Talabostat is a non-selective inhibitor of dipeptidyl peptidases (DPPs), including DPP-4, DPP-7, DPP-8, DPP-9, fibroblast activation protein (FAP), and prolyl endopeptidase (PREP; IC50s = >4, 310, 4, 11, 560, and 390 nM, respectively). It inhibits proliferation of superantigen-stimulated human peripheral blood mononuclear cells (PBMCs; IC50 = ~10 nM). Talabostat (5 μg twice per day) increases expression of a variety of cytokines, including those encoding IL-1β, IL-6, and G-CSF, and chemokines in tumors and tumor-draining lymph nodes in a WEHI-164 fibrosarcoma mouse model. It reduces tumor growth in WEHI-164, MM45T.Sp, and MM52.T fibrosarcoma, EL-4 and A20/2J lymphoma, B16/F10 melanoma, and P815 mastocytoma syngeneic mouse models. Talabostat also increases the efficacy of the antitumor antibodies rituximab and trastuzumab in Namalwa B cell lymphoma and LS180 colon carcinoma mouse xenograft models, respectively.
