The present invention relates to pharmaceutical compositions comprising an immunostimulatory amount of at least two immunopotentiators, wherein a first immunopotentiator is a non-methylated cytidyl guanosyl oligodeoxynucleotide (CpG ODN) and a second immunopotentiator is 3 ',5 '-cyclic diguanylic acid (c-di-GMP), and a pharmaceutically acceptable carrier. The invention also relates to the use of such pharmaceutical compositions for the induction of an immune response against tumor-specific antigens. Also the invention relates to their use in in situ tumor-destruction therapy and to such pharmaceutical compositions for use in the treatment of a mammal suffering from cancer.