Targeted drug delivery to enhance efficacy and shorten treatment duration in disseminated Mycobacterium avium infection in mice

Objectives: Improvement of the efficacy of drug treatment in mycobacterial infection by the development and application of targeted drug delivery. Methods: In disseminated Mycobacterium avium infection in mice, the relative efficacy of the antimycobacterial agents that are currently used in combination therapy was investigated. Next, the effect of the addition of targeted delivery of amikacin to the infected tissues in the initial phase of treatment was studied. Amikacin was chosen because of its unique rapid and high mycobacterial killing capacity. As drug delivery tool, long-circulating sterically stabilized liposomes were used. Results: Treatment with clarithromycin alone daily (6 days a week) slowly killed most of the mycobacteria in the lung, liver, spleen, inguinal and mesenterial lymph nodes. However, after 24 weeks of treatment, persistence of substantial numbers of mycobacteria in the infected organs was observed. The addition of ethambutol to the clarithromycin regimen did not significantly enhance the efficacy of treatment, neither did rifampicin as a third agent. In contrast, the addition of liposomal amikacin in the initial phase of therapy resulted in rapid and complete elimination of the mycobacteria in all infected organs within 12 weeks of treatment without relapse of infection. As a result, total treatment duration could be significantly reduced to 12 weeks. Conclusions: In M. avium infection in mice, the approach of targeted drug delivery was successful. The rapid decrease in the mycobacterial load followed by complete killing, including the persistent mycobacteria considered responsible for relapse of infection, allows a significant reduction of the total treatment duration.