PHSCN peptide (licensed as ATN-161) is an effective α5β1 integrin inhibitor that has advanced to phase II clinical trials to treat solid tumors. Here we developed ATN-161 functionalized self-cross-linkable and intracellularly de-cross-linkable polymersomes (ATN/SCID-Ps) for highly efficient and targeted delivery of doxorubicin hydrochloride (DOX·HCl) into B16F10 melanoma-bearing C57BL/6 mice. ATN/SCID-Ps exhibited a high loading capacity of DOX·HCl. The size of DOX-loaded ATN/SCID-Ps (DOX-ATN/SCID-Ps) decreased from 150 to 88 nm with increasing ATN surface densities from 0 to 100% (mol/mol). DOX-ATN/SCID-Ps were robust with low drug leakage under physiological conditions while quickly releasing DOX with the addition of 10 mM glutathione. MTT assay results displayed that DOX-ATN/SCID-Ps induced ATN density-dependent antitumor activity to α5β1 integrin overexpressing B16F10 melanoma cells, in which 56% ATN-161 was optimal. Flow cytometry and CLSM studies revealed significantly more efficient internalization and cytoplasmic DOX release in B16F10 cells for DOX-ATN/SCID-Ps than for DOX-SCID-Ps (nontargeting control) as well as clinically used pegylated liposomal doxorubicin (DOX-LPs). DOX-ATN/SCID-Ps displayed a long blood circulation time (elimination half-life = 4.13 h) and 4 times higher DOX accumulation in B16F10 bearing C57BL/6 mice than DOX-LPs. Interestingly, DOX-ATN/SCID-Ps exhibited a superior maximum-tolerated dose of over 100 mg DOX·HCl/kg, 10 times higher than DOX-LPs. Remarkably, DOX-ATN/SCID-Ps could significantly inhibit the growth of aggressive B16F10 melanoma with little adverse effects via either multiple or single injection of total dosage of 100 mg DOX·HCl/kg, resulting in greatly improved survival rates as compared to DOX-LPs. ATN/SCID-Ps are appealing nanovehicles for targeted chemotherapy of α5β1 integrin positive solid tumors.
Keywords: antiangiogenic peptide; liposomal doxorubicin; melanoma; polymersomes; reduction-sensitive; tumor targeting.