(DAK-tih-noh-MY-sin) 
A drug that comes from the bacterium Streptomyces parvulus and is used alone or with other drugs to treat adults and children with Ewing sarcoma, gestational trophoblastic tumor, rhabdomyosarcoma, Wilms tumor, or certain types of testicular cancer and adults with certain types of solid tumors. It is also being studied in the treatment of other types of cancer. Dactinomycin damages the cell’s DNA and may kill cancer cells. It is a type of antineoplastic antibiotic. Also called actinomycin D and Cosmegen.