Discovery of selective and nonpeptidic cathepsin S inhibitors

Design and synthesis of dual cathepsin L and S inhibitors and antimetastatic activity evaluation in pancreatic cancer cells

Currently, the migration and invasion of cancer cells remain the main factors of poor prognosis in the majority of cancer patients. Developing an effective antimetastatic agent is crucial for cancer therapy. Our recent research revealed that Cat L and S are expressed concurrently in metastatic pancreatic cancer cells. Asperphenamate analog ASPER-29, which exhibits dual Cat L and S inhibitory potency, showed a definite antimetastatic effect on pancreatic cancer BxPC-3 and PANC-1 cells. To further improve the antimetastatic ability of asperphenamate-type molecules, 24 derivatives were designed and synthesized by a scaffold-hopping strategy. The cathepsin inhibitory activity assay results showed that most of the derivatives exhibited dual inhibitory effects on Cat L and S. Among all derivatives, Compound B1a showed the strongest inhibitory activity, with IC50 values of 4.10 ± 0.14 μM and 1.79 ± 0.11 μM, which were 1.5-fold and 2.8-fold more potent than those of positive drugs against Cat L and S, respectively. Further wound-healing and transwell chamber assays demonstrated that B1a presented significant antimetastatic ability in vitro.

Cathepsins: Proteases that are vital for survival but can also be fatal

The state of enzymes in the human body determines the normal physiology or pathology, so all the six classes of enzymes are crucial. Proteases, the hydrolases, can be of several types based on the nucleophilic amino acid or the metal cofactor needed for their activity. Cathepsins are proteases with serine, cysteine, or aspartic acid residues as the nucleophiles, which are vital for digestion, coagulation, immune response, adipogenesis, hormone liberation, peptide synthesis, among a litany of other functions. But inflammatory state radically affects their normal roles. Released from the lysosomes, they degrade extracellular matrix proteins such as collagen and elastin, mediating parasite infection, autoimmune diseases, tumor metastasis, cardiovascular issues, and neural degeneration, among other health hazards. Over the years, the different types and isoforms of cathepsin, their optimal pH and functions have been studied, yet much information is still elusive. By taming and harnessing cathepsins, by inhibitors and judicious lifestyle, a gamut of malignancies can be resolved. This review discusses these aspects, which can be of clinical relevance.

Design, synthesis, and biological evaluation of pyrimidine-2-carboxamide analogs: investigation for novel RAGE inhibitors with reduced hydrophobicity and toxicity

This paper describes an investigation of novel RAGE inhibitors with improved drug-like properties. To identify the improved drug-like RAGE inhibitor, we designed and synthesized pyrimidine-2-carboxamide analogs based on our previous work. Several potent analogs with improved hydrophilicity were identified by evaluation of RAGE inhibitory activity. In particular, one of the potent (diethylamino)ethoxymethoxy analogs did not exhibit undesired cytotoxicity in contrast with the parent RAGE inhibitors.

Effects of novel human cathepsin S inhibitors on cell migration in human cancer cells

Elevated cathepsin S (Cat S) level is correlated with higher migration ability in tumor cells. This study investigates the inhibitory effect of novel synthetic α-ketoamide compounds on cathepsin activity and cancer cell migration. The effect of several α-ketoamide compounds on the activity of recombinant cathepsins (Cat S, Cat L and Cat K) was examined. Two highly metastatic cancer cell lines were incubated with three Cat S-specific compounds (6n, 6 w and 6r) to analyze their effect on cellular Cat S activity and cell migration. At a 100 nM concentration, compounds 6n, 6r and 6 w effectively inhibited Cat S activity. Cat S activity and cell migration were significantly reduced in CL1-3 cells after treatment with either 6n or 6 w at 5 μM. Similar results were also obtained when A2058 cells were treated with 6n. These results highlight the therapeutic potential of α-ketoamide compounds, especially 6n and 6 w, to prevent or delay cancer metastasis.

Azepanone-based inhibitors of human cathepsin S: optimization of selectivity via the P2 substituent

A series of azepanone inhibitors of cathepsin S is described. Selectivity over both cathepsin K and cathepsin L was achieved by varying the P2 substituent. Ultimately, a balanced potency and selectivity profile was achieved in compound 39 possessing a 1-methylcyclohexyl alanine at P2 and nicotinamide as the P' substituent. The cellular potency of selected analogs is also described.