A macrocyclic lactone isolated from the bryozoan Bugula neritina with antineoplastic activity. Bryostatin-1 binds to and inhibits the cell-signaling enzyme protein kinase C, resulting in the inhibition of tumor cell proliferation, the promotion of tumor cell differentiation, and the induction of tumor cell apoptosis. This agent may act synergistically with other chemotherapeutic agents. OR A substance being studied in the treatment of cancer. Brostallicin hydrochloride binds to DNA and may kill cancer cells. It may also help other drugs kill cancer cells. It is a type of DNA minor groove binding agent.