Talabostat mesylate (Val-boroPro mesylate; PT100 mesylate) is an orally active and nonselective dipeptidyl peptidase IV (DPP-IV) inhibitor (IC50 Ki = 0.18 nM) and the first clinical inhibitor of fibroblast activation protein (FAP) (IC50 = 560 nM), inhibits DPP8/9 (IC50 = 4/11 nM; Ki = 1.5/0.76 nM), quiescent cell proline dipeptidase (QPP) (IC50 = 310 nM), DPP2, and some other DASH family enzymes. Antineoplastic and hematopoiesis- stimulating activities.