A drug used to treat liposarcoma and leiomyosarcoma (types of soft tissue sarcoma) that cannot be removed by surgery or have spread to other parts of the body. It is used in patients who were treated with other anticancer drugs. It is also being studied in the treatment of other types of cancer. ET-743 may kill cancer cells by damaging their DNA and stopping them from dividing. It is a type of alkylating agent. Also called ecteinascidin 743, trabectedin, and Yondelis.