Structure-Guided In Vitro to In Vivo Pharmacokinetic Optimization of Propargyl-Linked Antifolates

Pharmacokinetic/pharmacodynamic properties are strongly correlated with the in vivo efficacy of antibiotics. Propargyl-linked antifolates, a novel class of antibiotics, demonstrate potent antibacterial activity against both Gram-positive and Gram-negative pathogenic bacteria, including multidrug-resistant Staphylococcus aureus. Here, we report our efforts to optimize the pharmacokinetic profile of this class to best match the established pharmacodynamic properties. High-resolution crystal structures were used in combination with in vitro pharmacokinetic models to design compounds that not only are metabolically stable in vivo but also retain potent antibacterial activity. The initial lead compound was prone to both N-oxidation and demethylation, which resulted in an abbreviated in vivo half-life (∼20 minutes) in mice. Stability of leads toward mouse liver microsomes was primarily used to guide medicinal chemistry efforts so robust efficacy could be demonstrated in a mouse disease model. Structure-based drug design guided mitigation of N-oxide formation through substitutions of sterically demanding groups adjacent to the pyridyl nitrogen. Additionally, deuterium and fluorine substitutions were evaluated for their effect on the rate of oxidative demethylation. The resulting compound was characterized and demonstrated to have a low projected clearance in humans with limited potential for drug-drug interactions as predicted by cytochrome P450 inhibition as well as an in vivo exposure profile that optimizes the potential for bactericidal activity, highlighting how structural data, merged with substitutions to introduce metabolic stability, are a powerful approach to drug design.

Impact of participation in a surgical site infection surveillance network: results from a large international cohort study

BACKGROUND

Surveillance of surgical site infections (SSIs) is a core component of effective infection control practices, though its impact has not been quantified on a large scale.

AIM

To determine the time-trend of SSI rates in surveillance networks.

METHODS

SSI surveillance networks provided procedure-specific data on numbers of SSIs and operations, stratified by hospitals' year of participation in the surveillance, to capture length of participation as an exposure. Pooled and procedure-specific random-effects Poisson regression was performed to obtain yearly rate ratios (RRs) with 95% confidence intervals (CIs), and including surveillance network as random intercept.

FINDINGS

Of 36 invited networks, 17 networks from 15 high-income countries across Asia, Australia and Europe participated in the study. Aggregated data on 17 surgical procedures (cardiovascular, digestive, gynaecological-obstetrical, neurosurgical, and orthopaedic) were collected, resulting in data concerning 5,831,737 operations and 113,166 SSIs. There was a significant decrease in overall SSI rates over surveillance time, resulting in a 35% reduction at the ninth (final) included year of surveillance (RR: 0.65; 95% CI: 0.63-0.67). There were large variations across procedure-specific trends, but strong consistent decreases were observed for colorectal surgery, herniorrhaphy, caesarean section, hip prosthesis, and knee prosthesis.

CONCLUSION

In this large, international cohort study, pooled SSI rates were associated with a stable and sustainable decrease after joining an SSI surveillance network; a causal relationship is possible, although unproven. There was heterogeneity in procedure-specific trends. These findings support the pivotal role of surveillance in reducing infection rates and call for widespread implementation of hospital-based SSI surveillance in high-income countries.

Preparation of evodiamine solid dispersions and its pharmacokinetics

In order to increase the dissolution rate and bioavailability, solid dispersions of evodiamine in PVP K₃₀ with different enriched samples of evodiamine to PVP K₃₀ ratios were prepared by solvent method. Our studies showed that the dissolution rate of evodiamine was significantly higher in the solid dispersion system in comparison with that in enriched samples of evodiamine or physical mixtures. The increase of the dissolution rate was evidently related to the ratio of evodiamine to PVP K₃₀. The solid dispersion system (enriched samples of evodiamine/PVP K₃₀= 1/6, w/w) gave the highest dissolution rate: about 27.7-fold higher than that of enriched samples of evodiamine in hard capsules. Powder X-ray diffraction studies showed that enriched samples of evodiamine presented a total chemical stability after its preparation as solid dispersions. In vivo administration studies indicated that solid dispersions of evodiamine in hard capsules had a higher C_max and a shorter T_max than those of physical mixture in hard capsules, and the differences of C_max and T_max between them were significant. These results suggest that solid dispersions of evodiamine in hard capsules has a notably faster and greater absorption rate than enriched samples of evodiamine in physical mixture hard capsule and corresponds with the in vitro dissolution.

Catalytic activities of human cytochrome P450 2C9*1, 2C9*3 and 2C9*13

Cytochrome P450 2C9 (CYP2C9) is a geneticly polymorphic enzyme responsible for the metabolism of some clinically important drugs. CYP2C9*13 is an allele identified in a Chinese poor metabolizer of lornoxicam which has a Leu90Pro amino acid substitution. This paper reports on a study aimed at comparing the catalytic properties of CYP2C9*13 with those of the wild-type CYP2C9*1 and mutant CYP2C9*3 (Ile359Leu) in the COS-7 expression system using various substrates. CYP2C9*3 and *13 produced far lower luminescence than CYP2C9*1 in luciferin H metabolism. CYP2C9*13 exhibited an 11-fold increase in Km but no change in Vmax with tolbutamide as the substrate, a five-fold increase in Km and an 88.8% reduction in Vmax with diclofenac. These data indicate that CYP2C9*13 exhibits reduced metabolic activity toward all studied CYP2C9 substrates. The magnitude of the CYP2C9*13-associated decrease in intrinsic clearance (Vmax/Km) is greater than that associated with CYP2C9*3.

On the human CYP2C9*13 variant activity reduction: a molecular dynamics simulation and docking study

Cytochrome P450 2C9 (CYP2C9) plays a key role in the metabolism of clinical drugs. CYP2C9 is a genetically polymorphic enzyme and some of its allelic variants have less activity compared to the wild-type form. Drugs with a narrow therapeutic index may cause serious toxicity to the individuals who carry such allele. CYP2C9*13, firstly identified by some of the present authors in a Chinese poor metabolizer of lornoxicam, is characterized by mutation encoding Leu90Pro substitution. Kinetic experiments show that CYP2C9*13 has less catalytic activity in elimination of diclofenac and lornoxicam in vitro. In order to explore the structure-activity relationship of CYP2C9*13, the three-dimensional structure models of the substrate-free CYP2C9*1 and its variant CYP2C9*13 are constructed on the basis of the X-ray crystal structure of human CYP2C9*1 (PDB code 1R9O) by molecular dynamics simulations. The structure change caused by Leu90Pro replacement is revealed and used to explain the dramatic decrease of the enzymatic activity in clearance of the two CYP2C9 substrates: diclofenac and lornoxicam. The trans configuration of the bond between Pro90 and Asp89 in CYP2C9*13 is firstly identified. The backbone of residues 106-108 in CYP2C9*13 turns over and their side chains block the entrance for substrates accessing so that the entrance of *13 shrinks greatly than that in the wild-type, which is believed to be the dominant mechanism of the catalytic activity reduction. Consequent docking study which is consistent with the results of the kinetic experiments by Guo et al. identifies the most important residues for enzyme-substrate complexes.

Biflavonoids from the aerial part of Stephania tetrandra

Investigation of the aerial part of Stephania tetrandra led to the isolation of two biflavonoids, stephaflavone A and stephaflavone B, with a 3-6" linkage pattern, together with beta-sitosterol. Their structures were established on the basis of their spectroscopic data and their physicochemical properties.

Two butylated aminooligosaccharides isolated from the culture filtrate of Streptomyces luteogriseus

Two novel aminooligosaccharides, butytatins M03 and M13 were isolated and purified from the culture filtrate of Streptomyces luteogriseus. Analysis by liquid chromatography coupled to electrospray ionization mass spectrometry indicated their resemblance to isovalertatin, with a four-carbon acyl group. Their structures were established by NMR as aminooligosaccharide derivatives possessing a butylated side chain.

Profiling of isovalertatin family aminooligosaccharides extracted from the culture of Streptomyces luteogriseus by using liquid chromatography/electrospray ionization mass spectrometry

A rapid and novel procedure using the liquid chromatography coupled to an electrospray ionization ion trap mass spectrometry technique was applied for the profiling of isovalertatin-family aminooligosaccharides in the extract from the culture filtrate of Streptomyces luteogriseus. The aminooligosaccharides were separated on a C-8 reversed-phase column with an acetonitrile-alkaline water gradient. The desired homologues were detected using the multiple reaction monitoring mode, and the chemical structures were confirmed by analyzing the characteristic fragment ions in their collision-induced dissociation spectra. This facile procedure led to the identification of all the five known aminooligosaccharides, isovalertatins M03, M13, M23, D03, and D23, in addition to the characterization of at least 41 novel isovalertatins, the molecular weights of which ranged from 729 to 2,793. This kind of assay should be intended as a simple and convenient way for the high-throughput analysis of screening aminooligosaccharides and potentially other structural families of natural products.

Structural revision of isovalertatins M03, M13, and M23 isolated from the culture of Streptomyces luteogriseus

Three aminooligosaccharides, isovalertatins M03 (1), M13 (2), and M23 (3) were isolated and purified from the culture filtrate of Streptomyces luteogriseus. Their physicochemical properties, liquid chromatographic behavior, and spectroscopic data were in full accordance with the reported compounds [Xu, Q.; Wang, Q.; Lu, D. CN Patent 1100756, 1995; Chem. Abstr. 1995, 123, 110278n], but their structures were reinvestigated and revised by spectroscopic methods, including ESI multistage mass spectrometry and 2-dimensional NMR techniques.

[Trend and causes of injury deaths among children in Macheng city of Hubei province during 1969 through 1998]

OBJECTIVES

To describe time trend of mortality and proportional mortality of injury and to determine the characteristics of distribution of injury deaths in children aged 0 - 14 in Macheng city during 1969 to 1998.

METHODS

Data were collected from Notification System for Deaths of Macheng City during 1969 to 1998. Injury claimed 14,510 deaths caused by injury in children in total during these years. Changes in mortality and proportional mortality for injury were fitted with log-linear and simple linear regression models to compare their difference in children with different gender and ages.

RESULTS

Both injury mortality and proportional mortality in infants declined during the past 30 years, and injury mortality dropped but proportional mortality due to injury increased gradually in children aged 1 - 14 years old. From 1984 to 1998, the average injury mortality was 81.36 per 100,000 children of 0 - 14 of age, with a potential years of life lost rate was 57.92 per 1,000 children. Boys had higher injury mortality than girls. Injury mortality in infants reached 560.15 per 100,000, and mechanical suffocation was the leading cause of injury deaths in infants. Injury mortality was 95.48 per 100,000 in children aged 1 - 4 years. Injury deaths in children aged 0 - 4 accounted for 73.2 percent of total injury deaths. And, drowning was the leading cause of injury deaths in children aged 1 - 14 years.

CONCLUSION

Children under five years old were the vulnerable population for injury death needed for special care and strategy and measures should be taken to control injury in children in the rural areas.

[Germination temperature of seeds of medicinal plants]

According to our experiments in the last ten years, the germination behaviour of the seeds of medicinal plants may be classified into five types by different temperature requirements for germination: (1) low temperature type; (2) middle temperature type; (3) high temperature type; (4) alternating temperature type; (5) wide ranging temperature type. This classification is helpful for cultivators to determine the time of sowing.