Didemnin B has been investigated primarily for its antitumor and immunosuppressive properties. It shows potent activity against various cancer cell lines by inhibiting protein synthesis and inducing apoptosis. Early studies highlighted its effectiveness in models of leukemia, breast cancer, and ovarian cancer. Due to its strong biological activity, it served as a lead compound in the development of analogs such as plitidepsin, which has shown improved safety and efficacy. Didemnin B also suppresses immune responses, suggesting potential in treating autoimmune disorders or preventing organ transplant rejection, although its clinical use has been limited by toxicity. Research continues to explore its mechanism and potential in targeted cancer therapies.