Current Medicinal Chemistry - Volume 13, Issue 11, 2006

Most of the signal transduction pathways are mediated by protein kinases regulating every aspect of cell function. Mutations which deregulate their expression or their function or both result in cancers. Therefore, protein kinase inhibitors have become the focus of development of new therapies for cancer. A comprehensive review of Choline kinase (ChoK) was published by us in 2003. Since then, molecular information of ChoK inhibitors has been accumulated. In this review, we intend to summarize the new lines of evidence that will include the design of the most active antiproliferative agents so far described against ChoK. Studies have been aimed at the establishment of structure-activity relationships and the structural parameters that define ChoK inhibitory and antiproliferative activities of a set of twenty-five acyclic biscationic pyridophane and forty acyclic biscationic quinolinephane compounds. The corresponding QSAR equation was obtained for the whole set of bisquinolinium compounds for the antiproliferative activity, taking into consideration the electronic parameter σR of R4, the molar refractivity (MR) of R8, and the lipophilic parameters clog P and πlinker. The most potent antiproliferative agent shows an IC50 = 0.45 μM, predicted by the QSAR equation, whilst its experimental value is IC50 = 0.20 μM. Finally, toxicity assays were performed for the most promising compounds because of their interesting antiproliferative activities [IC50 HT-29 = 0.70, 0.80, 1.50 and 1.90 μM] and low toxicity [LD50 = 16.7, 12.5, > 25 and > 20 μg/kg of mouse]. These biological activities justify further analysis for antitumoral assays under in vivo conditions.

As the significance of hematopoietic stem cell transplantation (HSCT) is constantly rising, the scarcity of matched donors is proving to be a troubling issue. Cord blood (CB) is an important source of stem cells (SC) for transplantation. It has been used in the last two decades for approximately 4500 transplantations. Its collection, cryopreservation, banking and thawing techniques pose unique challenges to clinicians and researchers CB has abundant stem cell with impressive proliferative capacity. On the other hand, CB's immunological system has a naïve and more tolerant nature. Except for the biological aspects, few ethical issues have become a concern for transplantation teams who use CB. There are few advantages of CB over bone marrow, especially the lower rates of acute and chronic graft-versus-host disease (GVHD) after transplantation. On the other hand, there are relatively high rates of early treatment related mortality in cord blood transplantation (CBT). This is related to the small nucleated cell (NC) dose infused from each CB unit. The clinical experience in CBT, especially in children, is encouraging. When using adequate number of NC/kg, results in CBT for malignant and non-malignant diseases are comparable to bone marrow transplantation (BMT). In this article, a comprehensive review of the largest scale studies is presented. There is a continuous search for an optimal way to deal with delayed engraftment of CB and its implication. The current investigational, and also first clinical trials using diverse methods to overcome high rates of TRM are reviewed. Almost twenty years after the first CBT was preformed, many advocate for a routine parallel search, BM and CB, for unrelated donor. Future uses of CB might also be in the field of gene transfer and non hematopietic injured tissues repair.

Corticotropin-releasing factor (CRF), a 41-amino acid peptide, has been recognized as an important factor mediating stress. Efforts to discover small molecule antagonists of the CRF type-1 receptor (CRF1-R) for potentially novel treatment of anxiety and depression started in the early 1990's. Although highly potent in vitro and efficacious in animal models, early reported compounds such as CP-154,526 and NBI-27914 are highly lipophilic and possess high plasma protein and tissue binding, long elimination half life, and toxicity, likely due in part to accumulation in tissues. Recently, several laboratories have reported potent CRF1-R antagonists with improved physicochemical properties. Compounds such as DMP696, NBI-30775/R121919 and R278995/CRA0450 possess at least one additional polar group in their structures and are therefore less lipophilic than the earlier compounds, while still maintaining high potency. For example, DMP696 has a Ki value of 1.7 nM and a cLogP of 3.2, which is similar to CP-154,526 in potency but about 4-log units lower in partition coefficient. Despite its high plasma protein binding (98.5% in rat), DMP696 occupies over 50% of brain CRF1-R at a total plasma concentration above 100 nM, which is consistent with the doses that produce anxiolytic effects in the rat defense withdrawal test of anxiety. This article will review small molecule CRF1-R antagonists by focusing on their pharmacological and pharmacokinetic properties. In addition, the pharmacology of small molecules binding to the CRF1 receptor will be discussed. An orally available compound with desirable properties in these categories will have a good chance to be developed into a novel treatment for anxiety and depression which may be devoid of the side effects of existing antidepressant treatments.

Within the pharmaceutical industry, the ultimate source of continuing profitability is the unremitting process of drug discovery. To be profitable, drugs must be marketable: legally novel, safe and relatively free of side effects, efficacious, and ideally inexpensive to produce. While drug discovery was once typified by a haphazard and empirical process, it is now increasingly driven by both knowledge of the receptor-mediated basis of disease and how drug molecules interact with receptors and the wider physiome. Medicinal chemistry postulates that to understand a congeneric ligand series, or set thereof, is to understand the nature and requirements of a ligand binding site. Likewise, structural molecular biology posits that to understand a binding site is to understand the nature of ligands bound therein. Reality sits somewhere between these extremes, yet subsumes them both. Complementary to rules of ligand design, arising through decades of medicinal chemistry, structural biology and computational chemistry are able to elucidate the nature of binding site-ligand interactions, facilitating, at both pragmatic and conceptual levels, the drug discovery process.

The transactivation responsive (TAR) RNA is the 5'-leader sequence of the HIV-1 mRNA genome and interacts with the Tat protein during transcription. Tat and the positive transcription elongation factor (PTEFb) complex bind to TAR to promote efficient transcription of the full-length HIV genome. In the absence of the TAR█Tat█P-TEFb interaction, viral transcription is inefficient, which makes this RNA-protein complex an important target for therapeutic intervention of HIV replication. Inhibitors of HIV-1 transactivation mainly target: 1) TAR RNA, 2) Tat protein and 3) Tat█P-TEFb complex. 1) Compounds against TAR RNA are the most numerous: besides cationic peptides, which were initially developed, recent advances in TAR binding inhibitors include oligonucleotide based-agents and small molecules. Specific research efforts are currently underway to increase cellular uptake. 2) By targeting the Tat protein, both transactivation and other Tatmediated intra/extracellular functions are affected. Various biopolymeric drugs are reported to effectively inhibit Tat activity. In addition, Tat-targeted antibodies have recently been developed. 3) Intracellular proteins have been discovered to disrupt Tat█P-TEFb interaction, raising the chance of inhibiting HIV-1 transcription via novel mechanisms.

The function of many endogenous molecules in all eukaryotic cells depends on their subcellular localisation, being active when localized in one cellular compartment and inactive in another. Translocation or re-localization of mislocalized components in the optimal subcellular site may contribute to the development of novel cancer therapies and to the re-evaluation of conventional treatment. For instance, various agents are able to entrap cytoplasmic anti-apoptotic pathways to the nucleus, thus activating apoptosis. Moreover, amongst the factors identified so far, the optimal location of the tumor suppressor p53 for promoting cell arrest and apoptosis seems to be the nucleus, while the nuclear factor kappa B (NFκB) is desirable to stay in the cytoplasm. Thus, the mechanisms of nuclear translocation of endogenous signaling components, like p53, NFκB and various heat shock proteins (HSPs), may serve as targets for pharmacological intervention, without excluding the possible role of uptake and active transport into the nucleus of extracellular proteins.

Fungi are one of the most neglected pathogens apparent from the fact that the Amphotericin B, a polyene antibiotic, discovered way back in 1956 is still used as a 'gold standard' for antifungal therapy. Past two decades have witnessed a dramatic rise in the incidences of life threatening systemic fungal infections. This can be ascribed to the increase in the number of immuno-compromised patients due to rise in HIV infected population, cancer chemotherapy and indiscriminate use of antibiotics. Majority of clinically used antifungals suffer from various drawbacks in terms of toxicity, efficacy and cost, and their frequent use has led to the emergence of resistant strains. Hence, there is a great demand for novel antifungals belonging to wide range of structural classes, selectively acting on novel targets with fewer side effects. This article aims at reviewing recent efforts made towards discovering novel antifungal drug targets and investigational molecules acting on them.

In the next two decades, the world is expected to see around 20 million cases of cancer. Moreover, the types of cancer will vary considerably from country to other. Therefore, all efforts will be needed to face such a vast diversity of problems. With current annual sales of about $500 millions, the platinum(II) complex known as cisplatin [cis- (NH3)2PtCl2] is still one of the most effective drugs to treat testicular, ovarian, bladder and neck cancers. Since it was launched in 1978 there has been a rapid expansion in research to find new, more effective metal-based anticancer drugs and to study their interactions with biological systems. This study gives an up to date overview of the anticancer chemistry of the platinum group elements platinum, palladium, and nickel with an emphasis on the new strategies used in the development of new antitumor agents. Methodologies for application of bulky aromatic or aliphatic nitrogen ligands, chiral organic moieties, chelates containing other donor atoms than nitrogen, and biologically active ligands in the design of agents analogous to cisplatin are presented. The review also aims to highlight the class of the unconventional complexes that violate the empirical structure-activity rules (SAR) of platinum compounds and the common features and structural differences between the most successful anticancer complexes that are currently in human clinical trials.