Abstract
For more than 20 years we have been trying to isolate metabolites with medicinally important activities from Japanese marine invertebrates, including sponges, soft corals, nudibranchs, and tunicates, which resulted in the discovery of more than 300 new compounds; some of them are structurally unique and show potent biological activities. Although none of our compounds entered clinical trials, several compounds whose modes of action were elucidated to some extent are used as research tools. Problems in drug development from marine organisms and their solutions are discussed.
