Dipeptidyl peptidase-4 (DPP-4) is expressed on keratinocytes and its activity is upregulated in psoriasis. DPP-4 inhibition suppresses keratinocyte proliferation and restores partially keratinocyte differentiation. The main site of DPP-4 activity is cluster of differentiation antigen 26 (CD26). CD26 is a marker of T cell activation and is a key molecule in the pathogenesis of autoimmune diseases. One case of DPP-4 inhibitor therapy improving psoriasis severity has been reported.