Rajani Giridhar

Current perspective of TACE inhibitors: A review

Rheumatoid Arthritis (RA) is one of the most common autoimmune inflammatory conditions, affecting approximately 1% of the adult population worldwide. TNF-alpha is a pleitropic, pro-inflammatory cytokine which plays a pivotal role in the origin and progression of RA and other immune mediated disorders. The success of anti-TNF-alpha biological agents proved that inhibition of TNF-alpha could result in effective control of RA. Since the discovery of anti-TNF-alpha biologicals, much efforts have gone into developing an orally bioavailable small size TNF-alpha antagonist. One of the ways to block TNF-alpha in biological fluids is to inhibit TNF-alpha converting enzyme (TACE). This target has been validated in preclinical trials using TACE inhibitors. But, even after more than a decade no single TACE inhibitor has passed the Phase II clinical trials. Very recently, it has been shown that TACE inhibitors could also be used for inhibition of pathogenic EGFR signaling in cancer. Hence, TACE inhibitors could perform a dual role, in curing not only RA but also certain cancerous conditions. Developments in the field have prompted us to review the research work on TACE inhibitors, especially their structure activity relationships and molecular modeling studies.

Angiotensin II receptor type 1 (AT1) selective nonpeptidic antagonists—A perspective

Hypertension is a major risk factor for human morbidity and mortality through its effects on target organs like heart, brain and kidneys. More intensive treatment for the effective control of blood pressure significantly reduces the morbidity and mortality. The renin angiotensin system (RAS) is a coordinated hormonal cascade of major clinical importance in the regulation of blood pressure. The principal effector peptide of RAS is angiotensin II, which acts by binding to one of the two major angiotensin II receptors AT(1) and AT(2). Angiotensin II through AT(1) receptor mediates vast majority of biologically detrimental actions. Nonpeptidic angiotensin II (AT(1)) antagonists are the most specific means to block the renin angiotensin enzymatic cascade available presently. Majority of AT(1) antagonists are based on modifications of losartan structure, the first clinically used AT(1) antagonist. In this review, a comprehensive presentation of the literature on AT(1) receptor antagonists has been given.

The search for potent, small molecule NNRTIs: A review

AIDS has become the leading pandemic disease, and is the cause of death worldwide. Presently, HAART treatment, a combination of reverse transcriptase (RT) and protease inhibitors is also unsuccessful due to the virus getting resistant to the drugs because of mutational changes. Two types of RT inhibitors exist namely nucleoside reverse transcriptase inhibitors (NRTIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs). The NNRTIs which bind to an allosteric site on RT are an important arsenal of drugs against HIV-1. The specificity of NNRTIs towards HIV-1 has led to extensive structural and molecular modelling studies of enzyme complexes and chemical synthesis of second and third-generation NNRTIs. The major drawbacks of NNRTIs are generation of resistance and pharmacokinetic problems. By mutational studies of non-nucleoside inhibitor binding pocket (NNIBP) some amino acids which were found to play an important role in proper binding resulted less prone to mutation. In this review we present a chronological history of NNRTI development, also highlighting the need for small molecules belonging to the NNRTI class for the management of AIDS.

Prodrug Designing of NSAIDs

Non-steroidal anti-inflammatory drugs (NSAIDs), commonly used for the treatment of chronic inflammatory diseases suffer from several undesired side effects, the most important being gastrointestinal (GI) irritation and ulceration. The prodrug designing is one of the several strategies used to overcome this drawback. The rationale behind the prodrug concept is to achieve temporary blockade of the free carboxylic group present in the NSAIDs till their systemic absorption. In this paper, a review on the concept of prodrugs designing of NSAIDs to improve their efficacy and reduce the toxicity is being presented.

Novel TACE inhibitors in drug discovery: a review of patented compounds.

TNF-α converting enzyme (TACE), a pro-inflammatory cytokine, catalyzes the formation of TNF-α from membrane bound TNF-α precursor protein. TNF-α is believed to play pathophysiological roles in inflammation, anorexia, cachexia, septic shock, viral replication and so on. TNF-α is a key player in inflammation and joint damage in rheumatoid arthritis. While a variety of TACE inhibitors have been reported in the literature, a vast majority of these compounds are peptidic and peptide-like compounds that are expected to have bioavailability and pharmacokinetic problems, common to such compounds, limiting their clinical effectiveness. Low molecular mass, long acting, orally bioavailable inhibitors of TACE are, therefore, highly desirable for the treatment of potential chronic diseases mentioned above. A review of patented compounds as TACE inhibitors in drug discovery is given. A selection of interesting patents recorded from 2001 to 2009 is presented. Various novel TACE inhibitors developed by different companies have been discussed.

Spectrophotometric determination of fluoxetine hydrochloride in bulk and in pharmaceutical formulations

Two new rapid, sensitive and economical spectrophotometric methods are described for the determination of fluoxetine hydrochloride in bulk and in pharmaceutical formulations. Both methods are based on the formation of a yellow ion-pair complex due to the action of methyl orange (MO) and thymol blue (TM) on fluoxetine in acidic (pH 4.0) and basic (pH 8.0) medium, respectively. Under optimised conditions they show an absorption maxima at 433 nm (MO) and 410 nm (TB), with molar absorptivities of 2.12 x 10(-4) and 4.207 x 10(-3) l mol(-1) cm(-1) and Sandells Sensitivities of 1.64 x 10(-2) and 0.082 microg cm(-2) per 0.001 absorbance unit for MO and TB, respectively. The colour is stable for 5 min after extraction. In both cases Beers Law is obeyed at 1-20 microg mol(-1) with MO and 4-24 microg mol(-1) with TB. The proposal method was successfully extended to pharmaceutical preparations capsules. The results obtained by both the agreement and E.P. (3rd edition) were in good agreement and statistical comparison by Students t-test and variance ratio F-test showed no significant difference in the three methods.

Antihiv, antibacterial and antifungal activities of some novel 1,4-disubstituted-1,2,4-triazolo[4,3-a] quinazolin-5(4H)-ones

The title compounds 1-substituted-4-phenyl-1,2,4-triazolo[4,3-a]quinazolin-5(4 H )-ones were synthesized by the cyclization of 2-hydrazino-3-phenylquinazolin-4(3 H )-one with various one carbon donors. The starting material 2-hydrazino-3-phenylquinazolin-4(3 H )-one was synthesized from aniline. Investigation of antimicrobial activity of the test compounds was made by agar cup-plate method against 8 pathogenic bacteria including Mycobacterium tuberculosis , 3 pathogenic fungi and antiHIV activity against replication of HIV-1(IIIB) and HIV-2(ROD) in MT-4 cells. The compound 7e inhibited 21% growth of M. tuberculosis at 6.25 µg/ml concentration, while the compounds 7c and 7d showed good antifungal activity against Candida albicans ; and the compounds 7c exhibited good antifungal activity against Aspergillus niger .

A rapid colorimetric method for the determination of Losartan potassium in bulk and in synthetic mixture for solid dosage form

Two new rapid reproducible and economical spectrophotometric methods are described for the determination of Losartan potassium in bulk and in synthetic mixture for solid dosage forms. Both methods are based on the formation of an orange-red and orange ion-pair complex due to the action of Calmagite (CT) and Orange-II (O-II) on Losartan potassium in acidic medium (pH 1.2). Under optimised conditions, they show an absorption maxima at 491 nm (CT) and 486 nm (O-II), with molar absorptivities of 1.74 x 10(3) and 1.75 x 10(3) l mol(-1) cm(-1) and Sandells sensitivities of 0.2649 and 0.2637 per 0.001 absorbance unit for CT and O-II, respectively. The colour is stable for 5 min after extraction. In both cases Beers law is obeyed between 10 and 100 microg ml(-1). The proposed method was successfully extended to synthetic mixture for solid dosage forms.

Prospective therapeutic agents for obesity: molecular modification approaches of centrally and peripherally acting selective cannabinoid 1 receptor antagonists.

Presently, obesity is one of the major health problems in the developed as well as developing countries due to lack of physical work and increasing sedentary life style. Endocannabinoid system (ECS) and especially cannabinoid 1 (CB1) receptor play a key role in energy homeostasis. Food intake and energy storage is enhanced due to the stimulation of ECS hence, inhibition of ECS by blocking CB1 receptors could be a promising approach in the treatment of obesity. Rimonabant, a diaryl pyrazole was the first potent and selective CB1 receptor antagonist that was introduced into the market in 2006 but was withdrawn in 2008 due to its psychiatric side effects. Researchers all over the world are interested to develop peripherally acting potent and selective CB1 receptor antagonists having a better pharmacokinetic profile and therapeutic index. In this development process, pyrazole ring of rimonabant has been replaced by different bioisosteric scaffolds like pyrrole, imidazole, triazole, pyrazoline, pyridine etc. Variations in substituents around the pyrazole ring have also been done. New strategies were also employed for minimizing the psychiatric side effects by making more polar and less lipophilic antagonists/inverse agonists along with neutral antagonists acting peripherally. It has been observed that some of the peripherally acting compounds do not show adverse effects and could be used as potential leads for the further design of selective CB1 receptor antagonists. Chemical modification strategies used for the development of selective CB1 receptor antagonists are discussed here in this review.

3D-Quantitative Structure–Activity Relationship Studies on Benzothiadiazepine Hydroxamates as Inhibitors of Tumor Necrosis Factor-α Converting Enzyme

A set of 29 benzothiadiazepine hydroxamates having selective tumor necrosis factor‐α converting enzyme inhibitory activity were used to compare the quality and predictive power of 3D‐quantitative structure–activity relationship, comparative molecular field analysis, and comparative molecular similarity indices models for the atom‐based, centroid/atom‐based, data‐based, and docked conformer‐based alignment. Removal of two outliers from the initial training set of molecules improved the predictivity of models. Among the 3D‐quantitative structure–activity relationship models developed using the above four alignments, the database alignment provided the optimal predictive comparative molecular field analysis model for the training set with cross‐validated r2 (q2) = 0.510, non‐cross‐validated r2 = 0.972, standard error of estimates (s) = 0.098, and F = 215.44 and the optimal comparative molecular similarity indices model with cross‐validated r2 (q2) = 0.556, non‐cross‐validated r2 = 0.946, standard error of estimates (s) = 0.163, and F = 99.785. These models also showed the best test set prediction for six compounds with predictive r2 values of 0.460 and 0.535, respectively. The contour maps obtained from 3D‐quantitative structure–activity relationship studies were appraised for activity trends for the molecules analyzed. The comparative molecular similarity indices models exhibited good external predictivity as compared with that of comparative molecular field analysis models. The data generated from the present study helped us to further design and report some novel and potent tumor necrosis factor‐α converting enzyme inhibitors.