Talabostat (PT100, Val-boroPro) is a potent, nonselective and orally available dipeptidyl peptidase IV (DPP-IV) inhibitor with a Ki of 0.18 nM. Talabostat is a nonselective DPP-IV inhibitor, inhibiting DPP8 9, FAP, DPP2 and some other DASH family enzymes essentially as potently as it inhibits DPP-IV[1]. Talabostat stimulates the immune system by triggering a proinflammatory form of cell death in monocytes and macrophages known as pyroptosis. The inhibition of two serine proteases, DPP8 and DPP9, activates the proprotein form of caspase-1 independent of the inflammasome adaptor ASC[2]. Talabostat competitively inhibits the dipeptidyl peptidase (DPP) activity of FAP and CD26 DPP-IV, and there is a high-affinity interaction with the catalytic site due to the formation of a complex between Ser630 624 and the boron of talabostat[3]. Talabostat can stimulate immune responses against tumors involving both the innate and adaptive branches of the immune system. In WEHI 164 fibrosarcoma and EL4 and A20 2J lymphoma models, PT-100 causes regression and rejection of tumors. The antitumor effect appears to involve tumor-specific CTL and protective immunological memory. Talabostat treatment of WEHI 164-inoculated mice increases mRNA expression of cytokines and chemokines known to promote T-cell priming and chemoattraction of T cells and innate effector cells[3]. Talabostat treated mice show significant less fibrosis and FAP expression is reduced. Upon PT100 treatment, significant differences in the MMP-12, MIP-1α, and MCP-3 mRNA expression levels in the lungs are also observed. Treatment with PT100 in this murine model of pulmonary fibrosis has an anti-fibro-proliferative effect and increases macrophage activation[4]. [1]. Connolly BA, et al. Dipeptide boronic acid inhibitors of dipeptidyl peptidase IV: determinants of potencyand in vivo efficacy and safety. J Med Chem. 2008 Oct 9;51(19):6005-13. [2]. Okondo MC, et al. DPP8 and DPP9 inhibition induces pro-caspase-1-dependent monocyte and macrophage pyroptosis. Nat Chem Biol. 2017 Jan;13(1):46-53. [3]. Adams S, et al. PT-100, a small molecule dipeptidyl peptidase inhibitor, has potent antitumor effects and augments antibody-mediated cytotoxicity via a novel immune mechanism. Cancer Res. 2004 Aug 1;64(15):5471-80. [4]. Egger C, et al. Effects of the fibroblast activation protein inhibitor, PT100, in a murine model of pulmonary fibrosis. Eur J Pharmacol. 2017 Aug 15;809:64-72.
(±)19(20)-EDP ethanolamide is an ω-3 endocannabinoid epoxide and cannabinoid (CB) receptor agonist (EC50s = 108 and 280 nM for CB1 and CB2, respectively). It is produced through direct epoxygenation of docosahexaenoyl ethanolamide by cytochrome P450 (CYP) epoxygenases. (±)19(20)-EDP ethanolamide (25 μM) reduces the viability of 143B metastatic osteosarcoma cells. It decreases the production of IL-6 and increases the production of IL-10 when used at concentrations ranging from 2.5 to 10 μM in BV-2 microglia stimulated by LPS and decreases LPS-induced cytotoxicity when used at concentrations ranging from 5 to 10 μM. It also decreases nitrite production when used at a concentration of 7.5 μM, an effect that can be partially reversed by the CB2 receptor antagonist AM630 and the PPARγ antagonist GW 9662 . (±)19(20)-EDP ethanolamide induces vasodilation of isolated preconstricted bovine coronary arteries (ED50 = 1.9 μM) and reduces tube formation by human microvascular endothelial cells (HMVECs) in a Matrigel assay.