An original oral formulation of docetaxel nanocapsules (NCs) embedded in microparticles elicited in rats a higher bioavailability compared with the i.v. administration of the commercial docetaxel solution, Taxotere. In the present study, various animal studies were designed to elucidate the absorption process of docetaxel from such a delivery system. Again, the docetaxel NC formulation elicited a marked enhanced absorption compared with oral Taxotere in minipigs, resulting in relative bioavailability and C max values 10-and 8.4-fold higher, respectively, confirming the previous rat study results. It was revealed that orally absorbed NCs altered the elimination and distribution of docetaxel, as shown in the organ biodistribution rat study, due to their reinforced coating, while transiting through the enterocytes by surface adsorption of apoproteins and phospholipids. These findings were demonstrated by the cryogenic-temperature transmission electron microscopy results and confirmed by the use of a chylomicron flow blocker, cycloheximide, that prevented the oral absorption of docetaxel from the NC formulation in an independent pharmacokinetic study. The lipoproteinated NCs reduced the docetaxel release in plasma and its distribution among the organs. The improved anticancer activity compared with i.v. Taxotere, observed in the metastatic lung cancer model in Severe Combined Immune Deficiency-beige (SCID-bg) mice, should be attributed to the extravasation effect, leading to the lipoproteinated NC accumulation in lung tumors, where they exert a significant therapeutic action. To the best of our knowledge, no study has reported that the absorption of NCs was mediated by a lymphatic process and reinforced during their transit. lymphatic system | nanoparticles | nanocarrier | taxanes

Aberrant signaling of the epidermal growth factor receptor (EGFR) is common to a variety of human cancers and is also found to be over-expressed in most cases of non-small cell lung cancer. For the development of a molecularly targeted therapy, cetuximab-conjugated nanoparticles (immunonanoparticles, INPs) are designed and loaded with the lipophilic paclitaxel palmitate (pcpl) prodrug. Oleyl cysteineamide (OCA) is synthesized whereby its amphiphilic nature enables interfacial anchoring and thiol surface functionalization of PLGA NPs, facilitating bioconjugation to cetuximab by thioether bonds. It is demonstrated that the in vitro targeting efficiency and improved cellular internalization and cytotoxicity of this targeted delivery system in lung cancer cells over-expressing EGFR. A quantitative measure of the high binding affinity of INPs to EGFR is demonstrated using surface plasmon resonance. In vivo tolerability and enhanced efficacy of cetuximab pcpl INPs in a metastatic lung cancer model are reported. Its therapeutic efficacy in A549-luc-C8 lung tumors is shown using non-invasive bioluminescent imaging. Intravenous administration of cetuximab pcpl INPs to mice results in significantly higher inhibition of tumor growth and increased survival rates as compared to the non-targeted drug solution, drug-loaded nanoparticles or blank INPs. Pharmacokinetics and organ biodistribution of the prodrug and parent drug are evaluated by LC-MS/MS in lung tumor bearing mice. No enhanced total accumulation of nanoparticles or INPs is found at the tumor tissue. However, persistent pcpl levels with sustained conversion and release of paclitaxel are observed for the encapsulated prodrug possibly suggesting the formation of a drug reservoir. The overall results indicate the potential of this promising targeted platform for the improved treatment of lung cancer and other EGFR positive tumors.

Cancer therapy often requires frequent and high drug dosing. Yet, despite the significant progress in cancer research and the wide versatility of potent available drugs, treatment efficacy is still hurdled and often failed by the lack of pharmaco-selectivity to diseased cells, indiscriminate drug toxicities and poor patient compliance. Thus, innovative pharmaceutical solutions are needed to effectively deliver the cytotoxic drugs specifically to the tumor site while minimizing systemic exposure to frequent and high drug doses. Polymeric nanocarriers, particularly nanoparticles, have been extensively studied for improved oncological use. Such nanocarriers hold great potential in cancer treatment as they can be biocompatible, adapted to specific needs, tolerated and deliver high drug payloads while targeting tumors. Active targeting, as opposed to passive targeting, should add value to selective and site specific treatment. Active targeting of nanosized drug delivery systems is firmly rooted in the Magic Bullet Concept as was envisioned by Paul Ehrlich over 100 years ago. This targeting strategy is based on the molecular recognition of tumor biomarkers which are over-expressed on cancer cells, via specific vector molecules conjugated to the surface of the drug carrier. These vector molecules dictate the carrier's biodistribution and its biological affinity to the desired site of action. Many recent publications have shown encouraging results suggesting that targeting nanocarriers represent a highly-promising strategy for improved cancer treatment. This chapter will focus mainly on polymeric nanoparticles as the main drug carriers to be conjugated to various ligands able to deliver the drug to the specific desired pathological tissue.

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