Search

Cilengitide is a stable cyclic pentapeptide containing an Arg-Gly-Asp motif responsible for selective binding to αVβ3 and αVβ5 integrins. The candidate drug showed unexpected inhibition of cytochrome P450 (P450) 3A4 at high concentrations, that is, a 15-mM concentration caused attenuation of P450 3A4 activity (depending on the probe substrate): 15-19% direct inhibition, 10-23% time-dependent inhibition (30-minute preincubation), and 54-60% metabolism-dependent inhibition (30-minute preincubation). The inactivation efficiency determined with human liver microsomes was 0.003 ± 0.001 min(-1) mM(-1) and was 0.04 ± 0.01 min(-1) mM(-1) with baculovirus-based microsomes containing recombinant P450 3A4. Neither heme loss nor covalent binding to apoprotein could explain the observed reductions in residual activity. Slowly forming type II difference spectra were observed, with maximum spectral changes after 2 hours. Binding to both reduced and oxidized P450 3A4 was observed, with apparent Kd values of 0.66 μM and 6 μM. The significance of the guanidine group in inhibition was demonstrated using ligand binding spectral changes and inactivation assays with guanidine analogs (debrisoquine, N-acetylarginine-O-methyl ester) and the acetylated ornithine derivative of cilengitide. The observed inhibition could be explained by direct inhibition, plus by formation of stable complexes with both ferric and ferrous forms of heme iron and to some extent by the formation of reactive species capable to react to the protein or heme. Formation of the complex required time and NADPH and is attributed to the guanidino group. Thus, the NADPH-dependent inhibition is considered to be mainly due to the formation of a stable complex rather than the formation of reactive species.

NAI-107 is a novel lantibiotic active against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), glycopeptide-intermediate S. aureus (GISA), and vancomycin-resistant enterococci (VRE). The aim of this study was to evaluate the in vivo efficacy of NAI-107 in animal models of severe infection. In acute lethal infections induced with a penicillin-intermediate Streptococcus pneumoniae strain in immunocompetent mice, or with MRSA, GISA, and VRE strains in neutropenic mice, the 50% effective dose (ED 50 ) values of NAI-107 were comparable or lower than those of reference compounds, irrespective of the strain and immune status (0.51 to 14.2 mg/kg of body weight for intravenous [i.v.] NAI-107, 5.1 to 22.4 for oral linezolid, and 22.4 for subcutaneous [s.c.] vancomycin). In t he granuloma pouch model induced in rats with a MRSA strain, intravenous NAI-107 showed a dose-proportional bactericidal activity that, at a single 40-mg/kg dose, compared with 2 20-mg/kg doses at a 12-h or 24-h interval, caused a 3-log 10 -CFU/ml reduction of viable MRSA in exudates that persisted for more than 72 h. Rat endocarditis was induced with a MRSA strain and treated for five consecutive days. In a first experiment, using 5, 10, or 20 mg/kg/day, and in a second experiment, when 10 mg/kg at 12-h intervals was compared to 20 mg/kg/day, intravenous NAI-107 was effective in reducing the bacterial load in heart vegetations in a dose-proportional manner. Trough plasma levels, as determined on days 2 and 5, were several times higher than the NAI-107 minimal bactericidal concentration (MBC). NAI-107 binding to rat and human serum ranges between 93% and 98.6%. The rapid bactericidal activity of NAI-107 observed in vitro was thus confirmed by the efficacy in several models of experimental infection induced by Gram-positive pathogens, supporting further investigation of the compound.

Objectives: The pharmacokinetics, tissue distribution and excretion routes of dalbavancin, a semi-synthetic glycopeptide, were investigated in rats. Methods: A 20 mg/kg intravenous dose of dalbavancin or [ 3 H]dalbavancin was administered to rats in three studies. Concentrations of dalbavancin or drug-derived radioactivity were assessed in blood, plasma, tissues, bile, urine and faeces by HPLC-MS/MS, scintillation counting or microbiological methods. Results: Dalbavancin decayed tri-exponentially in plasma with an apparent terminal t 1/2 of 187h (approximately 8 days). Dalbavancin has dual routes of elimination, with around two-thirds of the excreted drug-derived radioactivity being found in the urine and around one-third in the faeces. After 70 days, 44.2% and 22.3% of the drug-derived radioactivity had been recovered in the urine and faeces, respectively. Biliary excretion of drug-derived radioactivity accounted for over half of the radioactivity excreted faecally. At 70 days post-dose

Infections due to methicillin-resistant Staphylococcus aureus (MRSA) are an important cause of morbidity and mortality in hospital patients. Moreover, increased incidences of outpatient MRSA have been recently reported. This study investigated the bactericidal activity of dalbavancin, a novel, semisynthetic glycopeptide antibiotic, against methicillin-sensitive S. aureus (MSSA) and MRSA in the rat granuloma pouch infection model. A single intravenous dose of 10 mg of dalbavancin/kg of body weight reduced the viable MRSA count in pouch exudates by more than 2 log CFU/ml, and regrowth was prevented for up to 120 h. Comparable results with vancomycin required four 100-mg/kg intramuscular doses. With one or two doses of vancomycin, the bacterial load declined over proportionately shorter periods of time, followed by regrowth. Reduction of the bacterial load obtained with 100- and 200-mg/kg oral doses of linezolid was relatively transient, with regrowth starting at 48 h. A single 10-mg/kg dose of dalbavancin reduced the MSSA count at 24 h to below the limit of detection, with no regrowth for at least 96 h. Dalbavancin demonstrated good exudate penetration; the ratio of the area under the curve (AUC) in plasma to the AUC in pouch exudate was 1.01. The in vivo activity of dalbavancin in this model is consistent with the antibiotic concentrations that are reached and maintained for extended periods of time after a single 10-mg/kg dose and with in vitro data showing that these concentrations are bactericidal for staphylococci. The pharmacokinetic and efficacy data seen in this relevant model of infection suggest that dalbavancin may be administered less frequently than vancomycin and linezolid.

Evaluation of the in-vivo concentration of monoclonal antibody (mAb) mixtures is a challenging task. Here we report the application of an LC-MS bioanalytical method to quantify in monkey serum the Sym004, an equimolar mixture of two monoclonal antibodies, 992 mAb and 1024 mAb. This method has been assessed accordingly to industry standards and it is based on the determination of two specific signature peptides that report the single mAbs concentrations and on another one peptide, common to the two mAbs, that measures the total concentration of the two target proteins. It is shown that the total concentration is in agreement with the sum of the two measured single concentrations in spiked monkey serum samples. The consistency of the results will allow monitoring of the metabolic fate of different parts of the mAbs, at least in the central body compartment. This can then help to rationalize the design of the protein therapeutics modulating their stability accordingly.

NAI-603 is a ramoplanin derivative designed to overcome the tolerability issues of the parent drug as a systemic agent. NAI-603 is highly active against aerobic and anaerobic Gram-positive bacteria, with MICs ranging from 0.008 to 8 μg/ml. MICs were not significantly affected by pH (range, 6 to 8), by inoculum up to 10 8 CFU/ml, or by addition of 50% human serum. Against staphylococci and enterococci, NAI-603 was rapidly bactericidal, with minimum bactericidal concentration (MBC)/MIC ratios never exceeding 4. The frequency of spontaneous resistance was low at 2× to 4× MIC (≤1 × 10 −6 to ≤1 × 10 −8 ) and below the detection limit (about ≤1 × 10 −9 ) at 8× MIC. Serial subcultures at 0.5× MIC yielded at most an 8-fold increase in MICs. In a systemic infection induced by methicillin-resistant Staphylococcus aureus (MRSA), the 50% effective dose (ED 50 ) of intravenous (i.v.) NAI-603 was 0.4 mg/kg, lower than that of oral (p.o.) linezolid (1.4 mg/kg) and subcutaneous (s.c.) teicoplanin (1.4 mg/kg) or vancomycin (0.6 mg/kg). In neutropenic mice infected with vancomycin-resistant enterococci (VRE), the ED 50 s for NAI-603 were 1.1 to 1.6 mg/kg i.v., compared to 0.5 mg/kg i.v. of ramoplanin. The bactericidal activity was confirmed in vivo in the rat granuloma pouch model induced by MRSA, where NAI-603, at 40 mg/kg i.v., induced about a 2- to 3-log 10 -reduction in viable bacteria in the exudates, which persisted for more than 72 h. The pharmacokinetic (PK) profiles of NAI-603 and ramoplanin at 20 mg/kg show similar half-lives (3.27 and 3.80 h, respectively) with the maximum concentration ( C max ) markedly higher for NAI-603 (207 μg/ml versus 79 μg/ml). The favorable pharmacological profile of NAI-603, coupled with the absence of local tolerability issues, supports further investigation.

Alkylphosphocholines (APC) with one or more methylene groups in the alkyl chain replaced by oxygen atoms or carbonyl groups, or both have been assembled modularly using omega-diols as central building blocks. Out of 25 new compounds of this kind, 11 were evaluated for their antiproliferative activity on four cell lines and compared with miltefosine to evaluate their hemolytic activity (HA) and cytotoxicity on non-tumoral cells (MT2), used as markers of adverse effects. Compound 13 was more active on cancer cell lines than on non-tumoral cells and the data were similar for MTT and thymidine incorporation assays. It had less HA than miltefosine. Compound 13 could therefore be a candidate for the preparation of compounds with higher cytotoxicity on cancer cells and lower general toxicity.