A Library of Thiazolidin-4-one Derivatives as Protein Tyrosine Phosphatase 1B (PTP1B) Inhibitors: An Attempt To Discover Novel Antidiabetic Agents

Protein tyrosine phosphatase 1B (PTP1B) is an important target for the treatment of diabetes. A series of thiazolidin-4-one derivatives 8-22 was designed, synthesized and investigated as PTP1B inhibitors. The new molecules inhibited PTP1B with IC₅₀ values in the micromolar range. 5-(Furan-2-ylmethylene)-2-(4-nitrophenylimino)thiazolidin-4-one (17) exhibited potency with a competitive type of enzyme inhibition. structure-activity relationship studies revealed various structural facets important for the potency of these analogues. The findings revealed a requirement for a nitro group-including hydrophobic heteroaryl ring for PTP1B inhibition. Molecular docking studies afforded good correlation with experimental results. H-bonding and π-π interactions were responsible for optimal binding and effective stabilization of virtual protein-ligand complexes. Furthermore, in-silico pharmacokinetic properties of test compounds predicted their drug-like characteristics for potential oral use as antidiabetic agents.Additionally, a binding site model demonstrating crucial pharmacophoric characteristics influencing potency and binding affinity of inhibitors has been proposed, which can be employed in the design of future potential PTP1B inhibitors.

PTP1b Inhibition, A Promising Approach for the Treatment of Diabetes Type II

BACKGROUND

Diabetes Mellitus (DM), is a metabolic disorder characterized by high blood glucose levels. The main types of diabetes mellitus are Diabetes mellitus type I, Diabetes mellitus type II, gestational diabetes and Diabetes of other etiology. Diabetes type II, the Non Insulin Dependent Type (NIDDM) is the most common type, characterized by the impairment in activation of the intracellular mechanism leading to the insertion and usage of glucose after interaction of insulin with its receptor, known as insulin resistance. Although, a number of drugs have been developed for the treatment of diabetes type II, their ability to reduce blood glucose levels is limited, while several side effects are also observed. Furthermore, none of the market drugs targets the enhancement of the action of the intracellular part of insulin receptor or recuperation of the glucose transport mechanism in GLUT4 dependent cells. The Protein Tyrosine Phosphatase (PTP1b) is the main enzyme involved in insulin receptor desensitization and has become a drug target for the treatment of Diabetes type II. Several PTP1b inhibitors have already been found, interacting with the binding site of the enzyme, surrounding the catalytic amino acid Cys215 and the neighboring area or with the allosteric site of the enzyme, placed at a distance of 20 Å from the active site, around Phe280. However, the research continues for finding more potent inhibitors with increased cell permeability and specificity.

OBJECTIVE

The aim of this review is to show the attempts made in developing of Protein Tyrosine Phosphatase (PTP1b) inhibitors with high potency, selectivity and bioavailability and to sum up the indications for favorable structural characteristics of effective PTP1b inhibitors.

METHODS

The methods used include a literature survey and the use of Protein Structure Databanks such as PuBMed Structure and RCSB and the tools they provide.

CONCLUSION

The research for finding PTP1b inhibitors started with the design of molecules mimicking the Tyrosine substrate of the enzyme. The study revealed that an aromatic ring connected to a polar group, which preferably enables hydrogen bond formation, is the minimum requirement for small inhibitors binding to the active site surrounding Cys215. Molecules bearing two hydrogen bond donor/acceptor (Hb d/a) groups at a distance of 8.5-11.5 Å may form more stable complexes, interacting simultaneously with a secondary area A2. Longer molecules with two Hb d/a groups at a distance of 17 Å or 19 Å may enable additional interactions with secondary sites (B and C) that confer stability as well as specificity. An aromatic ring linked to polar or Hb d/a moieties is also required for allosteric inhibitors. A lower distance between Hb d/a moieties, around 7.5 Å may favor allosteric interaction. Permanent inhibition of the enzyme by oxidation of the catalytic Cys215 has also been referred. Moreover, covalent modification of Cys121, placed near but not inside the catalytic pocket has been associated with permanent inhibition of the enzyme.

Docking Assisted Prediction and Biological Evaluation of Sideritis L. Components with PTP1b Inhibitory Action and Probable Anti-Diabetic Properties

Background:

The main characteristic of Diabetes type II is the impaired activation of intracellular mechanisms triggered by the action of insulin. PTP1b is a Protein Tyrosine Phosphatase that dephosphorylates insulin receptor causing its desensitization. Since inhibition of PTP1b may prolong insulin receptor activity, PTP1b has become a drug target for the treatment of Diabetes II. Although a number of inhibitors have been synthesized during the last decades, the research still continues for the development of more effective and selective compounds. Moreover, several constituents of plants and edible algae with PTP1b inhibitory action have been found, adding this extra activity at the pallet of properties of the specific natural products.

Objective:

Sideritis L. (Lamiaceae) is a herbal plant growing around the Mediterranean sea which is included in the Mediterranean diet for centuries. The present study is the continuation of a previous work where the antioxidant and anti-inflammatory activities of the components of Sideritis L. were evaluated and aimed to investigate the potential of some sideritis’s components to act as PTP1b inhibitors, thus exhibiting the beneficial effect in the treatment of diabetes II.

Methods:

Docking analysis was done to predict PTP1b inhibitory action. Human recombinant PTP1b enzyme was used for the evaluation of the PTP1b inhibitory action, while inhibition of the human LAR and human T-cell PTP was tested for the estimation of the selectivity of the compounds.

Conclusion:

Docking analysis effectively predicted inhibition and mode of inhibitory action. According to the experimental results, four of the components exhibited PTP1b inhibitory action. The most active ones were acetoside, which acted as a competitive inhibitor, with an IC50 of 4 µM and lavandufolioside, which acted as an uncompetitive inhibitor, with an IC50 of 9.3 µM. All four compounds exhibited increased selectivity against PTP1b.

Discovery of anilino-furo[2,3-d]pyrimidine derivatives as dual inhibitors of EGFR/HER2 tyrosine kinase and their anticancer activity

Being responsible for the development of many cancer types, EGFR (Epidermal Growth Factor Receptor) and HER2 (Human Epidermal growth factor Receptor 2) were the focus of this study where a series of novel 4-anilino-furo[2,3-d]pyrimidine derivatives was designed, synthesized and biologically evaluated. Modification of the solvent accessible 5-position side chain greatly affected the in-vitro EGFR/HER2 inhibitory activity. Three derivatives bearing 5-carboxylic acid side chain, namely the 3-chloroanilino derivative (8c), the 3-bromoaniline (8d) and the lapatinib analogue (10) demonstrated the most significant submicromolar EGFR inhibition. Surprisingly, the in-vitro assay of the ester 7h and its acid analogue 10 showed a significant variation of results between the antiproliferative activity against A549 cell line (IC₅₀ 0.5 and 21.4 μM) respectively and EGFR inhibitory activity (18% and 100%) respectively, suggesting that 7h might be a prodrug for 10. This assumption was also affirmed by the in-vivo results, where the in-vivo antitumor assessment against EAC (Ehrlich Ascites Carcinoma) solid tumor model revealed that 7h and 8d (10 mg/kg dose) exhibited antitumor activity comparable to that of gefitinib at the same dose, exhibiting TGI% of 67%, 71% and 70%, respectively. This effect could be explained, at least partly, via activation of apoptosis, where 7h and 8d caused more than 2-fold increase of caspase 3 and cytochrome c expression than the control group which is comparable to that of gefitinib-treated group. Finally, 7h was the most effective apoptotic inducer, resulting in a significant elevation in annexin V-FITC-positive apoptotic cells (both early and late apoptosis) by 25 and 79-folds, respectively, compared to control, which is higher than that of gefitinib (22 and 61-folds, respectively).