Current Medicinal Chemistry - Volume 9, Issue 12, 2002

Resistance to antibiotics is currently a major health concern in treating infectious diseases. The most common mechanism of resistance to β-lactam antibiotics is the production of β-lactamases, which destroy β-lactam antibiotics before they reach the bacterial target. Combination therapy, which involves treatment with a β-lactam antibiotic and a β-lactamase inhibitor, has been successfully used to control resistance during last two decades. Due to the lack of effectiveness of the currently available β-lactamase inhibitors against class C enzymes and new variants of β-lactamases, there is a need to develop an inhibitor with broad-spectrum activity. Since the discovery of clavulanic acid, there has been an enormous research effort in this area to identify better antibiotic / inhibitor combinations and to understand the molecular bases for interactions between β-lactam antibiotics, β-lactamases, and β-lactamase inhibitors. This review describes some of the structure- and mechanism-based approaches to design of new β-lactamase inhibitors and the study of probable mechanisms of inhibition using X-ray, electrospray ionization mass spectrometry, and molecular modeling techniques.

Modification of cysteine (Cys) residues in proteins, due to (i) the participation of the thiol moiety of this amino acid in oxido-reductions reactions (ii) its ability to strongly coordinate transition metal ions or (iii) its nucleophilic nature and facile reaction with electrophiles, may be of critical importance for the design of novel types of pharmacological agents. Application of such procedures, recently led to the design of novel antivirals, mainly based on the reaction of zinc finger proteins with disulfides and related derivatives. This approach was particularly successful for developing novel anti-HIV and anti-HPV agents. Several new anticancer therapeutic approaches, mainly targeting tubulin, Ras and fanesyl transferase among others, have also been reported. Miscellaneous other agents / procedures which found less applications for the moment, and which are based on Cys modification reactions, are reviewed. This unique amino acid offers very interesting possibilities to develop particularly useful pharmacological agents, which generally possess a completely different mechanism of action as compared to classical agents in clinical use, avoiding their major problems such as multidrug-resistance of antivirals or antitumor agents or high toxicity associated with classical such chemotherapeutic agents.

Serotonin N-acetyltransferase (arylalkylamine N-acetyltransferase, AANAT) catalyzes the rate-limiting step in the biosynthesis of the circadian hormone melatonin from serotonin. Although melatonin was identified 40 years ago, relatively little is known about its (patho)physiological roles, and a solid scientific foundation is still lacking for most therapeutic applications currently claimed for melatonin. The development of potent, specific, and cell permeable inhibitors for AANAT should constitute an important strategy to address these issues. These inhibitors are also potential therapeutics for various sleep / mood disorders. This review will focus on the efforts toward developing in vitro and in vivo AANAT inhibitors, including basic mechanistic studies on AANAT, which have played an important role in design.

Bisphosphonates (BP) are pyrophosphate analogs having a P-C-P backbone. The oral bioavailability of BPs is ca. 1%, due to high ionisation at physiological pH. Using the prodrug approach, oral absorption can be increased by masking one or more ionizable groups (clodronate, etidronate), or using a targeting carrier system (alendronate, pamitronate).

The search for pharmacological approaches to neoplastic disease has made some impressive gains started after 1940 when the antileukemic activity of nitrogen mustard was discovered during world war II. It is generally accepted that neoplastic transformation is related to genes alteration or oncogene activation, so the progress in the development of the new drugs for treatment of malignant diseases has been rapid, both in revealing pathobiology of the diseases and discovery of new drugs. In addition attempts have been made to define optimal combinations, treatment strategies and patient support measures. Cancer chemotherapy is now of established value and a highly specialized field. Among the modifications to the family of antitumor compounds, heterocyclic organic compounds have been extensively applied by many groups in order to modify the reactivity profile. Pyrrole, pyrimidine, indole, quinoline and purine are few classes of heterocycles which showed interesting cytotoxicity profiles. The updated material related to these modifications has been rationalized and ordered, in order to offer an overview of the argument.