Effect of liposomal delivery on in vitro antitumor activity of lipophilic conjugates of methotrexate with lipoamino acids

Some selected lipophilic conjugates of the antifolate drug methotrexate (MTX) with lipoamino acids (LAA), previously described, were incorporated in liposomes with a different composition and charge ( neutral, positive, or negative). The properties of the liposomal systems were determined. The inhibitory activity of the conjugates after incorporation in the vesicles was determined in a preliminary assessment against a human erythroleukemic cell line (K562 cells) and compared with the activity of the parent drug and of free conjugates. The influence of liposome surface charge and of the type of conjugate (i.e., in the carboxylic or ester form) on the biological effect is discussed.