Comparative immunotoxicity of free doxorubicin and doxorubicin encapsulated in cardiolipin liposomes

The immunologic and pharmacologic effects of free doxorubicin and of doxorubicin entrapped in liposomes were compared in mice at a dose of 20 mg/kg. Liposomes for encapsulation of doxorubicin were prepared by using 39.35 μmol drug, 19.65 μmol cardiolipin, 100 μmol phosphatidylcholine, 68.4 μmol cholesterol, and 38.9 μmol stearylamine. Pharmacologic disposition studies after a dose of 20 mg/kg demonstrated 7- to 10-fold higher drug concentrations in the spleen at all time points following administration of doxorubicin entrapped in cardiolipin lipsosomes than after the free drug. The levels in liver were 4- to 5-fold higher with liposomal drug, whereas the cardiac uptake with liposomal doxorubicin was significantly lower than with free drug. Mice were sacrificed on days 1, 8, 15, and 22 after drug administration and spleen cells were isolated for studies of sensitization to alloantigens for cell-mediated cytolysis and of proliferation in response to mitogens. Mice treated with free doxorubicin demonstrated a decrease of more than 50 fold (compared with saline control) in allospecific cytotoxic activity on day 15; normal levels were recovered by day 22. The animals treated with doxorubicin encapsulated in liposomes showed a similar but not more pronounced fall to low levels. The total lytic activity per spleen after free drug or drug encapsulated in liposomes was markedly reduced at day 8, but this activity was fully recovered by day 15 in animals receiving liposomal doxorubicin; in those receiving free drug it had not recovered fully even at day 22. The proliferative response to concanavalin A was affected by the two forms of doxorubicin in a pattern very similar to the cytotoxic response. The proliferative response to lipopolysaccharide was markedly depressed by doxorubicin delivered in either form, and the kinetics were not altered by the mode of administration. The concentration of doxorubicin in spleen was markedly increased with liposomal delivery, but did not result in greater toxicity than that of free durg according to the immunologic parameters evaluated.