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.
Azalamellarin N is a pyroptosis inhibitor that exhibits varying inhibitory effects on different pyroptosis inducers. It functions by targeting molecules upstream of NLRP3 inflammasome activation, instead of directly affecting the components of the NLRP3 inflammasome. Its inhibitory potency against various inducers is ranked as follows: Nigericin > R837 [1].
LL-37 is a cationic and α-helical antimicrobial peptide expressed in human bone marrow, testis, granulocytes, and gingival epithelium and is upregulated in psoriatic lesions. It inhibits growth of Gram-positive E. coli D21 and Gram-negative B. megatarium in a concentration-dependent manner and LL-37 expression is induced in A549 epithelial cells, alveolar macrophages, neutrophils, and monocyte-derived macrophages following M. tuberculosis infection. LL-37 binds sheep erythrocytes coated with S. minnesota Re-LPS and induces agglutination with a minimal agglutinating concentration (MAC) of 12.1 μg/ml. It is a chemoattractant for, and can induce calcium mobilization in, human monocytes, neutrophils, and T cells that naturally express formyl peptide receptor-like 1 (FPRL1) and FPRL1-transfected HEK293 cells. LL-37 (10-15 μM) pretreatment of dengue virus type 2 (DENV-2) reduces its infectivity as well as levels of viral genomic RNA and NS1 antigen. In vivo, LL-37 inhibits cecal ligation and puncture-induced caspase-1 activation and pyroptosis of peritoneal macrophages, reduces levels of the inflammatory cytokines IL-1β, IL-6, and TNF-α, and improves survival in polybacterial septic mice.