Actinium-225 and checkpoint inhibitor combination therapy

A method of inducing an immune response to a tumor in a mammal, said method comprising:

• administering to the mammal Actinium-225 (225Ac) targeted to said tumor,
• wherein said administering results in a therapeutically effective immune response which comprises at least 15% of T cells in a tumor sample being specific for a tumor-associated or tumor-specific antigen expressed on the tumor, and
• wherein said mammal also receives one or more checkpoint inhibitors.