Augmentation of tumour delivery of macromolecular drugs with reduced bone marrow delivery by elevating blood pressure

Abstract

Effects of angiotensin II (AT-II)-induced hypertension on the distribution of macromolecules to Walker carcinoma and to bone marrow of SMANCS [poly(styrene-co-maleic-acid)-neocarzinostatin conjugate] were investigated in rats. AT-II-induced hypertension from about 100 to 150 mmHg significantly increased the accumulation of the macromolecular drug SMANCS and 51Cr-labelled bovine serum albumin ([51Cr]BSA), representatives of macromolecular drugs, in tumour tissue. At 1 h after i.v. administration, intratumour concentrations of [51Cr]BSA and SMANCS were elevated by 1.2-1.8-fold. The higher drug accumulation in the tumour that was produced by the artificial hypertension was retained even 6 h after administration. This observation indicates an additive effect to that under normotensive conditions where intratumour macromolecular drug concentrations increase steadily during this period. Furthermore, distributions of these drugs in the bone marrow and the small intestine decreased during artificial hypertension to 60-80% of those in the normotensive state. Therefore, the drug concentration ratios of tumour/bone marrow and tumour/small intestine were increased by 1.8-2.4-fold. A decreased distribution of SMANCS to normal tissues under hypertensive conditions was also confirmed by the significant reduction of its toxicity e.g. leukopenia, diarrhoea, and body weight loss, even at a lethal dose. On the contrary, [3H]methylglucose showed no remarkable difference in tumour or bone marrow accumulation under this hypertensive condition. These results show the advantages of macromolecules over small molecules for AT-II-induced hypertension chemotherapy.