Current Medicinal Chemistry - Volume 12, Issue 3, 2005

Since its introduction in the late 1970s for the treatment of strabismus and blepharospasm, botulinum toxin (BoNT) has been increasingly used in the interventional treatment of several other disorders characterized by excessive or inappropriate muscle contractions. The use of this pluripotential agent has extended to a plethora of conditions including: focal dystonia; spasticity; inappropriate contraction in most sphincters of the body such as those associated with spasmodic dysphonia, esophageal achalasia, chronic anal fissure, and vaginismus; eye movement disorders; other hyperkinetic disorders including tics and tremors; autonomic disorders such as hyperhidrosis; genitourinary disorders such as overactive and neurogenic bladder, nonbacterial prostatitis and benign prostatic hyperplasia; and aesthetically undesirable hyperfunctional facial lines. In addition, BoNT is being investigated for the control of the pain, and for the management of tension or migraine headaches and myofascial pain syndrome. BoNT injections have several advantages over drugs and surgical therapies in the management of intractable or chronic disease. Systemic pharmacologic effects are rare; permanent destruction of tissue does not occur. Graded degrees of relaxation may be achieved by varying the dose injected; most adverse effects are transient. Finally, patient acceptance is high. In this paper, clinical experience over the last years with BoNT in urological impaired patients will be illustrated. Moreover, this paper presents current data on the use of BoNT to treat pelvic floor disorders.

Macro- and microvascular disease are the most common causes of morbidity and mortality in patients with diabetes mellitus. Diabetic cardiovascular dysfunction represents a problem of great clinical importance underlying the development of various severe complications including retinopathy, nephropathy, neuropathy and increase the risk of stroke, hypertension and myocardial infarction. Hyperglycemic episodes, which complicate even well-controlled cases of diabetes, are closely associated with increased oxidative and nitrosative stress, which can trigger the development of diabetic complications. Hyperglycemia stimulates the production of advanced glycosylated end products, activates protein kinase C, and enhances the polyol pathway leading to increased superoxide anion formation. Superoxide anion interacts with nitric oxide, forming the potent cytotoxin peroxynitrite, which attacks various biomolecules in the vascular endothelium, vascular smooth muscle and myocardium, leading to cardiovascular dysfunction. The pathogenetic role of nitrosative stress and peroxynitrite, and downstream mechanisms including poly(ADP-ribose) polymerase (PARP) activation, is not limited to the diabetes-induced cardiovascular dysfunction, but also contributes to the development and progression of diabetic nephropathy, retinopathy and neuropathy. Accordingly, neutralization of peroxynitrite or pharmacological inhibition of PARP is a promising new approach in the therapy and prevention of diabetic complications. This review focuses on the role of nitrosative stress and downstream mechanisms including activation of PARP in diabetic complications and on novel emerging therapeutical strategies offered by neutralization of peroxynitrite and inhibition of PARP.

Hormone-refractory prostate cancer (HRPC) is an inevitable evolution of prostate carcinogenesis, through which the normal dependence on hormones for growth and survival is bypassed. Although advances in terms of symptoms palliation and quality of life improvement have been addressed with current treatment options, innovative approaches are needed to improve survival rates. A thorough understanding of HRPCassociated molecular pathways and mechanisms of resistance are a prerequisite for novel potential therapeutic interventions. Preclinical and early clinical studies are ongoing to evaluate new therapies that target specific molecular entities. Agents under development include growth factor receptor inhibitors, small molecules targeting signal transduction pathways, apoptosis and cell-cycle regulators, angiogenesis and metastasis inhibitors, differentiation agents, telomerase inactivators, and epigenetic therapeutics. Incorporation of these agents into existing treatment regimens will guide us in the development of a multidisciplinary treatment strategy of HRPC. This article critically reviews published data on new biological agents that are being tested in HRPC clinical trials, highlights ongoing research and considers the future perspectives of this new class of agents.

Breast cancer arises in about 48% of patients older than 65 years and more than 30% occurs in those over 70 years being the leading cause of cancer-related death in women older than 65. Elderly patients tolerate chemotherapy poorly compared to their younger counterpart because of progressive reduction of organ function and comorbidities related to age. For this reason, the elderly have been excluded from or underrepresented in most cancer studies and, in clinical practice, they often receive inadequate and untested treatments. For adjuvant chemotherapy, a low percentage of patients over 70 years of age were included in few trials and always in a proportion much lower than the prevalence of cancer in that age group. Adjuvant chemotherapy, preferably including an anthracycline especially in patients with HER-2 / neu-positive tumours, seems to be beneficial in older women who have substantial risk of dying of breast cancer. To date even if there is no specifically randomised study, single-agent chemotherapy probably might be considered a reasonable treatment for advanced breast cancer in the elderly. One of the actual main field of clinical research in the treatment of breast cancer is the role of targeted therapies. Chronologic age is a risk factor for toxicities such as myelosuppression and mucositis, and older patients may require more supportive care. In order to plan medical treatment in breast cancer elderly patients is mandatory to practice a comprehensive geriatric assessment that includes evaluation of comorbidities, functional dependence, socio-economic, emotional and cognitive conditions, an estimate of life expectancy and recognition of frailty. The authors review the literature regarding age-specific chemotherapeutic issues in the management of breast cancer elderly patients.

Arylamine N-acetyltransferases (NAT) are xenobiotic-metabolizing enzymes responsible for Nacetylation of many arylamines. They are also important for O-acetylation of N-hydroxylated heterocyclic amines. These enzymes play thus an important role in the detoxification and activation of numerous therapeutic drugs and carcinogens. Two closely related polymorphic isoforms (NAT1 and NAT2) have been described in humans and interindividual variations in NAT genes have been shown to be a potential source of adverse drug reaction. In addition, NAT1 and / or NAT2 phenotypes may modulate the risk of certain cancers in people exposed to aromatic amine carcinogens. Recent advances on the regulation of human NAT1 activity has shown that hydroxylamine and / or nitroso intermediates of NAT1 substrates inhibit the enzyme through direct irreversible interaction with its catalytic cysteine residue. Oxidative molecules such as hydrogen peroxide, Snitrosothiols and peroxynitrite have also been shown to inactivate reversibly or irreversibly the enzyme in a similar manner. In this review, after summarizing the general background on human NAT enzymes, we focus on the recent developments on the regulation of the activity of these drug-metabolizing enzymes by substrateintermediates and by oxidant molecules. The recent findings reviewed here provide possible mechanisms by which these non genetic determinants inhibit NAT1 activity and thereby may affect drug efficacy / toxicity.

Pretargeted delivery of radionuclides is based upon bispecific immunoconjugates that bind a target tumor antigen and a small molecule carrying the active payload. This strategy is supposed to combine the advantage of antibodies to track tumor cells in vivo and of small radiolabeled molecules that clear rapidly from normal organs and minimize toxicity. Many pretargeting approaches have been proposed, but only those using the biotin / avidin recognition system and those using bispecific anti-tumor x anti-hapten antibodies have been tested in the clinic for both immunoscintigraphy and radioimmunotherapy. Their respective advantages and drawbacks, as well as hurdles in the way of an effective therapy against solid tumors, are discussed. In the light of the encouraging results obtained so far in the clinic, pretargeting remains a most promising challenge for chemistry and biotechnology.

The matrix metalloproteinases (MMPs) are a family of more than 20 enzymes that are intimately involved in tissue remodelling. These zinc-containing endopeptidases consist of several subsets of enzymes, including collagenase, stromelysins and gelatinases and are involved in the degradation of the extracellullar matrix (ECM) that forms the connective material between cells and around tissues. Disease processes associated with the MMPs are generally related to imbalance between the inhibition and activation of MMPs resulting in excessive degradation of the ECM. These indications include osteoarthritis rheumatoid arthritis, tumour metastasis and congestive heart failure. Inhibitors for these enzymes have been developed for the treatment of a starthingly wide array of disease process where matrix remodelling plays a key role. There are three major components to most MMP inhibitorsthe zinc binding group ZBG, the peptidic backbone and the pocket occupying side chain. Most MMPs inhibitors are classified according to their ZBG. Inhibitors interactions at active-site zinc plays a critical role in defining the binding mode and relative inhibitor potency. The majority of MMP inhibitors reported in the literature contain an effective zinc binding group (e.g. hydroxamic acid, carboxylic acid, sulfhydryl group) that is either generally substituted with a peptide-like structure that mimics the substrates that they cleave or appended to smaller side chains that may interact with specific subsites (e.g., P1', P2', P3') within the active site. Although carboxylates exhibit weaker zinc binding properties than hydroxamates, they are known to show better oral bioavailability and are less prone to metabolic degradation. The expected loss of binding affinity after replacement of hydroxamates against carboxylates is faced by adequate choice of elongated S1' directed substituents. The need for novel selective MMP inhibitors makes them an attractive target for the QSAR and molecular modelling. 3-D QSAR models were derived using CoMFA, CoMSIA and GRID approaches leading to the identification of binding regions where steric, electronic or hydrophobic effects are important for affinity. Some structural requirements essential for achieving high binding affinity and selectivity are: an acidic unit tightly anchored through four contact points, bidentate chelation of Zn2+, carbonyl groups for hydrogen bonding, more than two extra units for hydrogen bonds, a hydrophobic moiety.

Nuclear-Factor kappa B (NF-κB) is an inducible transcription factor of the Rel family, sequestered in the cytoplasm by the IkB family of proteins. NF-κB exists in several dimeric forms, but the p50 / p65 heterodimer is the predominant one. Activation of NF-κB by a range of physical, chemical, and biological stimuli leads to phosphorylation and proteasome dependent degradation of IkB, leading to the release of free NF-κB. This free NF-κB then binds to its target sites (kB sites in the DNA), to initiate transcription. This transcription has been known to be involved in a number of diseases including cancer, AIDS, and inflammatory disorders. The present article focuses on two important issues of current and future interest- firstly a review of the main human diseases which are initiated due to NF-κB mediated transcription is presented. Next, comprehensive information on the current inhibitors which are targeted to interfere with the NF-κB pathway is provided. This latter section presents a critical review on different types of latest inhibitors targeting the complex NF-κB pathway at several stages. The inhibitors developed till date and still under investigation, include mainly those which interfere with the activation of NF-κB. Based on the complexity of NF-κB activation, and the current knowledge of the structural biology of NF-κB-DNA binding, finally it is proposed that a better approach to inhibit NF-κB induced transcription exists. In this context, a perspective is presented in the end, proposing de novo design of inhibitors which directly interact with the DNA Binding region of the free NF-κB (p50 subunit), so as to generate more specific and selective leads of NF-κB-DNA binding.