The efficacy of clarithromycin and the bicyclolide EDP-420 against Mycobacterium avium in a mouse model of pulmonary infection.

Lung disease caused by Mycobacterium avium complex (MAC) is increasing in prevalence. MAC disease occurs in patients with chronic preexisting obstructive pulmonary diseases but is also diagnosed in individuals with no history of lung pathology or identifiable immune defect. Histologically, the disease is characterized by either the development of nodular granulomatous lesions in the peribronchial region or cavitary peripheral disease in smokers. Response to long-term treatment is poor. Limited comparative-efficacy data on treatment exist. A model that resembles nodular MAC disease was established in C57 (bg+/bg+) mice infected intranasally. Therapy with clarithromycin, a compound commonly used to treat MAC disease, was evaluated in parallel with treatment using a new bicyclolide, EDP-420, that achieves high levels of intrapulmonary concentrations. Although clarithromycin administered daily resulted in a reduction in the bacterial load in the lung, EDP-420 administered either daily or twice a week was significantly more effective. These results suggest that this animal model can be used to evaluate novel regimens against MAC disease and that compounds with high concentration in the lung might have a significant impact on the outcome of MAC lung disease.

EDP-420, a bicyclolide (bridged bicyclic macrolide), is active against Mycobacterium avium.

Infection caused by Mycobacterium avium complex (MAC) is common in patients with immunosuppression, such as AIDS, and deficiencies of gamma interferon and interleukin-12, as well as patients with chronic lung diseases. Treatment of MAC disease is limited since few drugs show in vivo activity. We tested a new bridged bicyclic macrolide, EDP-420, against MAC in vitro and in beige mice. EDP-420 was inhibitory in vitro at a concentration ranging from 2 to 8 microg/ml (MIC(50) of 4 microg/ml and MIC(90) of 8 microg/ml). In macrophages, EDP-420 was inhibitory at 0.5 microg/ml, suggesting that the drug concentrates intracellularly. Mice infected with macrolide-susceptible MAC strain 101 were given 100 mg of EDP-420/kg of body weight daily for 4 weeks and showed a significant reduction in the number of bacteria in both liver and spleen which was greater than the reduction observed with clarithromycin treatment at the same dose (P < 0.05). However, macrolide-resistant MAC 101 did not respond to EDP-420 treatment. A combination of EDP-420 with mefloquine was shown to be indifferent; mefloquine alone was active against macrolide-resistant MAC. The frequency of resistance to EDP-420 in MAC 101 was 10(-9), which is significantly less than the emergence of resistance to clarithromycin, approximately 10(-7) (P < 0.05). Further evaluation of EDP-420 in the treatment of MAC disease is warranted.

Synthesis of novel 6,11-O-bridged bicyclic ketolides via a palladium-catalyzed bis-allylation.

A bridging chemistry process was developed to form an ether bridge between 6-O and 11-O of erythromycin A via a tandem or stepwise palladium-catalyzed bis-pi-allylation. By applying this bridging process, new 6,11-O-bridged bicyclic ketolides (BBKs) were synthesized. These BBKs showed good antibacterial activities against the macrolide-susceptible strains as well as mef-resistant strains and served as a good core for further modifications to study the structure-activity relationship (SAR) and to overcome bacterial resistance. [reaction: see text]