1,2,5-Thiadiazolidin-3-one 1,1 Dioxide: A Powerful Scaffold for Probing the S′ Subsites of (Chymo)trypsin-Like Serine Proteases

The 1,2,5-thiadiazolidin-3-one 1,1 dioxide scaffold (I) embodies a motif that allows it to dock to the active site of (chymo)trypsin-like proteases in a predictable and substrate-like fashion. Consequently, inhibitors derived from this heterocyclic scaffold interact with both the S and S' subsites of an enzyme. Exploitation of binding interactions with both the S and S' subsites of a target enzyme may lead to compounds with greatly enhanced enzyme selectivity and inhibitory potency. This preliminary report describes the use of a series of compounds having the heterocyclic scaffold linked to various amino acids to probe the S' subsites of human leukocyte elastase (HLE), proteinase 3 (PR 3), and cathepsin G (Cat G). For comparative purposes, a series of compounds derived from a related scaffold, isothiazolidin-3-one 1,1 dioxide (II), was also generated. Several of the compounds were found to be highly potent and selective time-dependent inhibitors of HLE, PR 3, and Cat G.

Novel approaches to the treatment of acute renal failure

Acute renal failure (ARF) occurs frequently in hospitalised patients and is associated with significant morbidity and mortality. Many therapeutic strategies have been undertaken both to prevent acute renal injury and, once ARF occurs, to improve renal function and reduce mortality. Among the available pharmacological options, no specific therapy has been shown to alter the course of ARF. This article reviews the efficacy of several strategies in experimental renal disease and raises the possibility that similar interventions might be available to the clinician in the near future for the prevention and management of ARF. The prospect of these novel strategies together with the ever-increasing understanding of the complex pathophysiology of ARF, offers the promise of effective and more physiological therapeutic interventions in this new millennium.

Characterization of a novel 8-oxoguanine-DNA glycosylase activity in Escherichia coli and identification of the enzyme as endonuclease VIII

8-Oxoguanine (G*), induced by reactive oxygen species, is mutagenic because it mispairs with A. The major G*-DNA glycosylase (OGG), namely, OGG1 in eukaryotes, or MutM in Escherichia coli, excises G* when paired in DNA with C, G, and T, but not A, presumably because removal of G* from a G*.A pair would be mutagenic. However, repair of G* will prevent mutation when it is incorporated in the nascent strand opposite A. This could be carried out by a second OGG, OGG2, identified in yeast and human cells. We have characterized a new OGG activity in E. coli and then identified it to be endonuclease VIII (Nei), discovered as a damaged pyrimidine-specific DNA glycosylase. Nei shares sequence homology and reaction mechanism with MutM and is similar to human OGG2 in being able to excise G* when paired with A (or G). Kinetic analysis of wild type Nei showed that it has significant activity for excising G* relative to dihydrouracil. The presence of OGG2 type enzyme in both E. coli and eukaryotes, which is at least as efficient in excising G* from a G*.A (or G) pair as from a G*.C pair, supports the possibility of G* repair in the nascent DNA strand.

Potent inhibition of serine proteases by heterocyclic sulfide derivatives of 1,2,5-thiadiazolidin-3-one 1,1 dioxide

The existence of subtle differences in the Sn' subsites of closely-related (chymo)trypsin-like serine proteases, and the fact that the 1,2,5-thiadiazolidin-3-one 1,1 dioxide scaffold docks to the active site of (chymo)trypsin-like enzymes in a substrate-like fashion, suggested that the introduction of recognition elements that can potentially interact with the Sn' subsites of these proteases might provide an effective means for optimizing enzyme potency and selectivity. Accordingly, a series of heterocyclic sulfide derivatives based on the 1,2,5-thiadiazolidin-3-one 1,1 dioxide scaffold (I) was synthesized and the inhibitory activity and selectivity of these compounds toward human leukocyte elastase (HLE), proteinase 3 (PR 3) and cathepsin G (Cat G) were then determined. Compounds with P1 = isobutyl were found to be potent, time-dependent inhibitors of HLE and, to a lesser extent PR 3, while those with P1 = benzyl inactivated Cat G rapidly and irreversibly. This study has demonstrated that 1,2,5-thiadiazolidin-3-one 1,1 dioxide-based heterocyclic sulfides are effective inhibitors of (chymo)trypsin-like serine proteases.

Utilization of the 1,2,5-thiadiazolidin-3-one 1,1 dioxide scaffold in the design of potent inhibitors of serine proteases: SAR studies using carboxylates

A series of carboxylate derivatives based on the 1,2,5-thiadiazolidin-3-one 1,1 dioxide and isothiazolidin-3-one 1,1 dioxide scaffolds has been synthesized and the inhibitory profile of these compounds toward human leukocyte elastase (HLE), cathepsin G (Cat G) and proteinase 3 (PR 3) was then determined. Most of the compounds were found to be potent, time-dependent inhibitors of elastase, with some of the compounds exhibiting k(inact)/K1 values as high as 4,928,300 M(-1) s(-1). The inhibitory potency of carboxylate derivatives based on the 1,2,5-thiadiazolidin-3-one 1,1 dioxide platform was found to be influenced by both the pKa and the inherent structure of the leaving group. Proper selection of the primary specificity group (R(I)) was found to lead to selective inhibition of HLE over Cat G, however, those compounds that inhibited HLE also inhibited PR 3, albeit less efficiently. The predictable mode of binding of these compounds suggests that, among closely-related serine proteases, highly selective inhibitors of a particular serine protease can be fashioned by exploiting subtle differences in their S' subsites. This study has also demonstrated that the degradative action of elastase on elastin can be abrogated in the presence of inhibitor 17.

Comparative pharmacogonostic studies of genuine and commercial samples of trianthema decandra linn

Trianthema decandra Linn. (Fam ficoidaceae) Commonly known a "Vellai sharunai'on Tamil and Punaranavi in Sanskrit the roots are used in hepatitis, asthma and suppression of menses the genuine and tree commercial samples of the root of R. Decandra in have been compared pharmacognostically for the first time in the present investigation all the pharmacognostic findings reveal adulteration in the commercial samples.

Management of quality, capacity, and productivity at Merck

Merck is one of the largest manufacturers of drugs in the world. With emphasis on research and development and quality, it invents, develops, and markets a wide variety of human and animal health products. Merck-Medco is the industry leader in managed pharmaceutical care. Merck's productivity increases are largely attributed to procurement, inventory policies, capacity initiatives, and strategic alliances.

Potent and specific inhibition of human leukocyte elastase, cathepsin G and proteinase 3 by sulfone derivatives employing the 1,2,5-thiadiazolidin-3-one 1,1 dioxide scaffold

This paper describes the results of structure-activity relationship studies in a series of heterocyclic mechanism-based inhibitors based on the 1,2,5-thiadiazolidin-3-one 1,1 dioxide scaffold I and capable of interacting with the Sn and Sn' subsites of a serine proteinase. Sulfone derivatives of I were found to be highly effective, time-dependent inhibitors of human leukocyte elastase (HLE), cathepsin G (Cat G) and proteinase 3 (PR 3). The judicious selection of an R1 group (accommodated at the primary specificity site S1) that is based on the known substrate specificity of a target serine proteinase, was found to yield highly selective inhibitors. The presence of a benzyl group (R2 = benzyl) at the S2 subsite was found to lead to a pronounced enhancement in inhibitory potency. Furthermore, the effective use of computer graphics and modeling has led to the design of potent, water-soluble inhibitors. The results of these studies demonstrate that the 1,2,5-thiadiazolidin-3-one 1,1, dioxide platform provides an effective means for appending recognition elements in a well-defined vector relationship, and in fashioning highly-selective and potent inhibitors of serine proteinases.

Use of the 1,2,5-thiadiazolidin-3-one 1,1 dioxide and isothiazolidin-3-one 1,1 dioxide scaffolds in the design of potent inhibitors of serine proteinases

The attachment of a phosphate leaving group to the 1,2,5-thiadiazolidin-3-one 1,1 dioxide and isothiazolidin-3-one 1,1 dioxide scaffolds was found to yield highly potent, time-dependent inhibitors of human leukocyte elastase (HLE).

Immunogenicity study of Haemophilus influenzae type B conjugate vaccine in Indian infants

OBJECTIVE

To assess the immunogenicity in Indian infants to Haemophilus influenzae b oligosaccharide conjugate vaccine (HbOC).

DESIGN

Prospective multicenter study.

SETTING

Pediatric Out Patient Department of general hospitals in Pune and Mumbai.

SUBJECTS

124 full term healthy infants brought for routine DPT/OPV immunization.

METHODS

Infants were administered 3 doses of 0.5 ml of HbOC, on the same day as their DPT/OPV immunization, injected intramuscularly on the limb opposite to that where DPT vaccine was administered. Data on local reactions and general symptoms was collected for three days after every dose. The children had their blood collected for assay of anti PRP (polyribosil ribitol phosphate) antibody titers, along with the first injection and one month after the third injection. One hundred and three infants completed the study protocol with two blood collections.

RESULTS

The initial geometric mean titers (GMT) of 0.124 mcg/ml rose by 37 times to 4.552 mcg/ml. Ninety eight children (95.1%) had a final titer of > or = 0.15 mcg/ml, the minimum level associated with protection, and 77 children (74.8%) had a final level of > or = 1.0 mcg/ml, a level associated with long term protection.

CONCLUSION

HbOC is immunogenic in Indian infants when used as per the locally recommended DPT/OPV immunization schedule.

Structure-based design of a general class of mechanism-based inhibitors of the serine proteinases employing a novel amino acid-derived heterocyclic scaffold

We describe in this paper the structure-based design of a general class of heterocyclic mechanism-based inhibitors of the serine proteinases that embody in their structure a novel peptidomimetic scaffold (1,2,5-thiadiazolidin-3-one 1,1-dioxide). Sulfone derivatives of this class (I) were found to be time-dependent, potent, and highly efficient irreversible inhibitors of human leukocyte elastase, cathepsin G, and proteinase 3. The partition ratios for a select number of inhibitors were found to range between 0 and 1. We furthermore demonstrate that these inhibitors exhibit remarkable enzyme selectivity that is dictated by the nature of the P1 residue and is consistent with the known substrate specificity reported for these enzymes. Thus, inhibitors with small hydrophobic side chains were found to be effective inhibitors of elastase, those with aromatic side chains of cathepsin G, and those with a basic side chain of bovine trypsin. Taken together, the findings cited herein reveal the emergence of a general class of stable mechanism-based inhibitors of the serine proteinases which can be readily synthesized using amino acid precursors. Biochemical and high-field NMR studies show that the interaction of this class of inhibitors with a serine proteinase results in the formation of a stable acyl complex(es) and the release of benzenesulfinate, formaldehyde, and a low molecular weight heterocycle. The data are consistent with initial formation of a Michaelis-Menten complex, acylation of Ser195, and tandem loss of the leaving group. The initial HLE-inhibitor complex reacts with water generating formaldehyde and a stable HLE-inhibitor complex. Whether the initial HLE-inhibitor complex also reacts with His57 to form a third complex is not known at this point. The desirable salient parameters associated with this class of inhibitors, including the expeditious generation of structurally diverse libraries of inhibitors based on I, suggest that this class of mechanism-based inhibitors is of general applicability and can be used in the development of inhibitors of human and viral serine proteinases of clinical relevance.

Design, synthesis, and in vitro inhibitory activity toward human leukocyte elastase, cathepsin G, and proteinase 3 of saccharin-derived sulfones and congeners

The inhibitory activity toward human leukocyte elastase (HLE), cathepsin G (Cat G), and proteinase 3 (PR 3) of a series of saccharin derivatives having a sulfinate leaving group was investigated. The results of this study revealed that (a) inhibitory activity is dependent on the nature and pKa of the leaving group, and (b) the synthesized saccharin derivatives exhibit selective inhibition toward HLE and PR 3, with low or no activity toward cathepsin G. The results of exploratory biochemical, HPLC and high-field 13C NMR studies are also described.

Amino acid-derived phthalimide and saccharin derivatives as inhibitors of human leukocyte elastase, cathepsin G, and proteinase 3

Amino acid-derived phthalimide and saccharin derivatives have been investigated for their inhibitory activity toward the serine proteinases human leukocyte elastase, cathepsin G, and proteinase 3. The saccharin derivatives were found to be effective time-dependent inhibitors of elastase and proteinase 3 (kobs/[I] values ranged between 180 and 3620 M-1 S-1) and showed weak or no inhibition toward cathepsin G. The corresponding phthalimide derivatives were found to be inactive.

Identification of a new noradrenaline induced gene in the rat heart by differential mRNA display

OBJECTIVE

Noradrenaline treatment of animals results in postnatal hypertrophy of the heart. This process requires many qualitative and quantitative changes in gene expression; however, the identities of the key regulatory genes which modulate the process are not known. The aim of this study was to investigate whether a recently developed technique, differential display, could provide a new route to the identification and characterisation of these critical genes.

METHODS

The technique of differential display was modified for use on cardiac RNA samples and the expression of clones identified by this approach was characterised by northern analysis.

RESULTS

Differential display was successfully adapted to the study of noradrenaline induced cardiac gene expression. A previously unsuspected gene was identified, the expression of which appears to be strongly modified during the onset of this process.

CONCLUSIONS

Differential display offers the potential to identify and clone many of the genes critically important in regulation of growth of the mammalian heart.

Design, synthesis and biological evaluation of succinimide derivatives as potential mechanism-based inhibitors of human leukocyte elastase, cathepsin G and proteinase 3

Structure-activity relationship study and in vitro biochemical studies with human leukocyte elastase, cathepsin G and proteinase 3 were conducted using a series of succinimide derivatives.

The Gabriel-Colman rearrangement in biological systems: design, synthesis and biological evaluation of phthalimide and saccharin derivatives as potential mechanism-based inhibitors of human leukocyte elastase, cathepsin G and proteinase 3

The results of a structure-activity relationship study focusing on the interaction of a series of phthalimide and saccharin derivatives with leukocyte elastase, cathepsin G and proteinase 3 are described. The phthalimide derivatives were found to be inactive while some of the saccharin derivatives were found to be fair inhibitors of these enzymes.

Mechanism-based inhibition of human leukocyte elastase and cathepsin G by substituted dihydrouracils

A series of dihydrouracil derivatives has been synthesized and investigated for their in vitro inhibitory activity toward human leukocyte elastase (HLE) and cathepsin G (Cath G). Alkyl [sulfonyl(oxy)] uracils 1-2 were found to be efficient, time-dependent inhibitors of elastase (kobs/[I] M-1 s-1 values ranged between 480 and 8110). These compounds formed acyl enzymes that exhibited variable hydrolytic stability which appeared to be dependent on the nature of the R1 group (believed to be accommodated at the primary specificity site, S1). The acyl enzymes formed with cathepsin G deacylated rapidly, leading to a significant regain of enzymatic activity. In sharp contrast, the corresponding phosphorus compounds 3-4 were found to be potent, time-dependent irreversible inhibitors of HLE. Furthermore, the results of the structure-activity relationship studies suggest that the binding modes of compounds 1-2 and 3-4 may be different.

Substituted 3-oxo-1,2,5-thiadiazolidine 1,1-dioxides: a new class of potential mechanism-based inhibitors of human leukocyte elastase and cathepsin G

A series of substituted 3-oxo-1,2,5-thiadiazolidine 1,1-dioxides has been synthesized and their in vitro inhibitory activity toward human leukocyte elastase and cathepsin G was investigated. These compounds were found to inactivate the two enzymes efficiently and in a time-dependent fashion.