Current Medicinal Chemistry - Volume 11, Issue 22, 2004

Matrix metalloproteinases (MMPs) are a family of zinc-containing enzymes involved in the degradation and remodeling of extracellular matrix proteins. Under normal physiological conditions, the activities of these enzymes are well-regulated by endogenous tissue inhibitors of metalloproteinases (TIMPs). Chronic stimulation of MMP activities due to an imbalance in the levels of MMPs and TIMPs has been implicated in the pathogenesis of a variety of diseases such as cancer, osteoarthritis, and rheumatoid arthritis. Thus, MMP inhibitors are expected to be useful for the treatment of these disorders. Because of their importance in a variety of pathological conditions, a number of small molecular weight MMP inhibitors have entered clinical trials in humans. However, the results of these trials have been extremely disappointing and have led many investigators to conclude that MMP inhibitors have no therapeutic benefit in human cancer. To date, the first generation MMP inhibitors exhibited poor bioavailability while second-generation compounds revealed that prolonged treatment caused musculoskeletal pain and inflammation or had a lack of efficacy. This article describes the design of small molecular weight MMP inhibitors, a brief description of available three-dimensional MMP structures, a review of the proposed therapeutic utility of MMP inhibitors, and a clinical update of compounds that have entered clinical trials in humans. The experimentally determined structures used in the structure-based design of MMP inhibitors are thoroughly covered. Major emphasis is on recently published and / or patented potent MMP inhibitors, from approximately January 2000 to April 2003, and their pharmacological properties. Protein inhibitors of these proteolytic enzymes, i.e. TIMPs, will not be discussed.

RNase P is an ubiquitous and essential endonuclease in tRNA biogenesis, which generates the mature 5'-termini of tRNAs. RNase P activities have been identified in all three kingdoms of life (Bacteria, Archaea, Eukarya). Most forms of RNase P are ribonucleoproteins, i.e., they consist of an essential RNA and protein subunits. In bacteria and in some archaea, the catalytic function of this enzyme resides entirely in its RNA subunit, which is one of firstly identified ribozymes. Its high structural and functional diversity among representatives of a vast variety of phylogenetic domains indicates that RNase P could also serve as a molecular target of and a useful screening system for the biological activity of different compounds and give more insight into the molecular mechanisms of their action inside the cell. The emerged information from recent studies on the mechanism and structural idiosyncrasies of RNase P provides a convenient platform for designing specific inhibitors for this ribozyme and potential areas of its application in gene therapy. This review summarises the current information on the effect of several protein synthesis inhibitors, retinoids and arotinoids, vitamin D analogues and anthalin on the activity of RNase P.

Perceiving a pharmacophore is the first essential step towards understanding the interaction between a receptor and a ligand. Once a pharmacophore is established, a beneficial use of it is 3D database searching to retrieve novel compounds that would match the pharmacophore. As the 3D searching technology has evolved over the years, it has been effectively used for lead optimization, combinatorial library focusing, as well as virtual high-throughput screening. This paper is an update to the original paper published in this journal earlier: Kurogi, Y, and Güner, O. F. “Pharmacophore Modeling and Three-Dimensional Database Searching for Drug Design Using Catalyst,” in Current Medicinal Chemistry, 2001, 8(9), 1035-1055.

Non-Toxic doses of tetrakis-μ-3,5-diisopropylsalicylatodicopper(II) [Cu(II)2(3,5-DIPS)4] have been found to have anti-inflammatory, analgesic, anti-ulcer, anti-colitis, anti-convulsant, anti-cancer, antimutagenic, anti-carcinogenic, and anti-diabetic activities and, in addition, facilitates recovery from lethal irradiation and ischemia-reperfusion injuries. The goal of this research was to determine the time-dependent tissue distribution and persistence of 67Cu and the 14C labeled salicylate ligand, carboxy-14C-3, 5- diisopropylsalicylate [3,5-DIP(carboxy-14C)S], following subcutaneous administration of a 50 μmole per kilogram of body mass dose of double labeled tetrakis-μ-3,5-diisopropyl[carboxy-14C]salicylatodiaquo [67Cu]dicopper(II) 67Cu(II)2[3,5-DIP(carboxy-14C)S]4. This compound was administered to nine groups of six 20 gram female C57BL / 6 mice and blood, liver, kidney, intestine, lung, thymus, femur, muscle, spleen, and brain tissues removed and analyzed for 67Cu and 14C at 0.5, 1, 3, 6, 12, 24, 48, 72, and 96 hours after treatment. These data were then analyzed using a pharmacokinetic model simulation program. Both 67Cu and 14C were found in all tissues as well as urine and feces at 0.5 hour after administration. As anticipated, 67Cu entered the liver storage pool; it was conserved by the kidneys, and subsequently underwent release in maintaining 67Cu levels in all other tissues. While the presence of 67Cu correlated with the presence of the salicylate ligand, 3,5- DIP (carboxy-14C)S, early in the course of this experiment, the ligand was lost via ligand exchange and could not be measured in blood, kidney, intestine, lung, thymus, spleen, and brain after 24 hours following administration. However, 3,5-DIP(carboxy-14C)S persisted in liver, femur, and muscle throughout the 5-day period of study. It is suggested that marked lipophilicity accounts for its very rapid distribution to all tissues wherein it undergoes ligand exchange as 67Cu is incorporated into Cu-dependent enzymes and proteins and persists in tissues based upon physiological demand for Cu in meeting normal biochemical requirements.

Gonadotropin-releasing hormone (GnRH) or luteinizing hormone-releasing hormone (LHRH) is a decapeptide (pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2) hypothalamic hormone that acts upon 7-trans membrane spanning GnRH receptors in the pituitary. This action leads to the secretion of the gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) that in turn act on the reproductive organs regulating gonadal steroid production, spermatogenesis and follicular development. Peptidic agonists of the GnRH receptor have been known for many years and are currently employed therapeutically in the treatment of prostate and breast tumours, uterine fibroids, precocious puberty, endometriosis, premenstrual syndrome, contraception and infertility. Peptidic antagonists to date have only been employed commercially in the treatment of infertility during assisted reproductive therapy; however, many peptidic antagonists are currently in late stage development for many of the aforementioned indications. Whilst peptidic agonists and antagonists of the GnRH receptor have been discovered and exploited clinically, they are limited to predominantly parenteral administration due to their poor oral bioavailability. Recently, several small molecule GnRH antagonist series have been discovered offering the prospect of orally active therapeutics based on GnRH receptor antagonism. This article will review the current medicinal chemistry literature and structure activity relationships known for non-peptidic GnRH receptor antagonists.