CYCLOBUT-A AND CYCLOBUT-G, CARBOCYCLIC OXETANOCIN ANALOGS THAT INHIBIT THE REPLICATION OF HUMAN-IMMUNODEFICIENCY-VIRUS IN T-CELLS AND MONOCYTES AND MACROPHAGES INVITRO

Two newly synthesized carbocyclic oxetanocin analogs, (±)-9-[(1β,2α,3β)-2,3-bis(hydroxymethyl)-1cyclobutyl]adenine (cyclobut-A) and (±)-9-[(1β,2α,3β)-2,3-bis(hydroxymethyl)-1-cyclobutyl]guanine (cyclobut-G) were tested for activity against the infectivity of human immunodeficiency virus (HIV) in vitro. A number of other carbocyclic oxetanocin analogs failed to exert good antiretroviral effects. Both cyclobut-A and cyclobut-G protected CD4+ ATH8 cells against the infectivity and cytopathic effect of HIV type 1 (HIV-1) and suppressed proviral DsNA synthesis in ATH8 cells exposed to HIV-1 in vitro at concentration of 50 to 100 μM. These compounds also inhibited the in vitro infectivity of another human pathogenic retrovirus, HIV-2. Furthermore, both compounds completely suppressed the replication of a monocytotropic strain of HIV-1 in monocytes and macrophages at concentrations as low as 0.5 μM, as assessed by inhibition of HIV-1 p24 gag protein production. We also found that 2'-deoxyguanosine readily reversed the antiretroviral activity of cyclobut-G in our system, whereas the activity of cyclobut-A was harly reversed by 2'-deoxyadenosine or 2'-deoxycytidine. We noted, however, that these compounds inhibited the proliferation of peripheral blood mononuclear cells at concentrations of ≥100 μM in vitro. Although both cyclobut-A and cyclobut-G appear to have a certain level of in vitro toxicity, our observations may have theoretical and clinical implications in understanding the structure-activity relationships of antiretroviral agents active against HIV.