class I and II presentation and Programmed death-ligand 1 (PD-L1) expression have been determined using flow cytometry. Proteins involved in apoptosis, autophagy and immunogenic cell death were identified through immunoblotting. At least three biological replicates have been performed for each experiment. RESULTS/ANTICIPATED RESULTS: MON and several of its derivatives shown activity in nanomolar range against MDA-MB-231 human BC cell line. MON and its most potent derivatives significantly increased MHC class I and II presentation and downregulated the expression of PD-L1 in BC cell lines. DISCUSSION/SIGNIFICANCE: Present findings will lead to the development of new therapeutic approaches that can serve as single agents or be used in combination with existing ICIs for the treatment of metastatic BC. By pushing the boundaries of our understanding and developing new therapies, this research can make an impact in improving outcomes for patients with metastatic BC.