Targeted delivery of doxorubicin

<p>Cancer is a group of diseases caused by uncontrolled cellular proliferation and dissemination. After heart disease, cancer is the second most common cause of death in the United States. Main treatment approaches for cancer are surgery, radiotherapy, chemotherapy, and immunotherapy approaches. However, cancer cells have ability to develop resistance to conventional chemotherapy thus lowering the efficacy of those chemotherapeutic agents including doxorubicin (DOX). DOX has been used for the treatment of various cancers. It is usually administered via continuous intravenous infusion. Nevertheless, the use of soluble DOX is often limited by its low therapeutic index. It has been reported that DOX-induced cardiotoxicity is a life-threatening adverse effect and DOX is also a potent vesicant that can cause tissue necrosis following injections. Therefore, this dissertation investigated alternative delivery approaches for DOX including systemic and local delivery systems for enhancing antitumor efficacy while reducing the side effects of free DOX.</p> <p>The first part of this research aimed at developing a formulation capable of actively targeting DOX to tumors. Advances in nanotechnology have provided new ways to delivering DOX into the body and to tumor sites. Among all active targeting ligands developed to date, cRGD peptide (cyclic arginylglycylaspartic acid) occupies a unique position owing to its inherent safety, biocompatibility, and targeting ability. Thus, cRGD was used here to decorate the surface of DOX-loaded PLGA-PEG nanoparticles (NPs) using two independent crosslink reactions, EDC-NHS and thiol-maleimide reactions. The results showed that the different modification reactions yielded NPs of similar size (110-140 nm diameter). All formulations exhibited provided similar burst release phases (of DOX) over the first 12 h followed by sustained release for up to 200 h. For in vivo antitumor activity, C57BL/6J mice carrying melanoma tumors were administered with cRGD-modified DOX-loaded PLGA-PEG NPs (equivalent to 8 μg DOX) by intravenous injection once every other day for up to four doses. Tumor volumes and survival were recorded. The toxicity of this therapy was examined using serum biomarkers including bilirubin, alanine aminotransferase (ALT), and aspartate transaminase (AST). Histopathology of organs (heart, lung, spleen, liver and kidney) was evaluated using hematoxylin and eosin staining (H&E) after euthanizing the treated mice. The results indicated that the cRGD-modified DOX-loaded PLGA-PEG NPs using PLGA-PEG-maleimide polymers (cRGD-DOX-M) demonstrated higher antitumor activity as compared to other groups (p < 0.05). Finally, administration of cRGD-modified DOX-loaded PLGA-PEG NPs had no significant effect on total bilirubin, serum ALT, serum AST levels or animal weight (P > 0.05). There were no signs of tissue damage in any of the tested organs as evaluated by H&E staining.</p> <p>The second part of this dissertation proposed to evaluate the therapeutic effect of combining chemotherapy and immunotherapy in a murine melanoma model. In this study, DOX-loaded PLGA-PEG NPs and anti-programmed death 1 (anti-PD-1) antibodies were chosen as the model of chemotherapy and immunotherapy, respectively. Anti-PD-1 antibodies have shown a great deal of promise in the treatment of melanoma in the clinic. In this study, DOX-loaded PLGA-PEG NPs were administered IV at a dose of 8 µg of DOX/dose per mouse once every other day (total of four injections). Mice in combination treatment groups were also administered with 200 µg of anti-PD-1 solution via intraperitoneal (IP) injection every 3 days for five doses. The combination therapy demonstrated higher antitumor efficacy in vivo as compared to control, soluble DOX, monotherapy of DOX-loaded PLGA-PEG NPs or anti-PD1 solution (p<0.05). Moreover, in vivo safety studies were investigated, and the results suggested that the combination therapy was safe.</p> <p>Lastly, DOX-loaded PLGA-PEG millirods were successfully fabricated by a hot-melt extrusion technique and characterized for in vitro release. It was demonstrated that DOX released from the millirods could be controlled by coating with polylactide (PLA). The locally implanted uncoated DOX- loaded PLGA millirods provided significantly greater antitumor activity against melanoma tumors in mice compared to naïve group and PLA-coated DOX-loaded PLGA millirods. Antitumor activity of the millirods was related to the release profile of DOX from the millirods. PLA-coated DOX-loaded millirods exhibited slower release of DOX compared to uncoated DOX-loaded millirods which probably explains the shorter survival time of mice treated with this formulation. Moreover, skin samples from tumor-free mice were also analyzed. The results demonstrated that uncoated and PLA-coated DOX-loaded millirods could be administered peritumorally without causing local skin necrosis.</p> <p>In conclusion, the novel systemic delivery system and local delivery system of DOX presented here have the potential to be used as alternative approaches for cancer therapy.</p>