Current Medicinal Chemistry - Volume 16, Issue 18, 2009

Chronic lymphoid leukemias include well defined mature B-cell and T-cell neoplasms with diverse natural history and specific morphological, immunophenotypic and molecular characteristics. The most common adult leukemia in the Western world is chronic lymphocytic leukemia (CLL). Rarer indolent lymphoid leukemias include prolymphocytic leukemia, hairy cell leukemia, large granular lymphocyte leukemia and T-cell leukemia/lymphoma. Recently, several new agents have been explored and have shown promise in CLL treatment. Novel therapies are being evaluated both in preclinical studies and in early clinical trials. These treatments include new purine nucleoside analogs, antisense oligonucleotides, agents targeting the antiapoptotic Bcl-2 family of proteins, receptors involved in mediation of survival signals from the microenvironment, cyclin-dependent kinase inhibitors, protein kinase C inhibitors, tyrosine kinase inhibitors, immunomodulating drugs, new monoclonal antibodies and other agents. At present, available therapies are only partially efficient and there is an obvious need to develop better strategies and new, more specific and active drugs. This review will focus on agents currently being explored in preclinical studies and in early clinical trials.

The ideal drug discovery process of new platinum based drugs should take into account three basic fundaments: on one side the mechanisms of action and the corresponding target biomolecules, on the other side, the possible mechanisms of resistance of cancer cells and their biochemical pathways and, finally, the pharmacokinetic and toxicity properties (ADMET) that will condition the clinical usefulness of the new drugs. At the end of this rational process always we face the necessity to design a molecule with a structure and certain physical and chemical properties. The structure is then a key fundamental issue when thinking of new anticancer platinum compounds. When analyzing the influence of molecular structure on anticancer activity it is useful to make the dissection of platinum complexes into different significant subunits or moieties, of the molecular structure. Thus, the following structural and electron dependent parameters are important to facilitate the comparison among platinum complexes: a) Nature of the non-labile ligand or carrier ligand (NLG); b) Nature of the labile ligand or leaving group (LG); c) Oxidation state of platinum atom; d) Type of atoms (connecting atoms X, Y, Z, W) that link ligands to platinum atom; e) Nature of the axial groups (AG) in platinum(IV) complexes; f) Nuclearity or number of Pt atoms in the platinum complexes; g) Formal charges present in the molecule and h) Intrinsic bioactivity of some ligands or bioactivity induced by molecules attached to ligands by linkers (in order to get a double mechanism of action or a parallel biological activity).

The hyaluronidases (HAases) are a group of less extensively studied glycosidases distributed throughout the animal kingdom and are popularly known as ‘spreading factors’. In recent years, HAases received much attention due to their ability to abruptly alter the hyaluronic acid (HA) homeostasis. HAases preferentially degrade HA, which is a megadalton acidic structural polysaccharide found exclusively in the extracellular matrix (ECM) of animals. The HA-HAase system has been suggested to participate in many pathophysiological conditions. The HA degradation in ECM, crack down the structural integrity with an eventual increased tissue permeability that is attributed for the spreading property. The spreading property has been widely accepted in functions including envenomation, acrosomal reaction/ovum fertilization, cancer progression, microbial pathogenesis such as wound infections, pneumonia, and other sepses like, bacteremia and meningitis. HA fragmentation has dual effects; generation of a wide molecular range bioactive oligosaccharides of angiogenic, pro-inflammatory, and immunostimulatory properties; and impairment in the reservoir capacity of ECM that holds metal ions, growth factors, cytokines and various enzymes for signal transduction. Hence, inhibition of HA degradation appears critical and imperative in HAase mediated pathological conditions. HAase inhibitors are thus potent regulators that maintain HA homeostasis and they might serve as anti-inflammatory, anti-aging, anti-microbial, anticancer and anti-venom/toxin and contraceptive agents. In addition, HAase inhibitors may serve as tools to understand several unexplained and complex functions of HAases in HA metabolism. Therefore, this review is expected to provide an integrated update as of 2008 on the HAase inhibitors and their possible role as therapeutics in the management of a wide range of pathological conditions.

Being one of the simplest and widely used isosteric replacements for the peptide bond, reduced amide has been successfully applied in the synthesis of many bioactive compounds. The introduction of reduced amide not only confers the pseudopeptide a higher enzymatic resistance and a linear and more flexible structure, but also increases its hydrophylicity due to the introduction of a protonable group. It has also proved adequate as a transition state mimetic for the tetrahedral intermediate formed during the hydrolysis of the peptide bond. Recent advances in the solution and solid-phase synthesis of reduced amides that emerged during the past ten years are presented. Most of them include the use of microwave irradiation to shorten the reaction times and improve the yields. The bioorganic chemistry of reduced-peptide-containing compounds represents an area of growing interest and it has recently been expanded to include analogues of endogenous peptides/ hormones that are resistant to hydrolysis by serum peptidases and enzyme inhibitors. Under certain conditions, synthetic peptides are highly immunogenic in animals, and might constitute chemically defined, safe and cheap vaccines. Linear pseudooligolysines, containing multiple adjacent CH2NH amide bond are potential candidates for future use as DNA carriers in gene delivery. Reduced amides have also seen use in the preparation of peptide nucleic acids and antibacterial peptides.

Antibodies (Abs), often associated with antimicrobial and antitumor agents, have emerged as an important class of novel drugs for antigen-driven therapeutic purposes in diverse clinical settings, including oncology and infectious diseases. Abs commonly give rise in the treated host to anti-Ab responses, which may induce adverse reactions and limit their therapeutic efficacy. Their modular domain architecture has been exploited to generate alternative reduced formats (Fabs, scFvs, dAbs, minibodies, multibodies), essentially devoid of the Fc region. The presence of complementarity determining regions (CDRs) ensures the maintenance of selective binding to antigens and supports their use for biotechnological and therapeutic applications. Paradigmatic Abs mimicking the wide-spectrum antimicrobial activity of a yeast killer toxin (killer Abs) have revealed the existence of a family of Abs exerting a direct in vitro and/or in vivo microbicidal activity. Based on the variable sequence of an antiidiotypic recombinant killer Ab, CDR-related peptides have been synthesized, engineered by alanine-scanning and selected according to antimicrobial, antiviral and immunomodulatory properties. Irrespective of the native Ab specificity, synthetic CDRs from unrelated murine and human monoclonal Abs, have shown to display differential in vitro, in vivo and/or ex vivo antifungal (Candida albicans), antiviral (HIV-1) and antitumor (melanoma cells) activities. Alanine substitution of single residues of synthetic CDR peptides resulted in further differential increased/unaltered/decreased biological activity. The intriguing potential of Abs as source of antiinfective and antitumor therapeutics will be discussed, in light of recent advances in peptide design, stability and delivery.

An overview of conjugates of coordination complexes and organometallic complexes of Pt, Ru, Fe, Re, lanthanoids and other metals with natural and synthetic estrogens and antiestrogens targeting the nuclear estrogen receptors is provided. These conjugates are used as targeted cytotoxic agents or - if radiolabeled - as imaging probes for the detection of estrogen receptor-rich tissues such as hormone-dependent tumours. They are assessed with respect to their estrogen receptor binding affinities, potential synergistic cytotoxic effects in cancer cells and their specificity for tumour over nonmalignant cells and tissues. The mechanisms of their modes of action are discussed. Pertinent literature is covered up to 2008.

Sulfated oligosaccharides display an important role in biological processes. They bind proteins through interactions mediated by highly specific sequences (heparin - antithrombin, heparan sulfate - growth factors / herpes simplex virus) or by electrostatic interaction between sulfate groups and cationic sites of proteins. Sulfated oligosaccharides are involved in biological events as protein localisation at cell surfaces, the control of proteolysis, the modulation of the angiogenesis and metastasis of tumours, the oligomerisation of cell growth factors. Sulfated residues have been recently found in glycoproteins, as GlcNAc or Mannose in N-glycosidic chains of different sources: gp120 of HIV, the envelope glycoprotein of influenza virus, the cysteine protease of Trypanosoma cruzi. This paper reviews recent findings concerning the implication of sulfated sugars in carbohydrate - protein interactions, from glycosaminoglycans to glycosidic chains in proteins, and their potential application as new targets for drugs/vaccines/diagnosis developments will be discussed. New approaches for their detection and analysis (ESI-MS, MALDI, Molecular Imprinting) are presented.

Maternal diabetes develops in 2-6% of total pregnancies, depending on geographical and ethnic background. About 10% of fetuses from diabetic pregnancy display congenital malformations in various organ systems including cardiovascular, gastrointestinal, genitourinary and neurological systems, among which the neural tube defects (NTDs) such as anencephaly, holoprosencephaly and syntelencephaly were more frequently demonstrated. Recent studies by the Diabetes Control and Complications Trial Research Group show that tight glycemic control early in pregnancy decreases the progression of a number of diabetic complications. However, it appears that the pre-existing tissue damage cannot be reversed even after normoglycemic levels are achieved during pregnancy. In recent years, considerable efforts have been made to investigate the etiology of birth defects among infants of diabetic mothers. It has been shown that diabetes-induced fetal abnormalities are accompanied by some metabolic disturbances including elevated superoxide dismutase (SOD) activity, reduced levels of myoinositol and arachidonic acid and inhibition of the pentose phosphate shunt pathway. Moreover, the frequency of fetal malformations in diabetic pregnancy has been reported to be markedly reduced by dietary supplements of antioxidants such as vitamin E, vitamin C and butylated hydroxytoluene, suggesting that oxidative stress is involved in the etiology of fetal dysmorphogenesis. Furthermore, several experimental studies have shown that NTDs in embryos of diabetic mice are associated with altered expression of genes, which control development of the neural tube. In this review, recent findings of possible molecular mechanisms which cause morphological changes during neural tube development in embryos of diabetic pregnancy are discussed.