A drug used to treat Ewing sarcoma, gestational trophoblastic tumor, Wilms tumor, and certain types of testicular cancer. It is also used to treat rhabdomyosarcoma in children. It is being studied in the treatment of other types of cancer. Dactinomycin comes from the bacterium Streptomyces parvulus. It damages the cell’s DNA and may kill cancer cells. It is a type of anticancer antibiotic. Also called actinomycin D and Cosmegen.