Small Molecule-Based Bone Targeted Drug Delivery Systems: An Overview

Abstract Bone-targeted drug delivery has received the utmost importance from the research community in the last decade since it is a major health concern among the aged population. Site-specific delivery can substantially advance the clinical treatment of bone disorders such as osteoporosis, osteoarthritis, Paget's disease, and osteosarcoma. Active moieties, including bisphosphonates, with bone-targeting capability, are studied as promising molecules in delivery systems intended to target bone tissue. Typically, bone-targeting agents can be characterized by high bone affinity, a tendency of an extended stay in bony tissues, and maintaining low concentration in the systemic circulation. Other than bisphosphonates, monoclonal antibodies and tetracyclines have shown potential as bonetargeting agents. However, proteins like antibodies-based agents can have several limitations, such as large molecular size, high manufacturing cost, and adverse immune reactions. Targeting moieties based on small molecules, such as bisphosphonates, can prove a better alternative having reduced adverse effects. This work sums up the latest findings concerning compounds having bone-targeting capabilities and the delivery approaches employing these small molecules for bone-targeted drug delivery.