Metallo-aminopeptidase inhibitors

Aminopeptidases are enzymes that selectively hydrolyze an amino acid residue from the N-terminus of proteins and peptides. They are important for the proper functioning of prokaryotic and eukaryotic cells, but very often are central players in the devastating human diseases like cancer, malaria and diabetes. The largest aminopeptidase group include enzymes containing metal ion(s) in their active centers, which often determines the type of inhibitors that are the most suitable for them. Effective ligands mostly bind in a non-covalent mode by forming complexes with the metal ion(s). Here, we present several approaches for the design of inhibitors for metallo-aminopeptidases. The optimized structures should be considered as potential leads in the drug discovery process against endogenous and infectious diseases. Crown Copyright (C) 2010 Published by Elsevier Masson SAS. All rights reserved.

Fluorobenzoyl dipeptidyl derivatives as inhibitors of the Fasciola hepatica cysteine protease cathepsin L1

Cathepsins are known to have many important physiological roles and provide a viable target for inhibition. Fluorobenzoyl dipeptide derivatives were synthesized and tested for biological activity in an effort to find an efficient inhibitor of the cysteine protease cathepsin L. Thirty-six novel inhibitors (1-36) were synthesized from protected amino acids via the standard DCC/HOBt coupling protocol, containing a benzyl ester or a nitrile as an electrophilic warhead. The activity of the inhibitors was evaluated against cathepsin L and IC50 values calculated. Modification of both amino acids and terminal groups afforded compounds with single digit micromolar inhibition. Results utilizing the benzoyl-L-leucine-glycine nitrile backbone are comparable to that for the commercially available inhibitor 39.

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers in cancer progression and survival: a systematic review

Objective: To investigate the association between angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) and disease progression and survival in cancer patients.

Methods: Using terms for cancer and ACEIs/ARBs, MEDLINE, EMBASE and Web of Science were systematically searched for observational/interventional studies that used clinically relevant outcomes for cancer progression and survival.

Results: Ten studies met the inclusion criteria. Two studies showed a significant improvement in overall survival (OS) with ACEI/ARB use among patients with advanced pancreatic (HR 0.52, 95% CI 0.29–0.88) and non-small cell lung cancer (HR 0.56, 95% CI 0.33–0.95). An improvement in progression-free survival (PFS) was also reported for pancreatic cancer patients (HR 0.58, 95% CI 0.34–0.95) and patients with renal cell carcinoma (HR 0.54, p = 0.02). ACEI/ARB use was protective against breast cancer recurrence (HR 0.60, 95% CI 0.37–0.96), colorectal cancer distant metastasis (OR 0.22, 95% CI 0.08–0.65) and prostate specific antigen (PSA) failure in prostate cancer patients (p = 0.034). One study observed a worse OS (HR 2.01, 95% CI 1.00–4.05) and PFS in ACEI users with multiple myeloma (p = 0.085) while another reported an increased risk of breast cancer recurrence (HR = 1.56, 95% CI 1.02–2.39).

Conclusion: There is some evidence to suggest that ACEI or ARB use may be associated with improved outcomes in cancer patients. Larger, more robust studies are required to explore this relationship further.

Design of potent GlyT1 inhibitors: In vitro and in vivo profiles

Inhibitors of Gly transporter type-1 (GlyT1) for the treatment of schizophrenia have been pursued on the basis of the NMDA receptor (R) hypofunction hypothesis, which stems largely from the observation that NMDAR antagonists induce symptoms that more closely mimic those characteristic of schizophrenia than do other classes of psychotic agents. GlyT1 is responsible for uptake of synaptic Gly, an NMDAR co-agonist amino acid, in neuronal populations throughout the forebrain. GlyT1 inhibition thereby potentiates NMDAR activity by increasing synaptic Gly levels. Correspondingly, a large body of data suggests that GlyT1 inhibitors likely confer more comprehensive symptom alleviation than current antipsychotics. To date, a number of small-molecule GlyT1 inhibitors have been reported by the pharmaceutical industry. Developments in the discovery and characterization of GlyT1 inhibitors are discussed in this review.

FASCIOLA-HEPATICA - THE EFFECT OF THE MICROTUBULE INHIBITORS COLCHICINE AND TUBULOZOLE-C ON THE ULTRASTRUCTURE OF THE ADULT FLUKE

The effect of the microtubule inhibitors colchicine (1 x 10(-3) M) and tubulozole-C(1 x 10(-6) M) on the ultrastructure of adult Fasciola hepatica has been determined in vitro by transmission electron microscopy (TEM), using both intact flukes and tissue-slice material. With colchicine treatment, the apical membrane of the tegument became increasingly convoluted and blebbed, while accumulations of T1 secretory bodies occurred in the basal region of the syncytium, leading to progressively fewer secretory bodies in the syncytium. In the tegumental cells there were distinct accumulations of Tl secretory bodies around the Golgi complexes, which remained active for up to 12 h incubation. Tubulozole-treated flukes showed more severe effects, with initial accumulations of secretory bodies, both at the tegumental apex and base. This was followed in the later time-periods by the sloughing of the tegumental syncytium. In the underlying tegumental cells, the granular endoplasmic reticulum (GER) cisternae were swollen and disrupted, becoming concentrated around the nucleus. The Golgi complexes were dispersed to the periphery of the cells and gradually disappeared from the cytoplasm. After treatment with both drugs, the cell population in the vitelline follicles was altered, with an abnormally large proportion of stem cells and relatively few intermediate type 1 cells. The nurse cell cytoplasm became fragmented and was no longer in contact with the vitelline cells, while the shell globule clusters within the intermediate type 2 and mature cells were loosely packed. In the mature vitelline cells, 'yolk' globules and glycogen deposits became fewer than normal and lipid droplets were observed. The results are discussed in relation to the different modes of action of the two drugs and potential significance of this to anthelmintic (benzimidazole) therapy.

Differences in the diagnostic yield of upper gastrointestinal endoscopy in dyspeptic patients receiving proton-pump inhibitors and H2-receptor antagonists

Patients attending for diagnostic oesophagogastroduodenoscopy (OGD) for dyspeptic symptoms are often receiving acid-suppression therapy that has not been discontinued prior to endoscopy, and this may reduce the diagnostic yield of endoscopy. The aim of this study was to compare the diagnostic yield of OGD in uncomplicated dyspepsia in patients receiving no medication, those receiving acid-suppression therapy, and those receiving nonsteroidal anti-inflammatory drugs (NSAIDs) at the time of endoscopy.

Distribution of atrophy in Helicobacter pylori-infected subjects taking proton pump inhibitors

Gastric atrophy is associated with Helicobacter pylori infection. Conflicting results have been obtained as to whether acid suppressant therapy hastens the development or changes the distribution of atrophy in the stomach. The aim of this study was to investigate whether concomitant proton pump inhibitor (PPI) therapy in H. pylori-infected individuals resulted in an increase or an alteration in atrophy distribution and whether this was reflected by the plasma gastrin.

Size-fitting of Intravaginal Rings for Macaques and in vitro Release Kinetics of Zinc Finger Inhibitors

Background: Small molecule inhibitors of the zinc finger domain (ZFI) in the nucleocapsid protein (NCp7) of HIV-1 are potent inhibitors of HIV and SIV
replication and may have utility as topical products to prevent infection. Furthermore, intravaginal rings (IVRs) were developed as coitally-independent,
sustained release devices which could be used for administration of HIV microbicides. The aims of these studies were to demonstrate that IVRs sized for
macaques are practical and compatible with the current generation of thioester-based NCp7 inhibitors.

Methods: Non-medicated silicone elastomer vaginal rings of various sizes thought to be applicable for macaques were prepared and tested for vaginal fit in Pigtailed and Chinese Rhesus macaques. Macaques were monitored for 8 weeks for mucosal disruption by colposcopy and proinflammatory cytokine markers in cervical vaginal lavages (CVL) using Luminex bead-based technology. Three different ZFIs (compounds 52, 89 and 122, each derived from an N-substituted S-acyl-2-mercaptobenzamide thioester scaffold) were loaded at 50 mg into an optimal matrix-type ring design. In vitro continuous release studies were then conducted over 28 days and analyzed by HPLC. Rate of release was determined by linear regression analysis.

Results: Qualitative evaluation at the time of ring insertion suggested that the 25 mm ring provided optimal fit in both macaque species. All rings remained in
place during the study period (2 to 4 weeks), and the animals did not attempt to remove the rings. No tissue irritation was observed, and no signs of physical
discomfort were noted. Also, no significant induction of cervicovaginal proinflammatory markers was observed during the 8-week period during and following ring insertion. One Pigtailed macaque showed elevated IL-8 levels in the CVL during the period when the ring was in place; however, these levels were comparable to those observed in two control macaques. In vitro release of the ZFIs peaked at day 1 and then continually declined to near steady-state rates between 20-30 mcg/day. The percent release after 14 days was 2.9, 2.0 and 0.9 for ZFI 89, 52 and 122, respectively.

Conclusions: IVRs of 25mm diameter, determined to be the optimal size for macaques, were well tolerated and did not induce inflammation. Release of all ZFI compounds followed t 0.5 kinetics. These findings suggest that efficacy testing in primate models is warranted to fully evaluate the potential to prevent
transmission.