Improving the systemic drug delivery efficacy of nanoparticles using a transferrin variant for targeting.

Targeted therapy for the treatment of cancers using nanoparticles (NPs) decorated with transferrin (Tf) has been relatively successful, as several such nanocarriers are currently undergoing clinical trials. However, since native Tf has a low probability of delivering its payload due to its short residence time in the cell, or low cellular association, there is room to significantly improve the potency of current systems. We pioneered the redesign of this targeting ligand by altering the ligand-metal interaction, as suggested by our mathematical model, and here we present the first study to investigate the enhanced therapeutic efficacy of NPs conjugated to our engineered oxalate Tf. Our mathematical model was first used to predict that NPs conjugated to oxalate Tf will exhibit a higher degree of cellular association compared to native Tf-conjugated NPs. Our in vitro trafficking experiments validated the model prediction, and subsequent in vitro and in vivo efficacy studies demonstrated that this increase in cellular association further translates into an enhanced ability to deliver chemotherapeutics. Our findings signify the importance of the cellular trafficking properties of targeting ligands, as they may significantly influence therapeutic potency when such ligands are conjugated to NPs. Given the early success of a number of native Tf-conjugated NPs in clinical trials, there is potential for using Tf-variant based therapeutics in systemic drug delivery applications for cancer treatment.

Intracellular trafficking considerations in the development of natural ligand-drug molecular conjugates for cancer.

Overexpressed receptors, characteristic of many cancers, have been targeted by various researchers to achieve a more specific treatment for cancer. A common approach is to use the natural ligand for the overexpressed receptor as a cancer-targeting agent which can deliver a chemically or genetically conjugated toxic molecule. However, it has been found that the therapeutic efficacy of such ligand-drug molecular conjugates can be limited, since they naturally follow the intracellular trafficking pathways of the endogenous ligands. Therefore, a thorough understanding of the intracellular trafficking properties of these ligands can lead to novel design criteria for engineering ligands to be more effective drug carriers. This review presents a few commonly used ligand/receptor systems where intracellular trafficking considerations can potentially improve the therapeutic efficacy of the ligand-drug molecular conjugates.