A compound composed of a two CYCLIC peptides attached to a phenoxazine that is derived from streptomyces parvullus. It binds to dna and inhibits rna synthesis (transcription), with chain elongation more sensitive than initiation, termination, or release. As a result of impaired mRNA production, protein synthesis also declines after dactinomycin therapy. (From AMA Drug Evaluations Annual, 1993, p2015)