Activities of (-)-carbovir and 3'-azido-3'-deoxythymidine against human immunodeficiency virus in vitro.

(-)-Carbovir, the minus optical isomer of carbocyclic-2',3'-didehydro-2',3'-dideoxyguanosine, has been shown to be the biologically active form for the inhibition of human immunodeficiency virus type 1 replication. The concentration of (-)-carbovir required to reduce reverse transcriptase activity by 50% compared with the control was 0.8 microM in H9 cells infected with the HTLV-IIIb strain; the 50% inhibitory concentration for cytotoxicity was greater than 2 mM in these cells. The effect of the timing of drug addition, pre- and postinfection, and the effect of increasing amounts of virus on the antiviral activities of (-)-carbovir and 3'-azido-3'-deoxythymidine were determined.