ESR1 peptides/GM-CSF/Montanide ISA vaccine

A vaccine comprised of estrogen receptor alpha (ERa; estrogen receptor 1; ESR1) mutant peptides, combined with the immunoadjuvants granulocyte-macrophage colony-stimulating factor (GM-CSF) and montanide ISA, with potential immunomodulating and antineoplastic activities. Upon subcutaneous administration, the ESR1 mutant peptides in the ESR1 peptides/GM-CSF/montanide ISA vaccine may activate the immune system to induce an immune response against tumor cells expressing these ESR1 mutations. Constitutively activating mutations in ESR1 sometimes emerge with the treatment of estrogen receptor (ER)-positive breast cancer with endocrine therapy, leading to resistance to endocrine therapy. GM-CSF and montanide ISA potentiate the anti-tumor immune response.