No Need for Lopinavir Dose Adjustment during Pregnancy: a Population Pharmacokinetic and Exposure-Response Analysis in Pregnant and Nonpregnant HIV-Infected Subjects.

Lopinavir-ritonavir is frequently prescribed to HIV-1-infected women during pregnancy. Decreased lopinavir exposure has been reported during pregnancy, but the clinical significance of this reduction is uncertain. This analysis aimed to evaluate the need for lopinavir dose adjustment during pregnancy. We conducted a population pharmacokinetic analysis of lopinavir and ritonavir concentrations collected from 84 pregnant and 595 nonpregnant treatment-naive and -experienced HIV-1-infected subjects enrolled in six clinical studies. Lopinavir-ritonavir doses in the studies ranged between 400/100 and 600/150 mg twice daily. In addition, linear mixed-effect analysis was used to compare the area under the concentration-time curve from 0 to 12 h (AUC0-12) and concentration prior to dosing (Cpredose) in pregnant women and nonpregnant subjects. The relationship between lopinavir exposure and virologic suppression in pregnant women and nonpregnant subjects was evaluated. Population pharmacokinetic analysis estimated 17% higher lopinavir clearance in pregnant women than in nonpregnant subjects. Lopinavir clearance values postpartum were 26.4% and 37.1% lower than in nonpregnant subjects and pregnant women, respectively. As the tablet formulation was estimated to be 20% more bioavailable than the capsule formulation, no statistically significant differences between lopinavir exposure in pregnant women receiving the tablet formulation and nonpregnant subjects receiving the capsule formulation were identified. In the range of lopinavir AUC0-12 or Cpredose values observed in the third trimester, there was no correlation between lopinavir exposure and viral load or proportion of subjects with virologic suppression. Similar efficacy was observed between pregnant women and nonpregnant subjects receiving lopinavir-ritonavir at 400/100 mg twice daily. The pharmacokinetic and pharmacodynamic results support the use of a lopinavir-ritonavir 400/100-mg twice-daily dose during pregnancy.

A novel ritonavir paediatric powder formulation is bioequivalent to ritonavir oral solution with a similar food effect.

BACKGROUND: A novel ritonavir oral powder formulation has been developed to eliminate the alcohol and propylene glycol contents in the current ritonavir oral solution for paediatric use. Two clinical studies were conducted to assess the bioequivalence of the powder formulation to the marketed oral solution and to evaluate the effect of food and vehicles on bioavailability. METHODS: Study 1 was a randomized, partial-crossover, 4-period study in 48 subjects. Regimens included: oral solution under moderate-fat conditions, powder formulation in water under fasting, moderate-fat or high-fat conditions, and powder formulation in chocolate milk or pudding under moderate-fat conditions. Study 2 was a randomized, crossover, 4-period study in 24 subjects. Subjects were randomized to a sequence of the oral solution and powder formulation in water, infant formula and apple sauce, all under moderate-fat conditions. Bioavailability comparisons were assessed by the 90% CIs for the geometric least-squares mean ratios. RESULTS: Ritonavir powder formulation in water was found to be bioequivalent to the marketed oral solution. Ritonavir powder formulation administered in chocolate milk, pudding, infant formula or apple sauce was bioequivalent to the powder formulation administered in water. Compared with fasting conditions, moderate-fat and high-fat meals were associated with approximately 25-40% and 35-50% reduction in ritonavir concentrations, respectively. CONCLUSIONS: The novel ritonavir powder formulation is bioequivalent to marketed ritonavir oral solution under moderate-fat conditions with a similar effect of meals. None of the vehicles tested negatively affected the bioavailability, which suggests the potential for use of a broad range of vehicles for dose preparation.

Examination of noninferiority, safety, and tolerability of lopinavir/ritonavir and raltegravir compared with lopinavir/ritonavir and tenofovir/ emtricitabine in antiretroviral-naïve subjects: the progress study, 48-week results.

PURPOSE: Current antiretroviral regimens recommended for treatment-naïve patients include 2 nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs). The purpose of this study is to evaluate whether a new NRTI-sparing regimen may provide an alternative for persons for whom traditional regimens may not be the best option. METHODS: PROGRESS is a 96-week, randomized, open-label, multicenter trial comparing the efficacy and safety of a boosted protease inhibitor (PI) and an integrase inhibitor (lopi-navir/ritonavir [LPV/r] + raltegravir [RAL]) to a boosted PI and 2 NRTIs (LPV/r + tenofovir/ emtricitabine [TDF/FTC]) in antiretroviral (ARV)-naïve HIV-1-infected adults. RESULTS: A total of 206 subjects were randomized to receive LPV/r + RAL (n=101) or LPV/r + TDF/FTC (n=105) and analyzed for ARV efficacy using the US Food and Drug Administration time to loss of virologic response (FDA-TLOVR) algorithm. The percentage of subjects with plasma HIV-1 RNA <40 copies/mL at week 48 was 83.2% in the LPV/r + RAL group and 84.8% in the LPV/r + TDF/FTC group (P = .850; difference -1.6%; exact 95% CI, -12.0% to 8.8%). As the lower limit of the exact 95% CI for the difference between regimens was at or above the protocol-defined threshold of -20% (as well as the more stringent threshold of -12%), LPV/r + RAL was noninferior to LPV/r + TDF/FTC. The occurrence of treatment-related, moderate/severe adverse events was similar between treatment groups through 48 weeks of treatment. CONCLUSIONS: The HIV treatment regimen of LPV/r + RAL resulted in noninferior efficacy and comparable safety and tolerability compared with a traditional NRTI-containing regimen through 48 weeks of treatment. These results support further evaluation of the LPV/r + RAL regimen.

Molecular characterization of Staphylococcus aureus isolates from a 2005 clinical trial of uncomplicated skin and skin structure infections.

A clinical trial of uncomplicated skin and skin structure infections (39 locations in 19 states) observed that community-associated or community-onset methicillin-resistant Staphylococcus aureus (CO-MRSA) represented 23% of all pathogens at baseline culture and 53% of 190 S. aureus isolates. CO-MRSA strains typically were Panton-Valentine leukocidin (PVL) positive (95%), contained staphylococcal cassette chromosome mec type IVa (99%), were USA300 or USA400 clones (92%), and exhibited minimal coresistances (macrolides and/or fluoroquinolones). Clinical results remained identical (89% cures) regardless of the antimicrobial used or CO-MRSA molecular patterns, PVL production, or antimicrobial susceptibility profiles.

From bacterial genomes to novel antibacterial agents: discovery, characterization, and antibacterial activity of compounds that bind to HI0065 (YjeE) from Haemophilus influenzae.

As part of a fully integrated and comprehensive strategy to discover novel antibacterial agents, NMR- and mass spectrometry-based affinity selection screens were performed to identify compounds that bind to protein targets uniquely found in bacteria and encoded by genes essential for microbial viability. A biphenyl acid lead series emerged from an NMR-based screen with the Haemophilus influenzae protein HI0065, a member of a family of probable ATP-binding proteins found exclusively in eubacteria. The structure-activity relationships developed around the NMR-derived biphenyl acid lead were consistent with on-target antibacterial activity as the Staphylococcus aureus antibacterial activity of the series correlated extremely well with binding affinity to HI0065, while the correlation of binding affinity with B-cell cytotoxicity was relatively poor. Although further studies are needed to conclusively establish the mode of action of the biphenyl series, these compounds represent novel leads that can serve as the basis for the development of novel antibacterial agents that appear to work via an unprecedented mechanism of action. Overall, these results support the genomics-driven hypothesis that targeting bacterial essential gene products that are not present in eukaryotic cells can identify novel antibacterial agents.

Efficacy, tolerability, and parent reported outcomes for cefdinir vs. high-dose amoxicillin/clavulanate oral suspension for acute otitis media in young children.

OBJECTIVES: To compare efficacy, tolerability, and parental satisfaction of cefdinir and high-dose amoxicillin/clavulanate oral suspensions given to young children with non-refractory acute otitis media (AOM) based on clinical endpoints and outcomes measures. RESEARCH DESIGN AND METHODS: This was an investigator-blinded, multicenter study in which 318 children 6 months through 6 years of age with a clinical diagnosis of AOM were randomized to receive 10 days of either cefdinir (14 mg/kg divided BID) or high-dose amoxicillin/clavulanate (90/6.4 mg/kg divided BID). MAIN OUTCOME MEASURES: Investigators evaluated clinical response at an end-of-therapy (EOT) office visit conducted on day 12-15. Outcomes of satisfaction, tolerability, and adherence were also assessed at that visit using an Otitis Parent Questionnaire. RESULTS: The treatment groups were similar at baseline with respect to patient demographics. At the EOT visit, for cefdinir and amoxicillin/clavulanate, respectively, intent-to-treat (ITT) clinical cure rates were 82% (129/158) and 85% (134/158) (p = 0.547; 95% confidence interval [CI] -11.7 to 5.4) and per-protocol cure rates were 82% (123/150) and 90% (129/143) (p = 0.045; 95% CI -16.4 to 0.0). This difference was driven primarily by reduced cefdinir response in patients with recurrent AOM (p = 0.010) and those younger than 24 months (p = 0.039). Comparing cefdinir with amoxicillin/clavulanate, parents more often reported significantly better ease of use (89% vs. 57%; p < 0.0001), better taste (85% vs. 39%; p < 0.0001), and better adherence (at least 95% of doses) (82% vs. 61%; p < 0.0001). Diarrhea/loose stools were more common in the amoxicillin/clavulanate group than in the cefdinir group (28% vs. 18%, respectively; p = 0.0341). One patient in the cefdinir group and eight patients in the amoxicillin/clavulanate group withdrew from the study prematurely due to at least one adverse event (p = 0.0364). Study limitations included assessment of clinical recurrence by telephone call rather than office visit, exclusion of children with refractory AOM, and no assessment of middle ear microbiology. CONCLUSIONS: Among young children with non-refractory AOM, cefdinir was as efficacious as high-dose amoxicillin/clavulanate in the ITT group, but somewhat less effective in per-protocol analysis. From the parental perspective, cefdinir was easier to administer, had a better taste, caused less diarrhea, and resulted in higher treatment adherence than high-dose amoxicillin clavulanate.

Novel antibacterial class: a series of tetracyclic derivatives.

We describe the synthesis and antibacterial activity of a series of tetracyclic naphthyridones. The members of this series act primarily via inhibition of bacterial translation and belong to the class of novel ribosome inhibitors (NRIs). In this paper we explore the structure-activity relationships (SAR) of these compounds to measure their ability both to inhibit bacterial translation and also to inhibit the growth of bacterial cells in culture. The most active of these compounds inhibit Streptococcus pneumoniae translation at concentrations of <5 microM and have minimum inhibitory concentrations (MICs) of <8 microg/mL against clinically relevant strains of bacteria.

Cefdinir vs. cephalexin for mild to moderate uncomplicated skin and skin structure infections in adolescents and adults.

OBJECTIVES: To compare the efficacy and safety of cefdinir to that of cephalexin in adolescents and adults with mild to moderate uncomplicated skin and skin structure infections (USSSI). RESEARCH DESIGN AND METHODS: This was an investigator-blinded, multicenter study in which patients at least 13 years of age with USSSI were randomized to receive 10 days of cefdinir 300 mg twice daily (BID) or cephalexin 250 mg four times daily (QID). Patients were evaluated at baseline, by telephone on Days 3-5, and during office visits on Days 12-14 (end-of-therapy [EOT] visit) and Days 17-24 (test-of-cure [TOC] visit). MAIN OUTCOME MEASURES: Clinical response was evaluated at the TOC visit. Patient reported outcomes, including a usefulness questionnaire, were also assessed. RESULTS: Three hundred and ninety-one patients were treated. The treatment groups were well matched with regard to demographic characteristics and types of infection. Abscess(es) (26%), wound infection (24%), and cellulitis (21%) were the most common infections. At the TOC visit, the clinical cure rate for both treatment groups was 89% (151/170 for cefdinir and 154/174 for cephalexin) in clinically evaluable patients (95% CI for difference in cure rates [-6.7 to 7.3]). In the intent-to-treat analysis, cure rates were 83% for cefdinir vs. 82% for cephalexin. Clinical cure rates for infections caused by methicillin-susceptible (MSSA) and methicillin-resistant (MRSA) Staphylococcus aureus were 93% (37/40) and 92% (35/38) for cefdinir vs. 91% (29/32) and 90% (37/41) for cephalexin (p > 0.999 comparing treatment groups for MSSA; p > 0.999 for MRSA). The usefulness questionnaire demonstrated that cefdinir was more highly rated in the mean composite score (87.4 vs. 83.6, p = 0.04), with the difference primarily due to the respondents' preference for the convenience of taking the study medication (mean score 93.5 vs. 74.1 for cephalexin, p < 0.001). The study had the following limitations: the requirement for culture at baseline likely skewed the enrollment of patients towards those with abscesses; the results of culture in patients with USSSIs are often nonspecific; in some patients entering the study with a diagnosis of cellulitis, the cellulitis was associated with an abscess; and, incision and drainage (I&D), spontaneous drainage, and needle aspiration are likely to have contributed to clinical response for purulent infections, and in particular MRSA-associated infections. Both study drugs were well tolerated. The most common treatment-related adverse events were diarrhea (10% cefdinir, 4% cephalexin, p = 0.017), nausea (3% and 6%, respectively, p = 0.203), and vaginal mycosis (3% and 6% of females, respectively, p = 0.500). CONCLUSIONS: This study demonstrated that empiric coverage of USSSIs with cephalosporin therapy remains an appropriate clinical strategy. MRSA infections responded well in both arms of the study, suggesting that the choice of a cephalosporin did not adversely affect patient outcome. However, cephalosporins do not have accepted, clinically relevant in vitro activity against MRSA. Hence, the clinical response rates seen in this study against MRSA infections must be interpreted with caution. Cefdinir was more highly rated than cephalexin in a composite usefulness assessment.

Design, synthesis and structure-activity relationships of 6-O-arylpropargyl diazalides with potent activity against multidrug-resistant Streptococcus pneumoniae.

A novel series of 6-O-arylpropargyl diazalides was synthesized and evaluated for their antibacterial activity. Members of this series exhibited potent activity against erythromycin-resistant respiratory tract pathogens.

Synthesis and antibacterial activity of 5-methoxy- and 5-hydroxy-6-fluoro-1,8-naphthyridone-3-carboxylic acid derivatives.

A series of 5-methoxy- and 5-hydroxy-6-fluoro-1,8-naphthyridone-3-carboxylic acid derivatives were prepared and evaluated for cell-free bacterial protein synthesis inhibition and whole cell antibacterial activity. When compared to the analogous 5-hydrogen compounds, the presence of the 5-OH group negatively affects biochemical potency. However, a tolerance of the 5-methoxy group is indicated. Only moderate whole cell antibacterial activity is seen, but this could be due to poor cellular penetration. Because only a few 7-position variants were made for this study, further investigation into this novel series combining a broader range of 7-amino derivatives with these 5-position modifications is warranted.

Ribosome affinity and the prolonged molecular postantibiotic effect of cethromycin (ABT-773) in Haemophilus influenzae.

Cethromycin (ABT-773) is a new ketolide currently in clinical trials, for treatment of community acquired respiratory tract infections. The drug is active in vitro and in vivo against Haemophilus influenzae. In this study, the mechanism of action of cethromycin was investigated in H. influenzae. The drug effect was studied using in vitro transcription-translation and whole cell amino acid incorporation. Both cethromycin and erythromycin inhibit protein synthesis with similar potencies; cethromycin, however, had a prolonged molecular postantibiotic effect (PAE) compared with erythromycin which was consistent with previously reported microbiological data. Ribosome binding assay using ribosomes isolated from H. influenzae NP200 revealed that the ribosome binding affinity of cethromycin was more than 20-fold tighter than that of erythromycin. Studies of binding kinetics showed that the tight binding of cethromycin mainly contributed to the 20-fold slower dissociation from cells. Further studies showed cethromycin had a four-fold faster drug accumulation rate than erythromycin. Therefore, the tight binding of cethromycin with ribosomes likely contributed to the faster drug accumulation, slower dissociation from cells and prolonged molecular PAE of cethromycin for H. influenzae.

Synthesis and antibacterial activity of novel bifunctional macrolides.

We report the discovery of a novel class of macrolide antibiotics that have improved antibacterial activity against Ery-resistant organisms.

Novel inhibitors of bacterial protein synthesis: structure-activity relationships for 1,8-naphthyridine derivatives incorporating position 3 and 4 variants.

Structure-activity relationships for a recently discovered novel ribosome inhibitor (NRI) class of antibacterials were investigated. Preliminary efforts to optimize protein synthesis inhibitory activity of the series through modification of positions 3 and 4 of the naphthyridone lead template resulted in the identification of several biochemically potent analogues. A lack of corresponding whole cell antibacterial activity is thought to be a consequence of poor cellular penetration as evidenced by the enhancement of activity observed for a lead analogue tested in the presence of a cell permeabilizing agent.

Synthesis and antibacterial activity of 6-O-arylpropargyl-9-oxime-11,12-carbamate ketolides.

A series of novel 6-O-arylpropargyl-9-oxime-ketolides was synthesized and evaluated against various pathogens. These new compounds show promising in vitro antibacterial potency and in vivo efficacy against macrolide resistant strains.

A strategy for discovery of novel broad-spectrum antibacterials using a high-throughput Streptococcus pneumoniae transcription/translation screen.

The authors report the development of a high-throughput screen for inhibitors of Streptococcus pneumoniae transcription and translation (TT) using a luciferase reporter, and the secondary assays used to determine the biochemical spectrum of activity and bacterial specificity. More than 220,000 compounds were screened in mixtures of 10 compounds per well, with 10,000 picks selected for further study. False-positive hits from inhibition of luciferase activity were an extremely common artifact. After filtering luciferase inhibitors and several known classes of antibiotics, approximately 50 hits remained. These compounds were examined for their ability to inhibit Escherichia coli TT, uncoupled S. pneumoniae translation or transcription, rabbit reticulocyte translation, and in vitro toxicity in human and bacterial cells. One of these compounds had the desired profile of broad-spectrum biochemical activity in bacteria and selectivity versus mammalian biochemical and whole-cell assays.

Elimination of antibacterial activities of non-peptide luteinizing hormone-releasing hormone (LHRH) antagonists derived from erythromycin A.

Antibacterial SAR for a series of macrolides derived from erythromycin A that are potent LHRH antagonists was developed in an attempt to eliminate the antibiotic activities of these compounds. Increasing the size of the alkyl substituents on the desosamine 3'-amine resulted in potent LHRH antagonists that were inactive against staphylococcal bacteria strains, and were significantly (>10-fold) less active against streptococcal bacteria strains. Complete elimination of antibacterial activities could be achieved by replacement of one or both methyl groups on the 3'-amine with a large alkyl substituent.

Novel antibacterial class.

We report the discovery and characterization of a novel ribosome inhibitor (NRI) class that exhibits selective and broad-spectrum antibacterial activity. Compounds in this class inhibit growth of many gram-positive and gram-negative bacteria, including the common respiratory pathogens Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, and Moraxella catarrhalis, and are nontoxic to human cell lines. The first NRI was discovered in a high-throughput screen designed to identify inhibitors of cell-free translation in extracts from S. pneumoniae. The chemical structure of the NRI class is related to antibacterial quinolones, but, interestingly, the differences in structure are sufficient to completely alter the biochemical and intracellular mechanisms of action. Expression array studies and analysis of NRI-resistant mutants confirm this difference in intracellular mechanism and provide evidence that the NRIs inhibit bacterial protein synthesis by inhibiting ribosomes. Furthermore, compounds in the NRI series appear to inhibit bacterial ribosomes by a new mechanism, because NRI-resistant strains are not cross-resistant to other ribosome inhibitors, such as macrolides, chloramphenicol, tetracycline, aminoglycosides, or oxazolidinones. The NRIs are a promising new antibacterial class with activity against all major drug-resistant respiratory pathogens.

In vitro antibacterial potency and spectrum of ABT-492, a new fluoroquinolone.

ABT-492 demonstrated potent antibacterial activity against most quinolone-susceptible pathogens. The rank order of potency was ABT-492 > trovafloxacin > levofloxacin > ciprofloxacin against quinolone-susceptible staphylococci, streptococci, and enterococci. ABT-492 had activity comparable to those of trovafloxacin, levofloxacin, and ciprofloxacin against seven species of quinolone-susceptible members of the family Enterobacteriaceae, although it was less active than the comparators against Citrobacter freundii and Serratia marcescens. The activity of ABT-492 was greater than those of the comparators against fastidious gram-negative species, including Haemophilus influenzae, Moraxella catarrhalis, Neisseria gonorrhoeae, and Legionella spp. and against Pseudomonas aeruginosa and Helicobacter pylori. ABT-492 was as active as trovafloxacin against Chlamydia trachomatis, indicating good intracellular penetration and antibacterial activity. In particular, ABT-492 was more active than trovafloxacin and levofloxacin against multidrug-resistant Streptococcus pneumoniae, including strains resistant to penicillin and macrolides, and H. influenzae, including beta-lactam-resistant strains. It retained greater in vitro activity than the comparators against S. pneumoniae and H. influenzae strains resistant to other quinolones due to amino acid alterations in the quinolone resistance-determining regions of the target topoisomerases. ABT-492 was a potent inhibitor of bacterial topoisomerases, and unlike the comparators, DNA gyrase and topoisomerase IV from either Staphylococcus aureus or Escherichia coli were almost equally sensitive to ABT-492. The profile of ABT-492 suggested that it may be a useful agent for the treatment of community-acquired respiratory tract infections, as well as infections of the urinary tract, bloodstream, and skin and skin structure and nosocomial lung infections.

Synthesis and SAR evaluation of oxadiazolopyrazines as selective Haemophilus influenzae antibacterial agents.

The parallel synthesis and antibacterial activity of 5-hydroxy[1,2,5] oxadiazolo[3,4-b]pyrazines is reported. The compounds were synthesized by condensing diaminofurazan with alpha-keto acids to give a variety of aryl-substituted analogues. Halogenated phenyl groups at C-6 give rise to the greatest Haemophilus influenzae antibacterial activity.