CTSB and neoplasm: was injected i.v. into C57 mice bearing subcutaneously (s.c.)palpable B16F10 tumours followed after 5 h by HPMA copolymer-cathepsin B there was a rapid increase in the rate of dox release within the tumour (3.6-fold increase in the AUC compared to that seen for PK1 alone).