Antibodies and associates: Partners in targeted drug delivery

Monoclonal antibodies (mAbs) are well established in the clinic due to their specificity and affinity to a diverse array of biochemical targets. More recently, mAbs are being exploited as targeting agents in modern drug delivery systems, aiming to bypass normal host tissue and to accumulate a therapeutic agent to a specific tissue or cell for enhanced pharmacology. At sizes ranging from ~ 10-100 nm, antibody-based bioconjugates have opened up a whole new realm of clinical possibilities with several platforms emerging on the market. Antibody-drug conjugates combine the killing power of cytotoxic agents with mAb specificity and have great potential to treat cancer and beyond. Partnering a mAb with a biologic (protein/peptide, oligonucleotide (ON) or another mAb) is also gaining clinical traction. For example, many bispecific mAbs target and recruit immune effector cells to a tumor, while ON-based therapeutics against intracellular (regulatory) RNAs may be safely delivered into specific cells with mAb support. Finally, nanoparticles (NPs) offer significant drug delivery advantages including controlled release, large and diverse payloads, intracellular delivery and multi-functionality. Coupling mAbs to the surface of NPs can add further targeting capacity, and yet, therapeutic mAbs can also be encapsulated to take advantage of the above NP qualities. Here, we present an updated overview of the different aspects required for the successful development and engineering of antibody bioconjugates in current and emerging drug delivery technologies.