Polysaccharides in Modern Therapeutics: Structural Diversity, Delivery Platforms, and Antitumor Applications

Polysaccharides, as structurally diverse and biologically versatile natural macromolecules, have long been recognized for their indispensable roles in immune regulation, intercellular communication, and tissue architecture. Their intrinsic biocompatibility, biodegradability, and chemical modifiability position them at the interface between small-molecule drugs, biologics, and functional biomaterials. This review provides a systematic overview of the biological characteristics, historical evolution, and clinical applications of polysaccharide-based drugs, with an emphasis on marketed products and advanced clinical candidates. We critically discuss recent progress in polysaccharide-based delivery platforms, including nanoparticles, hydrogels, and polysaccharide-drug conjugates, highlighting how molecular design—such as molecular weight control, glycosidic linkage configuration, and functional group substitution—governs pharmacological activity and targeting performance. Particular attention is given to antitumor applications, where natural and chemically modified polysaccharides (e.g., selenized, phosphorylated, and sulfated derivatives) exert multitarget effects through cell cycle arrest, apoptosis induction, tumor microenvironment remodeling, and immunomodulation. Despite significant advances, challenges related to structural heterogeneity, batch-to-batch variability, and incomplete structure-activity relationship elucidation continue to hinder clinical translation. By integrating structural precision with mechanistic clarity, polysaccharide-based drugs are poised to evolve from supportive agents into rationally designed, next-generation therapeutic platforms.