The present invention refers to immunosuppression-reverting oligonucleotides comprising 12 to 18 nucleotides, wherein at least one of the nucleotides is modified, and the oligonucleotide hybridizes with a nucleic acid sequence of indoleamine-2,3-dioxygenase (IDO-1) of SEQ ID NO.1 (human) in a hybridizing active area, wherein the oligonucleotide inhibits at least 50% of the IDO-1 expression. The invention is further directed to a pharmaceutical composition comprising such oligonucleotide.
