In some embodiments, the methods involve the use of a combination of at least two of the following: an inhibitor of indoleamine-2,3-dioxygenase (IDO), an inhibitor of the PD-L1/PD-1 pathway, an inhibitor of CTLA-4, an inhibitor of CD25, or IL-7. The inventors particularly observed a major synergistic effect of combining anti-CTLA-4 with either an IDO inhibitor, with anti-PD-L1 mAb, or with CD-25 depletion. Such combinations have been found to demonstrate a synergistic effect in treating cancer and tumors, for example by reducing tumor size, increasing the percentage of antigen-specific T cells, and increasing T cell function.
