Reduced cardiotoxicity and nephrotoxicity with preservation of antitumor activity of doxorubicin entrapped in stable liposomes in the LOU/M Wsl rat.

LOU M/Wsl rats inoculated s.c. with 10(4) immunoglobulin immunocytoma cells have a palpable tumor at Day 17. Doxorubicin (DXR) has been entrapped in negatively charged liposomes (lip- DXR) composed of egg phosphatidylcholine, cholesterol, and phosphatidylserine and in positively charged liposomes (lip+ DXR) composed of phosphatidylcholine, cholesterol, and stearylamine. DXR, lip- DXR, and lip+ DXR were administered i.v. (0, 0.25, 0.5, 1.0, and 2.0 mg/kg) at Day 17 for 5 consecutive days and then weekly. Control animals showed progressive tumor growth leading to death 27 days after inoculation. Antitumor activity for all three preparations was dose dependent. DXR and lip- DXR showed the same antitumor activity; lip+ DXR had less antitumor activity. The overall survival of tumor-bearing animals treated with 2.0-mg/kg lip- DXR was significantly prolonged (p less than 0.05) in comparison to the animals treated with 2.0-mg/kg free DXR. Grade III cardiomyopathy was observed 47 days after treatment with free DXR; treatment with lip- DXR resulted in Grade I cardiomyopathy. In animals treated with 1.0-mg/kg and 2.0-mg/kg free DXR urinary albumin concentrations of 10 g/liter were observed. Treatment with 1.0-mg/kg lip- DXR and 1.0-mg/kg lip+ DXR resulted in urinary albumin concentration of less than 3.0 and less than 1.0 g/liter, respectively. Free DXR, 1.0 mg/kg, resulted in a decline of serum albumin concentration from 27.8 +/- 3.2 g/liter to 9.6 +/- 4.2 g/liter. No such decline was observed after treatment with lip- DXR and lip+ DXR. Treatment with a 1.0-mg/kg dose of free DXR resulted in severe glomerular and tubular lesions which were not found after treatment with 1.0-mg/kg lip- DXR and 1.0 mg/kg lip+ DXR. Administration of lip- DXR resulted in lower DXR levels in cardiac and renal tissue compared to administration of free DXR. After administration of lip+ DXR, very low tissue and tumor DXR levels were found. In conclusion, treatment with lip- DXR or lip+ DXR resulted in a prolonged survival, less albuminuria, and higher serum albumin levels. Also, fewer lesions in heart and kidney were found, correlating with lower DXR levels in these organs. Only lip- DXR had the same antitumor effect as free DXR.