Abstract: Glioblastoma (GBM) remains one of the most lethal and treatment-resistant cancers, underscoring the urgent need for novel therapeutic strategies. Marine-derived nutraceuticals offer a promising avenue due to their unique and myriad bioactive compounds. Immune-12 is an orally available marine organism-derived product that has shown preliminary evidence of anticancer activity in the published literature. Now, our team is conducting a comprehensive investigation of Immune-12 to characterize its molecular makeup, mechanisms of action, and in vitro/in vivo antitumor potencies. We have already conducted proteomic, peptidomic, and metabolomic profiling of this complex compound alongside several in vitro and in vivo efficacy and safety studies. In vitro cytotoxicity assays across 18 tumor cell lines, including six GBM lines, revealed potent activity, with IC₅₀ values ranging from 0.1% to 1.4% Immune-12 in media (volume/volume). In vivo toxicity studies, in which healthy mice were given Immune-12 for 28 days via oral gavage, showed no signs of systemic toxicity or weight loss. Furthermore, in orthotopic tumor-bearing mouse models, including GBM, Immune-12 inhibited tumor growth as a monotherapy and enhanced the antitumor efficacy of standard therapeutics in combination regimens. These findings suggest that Immune-12 exerts broad-spectrum cytotoxic effects against tumor cells while maintaining a favorable safety profile in vivo, highlighting its potential as a marine-derived therapeutic candidate for GBM and other malignancies. Based on these promising early data, we are rapidly conducting further experiments to maximize its potential for clinical application.