AN INHIBITOR OF THE TAT TAR RNA INTERACTION THAT EFFECTIVELY SUPPRESSES HIV-1 REPLICATION/

One of the first steps in HIV gene expression is the recruitment of Ta t protein to the transcription machinery after its binding to the RNA response element TAR. Starting from a pool of 3.2 x 10(6) individual c hemical entities, we were able to select a hybrid peptoid/peptide olig omer of 9 residues (CGP64222) that was able to block the formation of the Tat/TAR RNA complex in vitro at nanomolar concentrations. NMR stud ies demonstrated that the compound binds similarly to polypeptides der ived from the Tat protein and induces a conformational change in TAR R NA at the Tat-binding site. In addition, 10-30 mu M CGP64222 specifica lly inhibited Tat activity in a cellular Tat-dependent transactivation assay [fusion-induced gene stimulation (FIGS) assay] and blocked HIV- 1 replication in primary human lymphocytes. By contrast, peptides of a comparable size and side-chain composition inhibited cell fusion in t he FIGS assay and only partially inhibited HIV-1 replication in primar y human lymphocytes. Thus, we have discovered a compound, CGP64222, th at specifically inhibits the Tat/TAR RNA interaction, both in vitro an d in vivo.