The present invention relates to an attenuated strain of Salmonella comprising at least one copy of a DNA molecule comprising an expression cassette encoding Wilms' Tumor Protein (WT1), for use in the treatment of cancer, wherein the treatment further comprises the administration of at least one checkpoint inhibitor, particularly selected from at least one antibody against PD-1, PD-L1,CTLA-4, IDO, OX-40, GITR, TIM-3, and LAG-3.The present invention further relates to a pharmaceutical composition comprising an attenuated strain of Salmonella comprising at least one copy of a DNA molecule comprising an expression cassette encoding WT1 for use in the treatment of cancer, wherein the treatment further comprises the administration of at least one checkpoint inhibitor, particularly selected from at least one antibody against PD-1, PD-L1,CTLA-4, IDO, OX-40, GITR, TIM-3, and LAG-3.
