Evaluation of 4-thiazolidinone derivatives as potential reverse transcriptase inhibitors against HIV-1 drug resistant strains.

Rapid emergence of drug resistance is crucial in management of HIV infection limiting implementation of efficacious drugs in the ART regimen. Designing new molecules against HIV drug resistant strains is utmost essential. Based on the anti-HIV-1 activity, we selected four 4-thiazolidinone derivatives (S009-1908, S009-1909, S009-1911, S009-1912) and studied their interaction with reverse transcriptase (RT) from a panel of 10 clinical isolates (8 nevirapine resistant and two susceptible) using in silico methods, and inhibition pattern using in vitro cell based assays. On the basis of binding affinity observed in in silico analysis, 2-(2-chloro-6-nitrophenyl)-3-(4, 6-dimethylpyridin-2-yl) thiazolidin-4-one (S009-1912) was identified as the lead molecule followed by S009-1908, S009-1909 and S009-1911. The in vitro activity against the same panel was assessed using TZM-bl assay (IC50: 0.4-11.44µg/ml, TI: 4-126) and subsequently in PBMC assay against a nevirapine resistant clinical isolate (IC50: 0.8-6.65µg/ml, TI: 8.31-11.43) and standard strain from NIH ARRRP (IC50: 0.95-3.6µg/ml, TI: 9-26). The study shows analogue with pyrimidin-2-yl amino substitution at N-3 position of thiazolidin-4-one ring (S009-1908, S009-1909, S009-1911) exhibited enhanced activity as compared to pyridin-2-yl substituted derivatives (S009-1912), suggesting the use 4-thiazolidinones for developing potent inhibitors against HIV-1 drug resistant strains.

Rational design and synthesis of novel thiazolidin-4-ones as non-nucleoside HIV-1 reverse transcriptase inhibitors.

A series of novel thiazolidin-4-one analogues, characterized by different substitution patterns at positions C-2 and N-3 of the thiazolidin-4-one scaffold for anti-HIV-1 activity has been investigated. Most of the compounds showed anti-HIV-1 activity at micromolar concentrations when tested in TZM-bl cells in vitro. Among the thirty-three compounds tested, compound 16 was the most potent inhibitor of HIV-1 replication against HIV-1IIIB, HIV-1ADA5, HIV-1UG070 and HIV-1VB59 (EC50=0.02, 0.08, 0.08 and 0.08 µM, respectively) with selectivity index (SI=6940, 1735, 1692 and 1692) against tested viral strains, respectively. The results of the present study suggested that the substitution of the nitro group at 6' position of the C-2 phenyl ring and 4,6-dimethylpyridin-2-yl at the N-3 position of thiazolidin-4-one had a major impact on the anti-HIV-1 activity and was found to lower cytotoxicity. The substitution of the heteroaryl ring with bromo group and bicyclic heteroaryl ring at N-3 thiazolidin-4-one was found to lower anti-HIV-1 activity and increase cytotoxicity. The undertaken docking studies thus facilitated the identification of crucial interactions between the HIV-1 RT enzyme and thiazolidin-4-one inhibitors, which can be used to design new potential inhibitors.

Lead optimization at C-2 and N-3 positions of thiazolidin-4-ones as HIV-1 non-nucleoside reverse transcriptase inhibitors.

Based on rational drug design approach, a series of novel thiazolidin-4-ones bearing different aryl/heteroaryl moieties at position C-2 and N-3 are synthesized and evaluated as potent inhibitors for human immunodeficiency virus type-1 reverse transcriptase enzyme (HIV-1 RT). An in vitro HIV-1 RT assay showed that the compounds 4, 5, 6, 8, 12, 13, 14 and 17 have shown high inhibition of reverse transcriptase (75.41, 95.50, 98.07, 91.24, 85.27, 77.59, 84.11 & 76.49% inhibition) enzyme activity. Further, cell based assay showed that compounds 4, 5, 8 &12 are identified as the best compounds of the series (EC(50) ranged from 0.09 to 0.8 µg/ml and 0.12 to 1.06 µg/ml) against HIV-1 III(B) and HIV-1 ADA5 strains, respectively. Moreover, the compounds which were active against HIV-1 III(B) and HIV-1 ADA5 were also found to be active against primary isolates (EC(50) ranged from 0.10 to 1.55 µg/ml against HIV-1 UG070 and 0.07 to 1.1 µg/ml against HIV-1 VB59), respectively. Structure-activity relationship (SAR) studies demonstrated the importance of the lipophilic bulky substituent pattern on compact heteroaryl ring at N-3, replacement of C4' at C-2 phenyl by trivalent bioisosteric nitrogen and dihalo groups at C-2 aryl/heteroaryl of thiazolidin-4-ones is crucial for anti-HIV-1 activity. Molecular modeling of compounds 4, 5, 8 and 12 in complex with HIV-1 RT demonstrate that there is good correlation of results obtained from SAR studies. Therefore the compounds 4, 5, 8 and 12 may be considered as good candidates for further optimization of anti-HIV-1 activity.

CoMFA and CoMSIA of diverse pyrrolidine analogues as dipeptidyl peptidase IV inhibitors: active site requirements.

The inhibition of dipeptidyl peptidase IV (DPP-IV) has emerged as an attractive target in the treatment of type 2 diabetes. In view of this development, a critical analysis of structural requirements of the DPP-IV inhibitors is envisioned to identify the significant features toward design of selective inhibitors. The comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) contour plots of pyrrolidine based analogues are used to analyze the structural requirements of a DPP-IV active site. The CoMFA model has shown a cross-validated q (2) of 0.651 with a non-cross-validated r (2) of 0.882 and explained 70.6% variance in the activity of external test compounds. In this, the steric and electrostatic fields have respectively contributed 59.8 and 40.2%, respectively, to the explained activity of the compounds. The CoMSIA model has shown optimum predictivity (cross-validated q (2) = 0.661; non-cross-validated r (2) = 0.803; external test set's predictive r (2) = 0.706) with four molecular fields namely, steric, electrostatic, hydrogen bond (HB)-donor, and HB-acceptor. The contour plots of molecular fields resulting from these studies have suggested: (i) steric restriction with small electron rich substituent at 2- and 3-position of pyrrolidine ring, (ii) presence of electropositive ring linker between the pyrrolidine head and aryl tail, (iii) presence of electron-rich groups around the aryl tail moiety, and (iv) presence of sulfonamide between the ring linker and aryl tail which would increase DPP-IV binding affinity of the compounds. These findings will help in the design of structurally related/new compounds as potential DPP-IV inhibitors.

Synthesis, antidiabetic, antioxidant and anti-inflammatory activities of novel hydroxytriazenes based on sulpha drugs.

The present study is aimed to investigate the anti-inflammatory, antioxidant and antidiabetic activities of three series of hydroxytriazenes based on sulfa drugs viz; Sulphathiazole (ST), Sulfisoxazole (SF) and Sulphamethoxazole (SM). Antidiabetic activities of the synthesized hydroxytriazenes were investigated by α-glucosidase and α-amylase inhibition method and IC50 values were recorded. The compounds presented significant α-glucosidase and α-amylase inhibition effect with IC50 values ranging from 122 to 341 µg/mL. Anti-inflammatory activity was also investigated by carrageenan-induced paw edema (CPE) method, where % inhibition was up to 89% after 4 h of treatment and antioxidant properties of the similar compounds were assessed by DPPH and ABTS radical scavenging assays. Antioxidant capacity of all the hydroxytriazenes detected by ABTS assay, was significantly higher as compared to DPPH assay. The hydroxytriazenes having highest antioxidant capacity presented IC50 values for compound ST-1 and ST-6 are 488 µg/mL for DPPH, 54.12 µg/mL for ABTS and 858.5 µg/mL for DPPH, 48.0 µg/mL for ABTS, respectively. These results suggested that ABTS assay may be more useful than DPPH assay for synthetic antioxidants. The findings from the molecular docking experiments may also expand the formation of new potent sulpha drugs based hydroxytriazenes targeting towards the subunit of C-terminal of human maltase-glucoamylase for the treatment of diabetes metabolic disorder. Overall, highlight the multifunctional role of hydroxytriazenes as antidiabetic, antioxidant and anti-inflammatory agents.

CoMFA and CoMSIA studies on thiazolidin-4-one as anti-HIV-1 agents.

Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were performed on thiazolidin-4-one class of compounds as HIV-1 reverse transcriptase (HIV-1 RT) inhibitors using global minima and crystal structure conformations. Results obtained from the crystal structure-based model yielded superior statistical data (r(cv)(2) values of 0.683 for CoMFA and 0.678 for CoMSIA) when compared to those obtained by the global minima-based model (r(cv)(2) values of 0.625 and 0.654 for CoMFA and CoMSIA, respectively). The models were validated using an external test set of 47 compounds. The predictive r(2) values for the crystal-based CoMFA and CoMSIA models were 0.735 and 0.739, respectively, while the corresponding predictive r(2) values for the global minima-based CoMFA and CoMSIA models were 0.654 and 0.635, respectively. 3D contour maps generated from these models provide the regions in space where interactive fields may influence the activity. The superimposition of contour maps on the active site of HIV-1 reverse transcriptase additionally helped in understanding the structural requirements of these inhibitors. The results provide insight for predictive and diagnostic aspects of this class of HIV-1 RT inhibitors for better activity.