Pharmacokinetic/pharmacodynamic evaluation of gamithromycin against rabbit pasteurellosis.

BACKGROUND: Gamithromycin is an effective therapy for bovine and swine respiratory diseases but not utilized for rabbits. Given its potent activity against respiratory pathogens, we sought to determine the pharmacokinetic profiles, antimicrobial activity and target pharmacokinetic/pharmacodynamic (PK/PD) exposures associated with therapeutic effect of gamithromycin against Pasteurella multocida in rabbits. RESULTS: Gamithromycin showed favorable PK properties in rabbits, including high subcutaneous bioavailability (86.7 ± 10.7%) and low plasma protein binding (18.5-31.9%). PK analysis identified a mean plasma peak concentration (Cmax) of 1.64 ± 0.86 mg/L and terminal half-life (T1/2) of 31.5 ± 5.74 h after subcutaneous injection. For P. multocida, short post-antibiotic effects (PAE) (1.1-5.3 h) and post-antibiotic sub-inhibitory concentration effects (PA-SME) (6.6-9.1 h) were observed after exposure to gamithromycin at 1 to 4× minimal inhibitory concentration (MIC). Gamithromycin demonstrated concentration-dependent bactericidal activity and the PK/PD index area under the concentration-time curve over 24 h (AUC24h)/MIC correlated well with efficacy (R2 > 0.99). The plasma AUC24h/MIC ratios of gamithromycin associated with the bacteriostatic, bactericidal and bacterial eradication against P. multocida were 15.4, 24.9 and 27.8 h in rabbits, respectively. CONCLUSIONS: Subcutaneous administration of 6 mg/kg gamithromycin reached therapeutic concentrations in rabbit plasma against P. multocida. The PK/PD ratios determined herein in combination with ex vivo activity and favorable rabbit PK indicate that gamithromycin may be used for the treatment of rabbit pasteurellosis.

Comparison of gamithromycin residue depletion in yellow-feather and white-feather broilers after one single subcutaneous injection.

This study aimed to compare the residue depletion of gamithromycin in yellow-feather and white-feather broilers, using Sanhuang and Arbor Acres chickens as typical examples, respectively. Each breed (54 chickens) received a single subcutaneous dose of gamithromycin at 7.5 mg/kg bodyweight (BW). Tissues, including muscle, skin + fat, liver, kidney, and injection site, were collected at 6 h, 3, 5, 7, 10, 14, 21, 28, and 35 d postdrug administration. Gamithromycin concentrations in these tissues were determined using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The kinetics of gamithromycin were analyzed in different tissues using a noncompartmental method in the Phoenix software. Differences were observed in gamithromycin concentrations and kinetic characteristics in both breeds of chickens, with higher residue concentrations and longer residue times found in yellow-feathered broilers. In Sanhuang broilers, the elimination rates of gamithromycin followed this order: injection site > muscle > liver > kidney > skin + fat. The corresponding elimination half-lives (t1/2λzs) in these samples were 1.22, 1.30, 1.71, 2.04, and 2.52 d, respectively. In contrast, in Arbor Acres broilers, a different order was noted: muscle > injection site > kidney > liver > skin + fat, with corresponding t1/2λzs of 1, 1.23, 1.88, 1.93, and 2.21 d, respectively. These differences may be related to variations in pigments in various tissues of chickens of the 2 breeds. However, further investigations are warranted to discern the underlying reasons.

Poloxamer 407/188 Binary Thermosensitive Gel as a Moxidectin Delivery System: In Vitro Release and In Vivo Evaluation.

Moxidectin (MXD) is an antiparasitic drug used extensively in veterinary clinics. In this study, to develop a new formulation of MXD, a thermosensitive gel of MXD (MXD-TG) was prepared based on poloxamer 407/188. Furthermore, the gelation temperature, the stability, in vitro release kinetics and in vivo pharmacokinetics of MXD-TG were evaluated. The results showed that the gelation temperature was approximately 27 °C. MXD-TG was physically stable and can be released continuously for more than 96 h in vitro. The Korsmeyer−Peppas model provided the best fit to the release kinetics, and the release mechanism followed a diffusive erosion style. MXD-TG was released persistently for over 70 days in sheep. Part of pharmacokinetic parameters had a difference in female and male sheep (p < 0.05). It was concluded that MXD-TG had a good stability, and its release followed the characteristics of a diffusive erosion style in vitro and a sustained release pattern in vivo.

Pharmacokinetics of Azalomycin F, a Natural Macrolide Produced by Streptomycete Strains, in Rats.

As antimicrobial resistance has been increasing, new antimicrobial agents are desperately needed. Azalomycin F, a natural polyhydroxy macrolide, presents remarkable antimicrobial activities. To investigate its pharmacokinetic characteristics in rats, the concentrations of azalomycin F contained in biological samples, in vitro, were determined using a validated high-performance liquid chromatography-ultraviolet (HPLC-UV) method, and, in vivo, samples were assayed by an ultra-high performance liquid chromatography-tandem mass spectrometric (UPLC-MS/MS) method. Based on these methods, the pharmacokinetics of azalomycin F were first investigated. Its plasma concentration-time courses and pharmacokinetic parameters in rats were obtained by a non-compartment model for oral (26.4 mg/kg) and intravenous (2.2 mg/kg) administrations. The results indicate that the oral absolute bioavailability of azalomycin F is very low (2.39 ± 1.28%). From combinational analyses of these pharmacokinetic parameters, and of the results of the in-vitro absorption and metabolism experiments, we conclude that azalomycin F is absorbed relatively slowly and with difficulty by the intestinal tract, and subsequently can be rapidly distributed into the tissues and/or intracellular f of rats. Azalomycin F is stable in plasma, whole blood, and the liver, and presents plasma protein binding ratios of more than 90%. Moreover, one of the major elimination routes of azalomycin F is its excretion through bile and feces. Together, the above indicate that azalomycin F is suitable for administration by intravenous injection when used for systemic diseases, while, by oral administration, it can be used in the treatment of diseases of the gastrointestinal tract.

Leveraging Physiologically Based Pharmacokinetic Modeling and Experimental Data to Guide Dosing Modification of CYP3A-Mediated Drug-Drug Interactions in the Pediatric Population.

Solithromycin is a novel fluoroketolide antibiotic that is both a substrate and time-dependent inhibitor of CYP3A. Solithromycin has demonstrated efficacy in adults with community-acquired bacterial pneumonia and has also been investigated in pediatric patients. The objective of this study was to develop a framework for leveraging physiologically based pharmacokinetic (PBPK) modeling to predict CYP3A-mediated drug-drug interaction (DDI) potential in the pediatric population using solithromycin as a case study. To account for age, we performed in vitro metabolism and time-dependent inhibition studies for solithromycin for CYP3A4, CYP3A5, and CYP3A7. The PBPK model included CYP3A4 and CYP3A5 metabolism and time-dependent inhibition, glomerular filtration, P-glycoprotein transport, and enterohepatic recirculation. The average fold error of simulated and observed plasma concentrations of solithromycin in both adults (1966 plasma samples) and pediatric patients from 4 days to 17.9 years (684 plasma samples) were within 0.5- to 2.0-fold. The geometric mean ratios for the simulated area under the concentration versus time curve (AUC) extrapolated to infinity were within 0.75- to 1.25-fold of observed values in healthy adults receiving solithromycin with midazolam or ketoconazole. DDI potential was simulated in pediatric patients (1 month to 17 years of age) and adults. Solithromycin increased the simulated midazolam AUC 4- to 6-fold, and ketoconazole increased the simulated solithromycin AUC 1- to 2-fold in virtual subjects ranging from 1 month to 65 years of age. This study presents a systematic approach for incorporating CYP3A in vitro data into adult and pediatric PBPK models to predict pediatric CYP3A-mediated DDI potential. SIGNIFICANCE STATEMENT: Using solithromycin, this study presents a framework for investigating and incorporating CYP3A4, CYP3A5, and CYP3A7 in vitro data into adult and pediatric physiologically based pharmacokinetic models to predict CYP3A-mediated DDI potential in adult and pediatric subjects during drug development. In this study, minor age-related differences in inhibitor concentration resulted in differences in the magnitude of the DDI. Therefore, age-related differences in DDI potential for substrates metabolized primarily by CYP3A4 can be minimized by closely matching adult and pediatric inhibitor concentrations.

Synthesis, Characterization, and in†vivo Distribution of Intracellular Delivered Macrolide Short-Chain Fatty Acid Derivatives.

Short-chain fatty acids (SCFAs) have a range of effects in metabolism and immune regulation. We have observed that delivery of SCFAs to lysosomes has potent immune regulatory effects, possibly as a surrogate signal for the presence of anaerobic organisms. To better understand the pharmacology of lysosomal SCFA donors, we investigated the distribution and metabolism of propionate and butyrate donors. Each analog (1 a and 2 a) can donate three SCFA equivalents via ester hydrolysis through six intermediate metabolites. The compounds are stabilized by low pH, and stability in cells is usually higher than in medium, but is cell-type specific. Butyrate derivatives were found to be more stable than propionates. Tri-esters were more stable than di- or mono-esters. The donors were surprisingly stable in vivo, and hydrolysis of each position was organ specific. Jejunum and liver caused rapid loss of 4'' esters. The gut metabolite pattern by i. v. differed from that of p.o. application, suggesting luminal and apical enzyme effects in the gut epithelium. Central organs could de-esterify the 11-position. Levels in lung relative to other organs were higher by p.o. than via i. v., suggesting that delivery route can influence the observed pharmacology and that gut metabolites distribute differently. The donors were largely eliminated by 24 h, following near linear decline in organs. The observed levels and distribution were found to be consistent with pharmacodynamic effects, particularly in the gut.

Development and validation of an LC-MS/MS method for the quantification of the anthelmintic drug moxidectin in a volumetric absorptive microsample, blood, and plasma: Application to a pharmacokinetic study of adults infected with Strongyloides stercoralis in Laos.

Moxidectin is a promising candidate for addition to the lean repertoire of drugs against neglected tropical diseases (NTD) including strongyloidiasis. Pharmacokinetic (PK) and -dynamic studies are required to support its clinical development. Microsampling approaches enable PK studies in the challenging environments where NTDs are most prevalent, due to simplified collection and processing. We developed a liquid chromatography tandem mass spectrometry method for the sensitive quantification of moxidectin in human blood obtained by capillary sampling with the microsampling device Mitra® compared to blood and plasma obtained by venous sampling. Sample preparation consisted of protein precipitation, evaporation and reconstitution and also included phospholipid filtration for blood and plasma. Moxidectin was detected by multiple reaction monitoring (640.4 â†’ 528.5 m/z) using a Luna C8(2) (30 × 2.0 mm, 3 µm particle size, 100 Å) analytical column with a gradient program of 6 min duration. Validation was performed with respect to accuracy, precision, sensitivity, selectivity, linearity, stability, recovery, and haematocrit influence with a limit of quantification of 0.5 and 2.5 ng/mL, for venous and capillary blood respectively. Moxidectin was stable up to 2 months at storage condition (blood and plasma: -20 °C, microsamples: room temperature), 3 cycles of temperature shift, for at least 4 h on the bench-top and 24 h in the autosampler (4 °C). Deviations of inter- and intra-assay accuracy and precision were smaller than 12.6% and recoveries were in the range of 80.7-111.2%. The method was applied to samples obtained from nine Strongyloides stercoralis-infected adults from northern Laos. A good agreement in the time-concentration profiles of moxidectin and a high consistency in PK parameters was found between the different matrixes and sampling strategies: e.g. identical time to reach maximal concentration of 4.0 h and a similar maximal concentration of 83.9-88.5 ng/mL of moxidectin. The simple and practical capillary procedure using Mitra® microsampling has been demonstrated to be suitable for PK studies of moxidectin and will pave the way for future PK studies.

Combined moxidectin-levamisole treatment against multidrug-resistant gastrointestinal nematodes: A four-year efficacy monitoring in lambs.

Nematicide combinations may be a valid strategy to achieve effective nematode control in the presence of drug resistance. The goal of the current trial was to evaluate the pharmaco-parasitological performance of the moxidectin (MOX) and levamisole (LEV) combination after four years of continuous use in lambs naturally parasitized with multi-resistant gastrointestinal nematodes. At the beginning of the trial, 40 lambs were divided into four groups (n = 10), which were untreated (control) or subcutaneously treated with MOX (0.2 mg/kg), LEV (8 mg/kg) or with the combination MOX + LEV (administered separately at 0.2 and 8 mg/kg, respectively). Blood samples were collected at different times post-treatment and LEV and MOX plasma concentrations were measured by HPLC. The clinical efficacy of the continuous use of MOX + LEV combination was assessed with the controlled efficacy test (CET), performed at the beginning and end of the study, and with the faecal egg count reduction (FECR) test, performed over the four-year study period. No significant adverse pharmacokinetic changes were observed either for MOX or LEV after their co-administration to infected lambs. The CET (first year) showed efficacies of 84.3 % (Haemonchus contortus), 100 % (Teladorsagia circumcincta and Trichostrongylus axei), and 97.4 % (T. colubriformis). After the repetitive use of the combined treatment for four years, those efficacies remained high (100 %) and only decreased to 58 % against T. colubriformis. The evaluation of the FECR over the study period showed fluctuations in the performance of the combined administration. The initial FECR (2014) was 99 % (MOX), 85 % (LEV) and 100 % (MOX + LEV). The co-administration of MOX + LEV during the four-year experimental period resulted in a significantly higher anthelmintic effect (87 %) than that of MOX (42 %) or LEV (69 %) given alone. The combined use of MOX + LEV to control resistant gastrointestinal nematodes appears to be a valid strategy under specific management conditions. A high initial therapeutic response to the combination would be a relevant feature for the success of this tool.

Gamithromycin in swine: Pharmacokinetics and clinical evaluation against swine respiratory disease.

The pharmacokinetics of gamithromycin were evaluated in 26 male castrated and female crossbred swine administered gamithromycin 15% w/v (Zactran®, Boehringer Ingelheim) intravenously at 6 mg/kg bodyweight or intramuscularly at 3, 6 or 12 mg/kg bodyweight. Blood samples were collected up to Day 10 to establish the plasma profile of gamithromycin, bioavailability and dose proportionality. When administered by intramuscular injection at 6 mg/kg BWT, pharmacokinetic parameters were as follows: area under the curve until last quantifiable plasma concentration, 5.13 ± 0.957 µg*hours/ml; maximum plasma concentration, 960 ± 153 ng/ml at 5 to 15 min; terminal half-life of 94.1 ± 20.4 hr. Absolute bioavailability was 92.2%. Increase in systemic exposure was proportional to the gamithromycin dose level over the range 3-12 mg/kg BWT. No gender-related statistically significant difference in exposure was observed. For clinical evaluation of Zactran® against swine respiratory disease, 305 pigs from six commercial farms in three countries in Europe with signs associated with Actinobacillus pleuropneumoniae and/or Haemophilus parasuis and/or Pasteurella multocida and/or Bordetella bronchiseptica were used. At each site, animals were treated once in a 1:1 ratio with a single intramuscular dose of Zactran® (6 mg gamithromycin/kg bodyweight) or Zuprevo® (4% w/v tildipirosin at 4 mg/kg bodyweight; MSD Animal Health) at the recommended dose respectively. Animals were observed and scored daily for 10 consecutive days for signs of swine respiratory disease (depression, respiration and rectal temperature), and animals presenting signs of clinical swine respiratory disease (Depression Score 3 and/or Respiratory Score 3 associated with Rectal Temperature > 40.0°C) were removed from the study and considered as treatment failure. Animals which remained in the study were individually assessed for 'treatment success' or 'treatment failure' (Depression Score ≥ 1 and Rectal Temperature > 40.0°C or Respiratory Score ≥ 1 and Rectal Temperature > 40.0°C). Using a non-inferiority hypothesis test (non-inferiority margin = 0.10), the proportion of treatment successes in the Zactran® group (97%) was equivalent to or better than that in the Zuprevo® group (93%).

Spatiotemporal analysis of mycolactone distribution in vivo reveals partial diffusion in the central nervous system.

Mycobacterium ulcerans, the causative agent of Buruli ulcer (BU) disease, is unique amongst human pathogens in its capacity to produce a lipid toxin called mycolactone. While previous studies have demonstrated that bacterially-released mycolactone diffuses beyond infection foci, the spatiotemporal distribution of mycolactone remained largely unknown. Here, we used the zebrafish model to provide the first global kinetic analysis of mycolactone's diffusion in vivo, and multicellular co-culture systems to address the critical question of the toxin's access to the brain. Zebrafish larvae were injected with a fluorescent-derivative of mycolactone to visualize the in vivo diffusion of the toxin from the peripheral circulation. A rapid, body-wide distribution of mycolactone was observed, with selective accumulation in tissues near the injection site and brain, together with an important excretion through the gastro-intestinal tract. Our conclusion that mycolactone reached the central nervous system was reinforced by an in cellulo model of human blood brain barrier and a mouse model of M. ulcerans-infection. Here we show that mycolactone has a broad but heterogenous profile of distribution in vivo. Our investigations in vitro and in vivo support the view that a fraction of bacterially-produced mycolactone gains access to the central nervous system. The relative persistence of mycolactone in the bloodstream suggests that assays of circulating mycolactone are relevant for BU disease monitoring and treatment optimization.

Nanoengineered Disruption of Heat Shock Protein 90 Targets Drug-Induced Resistance and Relieves Natural Killer Cell Suppression in Breast Cancer.

Drug-induced resistance, or tolerance, is an emerging yet poorly understood failure of anticancer therapy. The interplay between drug-tolerant cancer cells and innate immunity within the tumor, the consequence on tumor growth, and therapeutic strategies to address these challenges remain undescribed. Here, we elucidate the role of taxane-induced resistance on natural killer (NK) cell tumor immunity in triple-negative breast cancer (TNBC) and the design of spatiotemporally controlled nanomedicines, which boost therapeutic efficacy and invigorate "disabled" NK cells. Drug tolerance limited NK cell immune surveillance via drug-induced depletion of the NK-activating ligand receptor axis, NK group 2 member D, and MHC class I polypeptide-related sequence A, B. Systems biology supported by empirical evidence revealed the heat shock protein 90 (Hsp90) simultaneously controls immune surveillance and persistence of drug-treated tumor cells. On the basis of this evidence, we engineered a "chimeric" nanotherapeutic tool comprising taxanes and a cholesterol-tethered Hsp90 inhibitor, radicicol, which targets the tumor, reduces tolerance, and optimally reprimes NK cells via prolonged induction of NK-activating ligand receptors via temporal control of drug release in vitro and in vivo. A human ex vivo TNBC model confirmed the importance of NK cells in drug-induced death under pressure of clinically approved agents. These findings highlight a convergence between drug-induced resistance, the tumor immune contexture, and engineered approaches that consider the tumor and microenvironment to improve the success of combinatorial therapy. SIGNIFICANCE: This study uncovers a molecular mechanism linking drug-induced resistance and tumor immunity and provides novel engineered solutions that target these mechanisms in the tumor and improve immunity, thus mitigating off-target effects.

Determination of Lekethromycin, a Novel Macrolide Lactone, in Rat Plasma by UPLC-MS/MS and Its Application to a Pharmacokinetic Study.

Lekethromycin, a new macrolide lactone, exhibits significant antibacterial activity. In this study, a reliable analytical ultrahigh-performance liquid chromatography electrospray ionization quadrupole Orbitrap high-resolution mass spectrometry (UPLC-ESI-Orbitrap-MS) method was established and validated for the detection of lekethromycin in rat plasma. After a simple acetonitrile (ACN)-mediated plasma protein precipitation, chromatographic separation was performed on a Phenomenex Luna Omega PS C18 column (30 × 2.1 mm i.d. particle size = 3 µm) conducted in a gradient elution procedure using 0.5% formic acid (FA) in ACN and 0.5% FA in water as the mobile phase pumped at a flow rate of 0.3 mL/min. Detection was carried out under positive electrospray ionization (ESI+) conditions in parallel reaction monitoring (PRM) mode with observation of m/z 804.5580 > 577.4056 for lekethromycin and 777.5471 > 619.4522 for gamithromycin (internal standard, IS). The linear range was 5-1000 ng/mL (r2 > 0.99), and the lower limit of quantification (LLOQ) was 5 ng/mL. The intra- and inter-day precision (expressed as relative standard deviation, RSD) values were ≤7.3% and ≤6.3%, respectively, and the accuracy was ≥90% ± 5.3%. The mean extraction recovery RSD valWeue was <5.1%. Matrix effects and dilution integrity RSD values were <5.6% and <3.2%, respectively. Lekethromycin was deemed stable under certain storage conditions. This fully validated method was effectively applied to study the pharmacokinetics of lekethromycin after a single intravenous administration of 5 mg/kg in rats. The main pharmacokinetic parameters were T1/2λz, CL_obs and VZ_obs were 32.33 ± 14.63 h, 0.58 ± 0.17 L/h/kg and 25.56 ± 7.93 L/kg, respectively.

Clinical evidences on the antiviral properties of macrolide antibiotics in the COVID-19 era and beyond.

Macrolides are a large group of antibiotics characterised by the presence of a macro-lactone ring of variable size. The prototype of macrolide antibiotics, erythromycin was first produced by Streptomyces and associated species more than half a century ago; other related drugs were developed. These drugs have been shown to have several pharmacological properties: in addition to their antibiotic activity, they possess some anti-inflammatory properties and have been also considered against non-bacterial infections. In this review, we analysed the available clinical evidences regarding the potential anti-viral activity of macrolides, by focusing on erythromycin, clarithromycin and azithromycin. Overall, there is no significant evidences so far that macrolides might have a direct benefit on most of viral infections considered in this review (RSV, Influenza, coronaviruses, Ebola and Zika viruses). However, their clinical benefit cannot be ruled out without further and focused clinical studies. Macrolides may improve the clinical course of viral respiratory infections somehow, at least through indirect mechanisms relying on some and variable anti-inflammatory and/or immunomodulatory effects, in addition to their well-known antibacterial activity.

Short communication: A practical farm-based trial to compare ewe nematode control strategies in peri-parturient ewes.

The focus of gastro-intestinal parasite control in the sheep industry is increasingly on finding a balance between maintaining productivity of the flock whilst minimising selection for anthelmintic resistance to preserve anthelmintic efficacy for the future. Periparturient ewes represent the major source of gastro-intestinal parasites for growing lambs and are therefore a priority for parasite control. This study examines the impact on ewe faecal egg counts (FECs), lamb FECs, lamb daily live weight gains (DLWGs) and pasture larval counts of treating groups of ewes two weeks prior to lambing with either, a long-acting moxidectin treatment, short-acting doramectin or control. Six groups of twenty ewes were allocated to individual paddocks, two groups allocated to each treatment, and weekly faecal sampling was performed throughout from the ewes and from six weeks after the start of lambing in the lambs. Treatment group was found to have a significant effect on both ewe FEC (p<0.001) and lamb FEC (p = 0.001) with the group receiving the long-acting anthelmintic having the lowest ewe and lamb FECs. There was no significant effect on the DLWGs of the lambs. Pasture larval counts at the end of the study period were lowest in the long-acting wormer treatment group. The use of long-acting moxidectin may be helpful as part of a parasite control programme by reducing the worm burdens of ewes and their lambs, decreasing the number of anthelmintic treatments required in that year and by reducing pasture contamination for those sheep which will graze the pasture in the next year. However, like all anthelmintics, its use should be judicious to avoid selection for resistance.

A Review: Effects of Macrolides on CYP450 Enzymes.

As a kind of haemoglobin, cytochrome P450 enzymes (CYP450) participate in the metabolism of many substances, including endogenous substances, exogenous substances and drugs. It is estimated that 60% of common prescription drugs require bioconversion through CYP450. The influence of macrolides on CYP450 contributes to the metabolism and drug-drug interactions (DDIs) of macrolides. At present, most studies on the effects of macrolides on CYP450 are focused on CYP3A, but a few exist on other enzymes and drug combinations, such as telithromycin, which can decrease the activity of hepatic CYP1A2 and CYP3A2. This article summarizes some published applications of the influence of macrolides on CYP450 and the DDIs of macrolides caused by CYP450. And the article may subsequently guide the rational use of drugs in clinical trials. To a certain extent, poisoning caused by adverse drug interactions can be avoided. Unreasonable use of macrolide antibiotics may enable the presence of residue of macrolide antibiotics in animal-origin food. It is unhealthy for people to eat food with macrolide antibiotic residues. So it is of great significance to guarantee food safety and protect the health of consumers by the rational use of macrolides. This review gives a detailed description of the influence of macrolides on CYP450 and the DDIs of macrolides caused by CYP450. Moreover, it offers a perspective for researchers to further explore in this area.

[Intrapulmonary Pharmacokinetics and Drug Distribution Characteristics for the Treatment of Respiratory Diseases].

This study was designed to clarify the intrapulmonary pharmacokinetics and distribution characteristics of drugs in order to develop better therapies for respiratory diseases, including respiratory infections and pulmonary fibrosis. The distribution characteristics of three macrolide antimicrobial agents-clarithromycin, azithromycin, and telithromycin-in plasma, lung epithelial lining fluid (ELF), and alveolar macrophages (AMs), were examined for the optimization of antimicrobial therapy. The time course of the uptake of these agents in ELF and AMs, following oral administration to rats, resulted in markedly higher concentrations than that in plasma. The high concentration of the agents in AMs was due to their sustained distribution to ELF via multidrug resistance protein 1 and to high uptake by AMs themselves via active transport mechanisms and trapping and/or binding in acidic organelles. The intrapulmonary pharmacokinetics of aerosolized model compounds administered to animals with bleomycin-induced pulmonary fibrosis via aerosol formulations of model compounds (MicroSprayer) were then evaluated. The concentrations of these compounds in the plasma of pulmonary fibrotic rats were markedly higher than in that of control rats. The expression of epithelial tight junctions decreased in pulmonary fibrotic lesions. The accumulation of extracellular matrix inhibited the intrapulmonary distribution of aerosolized model compounds, indicating that aerosolized drugs are easily absorbed after leakage through damaged alveolar epithelia, but cannot become widely distributed in the lungs because of interruption by the extracellular matrix. This review provides useful findings for the development of therapies for respiratory infections and pulmonary fibrosis.

Epidemiological and PK/PD cutoff values determination and PK/PD-based dose assessment of gamithromycin against Haemophilus parasuis in piglets.

BACKGROUND: Gamithromycin is a macrolide approved for the treatment of bovine and swine respiratory diseases. Our study aims to establish the clinical breakpoint and optimum dose regimen for gamithromycin against Haemophilus parasuis in piglets. RESULTS: Gamithromycin was well absorbed and fully bioavailable (87.2-101%) after intramuscular and subcutaneous administrations. The MICs of gamithromycin for 192 clinical H. parasuis isolates ranged from 0.008 to 128 mg/L and the epidemiological cutoff (ECOFF) was calculated as 1.0 mg/L. A large potentiation effect of serum on in vitro susceptibility of gamithromycin was observed for H. parasuis, with broth/serum ratios of 8.93 for MICs and 4.46 for MBCs, respectively. The postantibiotic effects were 1.5 h (1 × MIC) and 2.4 h (4 × MIC), and the postantibiotic sub-MIC effects ranged from 2.7 to 4.3 h. Gamithromycin had rapid and concentration-dependent killing against H. parasuis, and the AUC24h/MIC ratio correlated well with ex vivo efficacy (R2 = 0.97). The AUC24h/MIC targets in serum associated with bacteriostatic, bactericidal and eradication activities were 15.8, 30.3 and 41.2, respectively. The PK/PD-based population dose prediction indicated a probability of target attainment (PTA) for the current marketed dose (6 mg/kg) of 88.9% against H. parasuis. The calculated gamithromycin dose for a PTA ≥ 90% was 6.55 mg/kg. Based on Monte Carlo simulations, the PK/PD cutoff (COPD) was determined to be 0.25 mg/L. CONCLUSION: The determined cutoffs and PK/PD-based dose prediction will be of great importance in gamithromycin resistance surveillance and serve as an important step in the establishment of optimum dose regimen and clinical breakpoints.

Synthesis of Novel Potent Archazolids: Pharmacology of an Emerging Class of Anticancer Drugs.

Vacuolar type ATPase (V-ATPase) has recently emerged as a promising novel anticancer target based on extensive in vitro and in vivo studies with archazolids, complex polyketide macrolides, which present the most potent V-ATPase inhibitors known to date. Herein, we report a biomimetic, one-step preparation of archazolid F, the most potent and least abundant archazolid, the design and synthesis of five novel, carefully selected archazolid analogues, and the biological evaluation of these antiproliferative agents, leading to the discovery of a very potent but profoundly simplified archazolid analogue. Furthermore, the first general biological profiling of the archazolids against a broad range of more than 100 therapeutically relevant targets is reported, leading to the discovery of novel and important targets. Finally, first pharmacokinetic data of these natural products are disclosed. All of these data are relevant in the further preclinical development of the archazolids as well as the evaluation of V-ATPases as a novel and powerful class of anticancer targets.

Lipid droplets can promote drug accumulation and activation.

Genetic screens in cultured human cells represent a powerful unbiased strategy to identify cellular pathways that determine drug efficacy, providing critical information for clinical development. We used insertional mutagenesis-based screens in haploid cells to identify genes required for the sensitivity to lasonolide A (LasA), a macrolide derived from a marine sponge that kills certain types of cancer cells at low nanomolar concentrations. Our screens converged on a single gene, LDAH, encoding a member of the metabolite serine hydrolase family that is localized on the surface of lipid droplets. Mechanistic studies revealed that LasA accumulates in lipid droplets, where it is cleaved into a toxic metabolite by LDAH. We suggest that selective partitioning of hydrophobic drugs into the oil phase of lipid droplets can influence their activation and eventual toxicity to cells.

Pharmacokinetics and lung distribution of macrolide antibiotics in sepsis model rats.

Recent studies have shown azithromycin-specific clinical efficacy against macrolide-resistant strains of Streptococcus pneumoniae, despite the low susceptibility of the bacteria in vitro. This discrepancy complicates dosing and selection for treatment of macrolide-resistant strains. Although phagocyte delivery of azithromycin to inflamed tissues is considered a possible factor for clinical efficacy, there is a lack of sufficient evidence, and other pharmacokinetic factors under systemic inflammation may contribute.The concentrations of azithromycin, clarithromycin and erythromycin in the plasma and buffy coat were determined in normal and sepsis model rats. Furthermore, we compared the transport of the drug into the lung.The levels of all three macrolides in the buffy coat were higher than the levels in the plasma, and lower leukocyte counts in plasma were observed in septic rats, suggesting accumulation of the drugs per leukocyte was increased. The concentrations in the lung tissue of septic rats at each sampling time were the same as those in normal rats, and azithromycin-specific long-term stasis in the lung was evident.These results suggest that both the phagocyte delivery and the stasis of azithromycin in the lung could contribute to its clinical efficacy in treating infections caused by macrolide-resistant strains.