Dutogliptin (PHX-1149T) is a small-molecule dipeptidyl peptidase-4 (DPP-4) inhibitor for the potential oral treatment of type 2 diabetes mellitus (T2DM). DPP-4 quickly degrades the insulin secretory hormones, glucose-dependent insulinotropic peptide and glucagon-like peptide-1; thus inhibiting the degradation of these hormones is a viable treatment option for patients with T2DM. In preclinical studies, dutogliptin potently inhibited DPP-4 and, in a model of T2DM, treatment with dutogliptin improved glucose homeostasis. Pharmacokinetic analyses in animals, healthy individuals and patients with T2DM demonstrated that drug exposure increased in a dose-dependent manner. Results from phase II clinical trials indicated that once-daily dutogliptin, in combination with other oral diabetes therapies, reduces postprandial blood glucose and HbA1c levels, both indicators of successful diabetes management. The incidence of adverse events was similar in treatment and placebo groups, with slightly more headache, arthralgia, sinusitis, and dizziness occurring in the 400 mg dutogliptin group compared with placebo. Phase II clinical trial for the myocardial infarction treatment is underway.

Talabostat is a prolineboronate ester derivative patented by Boehringer Ingelheim Pharmaceuticals, Inc. as an antineoplastic agent. Talabostat inhibits dipeptidyl peptidases, such as fibroblast activation protein (FAP), resulting in the stimulation of cytokine and chemokine production and specific T-cell immunity and T-cell dependent activity. Talabostat has been shown to cause caspase-1 activation and IL-1β induction in macrophages, which in turn causes upregulation of the cytokines and chemokines that characterize the responses to talabostat, both in vitro and in tumor-bearing mice. Talabostat may also stimulate the production of colony stimulating factors, such as granulocyte colony stimulating factor (G-CSF), resulting in the stimulation of hematopoiesis. In clinical trials, the combination of talabostat and cisplatin was well tolerated compared to historical data using cisplatin alone. The most frequent adverse events were nausea, vomiting, fatigue, anemia, edema, and constipation. Unfortunately was no evidence that Talabostat enhanced the clinical activity of other anticancer drugs and further development was discontinued.