Trypanocidal activity of new 1,6-diphenyl-1H-pyrazolo[3,4-b]pyridine derivatives: Synthesis, in vitro and in vivo studies.

Despite the serious public health problems caused by Chagas disease in several countries, the available therapy remains with only two drugs that are poorly active during the chronic phase of the disease in addition to having severe side effects. In search of new trypanocidal agents, herein we describe the synthesis and biological evaluation of eleven new 1,6-diphenyl-1H-pyrazolo[3,4-b]pyridine compounds containing the carbohydrazide or the 2,3-dihydro-1,3,4-oxadiazole moieties. Two of them showed promising in vitro activity against amastigote forms of T. cruzi and were evaluated in vivo in male BALB/c mice infected with T. cruzi Y strain. Our results suggest that the substitution at the C-2 position of the phenyl group connected to the carbohydrazide or to the 2,3-dihydro-1,3,4-oxadiazole moieties plays an important role in the trypanocidal activity of this class of compounds. Moreover, the compound containing the 2,3-dihydro-1,3,4-oxadiazole moiety has demonstrated more favorable structural requirements for in vivo activity than its carbohydrazide analog.

2H-1,2,3-Triazole-chalcones as novel cytotoxic agents against prostate cancer.

Prostate cancer is an important cause of death in the male population and for which there is no satisfactory chemotherapy. Herein a new series of chalcone hybrids containing 2H-1,2,3-triazole core as the ring B has been synthesized and evaluated in vitro against PC-3 prostate cancer cell line. Compounds 4a, 4c and 4e significantly reduced cell viability and showed IC50 of 28.55, 15.64 and 25.56 µM, respectively. The structure-activity relationship supported by computational chemistry points that the polarity of the molecular surface area should have some relevance to the efficiency of the compounds, in particular the ratio of the partial positive charge sites and the total molecular surface area exposed to the cell environment.

Biological evaluation and molecular modeling of peptidomimetic compounds as inhibitors for O-GlcNAc transferase (OGT).

The vital enzyme O-linked ß-N-acetylglucosamine transferase (OGT) catalyzes the O-GlcNAcylation of intracellular proteins coupling the metabolic status to cellular signaling and transcription pathways. Aberrant levels of O-GlcNAc and OGT have been linked to metabolic diseases as cancer and diabetes. Here, a new series of peptidomimetic OGT inhibitors was identified highlighting the compound LQMed 330, which presented better IC50 compared to the most potent inhibitors found in the literature. Molecular modeling study of selected inhibitors into the OGT binding site provided insight into the behavior by which these compounds interact with the enzyme. The results obtained in this study provided new perspectives on the design and synthesis of highly specific OGT inhibitors.

3-Acyltetramic acids as a novel class of inhibitors for human kallikreins 5 and 7.

Human kallikreins 5 and 7 (KLK5 and KLK7) exhibit trypsin- and chymotrypsin-like activities and are involved in pathologies related to skin desquamation process. A series of new 3-acyltetramic acids were developed as a novel class of inhibitors of KLK5, KLK7 and trypsin enzymes. The nature and length of the acyl chain is crucial to the KLK5, KLK7 and trypsin inhibition activities, and the most potent compounds (but not the most selective) 2b, 2c and 2g showed low micromolar IC50 values. While very few of the compounds were selective for KLK5, the selective inhibition of trypsin against chymotrypsin was achieved. Our molecular modelling studies revealed that the double bond in 2g provided the best fit in the binding site of KLK5, while the hydrogen bonding interactions modulated the best fit of 2c in the binding site of KLK7 due to the hydrophobicity of the cavity.

Isosorbide-based peptidomimetics as inhibitors of hepatitis C virus serine protease.

Hepatitis C infection is a cause of chronic liver diseases such as cirrhosis and carcinoma. The current therapy for hepatitis C has limited efficacy and low tolerance. The HCV encodes a serine protease which is critical for viral replication, and few protease inhibitors are currently on the market. In this paper, we describe the synthesis and screening of novel isosorbide-based peptidomimetic inhibitors, in which the compounds 1d, 1e, and 1i showed significant inhibition of the protease activity in vitro at 100µM. The compound 1e also showed dose-response (IC50=36±3µM) and inhibited the protease mutants D168A and V170A at 100µM, indicating it as a promising inhibitor of the HCV NS3/4A protease. Our molecular modeling studies suggest that the activity of 1e is associated with a change in the interactions of S2 and S4 subsites, since that the increased flexibility favors a decrease in activity against D168A, whereas the appearance of a hydrophobic cavity in the S4 subsite increase the inhibition against V170A strain.

Synthesis and mechanistic evaluation of novel N'-benzylidene-carbohydrazide-1H-pyrazolo[3,4-b]pyridine derivatives as non-anionic antiplatelet agents.

Cardiovascular diseases (CVDs) account for over 17 million deaths globally each year, with atherosclerosis as the underlying cause of most CVDs. Herein we describe the synthesis and in vitro mechanistic evaluation of novel N'-benzylidene-carbohydrazide-1H-pyrazolo[3,4-b]pyridines (3-22) designed as non-anionic antiplatelet agents and presenting a 30-fold increase in potency compared to aspirin. The mechanism underlying their antiplatelet activity was elucidated by eliminating potential targets through a series of in vitro assays including light transmission aggregometry, clot retraction, and quantitative ELISA, further identifying the reduction in biosynthesis of thromboxane B2 as their main mechanism of action. The intrinsic fluorescence of the compounds permits their binding to platelet membranes to be readily monitored. In silico structure-activity relationship, molecular docking and dynamics studies support the biological profile of the series revealing the molecular basis of their activity and their potential as future molecular therapeutic agents.

Discovery of a new isomannide-based peptidomimetic synthetized by Ugi multicomponent reaction as human tissue kallikrein 1 inhibitor.

Human kallikrein 1 (KLK1) is the most extensively studied member of this family and plays a major role in inflammation processes. From Ugi multicomponent reactions, isomannide-based peptidomimetic 10 and 13 where synthesized and showed low micromolar values of IC50 for KLK1 The most active compound (10) presented competitive mechanism, with three structural modifications important to interact with active site residues which corroborates its KLK1 inhibition. Finally, the most active compound also showed good ADMET profile, which indicates compound 10 as a potential hit in the search for new KLK1 inhibitors with low side effects.

New carbohydrazide derivatives of 1H-pyrazolo[3,4-b]pyridine and trypanocidal activity.

This paper reports the in vitro trypanocidal activity evaluation of new carbohydrazide derivatives from 3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridine, substituted at C-6 position by phenyl, methyl or trifluoromethyl group. These compounds were evaluated in order to identify the antiparasitic profile against trypomastigote and amastigote forms of Trypanosoma cruzi. The 4-carbohydrazide derivatives presented different profiles of activity. In the investigation of the chemical structure influence in the trypanocidal activity, the results indicated there are large lipophilicity and volume differences among these derivatives. The complementarities of their stereoelectronic and physical-chemical aspects seem to be relevant for the biological activity against T. cruzi.

Synthesis, biological evaluation and molecular modeling of pseudo-peptides based statine as inhibitors for human tissue kallikrein 5.

Human kallikrein 5 (KLK5) is a potential target for the treatment of skin inflammation and cancer. A new series of statine based peptidomimetic compounds were designed and synthesized through simple and efficient reactions. Some KLK5 inhibitors (2a-c compounds) were identified with nanomolar affinity showing Ki values of 0.12-0.13 µM. Our molecular modeling studies suggest that the inhibitors binding at the KLK5 through H-bond interactions with key residues (mainly His108, Gln242, Gly243, Ser245, and Ser260), disrupting the correlated motions mainly among the Ile67-Tyr127, Glu128-Val187, and Gly237-Ser293 subdomains, which seems to be crucial for KLK5 activity. Therefore, we believe that these findings will significantly facilitate our understanding of the conformational dynamics in the course of KLK5 inhibition and, consequently, the development of more potent molecules as alternative for cancer treatment.

Isomannide-based peptidomimetics as inhibitors for human tissue kallikreins 5 and 7.

Human kallikrein 5 (KLK5) and 7 (KLK7) are potential targets for the treatment of skin inflammation and cancer. Previously, we identified isomannide derivatives as potent and competitive KLK7 inhibitors. The introduction of N-protected amino acids into the isomannide-based scaffold was studied. Some KLK5 inhibitors with submicromolar affinity (K i values of 0.3-0.7 µM) were identified, and they were 6- to 13-fold more potent than our previous hits. Enzyme kinetics studies and the determination of the mechanism of inhibition confirmed that the new isomannide-based derivatives are competitive inhibitors of both KLK5 and KLK7. Molecular docking and MD simulations of selected inhibitors into the KLK5 binding site provide insight into the molecular mechanism by which these compounds interact with the enzyme. The promising results obtained in this study open new prospects on the design and synthesis of highly specific KLK5 and KLK7 inhibitors.

Isomannide derivatives as new class of inhibitors for human kallikrein 7.

Human kallikrein 7 (KLK7) is a potential target for the treatment of skin inflammation and cancer. Despite its potential, few KLK7-specific small-molecule inhibitors have been reported in the literature. As an extension of our program to design serine protease inhibitors, here we describe the in vitro assays and the investigation of the binding mechanism by molecular dynamics simulation of a novel class of pseudo-peptide inhibitors derived from isomannide. Of the inhibitors tested, two inhibited KLK7 with K(i) values in the low micromolar range (9g=1.8µM; 9j=3.0µM). Eadie-Hofstee and Dixon plots were used to evaluate the competitive mechanism of inhibition for the molecules. Calculated binding free energies using molecular MM/PB(GB)SA approach are in good agreement with experimental results, suggesting that the inhibitors share the same binding mode, which is stabilized by hydrophobic interactions and by a conserved network of hydrogen bonds. The promising results obtained in this study make these compounds valid leads for further optimization studies aiming to improve the potency of this new class of kallikrein inhibitors.

Pseudo-peptides derived from isomannide: inhibitors of serine proteases.

In this paper, we describe the synthesis of a novel class of pseudo-peptides derived from isomannide and several oxazolones as potential inhibitors of serine proteases as well as preliminary pharmacological assays for hepatitis C. Hepatitis C, dengue and West Nile fever are among the most important flaviviruses that share one important serine protease enzyme. Serine proteases belong to the most studied class of proteolytic enzymes and are a primary target in the drug development field. Several pseudo-peptides were obtained in good yields from the reaction of isomannide and oxazolones, and their anti-HCV potential using the HCV replicon-based assay was shown.