Advancements in marine-derived anticancer agents: From natural products to clinical pipelines

Cancer remains among the leading causes of death worldwide, with incidence and mortality projected to rise substantially by 2040. Because current chemotherapeutics are limited by toxicity, resistance, and modest efficacy, marine-derived natural products – particularly polysaccharides from algae, sponges, fungi, and bacteria – have attracted growing interest as safer, multi-targeted anticancer candidates with cytotoxic, immunomodulatory, and pro-apoptotic activities. This review provides a focused, critical synthesis of algal (seaweed-derived) polysaccharides as anticancer agents, tracing their progression from structural characterization and mechanistic discovery, through green extraction technologies, to clinical translation. Unlike broader surveys of marine natural products, we deliberately concentrate on fucoidan, ulvan, carrageenan, alginate, and related polysaccharide classes, benchmarking their molecular targets, preclinical evidence, and clinical-development status against marine-derived drugs already approved for oncology use. We further identify the principal translational barriers – structural heterogeneity, limited pharmacokinetic and toxicological data, standardization gaps, and the scarcity of well-designed clinical trials – that continue to separate promising preclinical findings from validated therapeutics, and outline priority directions, including omics-guided discovery, synthetic biology, and biorefinery-based standardization, for closing this gap.