A formulation consisting of SQL70, a prodrug-activating biomaterial, and SQP33, a prodrug of the anthracycline antineoplastic antibiotic doxorubicin, with potential antineoplastic activity. Upon administration of SQ3370, which consists of the injection of SQL70 at the tumor site followed by the intravenous administration of SQ3370, the prodrug SQP33 binds to, through an as of yet not identifiable mechanism, to SQL70 at the tumor site. After binding, doxorubicin is released over a period of days, intercalates into DNA and interacts with topoisomerase II. This leads to an inhibition of DNA replication and repair, and prevents RNA and protein synthesis. Compared to the systemic administration of doxorubicin alone, SQ3370 may allow for higher and sustained delivery of active doxorubicin directly to the tumor, which may increase its efficacy and limit its off-site, systemic toxicity.