Duchenne/Becker muscular dystrophy (DMD/BMD) is caused by a defective expression of the dystrophin gene resulting in the absence of the dystrophin protein in muscle fibers.1,2) Approximately 60% of DMD/BMD patients have deletions in the dystrophin gene itself, [3][4][5] while the remaining 40% have small deletions or point mutations in the region that encodes the gene. Furthermore, nonsense mutations located within the gene account for approximately 5-13% of the muscular dystrophies.
6,7)Aminoglycoside antibiotics such as gentamicin (GM) had the ability to allow the ribosome to read through a premature-termination codon of the dystrophin gene, which prevented normal translation of dystrophin protein.8,9) BartonDavis et al. demonstrated the possibility of treating X chromosome-linked muscular distrophy (mdx) mouse, which was an animal model for DMD that possessed a nonsense mutation in the dystrophin gene, with GM in vivo. 10) They used GM to suppress the nonsense mutations and could restore dystrophin expression successfully in mdx mouse. However, the GM therapy has been hindered by several problems such as severe side effects of GM, especially nephrotoxicity and ototoxicity, the poor delivery profile to muscle tissue, and short half-life in blood. Recently, the phase 2b clinical trial of PTC 124 (3-[5-(2-fluorophenyl)-[1,2,4]oxadiazol-3-yl]-benzoic acid), 11) which is a new drug to induce reading through a premature-termination codon without clear side-effects, showed that the primary endpoint of the change in 6 min walk distance tests did not reach any statistical significance within the 48 weeks duration of the study according to Genzyme corporation announcement.
12)Therefore, to overcome these inadequacies of GM therapy for DMD, we encapsulated GM in hybrid liposomes (HL) for the delivery system. HL can be prepared by just the sonication of vesicular and micellar molecules in a buffer solution.13,14) HL are free from any contamination with organic solvents and remain stable for longer periods. The physical properties of these liposomes such as size, membrane fluidity, phase transition temperature, and hydrophobicity can be controlled by changing the constituents and compositional ratios.In the course of our study for HL, the following interesting results have been obtained. 23) and hydrophobic agents in the drug delivery system (DDS).In this study, we reported the therapeutic effects of HL including GM (GM-HL) on the mdx mice in vivo. The reduction of side effects of GM-HL is also discussed on the basis of the results from auditory brainstem response (ABR) tests and biodistribution analysis of HL. Kumamoto 860-0811, Japan. Received December 14, 2010; accepted January 28, 2011; published online February 7, 2011 It is known that gentamicin (GM) could be a possible treatment for Duchenne Muscular Dystrophy (DMD). However, GM therapy has been hindered by several problems such as severe side effects of GM. In order to resolve these problems, we developed the drug delivery system (DDS) of GM using hybrid lip...