Biological properties of streptonigrin derivatives. III. In vitro and in vivo antiviral and antitumor activities.

Antitumor antibiotic streptonigrin (STN-COOH) is a potent inhibitor of avian myeloblastosis virus (AMV) and human immunodeficiency virus reverse transcriptases. The carboxyl group at 2'-position of STN-COOH was modified to give esters, hydrazide, amides and amino acid derivatives for biological studies. Against AMV reverse transcriptase, the hydrazide, amides and amino acid derivatives showed inhibitory activity, which compared favorably to that of STN-COOH, with the ID50 values ranging 2-8 micrograms/ml. In contrast, the esters lacked this activity except for those having a dimethylamino group in the substituent. Splenomegaly caused by Friend leukemia virus infection was significantly inhibited by STN-COOH and STN-COO(CH2)3N(CH3)2, but not STN-CONH(CH2)3N(CH3)2. Doxorubicin-resistant murine lymphoblastoma L5178Y cells showed collateral sensitivity to both STN-COOH and STN-COO(CH2)3N(CH3)2 not only in vitro but also in vivo.