Preparation of succinyl neocarzinostatin

All amino groups in a proteinous antitumor antibiotic, neocarzinostatin, were reacted with succinic anhydride yielding bis-N-succinyl neocarzinostatin which retained biological activity in vitro against human cell lines and a bacterium. Amino groups in neocarzinostatin do not appear to play an important role in the activity.