Strategies to drive chemotherapeutics to solid tumors: multifunctional nanoparticles from tailor-made block copolymers

Nanotechnologies promise to drive a drug to tumors with improvement of activity profile, alleviation of side effects and increased patient survival. However, poor accumulation of nanoparticles (NPs) in solid tumors remains the main drawback of nanotechnology-driven approaches. Decoration of NPs with folate is a reference strategy to promote NP entry inside cancer cells that overexpress folate receptor, which has demonstrated a certain potential. Nevertheless, exposition of peptides with specific peptide sequences (RGD and CendR) has been found to specifically activate NP transport through tumor capillaries. Capitalizing these recent findings, we intend to develop multifunctional NPs able to improve the activity and selectivity of a model anticancer drug through a multidisciplinary approach, comprising chemistry, pharmaceutical technology, cell biology and medicine. Our general strategy is to design double-targeted NPs exposing on the surface both Tumor Penetrating Peptides and folate groups binding folate receptor, which is over-expressed on the vast majority of cancer tissues while its expression is limited in healthy tissues. Furthermore, NPs slowly release their drug cargo in the body once homing at tumor level is achieved. NPs are based on amphiphilic block copolymers of polyethylenglycol-b-poly(-caprolactone) (PEG-b-PCL) that are fully biocompatibile, able to self-assemble in NPs with a polyester core and a PEG shell and to sustain the release of the entrapped drug. In Task 1, different PEG-b-PCL blocks, each designed with a specific role in the final NPs (Figure 1), will be synthesized. In particular: • PEG-b-PCL with optimal block length and hydrophilic/lipophilic balance providing NP stability in the blood and long circulation; • PEG-b-PCL with low molecular weight possibly reverting multi drug resistance (MDR) through P-glycoprotein (P-gp) inhibition; • PEG-b-PCL modified at PEG site through covalent linkage of already known or novel peptide sequences that promote specific transport of NPs through tumor vasculature and accumulation in the tumor; • PEG-b-PCL modified at PEG site with folate that promote NP uptake in cancer cells via receptor-mediated endocytosis. In task 2, rational assembly of each building element will provide a range of NPs with different properties and foreseen activities. The model drug Docetaxel will be loaded inside NPs by an in house fabrication method easy to translate at pilot scale and fully characterized in a translational perspective. In task 3, cell culture studies will validate our general strategies and provide a solid basis for further studies in animals. In task 4, proof-of-principle of translational potential of the most promising NP formulations will be provided by assessing biodistribution, toxicity and therapeutic activity in mouse models of colorectal cancer where folate receptor is over-expressed. As general outcome it is expected that NPs based on this novel design can i) carry a high drug payload at tumor/cell level; ii) generate high and constant drug concentration in tumor interstitium and inside cells, which can help to reach hypoxic regions; iii) revert possible MDR; iv) be tracked in vivo; v) improve drug toxicity/activity profile.