The present invention provides immunosuppression compounds capable of inhibiting the programmed cell death 1 (PDl) signalling pathway. The present invention further provides peptide based compositions for treatment of cancer or treatment of infections via immunopotentiation caused by inhibition of immunosuppressive signaling induced by PD 1 PD L1 or PD L2 and therapies using them immunopotentiative substrates included as the active ingredient. Further the invention provides an application of the compositions containing the peptide moieties for preventive and/or therapeutic agents for cancer cancer metastasis immunodeficiency an infectious disease or the like and an application of peptide moieties as a testing or diagnostic agent or a research agent for such a disease.
