In vivo efficacy of doxorubicin-prodrug-loaded PEG-pHPMAm-based micelles and free doxorubicin alone (A), and in combination with control (B) and β-glucuronidase-producing oncolytic vaccinia viruses (C), in nude mice bearing A549 NSCLC xenograft tumors. Individual relative tumor volumes at the last day of follow-up (day 26), showing significantly improved efficacy upon combining pg-micelles with β-glucuronidase-producing viruses (D). β-glucuronidase activity levels determined at pH 7.4 and pH 4.5 in lysates from tumors treated with PBS, control virus, and β-glucuronidase-producing virus (E). ** indicates p<0.01 and *** indicates p<0.005.