Marine natural products have long been recognized as a vast and diverse source of bioactive compounds with potential therapeutic applications, particularly in oncology. This review provides an updated overview of the significant advances made in the discovery and development of marine-derived anticancer drugs between 2019 and 2023. With a focus on recent research findings, the review explores the rich biodiversity of marine organisms, including sponges, corals, algae, and microorganisms, which have yielded numerous compounds exhibiting promising anticancer properties. Emphasizing the multifaceted mechanisms of action, the review discusses the molecular targets and pathways targeted by these compounds, such as cell cycle regulation, apoptosis induction, angiogenesis inhibition, and modulation of signaling pathways. Additionally, the review highlights the innovative strategies employed in the isolation, structural elucidation, and chemical modification of marine natural products to enhance their potency, selectivity, and pharmacological properties. Furthermore, it addresses the challenges and opportunities associated with the development of marine-derived anticancer drugs, including issues related to supply, sustainability, synthesis, and clinical translation. Finally, the review underscores the immense potential of marine natural products as a valuable reservoir of novel anticancer agents and advocates for continued exploration and exploitation of the marine environment to address the unmet medical needs in cancer therapy Graphical Abstract

Marine cyanobacteria are an ancient group of photosynthetic microbes dating back to 3.5 million years ago. They are prolific producers of bioactive secondary metabolites. Over millions of years, natural selection has optimized their metabolites to possess activities impacting various biological targets. This paper discusses the historical and existential records of cyanobacteria, and their role in understanding the evolution of marine cyanobacteria through the ages. Recent advancements have focused on isolating and screening bioactive compounds and their respective medicinal properties, and we also discuss chemical property space and clinical trials, where compounds with potential pharmacological effects, such as cytotoxicity, anticancer, and antiparasitic properties, are highlighted. The data have shown that about 43% of the compounds investigated have cytotoxic effects, and around 8% have anti-trypanosome activity. We discussed the role of different marine cyanobacteria groups in fixing nitrogen percentages on Earth and their outcomes in fish productivity by entering food webs and enhancing productivity in different agricultural and ecological fields. The role of marine cyanobacteria in the carbon cycle and their outcomes in improving the efficiency of photosynthetic CO₂ fixation in the chloroplasts of crop plants, thus enhancing the crop plant’s yield, was highlighted. Ultimately, climate changes have a significant impact on marine cyanobacteria where the temperature rises, and CO₂ improves the cyanobacterial nitrogen fixation.