Liposome formulation of a novel hydrophobic aryl-imidazole compound for anti-cancer therapy
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Purpose: A cholesterol-free liposome formulation formed from mixtures of egg phosphatidylcholine (ePC) and poly (ethylene glycol) conjugated distearoylphosphatidylethanolamine (DSPE-PEG 2000) was optimized and evaluated for delivery of a novel anti-cancer agent ML220 (2-(5-bromo-1H-indol-3-yl)-1H-phenanthro [9,10-d] imidazole). Results and Discussion: ML220 is highly lipophilic with a water solubility of 0.14 μg/ml and calculated log P of 5.69. The ML220-loaded liposomes had a unimodal size-distribution and a mean diameter of 89 nm. The drug to lipid ratio in the formulation was 1:3.5 (mol:mol) and the drug loading efficiency was 83% providing a more than 50,000-fold increase in the water solubility of ML220. The formulation was demonstrated to be stable in vitro at 37°C for over 2 weeks with a delayed drug release profile. Evaluation of the subacute toxicity of the liposome formulated drug in C3H mice revealed no overt signs of toxicity. Also, a biexponential drug plasma concentration pattern was found upon evaluation of the pharmacokinetics in Balb/C mice. The in vivo evaluation of the anti-cancer activity in a human colon HT29 carcinoma model revealed a significant delay in tumor growth. Conclusion: Overall, the ePC/DSPE-PEG liposomes were demonstrated to be a suitable delivery system for ML220. These studies also highlight the potential of cholesterol-free liposomes as a formulation strategy for highly lipophilic drugs.
KeywordsCholesterol-free liposome Hydrophobic drug Anti-cancer Drug delivery Solubilization Aryl-imidazole
The authors are grateful to NSERC and Lorus Therapeutics Inc. for funding this research. Dr. Ningping Feng and Ming Wang are acknowledged for their assistance with the in vivo evaluation of toxicity and efficacy. Dr. Gerald Guerin is acknowledged for his assistance with the multi-angle light scattering measurements.
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