Unprecedented Epimerization of an Azithromycin Analogue: Synthesis, Structure and Biological Activity of 2'-Dehydroxy-5″-Epi-Azithromycin.

Certain macrolide antibiotics, azithromycin included, possess anti-inflammatory properties that are considered fundamental for their efficacy in the treatment of chronic inflammatory diseases, such as diffuse pan-bronchiolitis and cystic fibrosis. In this study, we disclose a novel azithromycin analog obtained via Barton-McCombie oxidation during which an unprecedented epimerization on the cladinose sugar occurs. Its structure was thoroughly investigated using NMR spectroscopy and compared to the natural epimer, revealing how the change in configuration of one single stereocenter (out of 16) profoundly diminished the antimicrobial activity through spatial manipulation of ribosome binding epitopes. At the same time, the anti-inflammatory properties of parent macrolide were retained, as demonstrated by inhibition of LPS- and cigarette-smoke-induced pulmonary inflammation. Not surprisingly, the compound has promising developable properties including good oral bioavailability and a half-life that supports once-daily dosing. This novel anti-inflammatory candidate has significant potential to fill the gap in existing anti-inflammatory agents and broaden treatment possibilities.

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.