Current Medicinal Chemistry - Volume 9, Issue 4, 2002

The development of a vaccine for cancer has been difficult compared to the effective vaccines of infectious diseases. Most tumor antigens are not entirely foreign and are expressed on normal tissues, thus, making it difficult to induce strong immune responses against self antigens. A peptide mimic, however, may have the potential to generate greater immune responses than those induced to self peptides. In this review we discuss applications of peptide mimcs for cancer immunotherapy which may ultimately prove useful in humans.

In search of new molecular entities for discovering new drugs and materials, organic chemists are looking for innovative approaches that try to imitate nature in assembling quickly large number of distinct and diverse molecular structures from ‘nature-like’ and yet unnatural designer building blocks using combinatorial approach. The main objective in developing such libraries is to mimic the diversities displayed in structures and properties of natural products. The unnatural building blocks used in these assemblies are carefully designed to manifest the structural diversities of the monomeric units used by nature like amino acids, carbohydrates and nucleosides to build its arsenal. Compounds made of such unnatural building blocks are also expected to be more stable toward proteolytic cleavage in physiological systems than their natural counterparts. Sugar amino acids constitute an important class of such polyfunctional scaffolds where the carboxyl, amino and hydroxyl termini provide an excellent opportunity to organic chemists to create structural diversities akin to nature's molecular arsenal. Recent advances in the area of combinatorial chemistry give an unprecedented technological support for rapid compilations of sugar amino acid-based libraries exploiting the diversities of carbohydrate molecules and well-developed solid-phase peptide synthesis methods.This review describes the development of sugar amino acids as a novel class of peptidomimetic building blocks and their applications in creating large number of structurally diverse peptide-based molecules many of which display interesting three-dimensional structures as well as useful biological properties.

Activities of ciprofloxacin and levofloxacin against an SHV-5 extended-spectrum ß-lactamase (ESBL)-producing Klebsiella pneumoniae strain were studied in vitro and in vivo in septic mice using a high inoculum. Susceptibility to ciprofloxacin and levofloxacin was independent of the inoculum size. In killing curve studies, after 24 hours the initial 7.69 log 10 CFU / ml increased in the control to 9.34, while it was reduced to 4.83 by ciprofloxacin and to 4.25 by levofloxacin. Mice were infected with 10 7 CFU / g of K. pneumoniae intraperitoneally. Treatment started 2 hours later, when the mean blood bacterial counts were 7.33 log 10 CFU / ml, and lasted for 26 hours from the time of infection. Blood bacterial count was reduced from 7.33 log 10 CFU / ml to 4.08 log 10 CFU / ml by ciprofloxacin (20mg / kg / 6 hours), and to 3.60 log 10 CFU / ml by levofloxacin (50 mg / kg / 6 hours) 8 hours after the infection, which differed significantly from the infected untreated group. Ciprofloxacin and levofloxacin prolonged significantly the survival of mice compared with the infected untreated group (p<0.001 for both groups). There were not significant differences either in the survival (p=1.0) or in the blood bacterial counts (p=0.216 after 8 hours) between ciprofloxacin and levofloxacin group. Based on these results both ciprofloxacin and levofloxacin could be alternative therapeutic agents for the infection caused by ESBL-producing Klebsiella strains.

Serotonin (5-hydroxytryptamine, 5-HT) is one of the most attractive targets for medicinal chemists. Among 5-HTRs, the 5-HT 1A subtype is the best studied and it is generally accepted that it is involved in psychiatric disorders such as anxiety and depression. Several structurally different compounds are known to bind 5-HT 1A R sites. Among these, arylpiperazine derivatives represent one of the most important classes of 5-HT 1A R ligands. This article will review the development of arylpiperazine derivatives acting at 5-HT 1A Rs with an emphasis on structure-affinity relationships of agonists and antagonists, ligand-receptor interactions and pharmacological applications.

This review focuses on the major developments in depsipeptide research since 1995. Depsipeptides are bio-oligomers composed of hydroxy and amino acids linked by amide and ester bonds. Many depsipeptides show very promising biological activities, including anticancer, antibacterial, antiviral, antifungal, anti-inflammatory, and anti-clotting or anti-antherogenic properties. In this report depsipeptides exhibiting these properties are discussed. Their isolation, structural determination, and notable structural features are discussed, but their biological properties and therapeutic potentials are emphasized.Depsipeptides have shown the greatest therapeutic potential as anticancer agents. Four depsipeptides have entered clinical trials for cancer treatment. Among the antiviral compounds discovered, the callipeltins and the quinoxapeptins are particularly promising due to their inhibitory activities against HIV. These compounds have the potential to be developed as anti-AIDS drugs or to serve as lead compounds for the discovery of structurally related anti-AIDS compounds. Antifungal compounds, such as the jaspamides, may lead to therapies against many of the opportunistic infections that accompany AIDS. Anti-inflammatory compounds such as SCH217048 act as neurokinin antagonists and may lead to anti-inflammatory treatments. Some depsipeptides such as micropeptins and A90720A have been found to be effective plasmin inhibitors, which have implications as treatments for cardiovascular diseases. Compounds such as SCH58149 help control the levels of HDL and LDL.

2-oxo acid dehydrogenase complexes are a ubiquitous family of multienzyme systems that catalyse the oxidative decarboxylation of various 2-oxo acid substrates. They play a key role in the primary energy metabolism: in glycolysis (pyruvate dehydrogenase complex), the citric acid cycle (2-oxoglutarate dehydrogenase complex) and in amino acid catabolism (branched-chain 2-oxo acid dehydrogenase complex). Malfunctioning of any of these complexes leads to a broad variety of clinical mani-festations. Deficiency of the pyruvate dehydrogenase complex predominantly leads to lactic acidosis combined with impairment of neurological function and / or delayed growth and development. Maple urine disease is an inborn metabolic error caused by dysfunction of the branched-chain 2-oxo acid dehydrogenase complex. An association between both Alzheimer disease and Parkinson's disease and the 2-oxoglutarate dehydrogenase gene has been reported.Currently a wealth of both genetic and structural information is available. Three-dimensional structures of three components of the complex are presently available: of the pyruvate dehydrogenase component (E1), of the dihydrolipoyl acyltransferase component (E2) and of the lipoamide dehydrogenase component (E3). Moreover, detailed information on the reaction mechanism, regulation and the interactions between the different components of the complex is now at hand. Although only one of the structures is of human origin (E1b), model building by homology modelling allows us to investigate the causes of dysfunction.In this review we have combined this knowledge to gain more insight into the structural basis of the dysfunctioning of the 2-oxo acid dehydrogenase complexes.