Kamala K. Vasu

Synthesis of 4-benzyl-1,3-thiazole derivatives as potential anti-inflammatory agents: An analogue-based drug design approach

A series of novel 4-Benzyl-1,3-thiazole derivatives was synthesized by applying analogue-based drug design approach and they were screened for anti-inflammatory activity. Darbufelone (CI 1004) a dual COX/LOX inhibitor, served as a lead molecule for designing a molecular scaffold. The derivatives with the 1,3 thiazole molecular scaffold bearing a side chain at position-2 resembling that of Romazarit (Ro-31-3948) were synthesized. The substitution at the second position of thiazole scaffold consisted of either carbalkoxy amino or aryl amino side chain. The introduction of an NH linker at the second position was the bioisoteric approach to impart the metabolic stability to the carbalkoxy side chains in designed molecules so as to avoid the likelihood of generating toxic moieties, like in Romazarit, which was withdrawn due to its toxicity profile. An important outcome of this study is the optimization of the substitution at the second position of the thiazole scaffold in eliciting better biological activity. The biological activity exhibited by the two designed series were in the order of carbalkoxy amino series > phenyl amino series. Molecule RS31 had emerged to be best compound in the whole series, having the side chain -NH-(C = O)O-R which resemble to Romazerit with 1,3 thiazole scaffold and substituted phenyl carbonyl group at fifth position derived from the retro-analysis of Darbufelone. This novel three-point pharmacophore, which is necessarily evolved from a lead-based drug design strategy, has opened up new avenues in designing of molecules acting on more than one rate-limiting step along the inflammatory cascade.

Design, synthesis and characterization of novel 2-(2,4-disubstituted-thiazole-5-yl)-3-aryl-3H-quinazoline-4-one derivatives as inhibitors of NF-κB and AP-1 mediated transcription activation and as potential anti-inflammatory agents

A series of 2-(2,4-disubstituted-thiazole-5-yl)-3-aryl-3H-quinazoline-4-one derivatives were designed and synthesized. Synthesized molecules were further evaluated for their inhibitory activity towards transcription factors NF-kappaB and AP-1 mediated transcriptional activation in a cell line based in vitro assay as well as for their anti-inflammatory activity in in vivo model of acute inflammation. This series provides us with selective and dual inhibitors of NF-kappaB and AP-1 mediated transcriptional activation which also exhibit significant efficacy in in vivo model of inflammation. Two of the compounds 9m and 9o turned out to be the most promising dual inhibitors of NF-kappaB and AP-1 mediated transcriptional activation with an IC(50) of 3.3 microM for both. 9n (IC(50)=5.5 microM) and 9p (IC(50)=5.5 microM) emerged as selective inhibitors of NF-kappaB mediated transcriptional activation and 9c (IC(50)=5.5 microM) and 9d (IC(50)=5.5 microM) were found to be more selective inhibitor of AP-1 mediated transcriptional activity. Though the relationship between the activities shown by these compounds in in vivo and in vitro model is still to be established, these results suggest the suitability of the designed molecular framework as a potential anti-inflammatory molecular framework which also exhibits the inhibitory activity towards NF-kappaB and AP-1 mediated transcriptional activation. This will be worth studying further to explore its complete potential particularly in chronic inflammatory conditions. The structure activity relationship (SAR) of this series has been discussed herein.

Novel drug designing approach for dual inhibitors as anti-inflammatory agents: implication of pyridine template

Compounds incorporating thiophene moiety, a pi excess five membered heterocycle, have attracted a great deal of research interest, owing to the therapeutic utility of the template as useful drug molecular scaffolding. We report the synthesis and pharmacological evaluation of thiophenes substituted with 4-methanesulfonyl benzoyl moiety at the fifth position of the ring, as possible anti-inflammatory lead candidates. The aryl sulfonyl methyl thiophene analogs AP29, AP82, and AP37, when screened for anti-inflammatory activity in carrageenin induced rat paw edema, an acute in vivo model, exhibited moderate to good activity at a dose level of 100 mg/kg body weight P.o compared to Ibuprofen. In a five day formalin induced rat paw edema, a chronic in vivo anti-inflammatory model, candidates AP29, AP82, and AP37 inhibited the disease progression by 53%, 34%, and 65%, respectively on the fifth day, at a dose level of 100 mg/kg body weight P.o compared to Rofecoxib, Ibuprofen, and Dexamethasone at therapeutic doses which gave a protection of 53.8%, 81.5%, and 81.5%, respectively. The replacement of the 4-methanesulfonyl benzoyl moiety in AP82 with the pyridine template, 3,5-dimethyl-4-methoxy-2-pyridyl function, gave rise to AP84, which was less active in the acute model, but gave 54% and 75% protection both during the first day and fifth day, respectively, in the chronic model. A dual mechanism of action is proposed for AP84, a non-steroidal drug which has exhibited remarkable activity when compared to the steroid dexamethasone. These results open up new avenues in designing novel anti-inflammatory drugs as dual inhibitors with the incorporation of a pyridine template as part of the pharmacophore.

Gastroretentive delivery of rifampicin: In vitro mucoadhesion and in vivo gamma scintigraphy

Rifampicin, a first line anti-tubercular drug, has maximum solubility and permeability in the stomach. An oral multi-particulate formulation with site specific sustained delivery of rifampicin was developed. This oral gastroretentive rifampicin formulation consisted of rifampicin pellets for immediate release as the loading dose and a bio/mucoadhesive rifampicin tablet for extended release. Immediate release pellets of rifampicin were prepared by extrusion-spheronization process and were evaluated for physico-mechanical properties: usable yield, size, shape, abrasion resistance, mechanical crushing force, residual moisture and drug release. For the mucoadhesive rifampicin formulation, statistical experimental strategy was utilized to simultaneously optimize the effect of two independent variables namely amount of Carbopol and MCC. The two dependent responses selected were, work of adhesion; estimated using Texture Analyzer and T(50%); determined from dissolution studies. Graphical and mathematical analysis of the results allowed the identification and quantification of the formulation variables influencing the selected responses. To study the gastrointestinal transit of the optimized gastroretentive formulation, the in vivo gamma scintigraphy was carried out in six healthy human volunteers, after radiolabeling the formulation with (99m)Tc. The transit profiles demonstrated that the dosage form was retained in the stomach for more than 320 min. The human data validates the design concept and signifies the potential of the developed system for stomach targeted delivery of rifampicin for improved bioavailability.

Dissolution test for site-specific release isoniazid pellets in USP apparatus 3 (reciprocating cylinder): Optimization using response surface methodology

The present work aims to predict drug release from novel site-specific release isoniazid pellets, in USP dissolution test apparatus 3, using the response surface methodology (RSM). Site-specific release isoniazid pellets were prepared by extrusion-spheronization followed by aqueous coating of Acryl-EZE. RSM was employed for designing of the experiment, generation of mathematical models and optimization study. A 3(2) full factorial design was used to study the effect of two factors (at three levels), namely volume of dissolution medium (150, 200, 250 ml) and reciprocation rate (5, 15, 25 dips per min). Amount of drug released in 0.1N hydrochloric acid at 2h and in pH 6.8 phosphate buffer at 45 min were selected as responses. Results revealed that both, the volume of medium and reciprocation rate, are significant factors affecting isoniazid release. A second order polynomial equation fitted to the data was used to predict the responses in the optimal region. The optimized conditions resulted in dissolution data that were close to the predicted values. The proposed mathematical model is found to be robust and accurate for optimization of dissolution test conditions for site-specific release isoniazid pellets.

Design, synthesis and evaluation of novel 2-thiophen-5-yl-3H-quinazolin-4-one analogues as inhibitors of transcription factors NF-кB and AP-1 mediated transcriptional activation: Their possible utilization as anti-inflammatory and anti-cancer agents

In an attempt to discover novel inhibitors of NF-kappaB and AP-1 mediated transcriptional activation utilizing the concept of chemical lead based medicinal chemistry and bioisosterism a series of 2-(2,3-disubstituted-thiophen-5-yl)-3H-quinazolin-4-one analogs was designed. A facile and simple route for the synthesis of the designed molecules was developed. Synthesized molecules were evaluated for their activity as inhibitors towards NF-kappaB and AP-1 mediated transcriptional activation in a cell line report-based assay. This series provides us with a substantial number of compounds inhibiting the activity of NF-kappaB and/or AP-1 mediated transcriptional activation. These compounds also exhibit anti-inflammatory and anti-cancer activity in in vivo models of inflammation and cancer. The 4-pyridyl group is found to be the most important pharmacophore on the third position of thiophene ring for inhibiting NF-kappaB and AP-1 mediated transcriptional activation. The relationships between the activities shown by these compounds in the in vivo and in vitro models have been established by using FVB transgenic mice model. These results suggest the suitability of the designed molecular framework as a potential scaffold for the design of molecules with inhibitory activity towards NF-kappaB and AP-1 mediated transcriptional activation, which may also exhibit anti-inflammatory and anti-cancer activity. This series of molecules warrants further study to explore their potential as therapies for use in chronic inflammatory conditions and cancer. Development of the synthetic protocol for the synthesis of this series of molecules, biological activities and a structure-activity relationship (SAR) have been discussed herein.

Multivariate optimization of formulation and process variables influencing physico-mechanical characteristics of site-specific release isoniazid pellets

In the present study, isoniazid was formulated as site-specific release pellets with high drug loading (65%, w/w) using extrusion-spheronization followed by aqueous coating of Sureteric (35% weight gain). A statistical experimental strategy was developed to optimize simultaneously the effect of the two formulation variables and one process variable on the critical physico-mechanical properties of the core pellets of isoniazid. Amount of granulating fluid and amount of binder were selected as formulation variables and spheronization speed as a process variable. A 2(3) full factorial experimental design was employed for the present study. Pellets were characterized for physico-mechanical properties viz. usable yield, pellet size, pellips, porosity, abrasion resistance, mechanical crushing force, residual moisture and dissolution efficiency. Graphical and mathematical analysis of the results allowed the identification and quantification of the formulation and process variables active on the selected responses. A polynomial equation fitted to the data was used to predict the responses in the optimal region. The optimum formulation and process parameters were found to be 44.24% (w/w) of granulating fluid, 2.13% (w/w) of binder and spheronization speed of 1000rpm. Optimized formulation showed usable yield 84.95%, particle size 1021.32microm, pellips 0.945, porosity 46.11%, and abrasion resistance 0.485%. However, mechanical crushing force, residual moisture and dissolution efficiency were not significantly affected by the selected independent variables. These results demonstrate the importance of, amount of water, binder and spheronization speed, on physico-mechanical characteristics of the isoniazid core pellets with high drug loading.

Investigation of microemulsion system for transdermal delivery of itraconazole

A new oil-in-water microemulsion-based (ME) gel containing 1% itraconazole (ITZ) was developed for topical delivery. The solubility of ITZ in oils and surfactants was evaluated to identify potential excipients. The microemulsion existence ranges were defined through the construction of the pseudoternary phase diagrams. The optimized microemulsion was characterized for its morphology and particle size distribution. The optimized microemulsion was incorporated into polymeric gels of Lutrol F127, Xanthan gum, and Carbopol 934 for convenient application and evaluated for pH, drug content, viscosity, and spreadability. In vitro drug permeation of ME gels was determined across excised rat skins. Furthermore, in vitro antimycotic inhibitory activity of the gels was conducted using agar-cup method and Candida albicans as a test organism. The droplet size of the optimized microemulsion was found to be <100 nm. The optimized Lutrol F 127 ME gel showed pH in the range of 5.68±0.02 and spreadability of 5.75±1.396 gcm/s. The viscosity of ME gel was found to be 1805.535±542.4 mPa s. The permeation rate (flux) of ITZ from prepared ME gel was found to be 4.234 μg/cm/h. The release profile exhibited diffusion controlled mechanism of drug release from ME ITZ gel. The developed ME gels were nonirritant and there was no erythema or edema. The antifungal activity of ITZ showed the widest zone of inhibition with Lutrol F127 ME gel. These results indicate that the studied ME gel may be a promising vehicle for topical delivery of ITZ.

2-Amino-5-benzoyl-4-phenylthiazoles: Development of potent and selective adenosine A1 receptor antagonists

A series of 2-amino-5-benzoyl-4-phenylthiazole derivatives was investigated in radioligand binding studies at adenosine receptor (AdoR) subtypes with the goal to obtain potent and A(1)-selective antagonists. Acylation of the 2-amino group was found to be crucial for high A(1) affinity. The best compound of the present series was 2-benzoylamino-5-p-methylbenzoyl-4-phenylthiazole (16 m) showing a K(i) value of 4.83 nM at rat and 57.4 nM at human A(1) receptors combined with high selectivity versus the other AdoR subtypes. The compound behaved as an antagonist in GTP shift assays at A(1) receptors. Compound 16 m may serve as a new lead structure for the development of second-generation non-xanthine-derived A(1) antagonists which have potential as novel drugs.

New insight into adenosine receptors selectivity derived from a novel series of [5-substituted-4-phenyl-1,3-thiazol-2-yl] benzamides and furamides.

A series of [5-substituted-4-phenyl-1,3-thiazol-2-yl] benzamide and furamide analogues were investigated in radioligand binding studies at adenosine receptor subtypes with an aim to obtain potent and selective adenosine receptor ligands. Benzamide and furamide linked to thiazole was found to be crucial for high adenosine receptor affinity. The most potent compound indentified in this study was 5d with low nanomolar affinity for all four adenosine receptor subtypes. Compounds 5a and 5g showed moderate selectivity for A2A adenosine receptors. Molecular docking versus all four human adenosine receptors combined with membrane molecular dynamics studies were performed to rationalise the peculiar selectivity profile of 5d antagonist.