PHOSPHORYLATION OF TRICIRIBINE IS NECESSARY FOR ACTIVITY AGAINST HIV TYPE-1

Triciribine (TCN) is a tricyclic nucleoside with known antineoplastic and antiviral activity. It is a potent and selective inhibitor of HIV- 1 and HIV-2, including strains known to be resistant to AZT or TIBO, T CN is phosphorylated to its 5'-monophosphate (TCN-P) by intracellular adenosine kinase (AK), but is not converted to di- or triphosphates, W e now report that 5'-phosphorylation is requisite for the activity of TCN against HIV-1, CEM cells incubated with TCN at concentrations rang ing from 0.1 to 330 mu M gave intracellular TCN-P concentrations from 27 to 775 mu M, respectively. There was no difference in the amount of intracellular TCN-P detected in uninfected compared with HIV-l-infect ed CEM cells. The antiviral effect of TCN against HIV-1 was strongly a ntagonized by the AK inhibitor 5-iodotubercidin (ITu). In contrast, TC N and ITu only exhibited additive cytotoxicity, The 5'-deoxy analog of TCN, which cannot be phosphorylated, had no antiviral effect against HIV-1 at a concentration more than 100 times higher than the IC50 Of T CN, Similarly, TCN was not active against HIV-1 in an AK-deficient cel l line (AA-2) at concentrations shown to inhibit the virus by >95% in CEM cells. Consistent with its AK-deficient phenotype, this cell line phosphorylated TCN to only 3% of the extent observed in CEM cells. We conclude that TCN must be phosphorylated to TCN-P for activity against HIV-1.