Investigating the barriers to bioavailability of macrolide antibiotics in the rat.

The aim of this study was to compare the roles of gastrointestinal absorption and hepatic extraction as barriers to oral bioavailability for macrolide antibiotics erythromycin, clarithromycin, roxithromycin and telithromycin. In this study, the in vitro metabolic stability in rat liver microsomes and hepatocytes, as well as the in vivo pharmacokinetics in rats were determined following intravenous, intraportal, oral and intraduodenal routes of administration. Pharmacokinetic parameters were calculated for each compound for each route of administration. In vitro metabolic stability studies point to low intrinsic clearance of the tested macrolides in both microsomes (<1 mL/min/g) and hepatocytes (<1 mL/min/g), indicating good stability. The oral bioavailability in rat was low to moderate (14, 36, 36 and 25% for erythromycin, clarithromycin, roxithromycin and telithromycin, respectively). Upon intraduodenal dosing, the bioavailability increased by 1.3-3-fold, the highest increase being with roxithromycin, suggesting some loss due to gastric instability. Following portal vein administration, no hepatic first pass effect was observed with roxithromycin, less than 10% with telithromycin, and ca. 20 and 25% for clarithromycin and erythromycin. Our data showed that the tested macrolides display good in vitro metabolic stability, as was confirmed in vivo where a low hepatic first pass effect was observed. The limited oral bioavailability is likely due to poor oral absorption and/or intestinal first pass metabolism.

Macrolide Inspired Macrocycles as Modulators of the IL-17A/IL-17RA Interaction.

Interleukin 17 (IL-17) cytokines promote inflammatory pathophysiology in many autoimmune diseases, including psoriasis, multiple sclerosis, rheumatoid arthritis, and inflammatory bowel disease. Such broad involvement of IL-17 in various autoimmune diseases makes it an ideal target for drug discovery. Psoriasis is a chronic inflammatory disease characterized by numerous defective components of the immune system. Significantly higher levels of IL-17A have been noticed in lesions of psoriatic patients, if compared to non-lesion parts. Therefore, this paper is focused on the macrolide inspired macrocycles as potential IL-17A/IL-17RA modulators and covers the molecular design, synthesis, and in vitro profiling. Macrocycles are designed to diversify and enrich chemical space through different ring sizes and a variety of three-dimensional shapes. Inhibitors in the nM range were identified in both target-based and phenotypic assays. In vitro ADME as well as in vivo PK properties are reported.

A novel class of fast-acting antimalarial agents: Substituted 15-membered azalides.

BACKGROUND AND PURPOSE: Efficacy of current antimalarial treatments is declining as a result of increasing antimalarial drug resistance, so new and potent antimalarial drugs are urgently needed. Azithromycin, an azalide antibiotic, was found useful in malaria therapy, but its efficacy in humans is low. EXPERIMENTAL APPROACH: Four compounds belonging to structurally different azalide classes were tested and their activities compared to azithromycin and chloroquine. in vitro evaluation included testing against sensitive and resistant Plasmodium falciparum, cytotoxicity against HepG2 cells, accumulation and retention in human erythrocytes, antibacterial activity, and mode of action studies (delayed death phenotype and haem polymerization). in vivo assessment enabled determination of pharmacokinetic profiles in mice, rats, dogs, and monkeys and in vivo efficacy in a humanized mouse model. KEY RESULTS: Novel fast-acting azalides were highly active in vitro against P. falciparum strains exhibiting various resistance patterns, including chloroquine-resistant strains. Excellent antimalarial activity was confirmed in a P. falciparum murine model by strong inhibition of haemozoin-containing trophozoites and quick clearance of parasites from the blood. Pharmacokinetic analysis revealed that compounds are metabolically stable and have moderate oral bioavailability, long half-lives, low clearance, and substantial exposures, with blood cells as the preferred compartment, especially infected erythrocytes. Fast anti-plasmodial action is achieved by the high accumulation into infected erythrocytes and interference with parasite haem polymerization, a mode of action different from slow-acting azithromycin. CONCLUSION AND IMPLICATIONS: The hybrid derivatives described here represent excellent antimalarial drug candidates with the potential for clinical use in malaria therapy.

Induction of Amyloid-ß42 Production by Fipronil and Other Pyrazole Insecticides.

Generation of amyloid-ß peptides (Aßs) by proteolytic cleavage of the amyloid-ß protein precursor (AßPP), especially increased production of Aß42/Aß43 over Aß40, and their aggregation as oligomers and plaques, represent a characteristic feature of Alzheimer's disease (AD). In familial AD (FAD), altered Aß production originates from specific mutations of AßPP or presenilins 1/2 (PS1/PS2), the catalytic subunits of γ-secretase. In sporadic AD, the origin of altered production of Aßs remains unknown. We hypothesize that the 'human chemical exposome' contains products able to favor the production of Aß42/Aß43 over Aß40 and shorter Aßs. To detect such products, we screened a library of 3500 + compounds in a cell-based assay for enhanced Aß42/Aß43 production. Nine pyrazole insecticides were found to induce a ß- and γ-secretase-dependent, 3-10-fold increase in the production of extracellular Aß42 in various cell lines and neurons differentiated from induced pluripotent stem cells derived from healthy and FAD patients. Immunoprecipitation/mass spectrometry analyses showed increased production of Aßs cleaved at positions 42/43, and reduced production of peptides cleaved at positions 38 and shorter. Strongly supporting a direct effect on γ-secretase activity, pyrazoles shifted the cleavage pattern of another γ-secretase substrate, alcadeinα, and shifted the cleavage of AßPP by highly purified γ-secretase toward Aß42/Aß43. Focusing on fipronil, we showed that some of its metabolites, in particular the persistent fipronil sulfone, also favor the production of Aß42/Aß43 in both cell-based and cell-free systems. Fipronil administered orally to mice and rats is known to be metabolized rapidly, mostly to fipronil sulfone, which stably accumulates in adipose tissue and brain. In conclusion, several widely used pyrazole insecticides enhance the production of toxic, aggregation prone Aß42/Aß43 peptides, suggesting the possible existence of environmental "Alzheimerogens" which may contribute to the initiation and propagation of the amyloidogenic process in sporadic AD.

N'-substituted-2'-O,3'-N-carbonimidoyl bridged macrolides: novel anti-inflammatory macrolides without antimicrobial activity.

Macrolide antibiotics, like erythromycin, clarithromycin, and azithromycin, possess anti-inflammatory properties. These properties are considered fundamental to the efficacy of these three macrolides in the treatment of chronic inflammatory diseases like diffuse panbronchiolitis and cystic fibrosis. However, long-term treatment with macrolide antibiotics presents a considerable risk for promotion of bacterial resistance. We have examined antibacterial and anti-inflammatory effects of a novel macrolide class: N'-substituted 2'-O,3'-N-carbonimidoyl bridged erythromycin-derived 14- and 15-membered macrolides. A small focused library was prepared, and compounds without antimicrobial activity, which inhibited IL-6 production, were selected. Data analysis led to a statistical model that could be used for the design of novel anti-inflammatory macrolides. The most promising compound from this library retained the anti-inflammatory activity observed with azithromycin in lipopolysaccharide-induced pulmonary neutrophilia in vivo. Importantly, this study strongly suggests that antimicrobial and anti-inflammatory activities of macrolides are independent and can be separated, which raises development plausibility of novel anti-inflammatory therapeutics.

Determination of aqueous stability and degradation products of series of coumarin dimers.

The stability in aqueous solution of five classes of coumarin dimers (I-V, compounds 1-29) was studied by HPLC-MS/MS at various pH values. The relationship between chemical structure and stability is discussed. It was found that dimeric compounds with strong electron withdrawing groups (EWGs) on the α-carbon to the bridging C-atom are stable at all pH values, whereas other derivatives undergo retro-Michael addition at rates which are also affected by the substituents on the aromatic rings. In some cases formation of stable isomers or oxidation products was observed. In order to evaluate their developability and potential for progression to in vivo studies, representative compounds were tested in an in vitro microsomal stability assay.