The Safety and Antiviral Activity of BZF961 with or without Ritonavir in Patients Infected with Hepatitis C Virus: A Randomized, Multicenter Trial

PURPOSE

Infection with hepatitis C virus is the leading cause of infectious disease mortality in the United States. BZF961 is a novel small molecule inhibitor of the hepatitis C virus NS3-4A protease. Here we present the results of a randomized, double-blinded, placebo-controlled, multicentered study in treatment-naïve patients with chronic hepatitis C virus genotype-1 infection.

METHODS

Patients were enrolled sequentially in 2 parts and treated for 3days. BZF961 was administered as monotherapy (500mg BID for 3 days) or in combination with the cytochrome P450 3A4 inhibitor ritonavir to boost its exposure (BZF961 10, 20, or 50mg QD or BID).

FINDINGS

BZF961 was safe and well tolerated in the patients studied with no serious adverse events. There were no appreciable differences in adverse events among patients who received BZF961, BZF961 with ritonavir, or placebo. There was a significant, clinically meaningful reduction in viral load from baseline in patients treated either with BZF961 500mg every 12hours alone or BZF961 50mg every 12hours in combination with ritonavir. Activity against the hepatitis C virus of the lower-dose regimens was apparent but more modest. There were no relevant changes from baseline viral loads in placebo-treated patients.

IMPLICATIONS

Coadministration of ritonavir with BZF961 boosted BZF961 exposure (including C_min, which is the clinically relevant parameter associated with antiviral activity) in a therapeutic range with less variability compared with BZF961 alone. For strategic reasons, BZF961 is no longer under development.

Peptide deformylase inhibitors as potent antimycobacterial agents

Peptide deformylase (PDF) catalyzes the hydrolytic removal of the N-terminal formyl group from nascent proteins. This is an essential step in bacterial protein synthesis, making PDF an attractive target for antibacterial drug development. Essentiality of the def gene, encoding PDF from Mycobacterium tuberculosis, was demonstrated through genetic knockout experiments with Mycobacterium bovis BCG. PDF from M. tuberculosis strain H37Rv was cloned, expressed, and purified as an N-terminal histidine-tagged recombinant protein in Escherichia coli. A novel class of PDF inhibitors (PDF-I), the N-alkyl urea hydroxamic acids, were synthesized and evaluated for their activities against the M. tuberculosis PDF enzyme as well as their antimycobacterial effects. Several compounds from the new class had 50% inhibitory concentration (IC50) values of <100 nM. Some of the PDF-I displayed antibacterial activity against M. tuberculosis, including MDR strains with MIC90 values of <1 microM. Pharmacokinetic studies of potential leads showed that the compounds were orally bioavailable. Spontaneous resistance towards these inhibitors arose at a frequency of < or =5 x 10(-7) in M. bovis BCG. DNA sequence analysis of several spontaneous PDF-I-resistant mutants revealed that half of the mutants had acquired point mutations in their formyl methyltransferase gene (fmt), which formylated Met-tRNA. The results from this study validate M. tuberculosis PDF as a drug target and suggest that this class of compounds have the potential to be developed as novel antimycobacterial agents.

Peptide deformylase inhibitors as antibacterial agents: identification of VRC3375, a proline-3-alkylsuccinyl hydroxamate derivative, by using an integrated combinatorial and medicinal chemistry approach

Peptide deformylase (PDF), a metallohydrolase essential for bacterial growth, is an attractive target for use in the discovery of novel antibiotics. Focused chelator-based chemical libraries were constructed and screened for inhibition of enzymatic activity, inhibition of Staphylococcus aureus growth, and cytotoxicity. Positive compounds were selected based on the results of all three assays. VRC3375 [N-hydroxy-3-R-butyl-3-(2-S-(tert-butoxycarbonyl)-pyrrolidin-1-ylcarbonyl)propionamide] was identified as having the most favorable properties through an integrated combinatorial and medicinal chemistry effort. This compound is a potent PDF inhibitor with a K(i) of 0.24 nM against the Escherichia coli Ni(2+) enzyme, possesses activity against gram-positive and gram-negative bacterial pathogens, and has a low cytotoxicity. Mechanistic experiments demonstrate that the compound inhibits bacterial growth through PDF inhibition. Pharmacokinetic studies of this drug in mice indicate that VRC3375 is orally bioavailable and rapidly distributed among various tissues. VRC3375 has in vivo activity against S. aureus in a murine septicemia model, with 50% effective doses of 32, 17, and 21 mg/kg of body weight after dosing by intravenous (i.v.), subcutaneous (s.c.), and oral (p.o.) administration, respectively. In murine single-dose toxicity studies, no adverse effects were observed after dosing with more than 400 mg of VRC3375 per kg by i.v., p.o., or s.c. administration. The in vivo efficacy and low toxicity of VRC3375 suggest the potential for developing this class of compounds to be used in future antibacterial drugs.

Bovine endometrial epithelial cells as a model system to study oxytocin receptor regulation

Endometrial epithelial cell cultures were established from bovine uterine tissue collected during the oestrous cycle from commercially slaughtered animals. These cells were shown to express moderately high levels of oxytocin receptors (OTR) (up to 30000 per cell) after about one week in culture. These receptors have been characterized at the molecular, pharmacological and functional level and shown to be identical to those expressed in the bovine endometrium in vivo. Preliminary experiments to investigate the regulation of the OTR and its gene using this system, have shown that expression is to a large degree constitutive, the receptors being spontaneously upregulated during culture. Sex steroids at concentrations close to or above the serum limits observed in vivo appeared to have no effect, although the cells were shown to express mRNA for the specific steroid receptors throughout culture. Only the blastocyst product, interferon-tau, showed a significant effect, downregulating both OTR and their gene transcripts in the cultured endometrial epithelial cells. Although more extensive studies are necessary, these results support the view that the OTR gene is controlled in part at least by a combination of constitutive and inhibitory elements.

Confocal and conventional immunofluorescence and ultrastructural localisation of intracellular strength-giving components of human amniochorion

Key cytoskeletal polypeptides of human fetal membranes have been localised at subcellular level using confocal and conventional indirect immunofluorescence microscopy. Correlation with electron microscope data has allowed us to examine how cellular compartments of this multilaminar tissue maintain their mechanical integrity until the time of membrane rupture at parturition. Evidence is presented for myofibroblastic characteristics of cells in both the fibroblast and reticular layers which may therefore have tension-generating, position-adjustment and wound-healing roles in the amniochorion. Desmin and vimentin are coexpressed in these cells, but a small localised population of cells in the fibroblast layer contains vimentin alone. An interaction of cytokeratin filaments with nuclei and desmosomes of amniotic epithelium in vivo is demonstrated, indicating that nuclei of cells of ectodermal origin are integrated into a mechanical structure extending throughout the tissue as a whole. Cells of the basal 1 or 2 layers of trophoblast have been shown to have a more extensive and better integrated cytoskeletal organisation than those overlying and forming the boundary with decidua. Structures within the trophoblast, identified previously as degenerate villi, contain cells with intermediate filaments with similar immunofluorescence properties to those of the neighbouring reticular layer and thus may represent papillae that prevent shearing at this interface.