Design, synthesis, and structure-activity relationships of novel insulin receptor tyrosine kinase activators

Design, Synthesis and Antitumor Assessment of Phenylureas Bearing 5-Fluoroindolin-2-one Moiety

BACKGROUND

The development of novel antineoplastic agents remains highly desirable.

OBJECTIVE

This study focuses on the design, synthesis, and antitumor evaluation of phenyl ureas bearing 5-fluoroindolin-2-one moiety.

METHODS

Three sets of phenylureas were designed and synthesized and their antiproliferative ability was measured against four human carcinoma cell lines (Hela, Eca-109, A549, and MCF-7) via MTT assay. In vivo anticancer activity was further evaluated in xenograft models of human breast cancer (MCF-7).

RESULTS

A total of twenty-one new compounds were synthesized and characterized by means of 1H and 13C NMR as well as HR-MS. Three sets of compounds (1a‒1c, 2a‒2c, and 3a‒3c) were initially constructed, and preliminary antiproliferative activities of these molecules were evaluated against Hela, Eca-109, A549 and MCF-7, highlighting the meta-substituted phenylureas (1a‒1c) as the most cytotoxic set. A series of meta-substituted phenylureas derivatives (1d‒1o) were then designed and synthesized for structure-activity relationship study. Most of the new compounds showed desirable cytotoxicity, among which compound 1g exhibited the most remarkable cytotoxic effects against the tested human cancer cells with IC50 values ranging from 1.47 to 6.79 μM. Further studies showed that compound 1g suppressed tumor growth in human breast cancer (MCF- 7) xenograft models without affecting the body weight of its recipients.

CONCLUSION

In this study, twenty-one new compounds, containing the privileged structures of phenylurea and 5-fluoroindolin-2-one, were designed and synthesized. Subsequent structureactivity studies showed that 1g was the most bioactive antitumor agent among all tested compounds, hence a potentially promising lead compound once given further optimization.

Selective Late-Stage Sulfonyl Chloride Formation from Sulfonamides Enabled by Pyry-BF4

Reported here is a simple and practical functionalization of primary sulfonamides, by means of a pyrylium salt (Pyry‐BF₄), with nucleophiles. This simple reagent activates the poorly nucleophilic NH₂ group in a sulfonamide, enabling the formation of one of the best electrophiles in organic synthesis: a sulfonyl chloride. Because of the variety of primary sulfonamides in pharmaceutical contexts, special attention has been focused on the direct conversion of densely functionalized primary sulfonamides by a late‐stage formation of the corresponding sulfonyl chloride. A variety of nucleophiles could be engaged in this transformation, thus permitting the synthesis of complex sulfonamides, sulfonates, sulfides, sulfonyl fluorides, and sulfonic acids. The mild reaction conditions and the high selectivity of Pyry‐BF₄ towards NH₂ groups permit the formation of sulfonyl chlorides in a late‐stage fashion, tolerating a preponderance of sensitive functionalities.

Synthesis of 11C-Labelled Ureas by Palladium(II)-Mediated Oxidative Carbonylation

Positron emission tomography is an imaging technique with applications in clinical settings as well as in basic research for the study of biological processes. A PET tracer, a biologically active molecule where a positron-emitting radioisotope such as carbon-11 has been incorporated, is used for the studies. Development of robust methods for incorporation of the radioisotope is therefore of the utmost importance. The urea functional group is present in many biologically active compounds and is thus an attractive target for incorporation of carbon-11 in the form of [¹¹C]carbon monoxide. Starting with amines and [¹¹C]carbon monoxide, both symmetrical and unsymmetrical ¹¹C-labelled ureas were synthesised via a palladium(II)-mediated oxidative carbonylation and obtained in decay-corrected radiochemical yields up to 65%. The added advantage of using [¹¹C]carbon monoxide was shown by the molar activity obtained for an inhibitor of soluble epoxide hydrolase (247 GBq/μmol–319 GBq/μmol). DFT calculations were found to support a reaction mechanism proceeding through an ¹¹C-labelled isocyanate intermediate.

Potentiation of insulin-mediated glucose lowering without elevated hypoglycemia risk by a small molecule insulin receptor modulator

Insulin resistance is the key feature of type 2 diabetes and is manifested as attenuated insulin receptor (IR) signaling in response to same levels of insulin binding. Several small molecule IR activators have been identified and reported to exhibit insulin sensitization properties. One of these molecules, TLK19781 (Cmpd1), was investigated to examine its IR sensitizing action in vivo. Our data demonstrate that Cmpd1, at doses that produced minimal efficacy in the absence of insulin, potentiated insulin action during an OGTT in non-diabetic mice and enhanced insulin-mediated glucose lowering in diabetic mice. Interestingly, different from insulin alone, Cmpd1 combined with insulin showed enhanced efficacy and duration of action without increased hypoglycemia. To explore the mechanism underlying the apparent glucose dependent efficacy, tissue insulin signaling was compared in healthy and diabetic mice. Cmpd1 enhanced insulin’s effects on IR phosphorylation in both healthy and diabetic mice. In contrast, the compound potentiated insulin’s effects on Akt phosphorylation in diabetic but not in non-diabetic mice. These differential effects on signaling corresponding to glucose levels could be part of the mechanism for reduced hypoglycemia risk. The in vivo efficacy of Cmpd1 is specific and dependent on IR expression. Results from these studies support the idea of targeting IR for insulin sensitization, which carries low hypoglycemia risk by standalone treatment and could improve the effectiveness of insulin therapies.

Novel symmetrical ureas as modulators of protein arginine methyl transferases

Methylation of histone arginine residues is an epigenetic mark related to gene expression that is implicated in a variety of biological processes and can be reversed by small-molecule modulators of protein arginine methyltransferases (PRMTs). A series of symmetrical ureas, designed as analogues of the known PRMT1 inhibitor AMI-1 have been synthesized using Pd-catalyzed Ar-N amide bond formation processes or carbonylation reactions as key steps. Their inhibitory profile has been characterized. The enzymatic assays showed a weak effect on PRMT1 and PRMT5 activity for most of the compounds. The acyclic urea that exhibited the strongest effect on the inhibition of the PRMT1 activity also showed the greatest effect on the expression of some androgen receptor target genes (TMPRSS2 and FKBP5), which may be related with its enzymatic activity. Surprisingly, AMI-1 behaved as an activator of PRMT5 activity, a result not reported so far.

Amino acids potentiate insulin signaling in CHO-K1 at high glucose conditions

BACKGROUND AND AIMS

Amino acids reportedly increase the glucose uptake under high glucose conditions. However, there are controversies in the role of amino acids in diabetes mellitus. The present study explores the insulin signaling pathway involved in glucose uptake mediated by amino acids in CHO-K1 cells.

METHODS

CHO-K1 cells were exposed to normal (7 mM) and high glucose (17 and 27 mM) with 100 nM insulin in the presence and absence of amino acid mixtures (AAM) in varying concentration (5 and 20 mM) followed by the assays, insulin receptor tyrosine kinase (IRTK) and phosphatidylinositol 3 kinase (PI3K) by autoradiography, protein kinase B (Akt) and glucose transporter (GLUT4) by Western blot and glycogen synthase (GS) by HPLC.

RESULTS

The addition of 5 and 20 mM AAM significantly increased IRTK and PI3K activity (ANOVA p = 0.025, p = 0.003, respectively) with increasing glucose concentration. Addition of 5 mM AAM in the presence of normal glucose significantly increased the levels of phosphorylated Akt Ser473 (p = 0.02) with no significant change at high glucose. At 20 mM AAM there was a significant decrease in Akt phosphorylation (p = 0.035) that was increased by high glucose concentration. GLUT4 protein levels were increased with AAM (5 mM) along with increase in glycogen synthase activity at all glucose concentrations (p <0.05).

CONCLUSIONS

Amino acids as a mixture is beneficial in augmenting insulin signaling pathway via IRTK/PI3K/GLUT4 pathway along with activation of GS in CHO-K1 cells, thereby ensuring increased intracellular glucose availability.