[A tetrahydroisoquinoline alkaloid isolated from the marine tunicate Ecteinascidia turbinate. Ecteinascidin 743 (ET743) exhibits potent tumor cytotoxicity by prolonging the G2-M phase of the cell cycle. This agent interacts with the transcription-coupled nucleotide excision repair machinery to induce lethal DNA strand breaks. (NCI04) ( NCI )]