Antitumor activity of N-(2-hydroxypropyl) methacrylamide copolymer-Mesochlorine e6 and adriamycin conjugates in combination treatments

This study demonstrates the selective tumor targeting and the antitumor efficacy of the N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-bound mesochlorin e6 monoethylenediamine (Mce6) and HPMA copolymer-bound Adriamycin (ADR) in combination photodynamic therapy (PDT) and chemotherapy against human ovarian OVCAR-3 carcinoma xenografted in female athynmic mice. The concentrations of Mce6 and ADR in blood and tissues, in free or HPMA copolymer-bound form, were determined by fluorescence and high-performance liquid chromatography fluorescence assays, respectively. Xenograft responses to single and combination therapies were recorded. The peak concentration of HPMA copolymer-Mce6 conjugate in tumor was achieved 18 h after administration. For HPMA copolymer-bound drugs, the concentration ratios of liver and spleen versus muscle were significantly higher than those of free drugs. The HPMA copolymer-bound drugs demonstrated selective targeting and accumulation in the tumor, probably attributed to the enhanced permeability and retention effect. In vivo studies revealed that all tumors in the treatment groups showed significant responses after receiving any of the various types of therapy as compared with controls (P0.001). PDT with HPMA copolymer-Mce6 conjugate (PDTMC) at a dose of 13.4 mg/kg (1.5 mg/kg of Mce6 equivalent) and light doses of 110 J/cm2 at 12 and 18 h, respectively, resulted in significant suppression of the growth of OVCAR-3 tumors. Three courses of chemotherapy using 35 mg/kg (2.2 mg/kg of ADR equivalent) of HPMA copolymer-ADR conjugate (CHEMO) were effective in suppressing the growth of tumors. Single PDTMC plus multiple CHEMO exhibited significantly greater therapeutic efficacy than multiple CHEMO. In the group of mice receiving multiple PDTMC, tumor recurrence became obvious after day 20. However, 10 of 12 tumors exhibited complete responses in the group of mice receiving multiple PDTMC plus multiple CHEMO. The least to most effective treatments were ranked as follows: multiple CHEMOsingle PDTMC plus multiple CHEMOmultiple PDTMCmultiple PDTMC plus multiple CHEMO. The results clearly demonstrate that: (a) HPMA copolymer-bound drugs exhibited selective tumor accumulation contrary to free drugs; (b) PDT using HPMA copolymer-Mce6 conjugate with multiple light irradiations was a better therapy than that with single light irradiation; and (c) combination chemotherapy and photodynamic therapy with HPMA copolymer-ADR and HPMA copolymer-Mce6 conjugates was the most effective regimen.